1000 Sentences With "lavas" | Random Sentence Generator

That makes sense, said Dr. Sieh, since the lavas that buried the crater must be younger than the impact and the lavas that were incorporated into the tektites must be older.

Map of basaltic lavas that produced gases on the Moon's visible side.

Most typically, volcanoes that erupt sticky lavas like andesite and dacite form stratovolcanoes.

The thieves attacked with their long-handled machetes, known locally as antsy lavas.

His group and others will be trying to replicate it using lavas elsewhere.

Ridley tossed me into the lavas of Norfair and KO'd me before I ever got a good hit on him.

Artist's impression of the Moon, looking over the Imbrium Basin, with lavas erupting, venting gases, and producing a visible atmosphere.

Si te lavas las manos antes de tocarte el rostro, deberías estar bien, pues las gotas virales no atraviesan la piel.

So, kind of like big flood basalt provinces and komatiite lavas, kimberlites seem to have been more common in the planet's past.

A few hundred million years ago, briny ice lavas from deep beneath the surface pushed Ahuna Mons up, freezing again as they oozed across the mountain's rugged peak.

The usual activity of the volcano, with lavas coming out of the Puu Oo vent, and at the summit, could have easily convinced anyone that the eastern edge was off the hook.

Why it matters: "What is really fascinating about this study is that we show that the planet is still capable of producing lavas as hot as during the Archean time period," Gazel said in a statement.

In the rarefied air atop the solidified lavas of Mauna Loa, more than 23.4,22100 meters above the hubbub of modern civilization, sophisticated instruments hosted at the Mauna Loa Observatory take daily measurements of atmospheric CO22 concentrations.

Scientists will next need to "drill down a few hundred meters to see if the rocks below the lavas are indeed the rocks you'd expect at an impact site -- that is, lots of evidence for melting and shattering," Sieh said.

Messenger "had previously discovered that past volcanic activity buried this portion of the planet beneath extensive lavas, more than a mile deep in some areas and covering a vast area equivalent to approximately 60% of the continental United States," said APL's Nancy Chabo.

Aunque el coronavirus puede sobrevivir en superficies como bandejas de servicio, pantallas táctiles, agarraderas y grifos —un estudio descubrió que otros coronavirus, como el SRAS y el MERS, permanecen en objetos de metal, vidrio y plástico hasta nueve días—, la aplicación de un desinfectante sobre una superficie dura, o de jabón mientras lavas tus manos, matará al virus.

Andesitic lavas erupted 2.3±0.2 Ma are named Wichhu Qullu lavas. Another effusive activity generated the Carbón Qullu lavas (Carbon Kollu) and finally the Pukara lava dome, whose collapse generated the Thuwas Ventilla pyroclastic flow.

Basalt lavas tend to produce low- profile shield volcanoes or "flood basalt fields", because the fluidal lava flows for long distances from the vent. The thickness of a basalt lava, particularly on a low slope, may be much greater than the thickness of the moving lava flow at any one time, because basalt lavas may "inflate" by supply of lava beneath a solidified crust. Most basalt lavas are of ʻAʻā or pāhoehoe types, rather than block lavas. Underwater, they can form pillow lavas, which are rather similar to entrail-type pahoehoe lavas on land.

The uppermost part is the Helvellyn Basin succession, consisting of volcaniclastic sandstones, dacitic lavas, andesitic lavas and tuffs, and dacitic ignimbrites.

High resolution images show the bulk of the Cerberus plains is covered by platy-ridged and inflated lavas, which are interpreted as insulated sheet flows. Eastern Cerberus plains lavas originate at Cerberus Fossae fissures and shields. Some flows extend for 2000 km through Marte Vallis into Amazonis Planitia. The Athabasca Valles are both incised into pristine lavas and embayed by pristine lavas, indicating that Athabascan fluvial events were contemporaneous with volcanic eruptions.

Whereas most lavas are rich in silicate minerals, the natrocarbonatite lavas of Ol Doinyo Lengai are rich in the rare sodium and potassium carbonate minerals, nyerereite and gregoryite. Due to this unusual composition, the lava is erupted at relatively low temperatures (approximately 500-600 °C). This temperature is so low that the molten lava appears black in sunlight, rather than having the red glow common to most lavas. It is also much more fluid than silicate lavas.

Some phenocrysts show evidence of a complex history. Quartz is rare. Older lavas have developed a red colour and contain oxidized iron in form of hematite. Lavas from Llullaillaco I are grey.

Intermediate or andesitic lavas are lower in aluminium and silica, and usually somewhat richer in magnesium and iron. Intermediate lavas form andesite domes and block lavas, and may occur on steep composite volcanoes, such as in the Andes. Poorer in aluminium and silica than felsic lavas, and also commonly hotter (in the range of ), they tend to be less viscous. Greater temperatures tend to destroy polymerized bonds within the magma, promoting more fluid behaviour and also a greater tendency to form phenocrysts.

Very little soil is developed on the Khorgo lavas. Lavas from this cone dammed a river, generating the Terkhiin Tsagaan Lake. The eruption of Khorgo was probably fed from a north-northeast striking eruption fissure.

View along The Whangie from the south. The Kilpatrick Hills are a part of the Clyde Plateau Lavas. These are about 340 million years old. Basaltic types of rocks (lavas, tuffs and agglomerates) predominate here.

Platanar has erupted lavas ranging from basalts to andesites in composition.

The lavas formed have been plagioclase ultraphyric basalts with large 4 cm crystals. This chemical makeup is similar to those found in lavas from the northern Galápagos Islands. The extent of the ultraphyric flows make up an unusually large percentage of the volume. There is large variation in the composition of the lavas between eruptive phases, with later flows being depleted.

Tofua's pre-caldera activity is recorded by a sequence of pyroclastic deposits and lavas constituting the older cone, followed on the northern part of the island by froth lavas or welded and unwelded ignimbrite. Following the caldera collapse, lavas were erupted from the northern part of the island and the caldera-rim fissure zone, scoria and lavas from the caldera-wall fissure zones, pyroclastics and lavas from intracaldera cones, and recent pyroclastic fall deposits on the outer cone. Eruptive products are mainly basaltic andesites and andesites, plus occasional dacite flows within the older cone. A postcaldera cone with fumarolic activity (Lofia) is in the northern part of the caldera; a crater lake with depth occupies most of the remainder.

The basalt lavas are related to carbonatite intrusions in the Zambezi valley.

Cinder cones, lavas, and small explosion craters are still clearly seen today.

The canyon is carved into the tholeiitic and post-shield calc-alkaline lavas of the canyon basalt. The lavas of the canyon provide evidence for massive faulting and collapse in the early history of the island. The west side of the canyon is all thin, west-dipping lavas of the Napali Member, while the east side is very thick, flat-lying lavas of the Olokele and Makaweli Members. The two sides are separated by an enormous fault along which a large part of the island moved downwards in a big collapse.

The Drakensberg Group lavas compose the upper levels of the entire Drakensberg mountain range. The lavas stretch out over most of Lesotho and into the northeastern Eastern Cape, the southern Free State, and eastern KwaZulu-Natal provinces of South Africa. Basalt provinces of the same low Ti-Zr chemical composition as the Drakensberg lavas are found in the Springbok Flats province in Limpopo, and other basalt sub-outcrops are found in eastern Botswana and central Namibia. These occurrences suggest that the Drakensberg Group lavas once covered a vast area over southern Africa.

Lavas contain phenocrysts of plagioclase with variable amounts of biotite, clinopyroxene, opaque minerals and orthopyroxene. The matrix is glassy and contains hornblende and plagioclase. The lavas have vesicular and minor proportions of amygdaloid, porphyric, trachytic and vitrophyric texture.

The lava production was high when the rhomb porphyry lavas were deposited. The lavas reflect a period of abundant earthquake- related movements, when tectonic forces tore the crust apart. In the Vestfold district, one lava flow was deposited on average every 250,000 years, resulting in a 3000-metre thick sequence of mainly volcanic material. In the Oslo area, lavas were deposited on average every 800,000 years.

Mechanism Bimodal volcanism is the eruption of both mafic and felsic lavas from a single volcanic centre with little or no lavas of intermediate composition. This type of volcanism is normally associated with areas of extensional tectonics, particularly rifts.

Lavas of the Batoka Formation have been dated at 180 to 179 Ma.

Catálogo das Árvores nativas de Minas Gerais: 1-423. Editora UFLA, Lavas, Brasil.

The lavas of the Ethiopia-Yemen CFB show systematic variations in composition both vertically and laterally. Most of the lavas are basalts, but those closest to the Afar Triangle being very high Titanium transitional basalts and picrites, passing outwards into high-Ti tholeiitic basalts and finally into low-Ti tholeiitic basalts. The sequence is also an example of bimodal volcanism and the uppermost part typically contains significant amounts of rhyolitic lavas.

Some of the most ancient geological remnants of basaltic plains lie in Canada's Precambrian Shield. Eruption of plateau lavas near the Coppermine River southwest of Coronation Gulf in the Arctic, built an extensive plateau about 1200 million years ago with an area of about , representing a volume of lavas of at least . The lavas are thought to have originated from a mantle plume center called the Mackenzie hotspot.

The lavas and ashes ejected by these volcanoes consist of liparite, dacite, andesite and basalt.

Among these andesitic lavas were some small quantities of dacitic lavas, formed when more viscous (more silica-rich) magma was erupted. Such dacitic rock is found on the lower parts of the southern and eastern slopes of the fell (but not including Stybarrow Crag).

These lavas erupted and cooled into rock about 4 million years ago in the Pliocene Epoch.

This was done arguing that numerous lavas and dykes in the ophiolite had calc-alkaline chemistries.

The volcanic complex occupies the eastern part of the island and consists of basalt lavas, hawaiite and mugearite (aa) lavas, from explosive pyroclastic rocks and cinder cones originating from Strombolian eruptions. Its features around the complex includes the Pico do Brejo do Cordeiro and several others.

Eruptive activity in the Northern Cordilleran Volcanic Province throughout its 20 million year history has been mainly the production of alkaline lavas, including alkaline basalts. A range of alkaline rock types not commonly found in the Western Cordillera are regionally widespread in the Northern Cordilleran Volcanic Province. These include nephelinite, basanite and peralkaline phonolite, trachyte and comendite lavas. The trachyte and comendite lavas are understood to have been created by fractionation of mainly alkali basalt magma in crustal reservoirs.

Meanwhile, within the park boundary other volcanic events were taking place. Basaltic lavas poured forth in the vicinity of Willow Lake in the southwestern portion of the park. These were followed by a very thick sequence of very fluid andesitic lavas which erupted near Juniper Lake and flowed westward about four miles (6 km). At about the same time, other andesitic lavas poured from several vents on the central plateau to cover an area of at least .

Mathews based his suggestion on the age of the underlying till, the existence of pillow lava close to the bottom of some lavas that indicate subaqueous volcanism, horizontal jointing at the edges of the lavas that indicate rapid cooling, and the absence of apparent paleotopography to explain these features.

Some of the summit vent lavas are among the most vesicular of this stage. They are also less weathered (oxidation rinds are c. thick) and less subject to solfataric alteration. The Cerro Chinchillas lavas are the oldest of this stage; erupted from an unknown vent, they lack amphiboles.

Old Cone lavas range from andesite to olivine-containing basaltic andesite. Young Cone lavas include both andesite and hornblende-containing dacite. Volcanic rocks erupted during both stages of San Pedro belong to the potassium-rich calc- alkaline suite. San Pedro volcanic rocks are usually glassy with only tiny phenocrysts.

Prior kimberlite activity in the Tanzania craton is recorded 1,150, 189 and 53 million years ago. The tuffs are highly calcitic, vesicular and contain numerous microxenoliths. The petrologically similar lavas show evidence of a differentiation by flow and gravity and have trachytic textures. Lavas have a carbonatitic composition.

The CLF consists of 5 km of pillow lavas with some basalt intrusions. The ages of these rocks include 89 Ma for the lavas and 75 Ma for the poikilitic sills, though some sequences may have erupted as late as 62–66 Ma, placing them in the Cretaceous. Their composition includes picrite pillows at the base, followed by tholeiitic lavas, then hyaloclastites, then the poikilitic sills. The CLF was gradually uplifted until Eocene-Miocene limestone caps formed, before final exposure above sea level.

In addition, National Route 3 passes through the Pali-Aike volcanic field. Pali-Aike is part of the Patagonian back-arc, a province of plateau lavas of Cenozoic age. These plateau lavas are of alkaline to tholeiitic composition; hawaiite, trachyandesite and trachyte are present in smaller amounts. From south to north these plateau lavas include Pali-Aike itself, Meseta Vizcachas, Meseta de la Muerte, Gran Meseta Central, Meseta Buenos Aires, Cerro Pedrero, Meseta de Somuncura, Pino Hachado and Buta Ranquil.

PLUME lavas are also found in the lavas from the Galapagos Spreading Centre due to convection and mixing of all of these lavas. In the upper mantle convection currents bring in mantle material at shallow angles from the south of the Galapagos Spreading Centre. These convection current will draw in some PLUME type magma to the spreading centre where it is then erupted. DGM – (Depleted Galapagos Mantle), this has similar characteristics to ocean ridge basalts throughout the Pacific and the Galapagos Spreading Centre.

The lavas are potassium- rich dacitic and rhyolitic save for an andesitic mafic component, and rich in crystals.

Lavas have gray-black porphyric and in some places vesicular textures. Andesine-labradorite plagioclase and pyroxene phenocrysts are found in the lavas, which has a fine grained groundmass. Apatite, augite and opaque mineral inclusions are also found. Some lava flows display very small scale flow bands with feldspat and plagioclase inclusions.

This was the last confirmed large-scale eruption of the Tengchong volcanic field. It produced basaltic and andesitic lavas.

Catálogo das Árvores nativas de Minas Gerais: 1-423. Editora UFLA, Lavas, Brasil.Morokawa, R. & al. (2013). Apocynaceae s. str.

No modern komatiite lavas are known, as the Earth's mantle has cooled too much to produce highly magnesian magmas.

Kīlauea's eruptive history has been a long and active one; its name means "spewing" or "much spreading" in the Hawaiian language, referring to its frequent outpouring of lava. The earliest lavas from the volcano date back to its submarine preshield stage, samples having been recovered by remotely operated underwater vehicles from its submerged slopes; samples of other flows have been recovered as core samples. Lavas younger than 1,000 years cover 90 percent of the volcano's surface. The oldest exposed lavas date back 2,800 years.

There is evidence of magma mixing and mingling. Rocks have a porphyritic texture. Basaltic andesites typically contain less than 10% crystals while dacites generally have more than 20% crystals. The Alconcha group lavas of the first one million years are crystal-poor and lack biotite; later lavas contain biotite and more crystals.

The Brabant Island Tectonic Block includes up to 2000 m of basaltic-andesitic lavas and volcaniclastics, possibly corresponding to the Lower Cretaceous Antarctic Peninsula Volcanic Group of the Danco Coast. This group is intruded by a granodiorite sill and Early Eocene hypabyssal dykes. Late Tertiary to Pleistocene basaltic lavas uncomformably overlay this complex.

The deposits consist of dykes, hydrothermal deposits, lava flows, pyroclastics, and subvolcanic structures and were erupted from parasitic vents and fissures. The magnetite is classified as porphyry-like. Apatite is present as an accessory mineral in the lavas and is abundant in the intrusions. Iron-rich zones also formed in tuffs and lavas.

Volcanic rocks at Pairique include dacite with cordierite inclusions. Older lavas feature rhyodacite intrusions. Mineral deposits are associated with Pairique.

Oliveira-Filho, A.T. (2006). Catálogo das Árvores nativas de Minas Gerais: 1-423. Editora UFLA, Lavas, Brasil.Morokawa, R. & al. (2013).

Editora UFLA, Lavas, Brasil.Morokawa, R. & al. (2013). Apocynaceae s. str. do Parque Nacional da Serra da Canastra, Minas Gerais, Brasil.

Compositionally, lava from the Newberry Volcano has varied from primitive basalts with high magnesium levels to more evolved tholeiitic and calc- alkaline deposits (based on the major element characteristics of the lavas). Primitive lavas exhibit high abundances of chromium and nickel as well as variable concentrations of fluid-mobile elements like barium and strontium. Tholeiitic and calc-alkaline lavas display overlap in magnesium, calcium oxide, and aluminum oxide levels but differ in that the tholeiites have lower contents of silica and potassium oxide and higher iron(II) oxide, titanium dioxide, and sodium oxide. There is also much overlap in isotopic composition, though the tholeiitic lavas mark the low point for 87Sr/86Sr and the high point for 143Nd/144Nd and 176Hf/177Hf.

Most of the Datil-Mogollon Section in Arizona is the White Mountain volcanic field. It is an extensive area covered with thick lavas and tuffs. There are also remnants of large stratovolcanoes, mainly composed of basaltic andesite. High tablelands are capped with tuffs, andesite, and basalt lavas, and volcanic-derived conglomeratic sandstones and mudstones.

This small volcano produced an astonishing quantity of lavas reaching like a girdle over the peninsula of Reykjanes, entering the sea to the north next to the present capital city of Iceland Reykjavík as well as to the south in the bay of Selvogur. Today, these lavas are partially covered by younger lava flows.

The halleflintas of Sweden are also in part acid igneous rocks with a well-banded schistose or granulitic texture. The quartz-porphyries are distinguished from the rhyolites by being either intrusive rocks or Palaeozoic lavas. All Tertiary acid lavas are included under rhyolites. The intrusive quartz-porphyries are equally well described as granite-porphyries.

Pillow lava on the ocean floor of Hawaii Pillow lava near Oamaru, New Zealand Weathered Archean pillow lava in the Temagami Greenstone Belt of the Canadian Shield Pillow lava formations from an ophiolite sequence, Northern Apennines, Italy Pillow lavas are lavas that contain characteristic pillow-shaped structures that are attributed to the extrusion of the lava underwater, or subaqueous extrusion. Pillow lavas in volcanic rock are characterized by thick sequences of discontinuous pillow-shaped masses, commonly up to one meter in diameter. They form the upper part of Layer 2 of normal oceanic crust.

Deposits of the Medusae Fossae Formation lie both over and under lavas, suggesting the deposition of this formation was contemporaneous with volcanism. Statistics of small craters indicate lavas in the western Cerberus plains may be less than a million years old, but the model isochrons may be unreliable if the small crater population is dominated by secondary craters (craters formed by material ejected from larger impacts). Images showing no large craters with diameters larger than 500 meters superimposed on western Cerberus plains lavas indicate the same surface is younger than 49 Ma (million years).

There are important exposures of rocks of the Skiddaw Group in contact with lavas and tuffs of the Borrowdale Volcanic Group.

Pillow lavas often show such chilled margins which are glassy and prove the sudden cooling undergone due to contact with water.

Instituto de Botânica, São Paulo.Oliveira-Filho, A.T. (2006). Catálogo das Árvores nativas de Minas Gerais: 1-423. Editora UFLA, Lavas, Brasil.

The bedrock of the archipelago is varied. In the northwest it is made of metamorphic rock, with rocks such as phyllite, metacherts and greenschist. In the southeast granitoids, lavas and brecciated lavas make most of the bedrock. The archipelago bears various marks of erosion from the glaciers that repeatedly covered the area during the last 2 million years.

This volcano was probably an isolated cone, but the existence of a previous stage cannot be excluded. The second stage, named Rodado, lasted from 0.95 to 0.85 mya. It formed on the eastern slopes of the Azufrera volcano, with one vent at the summit. Rodado stage lavas are blocky and platy and usually thicker than Azufrera stage lavas.

They substantiated, based on geochemistry, that the lavas were derived by subduction (calc-alkaline). Radiometric dates also showed that the volcanism falls into two groups that range from 20 million years to recent. They also showed that the youngest volcanism consists primarily of adakites (partial melts from the subducted slab) whereas the older volcanism is normal calc-alkaline lavas.

At its base the Thornhill Basin has a sequence of olivine basalt lavas with some interbedded breccia and sandstone, known as the Carron Basalt Formation. The lavas are overlain by either the Durisdeer Breccia Formation or the Locherben Breccia Formation. Both of these breccia formations pass laterally and upwards into aeolian sandstones of the Thornhill Sandstone Formation.

Viðskiptafræðideild Háskóla Íslands. June 2010. Retrieved 26 July 2020 When scientists examined the outcrops in the quarry, they found many layers of pillow lavas. One theory about their origin is, that during the last stages of Vífilsfell's eruptions, subaerial lavas had emerged up on the mountain, degassed there and then run into a deep lake or the sea.

It is also much more fluid than silicate lavas, often less viscous than water. The sodium and potassium carbonate minerals of the lavas erupted at Ol Doinyo Lengai are unstable at the Earth's surface and susceptible to rapid weathering, quickly turning from black to grey in colour. The resulting volcanic landscape is different from any other in the world.

The alkalinity of the lake can reach a pH of greater than 12. The surrounding bedrock is composed of alkaline, sodium-dominated trachyte lavas that were laid down during the Pleistocene period. The lavas have significant amounts of carbonate but very low calcium and magnesium levels. This has allowed the lake to concentrate into a caustic alkaline brine.

In addition, basalt xenoliths of the same chemical structure as the Drakensberg lavas have been found in the Northern Cape within Cretaceous-aged kimberlite pipes (~ 90 Ma) that intruded older rocks of the Karoo Supergroup. In the Lesotho highlands and the highest sections of the Drakensberg mountain range, only erosional remnants of the Drakensberg lavas remain.

They range from moderately to intensely fractionated. REE-profiles are similar to those from tholeiitic basalts to extremely alkaline lavas in Hawaii.

Some were mixed and fused by volcanic rocks. The multi-hued lavas, intrusive rocks, and cemented gravels give the mountain its brilliant colors.

The sulfide ore occurs at the same stratigraphic level as the Lower and Upper pillow lava contact, and is overlain by unmineralised lavas.

Víðáttumestu hraun Íslands. (The Largest Lavas of Iceland). Náttúrufræðingurinn 81, 37-49. An estimated 18 km3 of magma poured out of the earth.

Most of the rocks are basaltic andesite, dacite is also present in the central parts of the volcano and -rich basalt has also been found. Some lava flows contain olivine. The magmas that formed the volcano are partially evolved magmas, with their formation influenced by the crust. These lavas are considered to be backarc lavas and resemble these of volcanoes farther south.

The volcanic history of Aracar is poorly understood. The bottom lava flows have ages of 3.4 ± 1.2 to 2.6 ± 0.4 mya but an age of 100,000 years has also been given. Presumably at first fluid basaltic lavas were erupted. Subsequently, dacite lavas were erupted, accompanied with the formation of a strong slope in the edifice and hydrothermal activity at a northwestern lava dome.

The rocks follow the calc-alkaline trend of magmatic differentiation, containing silicic lavas such as dacite. Their overall composition ranges from basaltic andesite to dacite, and the dominant lava rocks are andesite and basalt. Andesites range from green to gray in colour, and dacites are pink- and light-gray. The andesitic lavas contain phenocrysts of andesine, hornblende, plagioclase and hypersthene.

Rocks dredged from the seamounts include lavas, pillow lavas and volcaniclastic rocks. Geochemically they are classified as alkali basalt, basalt, phonolite, tephriphonolite trachyandesite, trachybasalt and trachyte. Minerals contained in the rocks include alkali feldspar, apatite, biotite, clinopyroxene, iron and titanium oxides, olivine, plagioclase, sphene and spinel. Continental crust rocks dredged at the seamounts may be glacial dropstones, manganese have also been found.

Geologically Jebel Ghawil constitutes a formation with Jebel Suweini. It consists of Triassic limestone, which is said to be "underlain by a thick sequence of pillow lavas, which are partly imbricated with cherts". There are three sills intruded into basaltic lavas and tuffs dated to the late Triassic and its sills reportedly give K-Ar ages on separated biotites of 93-4 ±4Ma.

The total volume of the edifice is about . The (also known as Big Joe) lava flow complex lies southwest of the Lastarria volcano and covers an extensive surface. It is formed by several massive flows erupted from a single vent during three or eight pulses; the longest reaches a length of . These lavas are block lavas with flow ridges and levees.

Bimodal deposition followed with lavas, minor intrusions, ash-flows and volcaniclastic rocks with some ash-flows exhibiting Ediacaran body fossils.J. C. W. Cope, An Ediacara type fauna from South Wales 1977, Nature, London 264,624 The geochemistry notes that fractional crystallisation process within the magma chamber links the lavas with the tuffs and gives intra-plate as well as subduction geochemical signatures.

A repeat of wildfires in the Lava Fork valley is also a possibility due to the existence of vegetation on and around the erupted lavas.

In the 1970s and 1980s this volcano was prospected and mined for garnets. The Terkhiin Tsagaan Lake was dammed by Holocene lavas from Khorgo cone.

Sicily remains active as a producer of sulfur and potassium salts and aluminum production has shifted into leucitic lavas in the center of the country.

Jesus Lava was the youngest of nine children of Adeodato Lava and Maria Baltazar. The Lavas were a prominent family in Bulacan in the Philippines.

The vents of El Jorullo are aligned in a northeast to southwest direction. Lava from these vents cover nine square km around the volcano. Later eruptions produced lavas that had higher silica contents making them thicker than the earlier basalts and basaltic andesite lavas. El Jorullo's crater is about 1,300 by 1,640 feet (400 by 500 m) wide and 490 feet (150 m) deep.

The lavas of this complex are of potassium-rich calc-alkaline origin, and are highly viscous with large difference between two magma types. The lava domes are formed from andesite in the south and dacite in the north. The dacites are crystal rich and some lavas show evidence of magma mixing. Phenocryst contents ranges from 35% by volume in dacite and 48% by volume of rhyolite.

Whereas most lavas are rich in silicate minerals, the lava of Ol Doinyo Lengai is a carbonatite. It is rich in the rare sodium and potassium carbonates, nyerereite and gregoryite. Due to this unusual composition, the lava erupts at relatively low temperatures of approximately . This temperature is so low that the molten lava appears black in sunlight, rather than having the red glow common to most lavas.

Later, the more acidic magma erupted. The lava flows of 1669 contain up to 18% bubbles, a large proportion and considerably more than expected from lava flows on the surface that might explain the fluidity of the flows that maintained pahoehoe morphology from the vents. The lava also contains large phenocrysts of plagioclase, as do lavas of other eruptions of the 17th century; these lavas are called .

Pillow lava of the Troodos ophiolite (The red lines have been added to the photo by the photographer to outline the shape of some of the lava pillows) The lowest units of the ophiolite are the Lower Pillow Lavas, controversially separated from the Upper Pillow Lavas. Filling spaces in between the pillows in the pillow lava units are dispersed metal oxide sediments that can also be seen as veins filling cooling fractures within the lavas. The metal oxides are ferruginous with ferromanganese oxides, clays, carbonates, volcanic glass and pelagic sediments. Above the pillow lava units lies a layer of ferromaganiferous mudstones and clastic volcanics (the epiclastics).

Nemo is an andesitic volcano. Basaltic andesite and dacite have been found as well. Augite, hypersthene, labradorite, olivine and pyroxene are minerals found in Nemo lavas.

The lavas contain inclusions of lithic material as well as pyroxene and peridotite lherzolite. Phonolite and trachyte are absent. The magmas ultimately originated at depths of .

Editora UFLA, Lavas, Brasil.Hokche, O., Berry, P.E. & Huber, O. (eds.) (2008). Nuevo Catálogo de la Flora Vascular de Venezuela: 1-859. Fundación Instituto Botánico de Venezuela.

Salado's rock is predominantly potassium-rich dacite and rhyodacite. Its lavas are high in biotite, hornblende, plagioclase, and opaques, with lower levels of augite, quartz, and hypersthene.

Charrier et al. 2006, pp. 93–94. Lavas and volcanic material that are now part of Farellones Formation accumulated while the basin was being inverted and uplifted.

Hot basaltic magma rises along these fractures to create passive lava eruptions. The compositions of lavas in the Northern Cordilleran Volcanic Province are mantle-derived alkali olivine basalt, lesser hawaiite and basanite, which form the large shield volcanoes and small cinder cones throughout the volcanic province. Many of them contain inclusions of lherzolite. The large central volcanoes of the volcanic province consist largely of trachyte, pantellerite, and comendite lavas.

Their chemical composition indicates that they share a common source with the pyroclastic deposits and lavas of the Cardenas Basalt. The isochron ages of these sills and dikes and the Cardenas Basalt lavas are basically identical. Only sills are exposed in outcrops of the Bass Formation and Hakatai Shale. These sills range in thickness from at Hance Rapids, eastern Grand Canyon, to in Hakatai Canyon in the Shinumo Creek area.

The Mackenzie hotspot is responsible for the creation of the Mackenzie Large Igneous Province, which contains the largest dike swarm on Earth. During its formation, eruption of plateau lavas near the Coppermine River, built an extensive volcanic plateau about 1,200 million years ago with an area of about representing a volume of lavas of at least . The Mackenzie hotspot also resulted in the opening of the Mesoproterozoic Poseidon Ocean.

Low viscosity permits rapid nucleation and ion migration, necessary for crystal formation. The high silica content of rhyolitic lavas gives them much higher viscosities. Such lavas tend to form glass (obsidian) when they cool rapidly from a fully melted liquid state; though many obsidians also contain microlites. Low viscosity mafic magmas must be quenched very rapidly from a high temperature to form glass that is free of any crystalline content.

Medicine Lake Volcano began to grow about one million years ago in Pleistocene time, following the eruption of a large volume of tholeiitic high-alumina basalt. Similar high-alumina basalt has continued to erupt around the volcano throughout its history. Although mafic lavas predominate on the volcano's flanks, all lava compositions from basalt to rhyolite have erupted during Pleistocene time. The lower flanks consist of mostly basaltic and some andesitic lavas.

Included among these flows were the Twin Lake lavas of black porphyritic andesite, which are notable in that they contain xenocrysts of quartz.Harris, Ann (1997). Geology of National Parks, page 474 The Flatiron andesites spread over the southwestern part of the park area around this time. Apparently, the vents of these lavas renewed activity at a much later date to form three cinder cones: Hat Mountain, Crater Butte and Fairfield Peak.

Kjerringberget partly consists of green rocks formed when subterranean magma solidified after flowing out and coming into contact with water, forming pillow lavas. These lavas were later cross-cut by intrusions of trondhjemite. Bymarka west of Trondheim also has similar geological structures, both forming part of the early Ordovician Bymarka ophiolite. Kjerringberget also has some connections to World War II. Stone from Kjerringberget was used to build a mole in Korsvika.

Magnetite, and in lesser measure hematite, are the most abundant iron minerals; anhydrite, diopside, goethite, limonite, maghemite, pyrite, and diadochite are also found. Erupted magma was probably gas-rich, as the magnetite lavas would otherwise have melting points of over . The lavas lost most of their sulfur and phosphorus after their eruption. High oxygen-18 amounts in the Laco magmas indicate either crustal contamination or isotopic effects during fractional crystallization.

Succession and relation of lavas in the Great Basin region: Journal of Geology, v. 8, p. 621–646. Structure of the Basin ranges (abstract): Science, new ser., v.

Editora UFLA, Lavas, Brasil.Walderley, M.G.L., Shepherd, G.J., Melhem, T.S. & Giulietti, A.M. (eds.) (2005). Flora Fanerogâmica do Estado de São Paulo 4: 1-392. Instituto de Botânica, São Paulo.

Breccias, tuffs and dacite lavas were formed during its eruption sequence. The age of the dome is unknown. Minerals in its rocks include amphibole, biotite, orthopyroxene and plagioclase.

The El Tatio ignimbrite ponded in the Tatio graben and may have originated at the Tocorpuri rhyolite dome, which is less than one million years old, in a vent now buried beneath the El Tatio volcanic group, or at the Laguna Colorada caldera. The El Tatio volcanic group has likewise been dated to be less than one million years old, and its lavas overlie the older formations. Volcan Tatio erupted mafic lavas probably during the Holocene; later this volcano was reinterpreted to be of Pleistocene age. Petrological data suggest that over time the erupted lavas of the El Tatio volcanic group have become more mafic, with older products being andesitic and later ones basaltic-andesitic.

Nyiragongo's lavas are made of melilite nephelinite, an alkali-rich type of volcanic rock whose unusual chemical composition may be a factor in the unusual fluidity of the lavas there. Whereas most lava flows move rather slowly and rarely pose a danger to human life, Nyiragongo's lava flows may race downhill at up to . This is because of the extremely low silica content (the lava is mafic). Hawaiian volcanic eruptions are also characterized by lavas with low silica content, but the Hawaiian volcanoes are broad, shallow-sloped shield volcanoes in contrast to the steep-sided cone of Nyiragongo, and the silica content is high enough to slow most Hawaiian flows to walking pace.

The Musgravetown Group is a terminal Ediacaran stratigraphic group of terrestrialish sandstones, lavas and tuffs cropping out in Newfoundland. It corresponds temporally to the Signal Hill Group further east.

These ridges probably were formed by local to regional surface compression caused by lithospheric loading by dense stacks of volcanic lavas, as suggested for those of the lunar maria.

The slide flowed northwestward into Shasta Valley, where the Shasta River now cuts through the flow. What remains of the oldest of Mount Shasta's four cones is exposed at Sargents Ridge on the south side of the mountain. Lavas from the Sargents Ridge vent cover the Everitt Hill shield at Mount Shasta's southern foot. The last lavas to erupt from the vent were hornblende-pyroxene andesites with a hornblende dacite dome at its summit.

Tendürek (, ) is a shield volcano located in the Ağrı and Van provinces of eastern Turkey, close to the borders with Iran. The elongated volcano rises above the Doğubeyazıt plain, south of Mount Ararat. Two main cones with a crater each and several minor lateral cones form the edifice. The edifice dates 700,000–500,000 years BP to 13,000 BP and is mostly constructed from basaltic lavas, with some pyroclastics and trachytic/trachyandesitic lavas.

In 1958, Canadian volcanologist Bill Mathews suggested that the lava flows were erupted during periods of subglacial activity and traveled through trenches or tunnels melted in glacial ice of the Fraser Glaciation. Mathews based this on the age of the underlying till, the existence of pillow lava close to the bottom of some lavas, indicating subaqueous volcanism, the columnar jointing at the edges of the lavas, indicating rapid cooling, and the absence of apparent palaeogeography.

In addition to lava flow structures, pyroclastics containing iron ore are also found within the complex. The magmas formed within a magma chamber with a volume of about ; whether the iron-rich lavas are native magnetite lavas or were formed by hydrothermal processes acting on regular rock is under debate. After their discovery in 1958, these iron deposits have been mined. Similar deposits of volcanic iron ore exist in Australia, Chile, and Iran.

Ultramafic lavas such as komatiite and highly magnesian magmas that form boninite take the composition and temperatures of eruptions to the extreme. Komatiites contain over 18% magnesium oxide, and are thought to have erupted at temperatures of . At this temperature there is no polymerization of the mineral compounds, creating a highly mobile liquid. Most if not all ultramafic lavas are no younger than the Proterozoic, with a few ultramafic magmas known from the Phanerozoic.

In igneous rocks, small- scale structures are mostly observed in lavas such as pahoehoe versus ʻAʻā basaltic flows, and pillows showing eruption within a body of water or beneath ice.

It is predominantly of a brown forest soil type with some gleying, the lower parts being formed from raised beach sands and gravels derived from Old Red Sandstone and lavas.

The eruption of the Chillahuita dome appears to have been controlled by local fault systems associated with the Altiplano-Puna volcanic complex, which also has geochemical similarity with Chillahuita lavas.

Unusually hot (>950 °C; >1,740 °F) rhyolite lavas, however, may flow for distances of many tens of kilometres, such as in the Snake River Plain of the northwestern United States.

Silver saxifrage grows in rock fissures and occurs only in areas of Tertiary basalt lavas, which are mostly located in the east of Iceland, but also in the west and northwest.

He noted the existence of pillow lavas, indicating a lava being rapidly cooled in water, as well as the spinifex textures created by crystals formed under rapidly cooling environments, namely water.

The old quarry The hill origin is volcanic and it shows both trachitic and basic lavas, recognisable thanks to the excavations connected to the disused quarry opened in its eastern flanks.

The megabreccia could reveal the nature of the remnant of Mars's primary crust or the Noachian-aged low-calcium pyroxene lavas. It also could constrain the timing of Martian dynamo activity.

They occur wherever lava is extruded underwater, such as along marine hotspot volcano chains and the constructive plate boundaries of mid-ocean ridges. As new oceanic crust is formed, thick sequences of pillow lavas are erupted at the spreading center fed by dykes from the underlying magma chamber. Pillow lavas and the related sheeted dyke complexes form part of a classic ophiolite sequence (when a segment of oceanic crust is thrust over the continental crust, thus exposing the oceanic segment above sea level). The presence of pillow lavas in the oldest preserved volcanic sequences on the planet, the Isua and Barberton greenstone belts, confirms the presence of large bodies of water on the Earth's surface early in the Archean Eon.

Once the sedimentary material was compressed, it created the shale that now forms portions of Whistler Mountain. The most common rocks, andesite and dacite lavas, were said to have been deposited when volcanic activity created a series of islands and lava flows in the ancient ocean. Once the shale and lavas were deposited, they began to deform, crumple and uplift due to the extreme pressures created by movement of the North American Plate and the tectonic plates under the Pacific Ocean. The large masses of solidified lava that formerly created the volcanic island chain and underwater lava flows yielded by demolishing into massive, mountain-sized blocks while the less dense, thinly layered shale was compressed, folded and crushed between the associated lavas.

Thus, the contact between the Cardenas Lavas and the Dox Formation is conformable and interfingering. This indicates that sands were still being deposited when the first lavas erupted and that deposition occurred during the transition from the accumulation of Dox Formation to Cardenas Basalt.Timmons, JM, J. Bloch, K. Fletcher, KE Karlstrom, M Heizler, and LJ Crossey (2012) The Grand Canyon Unkar Group: Mesoproterozoic basin formation in the continental interior during supercontinent assembly. In JM Timmons and KE Karlstrom, eds.

Isluga's lavas are andesitic to trachyandesitic in composition with SiO2 contents between 56-61%. The andesites are porphyritic with more than half phenocrysts and high potassium content (2.7-3.6%), moderate aluminium and high magnesium, although some hornblendes have high Na/K ratios. The petrology of the Isluga lineament lavas indicates an origin either in 3-5% partial melting of the mantle, or by a 15% partial melting of a granite-containing mantle with subsequent fractionation of mafic components.

Journal of the Geological Society, 150, 515-527. It has been proposed that the Hoy sandstones are the lateral equivalents of the Eday Group, the thickness and associated facies changes being caused by active extensional faulting during deposition. The presence of lavas within the Eday Flagstone Formation has been used to lend support to this idea, but differences in the chemistry between these lavas and those on Hoy mean that such a correlation remains uncertain.Odling, N.W.A. 2000.

The volcanic crater is distinct, and has erupted in historical times, only "blocky" lava flows. Charles Wood and Jürgen Kienle, volcanologists, propose that earlier activity, 4,000–5,000 years ago, consisted primarily of lavas of ethereal (fine) platy and thick andesite. Amak Volcano is unique in that its andesitic lavas, while composed the same as the other Aleutians, contain an abundance of potash. They also could contain more sodium carbonate and rare-earth element deposits than the Aleutian norm.

Many of Canada's major ore deposits are associated with Precambrian volcanoes. There are pillow lavas in the Northwest Territories that are about 2.6 billion years old and are preserved in the Cameron River Volcanic Belt. The pillow lavas in rocks over 2 billion years old in the Canadian Shield signify that great oceanic volcanoes existed during the early stages of the formation of the Earth's crust. Ancient volcanoes play an important role in estimating Canada's mineral potential.

Communications towers atop Mount Canobolas Mount Canobolas is an extinct volcanic complex which erupted in several phases between 13 and 11 million years ago, making the mountain a relatively recent geological feature. Earlier eruptions were less violent with free flowing lavas reaching a maximum coverage extent of approximately. Later eruptions became more violent, and producing increasingly viscous lavas with less extensive coverage. The contemporary landscape of Mount Canobolas exhibits erosional features dominated by several remnant peaks.

The summit rocks are of the Birker Fell Formation, plagioclase-phyric andesite lavas. Interbeds of volcaniclastic sandstone and lapilli-tuff also appear. Seat is an outcrop of the flow banded andesite lavas of the Haystacks Member, shot through with quartz-feldspar phyric microgranite.British Geological Survey: 1:50,000 series maps, England & Wales Sheet 29: BGS (1999) There was small scale mining activity in the late nineteenth century beneath Low Wax Knott, adjacent to the Scarth Gap path.

Slieve Gullion itself is in fact a more recent addition than the ring dykes which surround it and is made up of layers of igneous rock. As with the ring itself, there has been some debate as to their origins. One suggestion is that a huge explosive eruption of the volcano created a vast crater, or caldera, into which lavas were excluded in layers. Another more plausible explanation is that the lavas were extruded in layers.

The Chao flow is of dacitic composition, with some non-vesicular small andesitic inclusions that are more numerous in the Chao III and upper Chao II stages, up to 5% of the volume of some Chao III lavas and vesiculated there. The lava has a porphyric texture owing to its high crystal content of 45% and displays extensive flow banding. Chao III lavas have lower concentrations of crystals. Phenocrysts in the lava contain biotite, hornblende, plagioclase and quartz.

Partial melting of the upper mantle as a result of the spreading centre will leave mantle material depleted in some compounds. It has low Sr and Pb isotope ratios and high Nd ratios. DGM is found in the central islands of the Galapagos such as Santiago, Santa Cruz, San Cristobal and Santa Fe. It fills in the centre of the horseshoe formed by the PLUME lavas to the west, north and south. FLO – (Floreana), characteristic of that island's lavas.

The 7 million year-old Chaxas ignimbrite massif has been related to the caldera-forming eruption at Sairecabur. These dacitic ignimbrites spread southwest towards the Salar de Atacama. This high age estimate for the Chaxas ignimbrite however has been questioned, considering that it is inconsistent with stratigraphic relationships of this ignimbrite to older ignimbrite. The lava formations are named Post-Caldera Lavas I and Post-Caldera Lavas II; the first is of Pleistocene and the second of Holocene age.

Modified from Moyen & Martin, 2012. Geochemical similarity shared between TTGs and adakites was long noted by researchers. Adakites are one type of modern arc lavas, which differ from common arc lavas (mostly granitoids) in their felsic and sodic nature with high LREE but low HREE content. Their production is interpreted to be the partial melting of young and hot subducting oceanic slabs with minor interaction with surrounding mantle wedges, rather than mantle wedge melts like other arc-granitoids.

The Early Cretaceous Milestone Bluff Formation (113.9 Ma) is a sandstone-conglomerate indicating a shallowing trend. Volcanic formations on Adelaide Island include the Bond Nunatak Formation (75 Ma), which consists of basaltic andesite lavas interbedded with coarse grained volcaniclastics, and overlays the Buchia Buttress Formation. The Mount Leotard Formation (75-65 Ma), has up to 1800 m of basaltic andesite lavas, hyaloclastites and breccias. The Reptile Ridge Formation (67.6 Ma) is a rhyolitic ignimbrite up to 400 m thick.

Kalsilite (KAlSiO4) is a vitreous white to grey feldspathoidal mineral that is found in some potassium-rich lavas, such as from Chamengo Crater in Uganda. It has a relative hardness of 5.5.

In the last 2.5 million years of the Quaternary, andesite lavas erupted, forming the Arequipa and Barosso groups in the south, including partially melted Precambrian granulite gneiss, with a high lead concentration.

There is no evidence of large ignimbrite eruptions nor of large flank collapses but some lavas may have interacted with water or ice as they were erupted and were reportedly emplaced over moraines.

No mammalian fauna were found in the lower unit of the Laetolil Beds, and no date could be assigned to this layer. The Ndolanya Beds, which are located above the Laetolil Beds and underlie the Ogol lavas, are clearly divisible into upper and lower units separated by a widespread deposit of calcrete up to one meter thick. However, like the Lower Laetolil Beds, no date can be assigned to the Ndolanya Beds. The Ogol lavas date back 2.4 million years.

While the Drakensberg lavas form nearly horizontal layers, the Lebombo lavas dip to the east, so it is difficult to gauge how far the lava spread laterally. Cradock region of the Great Karoo. The dolerite sills are harder and more erosion resistant than the Beaufort shales into which they were intruded, giving these hills their tabletop summits and stepped sides. The uplifting of Southern Africa heralded a phase of massive erosion, removing a layer several kilometers thick from the African Surface.

The mountain was identified by the crash mapping program of Operation Stikine in 1956. This program, masterminded by Canadian volcanologist Jack Souther, was carried out over the Stikine River area using a Bell helicopter. Reconnaissance mapping in 1962 by Jack Souther and Hu Gabrielse identified a sequence of lavas of late Tertiary to Quaternary age. Level Mountain was then studied by T. S. Hamilton in the 1970s who produced a detailed map and the first petrochemical study of the lavas.

These characteristics are similar to enriched mantle sources with minor crustal contamination. There has also been no clear evidence that the geochemical characteristics in the Madagascar flood basalts are similar to observed in the Marion hotspot lavas, basaltic and rhyolitic lavas that also erupted in Madagascar during the Late Cretaceous. Storey, M., Mahoney, J. J., Saunders, A. D., Duncan, R. A., Kelley, S. P., & Coffin, M. F. (1995). Timing of Hot Spot--Related Volcanism and the Breakup of Madagascar and India.

The lavas from this cycle had little silica, and originated in the mantle. Additional pulses of volcanism occurred between 7-10 million years ago, between 6-7 million years ago, between 3-6 million years ago, and between 2-3 million years ago. The last of these pulses is believed to have created the Cerros del Rio volcanic field, which covers the entire Caja del Rio Plateau. Several of the later eruptions involved not only basalts, but lavas made of rhyolite or dacite.

As part of Operation St. Elias, Jack Souther studied the stratigraphy, structure and evolution of the Wrangell lavas of southwest Yukon in the mid 1970s. He was surprised by the difference in volcanic style between the Wrangell lavas where an enormous volume of andesite lava had issued without any apparent breaks and was accompanied by profound tectonic uplift and compressive folding, in contrast to the episodic eruption of alkaline basalt and highly fractionated silicic peralkaline rocks at Edziza. The differences in eruptive style and chemistry of the Wrangell lavas led Souther to speculate they were related to a calc-alkaline volcanic arc that formed along a converging plate boundary. In 1977, a book published under the title Volcanic Regimes in Canada included a chapter on Cordilleran tectonics by Jack Souther.

Some lavas from Sairecabur have also overrun the Purico formation, which is of Pleistocene age and includes ignimbrites from the Purico Complex. The basement beneath Sairecabur and Licancabur contains a large number of faults.

The pyroclastics at Laco Sur contain spherules of magnetite. An age of 2.1±0.1 million years has been found for ore by fission track dating. The lavas contain veins likely generated by hydrothermal activity.

Age progressive rhyolitic lavas (light blue) from the McDermitt Caldera (MC) to the Yellowstone Caldera (YC) track the movement of the North American plate over the Yellowstone Hotspot. Similar age progressive lavas across the High Lava Plains (HLP) towards the Newberry Caldera (NC) have been termed the Newberry Hotspot Track, but this goes the wrong direction to be attributed to movement of the plate over a hotspot. Numbers are ages in millions of years. VF = Vale Fault, SMF = Steens Mountain Fault, NNR = North Nevada Rift.

Cerros Negros de Jama is a monogenetic volcanic group in the Andes, Jujuy Province, Argentina. The group is formed by about four well preserved scoria cones (between high and wide at the basis, subcircular to elliptic) with lava fields and one isolated lava field, constructed on Ordovician marine sediments and dacitic lavas from the adjacent Cerro Bayo de Archibarca (7.2 million years old) volcano. These cones are aligned submeridionally with a fault system in the ground. The lavas and associated dykes have porphyritic appearance and variable morphology.

Lavas within the breach are dated 10.78–10.43 mya. The centres of Volcan Tuco and Alconcha are heavily eroded, and Alconcha's lavas and scoria lie on top of Tuco. The Ujina ignimbrite was erupted 9.4 mya from an unknown vent and has a volume of of dacite. While the vent location is unknown, the composition of the ignimbrite, and its dating and distribution, indicate an association with this group. The domes are poorly researched, with the Coscalito dome dated 8.9–8.7 mya and Cerro Amincha 8.01.

The composition of the current eruptive products of Erebus are anorthoclase-porphyritic tephritic phonolite and phonolite, which are the bulk of exposed lava flow on the volcano. The oldest eruptive products consist of relatively undifferentiated and nonviscous basanite lavas that form the low broad platform shield of Erebus. Slightly younger basanite and phonotephrite lavas crop out on Fang Ridge—an eroded remnant of an early Erebus volcano—and at other isolated locations on the flanks of Erebus. Erebus is the world's only presently erupting phonolite volcano.

In the later Pliocene and into the Pleistocene, these basaltic flows were covered by successive thick and fluid flows of andesite lava, which geologists call the Juniper lavas and the Twin Lakes lavas. The Twin Lakes lava is black, porphyritic and has abundant xenocrysts of quartz (see Cinder Cone). Another group of andesite lava flows called the Flatiron, erupted during this time and covered the southwestern part of the park's area. The park by this time was a relatively featureless and large lava plain.

Mafic or basaltic lavas are typified by their high ferromagnesian content, and generally erupt at temperatures in excess of . Basaltic magma is high in iron and magnesium, and has relatively lower aluminium and silica, which taken together reduces the degree of polymerization within the melt. Owing to the higher temperatures, viscosities can be relatively low, although still thousands of times higher than water. The low degree of polymerization and high temperature favors chemical diffusion, so it is common to see large, well-formed phenocrysts within mafic lavas.

The ore horizons are known locally as amygdaloids, after the amygdaloidal-shaped gas bubbles in the lavas that filled with minerals. Copper Range shut down the Champion mine, its last operating native copper property, in 1967.

Retrieved 4 August 2020. The volcanic cones sits on older lava layers, the Teriary Grey Basalt lavas which are the basement rocks of the area of Heiðmörk.Thor Thordarson, Armann Hoskuldsson: Iceland. Classic geology in Europe 3.

Incompatible elements and rare-earth elements are enriched in these lavas. The volcanic rocks are derived from decompression melting of the asthenosphere, with garnet and lherzolite as precursors. Dunite xenoliths are found within the erupted basalts.

190: a sketch; and p. 172: a sketch of the geological findings by C. Katsimbinis, 1976: "der Felsblock ist zu 1/8 unterhalb des Kirchenbodens, verbreitert sich dort auf etwa 6,40 Meter und verläuft weiter in die Tiefe"; and p. 192, a sketch by Corbo, 1980: Golgotha is distant 10 meters outside from the southwest corner of the Martyrion-basilica During a 1986 repair to the floor of the Calvary Chapel by the art historian George Lavas and architect Theo Mitropoulos, a round slot of diameter was discovered in the rock, partly open on one side (Lavas attributes the open side to accidental damage during his repairs);George Lavas, The Rock of Calvary, published (1996) in The Real and Ideal Jerusalem in Jewish, Christian and Islamic Art (proceedings of the 5th International Seminar in Jewish Art), pp.

These flood basalt lava flows were erupted during a single event that lasted less than five million years. Analysis of the chemical composition of the lavas gives important clues about the origin and dynamics of the flood basalt volcanism. The lowermost lavas were produced by melting in the garnet stability field below the surface at a depth of more than in a mantle plume environment beneath the North American lithosphere. As the mantle plume intruded rocks of the Canadian Shield, it created an upwelling zone of molten rock known as the Mackenzie hotspot.

Yet another type of fluvial erosion formed cirque is found on Réunion island, which includes the tallest volcanic structure in the Indian Ocean. The island consists of an active shield-volcano (Piton de la Fournaise) and an extinct, deeply eroded volcano (Piton des Neiges). Three cirques have eroded there in a sequence of agglomerated, fragmented rock and volcanic breccia associated with pillow- lavas overlain by more coherent, solid lavas. A common feature for all fluvial-erosion cirques is a terrain which includes erosion resistant upper structures overlying materials which are more easily eroded.

The strata consist of breccias, falsebedded sandstones and mans, the sandstones being extensively quarried for building purposes. In the sandstones of Corncockle Moor reptilian footprints have been obtained. In the Thornhill basin there is a thin zone of volcanic rocks at the base of this series which are evidently on-the horizon of the lavas beneath the Mauchline sandstones in Ayrshire. In the Sanquhar basin there are small outliers of lavas probably of this age and several vents filled with agglomerate from which these igneous materials in the Thornhill basin may have been derived.

There are two subsidiary structures, Cherro Chico and Loma Sur of small dimensions. Chemically, the lavas of Agua Poca are intra-plate alkali basalts, with some lavas transitioning in tholeite. Various geologists have attributed varying ages to these volcanoes, ranging from Pliocene to Holocene. The volcano was active in the Pleistocene, with K-Ar dating indicating an age of 0.6±1 Ma. There have been numerous phases of volcanic activity in the region until recent times, with Agua Poca belonging to the Puente Group given stratigraphic and radiometric data.

The mafic shield- building stage began with the eruption of thin mafic lava flows over an erosion surface. Successive eruptions sent lava pouring in all directions from central vents, forming a broad, gently sloping volcano of flat, domical shape, with a profile much like that of a warrior's shield. Alkali basalts and ankaramites were the primary lavas produced during this stage of activity which, due to their low silica content, were able to travel great distances away from their source. These lavas also erupted from vents on the flanks of the volcano.

In addition, the most common hypotheses for the source of the 1755 Lisbon earthquake localize it in the area between Coral Patch Seamount and Gorringe Bank. Dredging has recovered volcanic rocks from the seamount, including volcanic breccia, hyaloclastites, and lavas, which occur both in the form of slabs and pillow lavas. The volcanic rocks are alkali basalts, basalts and hawaiites containing clinopyroxene, diopside and olivine phenocrysts and are heavily altered with the formation of palagonite and zeolites. Their geochemistry indicates that the magma forming them was influenced by crustal components.

Nephelinite lavas are usually interpreted to have originated much deeper in the Earth's mantle unlike the typical basaltic lava found throughout the Northern Cordilleran Volcanic Province. The nephelinite lava flows at Volcano Mountain remain clear from vegetation and seem to be only a few hundred years old. However, dating of sediments in a lake dammed by the nephelinite lavas suggest the lava flows could not be younger than mid- Holocene and could be early Holocene or older. Therefore, the exact age for the most recent eruptions at Volcano Mountain are unknown.

The last summit eruption from Teide occurred about the year 850 AD, and this eruption produced the "Lavas Negras" or "Black Lavas" that cover much of the flanks of the volcano. About 150,000 years ago, a much larger explosive eruption occurred, probably of Volcanic Explosivity Index 5. It created the Las Cañadas caldera, a large caldera at about 2,000 m above sea level, around from east to west and from north to south. At Guajara, on the south side of the structure, the internal walls rise as almost sheer cliffs from .

The rim of the caldera lies at a depth of about . Parasitic cones occur around the caldera, and a cone is also found within the inner caldera and appears to be about high resurgent dome; additional cones can be found on the caldera floor which is covered by sediments. On Mussel Ridge, a ridge located within the caldera and close to its southwestern margin, seafloor observations have found cemented volcanic ash, dispersed rocks, mud, pillow lavas, pillow tube lavas, and talus. Another about high cone is situated between the Monowai cone and the caldera.

The newest lavas are on the eastern and southern sides as well as within the caldera. Lava flows from Wolf are unusual for a mid-ocean island and also differ from the two volcanoes next to it, Ecuador and Darwin, and other volcanoes closer to the centre of the plume. The lavas from Wolf are similar to those erupted from the Galapagos Spreading Center, a mid-ocean ridge over 200 km away, which may be due to interaction between the plume, which is centred on Fernandina, and the upper mantle.

These flood basalt lava flows were erupted during a single event that lasted less than five million years. Analysis of the chemical composition of the lavas gives important clues about the origin and dynamics of the flood basalt volcanism. The lowermost lavas were produced by melting in the garnet stability field below the surface at a depth of more than in a mantle plume environment beneath the North American lithosphere. As the mantle plume intruded rocks of the Canadian Shield, it created an upwelling zone of molten rock known as the Mackenzie hotspot.

Some xenoliths of calc-alkaline material are found in Aguas Calientes lavas, and magma mixing has generated lavas containing andesite inclusions in dacites. One eruption of Aguas Calientes postdates the first centre of Lascar and was originally linked to the Lascar Piedras Grandes eruption, before sampling on the deposits of this eruption indicated a relationship with the Lascar volcano itself. Effusion of lava ceased after the cone was built. One summit lava flow may be of Holocene age, but no evidence of historical activity is found (González-Ferrán 1985).

Boardwalks allow visitors to safely approach the thermal features, such as Grand Prismatic Spring. A subsequent caldera-forming eruption occurred about 160,000 years ago. It formed the relatively small caldera that contains the West Thumb of Yellowstone Lake. Since the last supereruption, a series of smaller eruptive cycles between 640,000 and 70,000 years ago, has nearly filled in the Yellowstone Caldera with 80 different eruptions of rhyolitic lavas such as those that can be seen at Obsidian Cliffs and basaltic lavas which can be viewed at Sheepeater Cliff.

The Taessa lavas from this volcanic complex have a porphyritic texture. The volcanic rocks appear to ultimately derive from mantle plume melts, although a tectonic origin resulting from the convergence between African and Europe has also been suggested.

It occurs on lavas and sand, at elevation. The forest is maintained through condensating moisture from ascending air. It is unprotected but the local population considers it sacred. The WWF includes it in the "sub-humid forests" ecoregion.

Deligne et al (2016) argue that the field also has calc-alkaline basalt. Morphologically, Sand Mountain Field lavas have blocky appearances, reaching thicknesses up to though certain parts of the Lost Lake group have a ropy, pāhoehoe surface.

Oxford University Press, New York.Lucchitta, I, and JD Hendricks (1983) Characteristics, depositional environment and tectonic interpretations of the Proterozoic Cardenas Lavas, eastern Grand Canyon, Arizona. Geology. 11(3):177–181. The Cardenas Basalt is part of the Unkar Group.

Lava flows less than thick issued from the stage I cone and reached lengths of . They occur beneath altitudes of , their vents buried by later activity. The lavas from stage I are mostly exposed north and west of Lascar.

These lavas commonly fill and overflow the caldera. Eruption rate gradually decreases over a period of about 250,000 years, eventually stopping altogether as the volcano becomes dormant. Mauna Kea, Hualālai, and Haleakalā volcanoes are in this stage of activity.

The Puripica Chico lavas on the western side of the caldera are not associated with a collapse. Dark coloured lava flows are found to the southwest of the caldera. Some geothermal activity occurs within the caldera. Laudrum et al.

The bulk of the volcanism of a Hawaiian volcano is made up by the shield stage during which tholeiitic lavas are erupted. This stage is after between 250,000 - 2,500,000 years followed by a "post-erosional" or "rejuvenated" stage during which lavas of alkali basalt, melilitite and nephelinite composition; such volcanism has been observed on Koolau, Kauai and Niihau and covers large parts of the Hawaiian Islands even though it makes up less than one percent of their volume. The North Arch volcanic rocks resemble the composition of these rejuvenated stage volcanics of Hawaii such as the Honolulu Volcanics, and another unit of these volcanics forms the South Arch volcanic field south of Kilauea, and have been deemed "peripheral lavas" of the Hawaii hotspot. In fact, it has been proposed that the rejuvenated volcanics of Niihau, Kauai, Oahu and Molokai might actually be part of the North Arch volcanic field.

The Crimson Creek Formation consists of greywacke with tholeiitic basalt. It is from 4000 to 5000 metres thick. This formation could be as late as the early Cambrian. The basalt is probably the same as mafic lavas of the Kanunnah Subgroup.

Petrology indicates that the andesitic lavas of the southern domes are derived from the more silicic magmas by addition of more mafic andeistes. Conversely, the northern dome magmas formed by fractional crystallization with the most evolved components being erupted explosively.

This helps provide insight on how the lavas of the region operate. Lava rises along rim fractures. This observation hints that the paterae on Io are formed by a combination of volcanism and tectonics. The kidney shape is Chaac Patera.

The Lorne plateau lavas are basaltic lava flows extruded in the late Silurian, 424 to 415 million years ago,which are found today in the Oban - Kerrera area of Scotland. Peperite occurs where they flowed into Old Red Sandstone lakes.

Komatiite lavas in the Abitibi greenstone belt (pictured) occur in four lithotectonic assemblages known as Pacaud, Stoughton-Roquemaure, Kidd-Munro and Tisdale. The Swayze greenstone belt further south is interpreted to be a southwestern extension of the Abitibi greenstone belt.

Helgafell is made mostly from palagonite, i.e. palagonitized tephra, dikes and a small amount of pillow lavas. Since its formation, the mountain was not touched by another glacier, so it must be from the end of the last glacial spell.

The rim of the caldera reaches a maximum elevation of in the southwest. The caldera is cut into volcanic ash, lapilli, lavas, obsidian and tuffs, and the floor is strewn with pumice blocks. A gap lies in the eastern caldera wall.

The content of is 65–67%. The rocks belong to the calc-alkaline series. Trace element data are typical for Central Volcanic Zone rocks. High potassium content is typical for shoshonite-like lavas erupted at large distance from the trenches.

Girdas and lavas are served with butter. Kashmiri bakerkhani has a special place in Kashmiri cuisine. It is similar to a round naan in appearance, but crisp and layered, and sprinkled with sesame seeds. It is typically consumed hot during breakfast.

Apatite and zircon form accessory minerals. Dacites have similar composition but also contain hornblende. Olivine is found in the andesites and quartz in the dacites. Some chemical differences exist among the Negriales rocks, the Lastarria lavas, and the Lastarria pyroclastics.

Aā lavas typically erupt at temperatures of . The word is also spelled aa, aa, aa, and a-aa, and pronounced . It originates from Hawaiian where it is pronounced ,Hawaiian Dictionaries meaning "stony rough lava", but also to "burn" or "blaze".

Detailed geomorphic and geologic studies of the Canary Islands clearly demonstrate that over the last 4 million years, they have been steadily uplifted, without any significant periods of subsidence, by geologic processes such as erosional unloading, gravitational unloading, lithospheric flexure induced by adjacent islands, and volcanic underplating. For example, Pliocene pillow lavas, which solidified underwater and now exposed on the northeast flanks of Gran Canaria, have been uplifted between 46 and 143 meters above sea level. Also, marine deposits associated with lavas dated as being 4.1 and 9.3 million years old in Gran Canaria, ca. 4.8 million years old in Fuerteventura, and ca.

The lower volcanic section is covered by garnet and diopside bearing calc–silicate layers and finely layered metasediments composed of coarse-grained actinolite, hornblende and biotite followed by pelites and semi-pelites that are intruded by separate sills. In the Ridge Lake area, the volcanic belt includes an interlayered series of amphibolite, gabbro, iron formation, sulfidic schist and metasediments. Geochemical results of pillow lavas and chill boundaries along five transects across the volcanic belt suggest the existence of three chemically different magma types within the Bravo Lake Formation. Lavas of the volcanic belt display geochemical characteristics similar to modern ocean- island–basalt groups.

Soil types found in the municipality are: red clay and Lithosols Latosols Alfisols (shallow stony phase of a very rugged mountainous hilly), Andosols and Regosols Inceptisols and Entisols (undulating to hilly stage), Regosols, Clay Latosols Anaosoles reddish, Entisols, Alfisols and Inceptisols (phases rolling to rugged mountain), and Regosols Lithosols. Entisols (phase very rugged mountainous hilly) and Latosol reddish clay, and Lithosols Andosols. Alfisols and Inceptisols (phase rolling to hilly terrain, the stoniness variable). Pyroclastic materials abound, andesitic and basaltic lavas, volcanic detrital sediments with pyroclastic material and lava flows intercalated dacite lavas and adesíticas and basaltic lava flows.

The Coppermine River Group was formed when vast volumes of basaltic lava paved over a large area of the northwestern Canadian Shield about 1,267 million years ago. These basalts form flood basalts that reach thicknesses ranging from to and consists of about 150 lava flows, each about 10–25 m thick. Except for the lowermost flows, which contain evidence of interaction with water, the entire sequence was erupted subaerially. Eruption of plateau lavas near the Coppermine River, built an extensive volcanic plateau about 1,200 million years ago with an area of about representing a volume of lavas of at least .

San Salvador Metropolitan Area is pinned between San Salvador (volcano) and Lake Ilopango Caldera. The Pacific Coast is adjacent south of the city San Salvador volcano crater View of San Salvador City from San Salvador volcano's highest point The main edifice, known as the Boquerón edifice, formed between 700 and 1,000 years ago, filling up a former caldera. The crescent-shaped ridge on the northeast side of the volcano is a remnant of the caldera rim. The lavas of the Boquerón edifice contain more alkali elements and iron oxide than the lavas of the older edifice.

The volume of the volcanoes exceeds and the edifices consist of lavas, hydrovolcanic deposits such as hyaloclastite, fragments of pillow lavas and tuffs, and scoria. Unlike many other mountains in Marie Byrd Land, which owing to a lack of erosion display only their highest and youngest parts, in the Crary Mountains the internal structure of the volcanoes are well exposed. The Crary Mountains form a drainage divide for the West Antarctic Ice Sheet; they dam it, which is thus higher on one side of the range. Debris stripes have been observed on the ice near the foot of the mountains.

The oldest bedrock of Kerrera is black slate ascribed to the Easdale Subgroup of the Dalradian Argyll Group. Overlying this across half of the island are conglomeratic sandstones and basalt and augite-andesite lavas of early Devonian age, the former being the local representative of the Old Red Sandstone and the latter constituting part of the ‘Lorne Plateau Lavas’. Ripple marks and sun cracks are preserved in shale strata on the south coast, belying the subaerial environment in which deposition of these sediments took place. There are thin limestones within both the Easdale Slate Formation and the younger sandstones.

Dunite bodies (olivine) are common in the mantle series of the Troodos, and contain chromite concentrations. Sheeted dyke complex of the Troodos ophiolite The sheeted dykes show a general tholeiitic trend, of basalts, andesites and dacites. There is no obvious boundary for the compositional differences, but the lower lavas are generally more enriched and evolved (silicic) while the upper lavas are less evolved and depleted. The geochemical evidence implies that the Troodos ophiolite has come from mantle that has already been depleted, with extraction of mid ocean ridge basalt, but then subsequently enriched in certain trace elements as well as water.

Lava flows from the cone traveled north and east to produce a "continuously expanding lava delta" along the east coast of the island and into the harbor, where small explosions built up a diminutive island that was soon overtaken by the advancing delta. The first lavas erupted by Eldfell had a mugearitic chemical composition but within a few weeks the volcano was erupting less fractionated lavas which had a hawaiitic composition. Basalt volcanic bomb from Eldfell By early May, the lava flow was between and in height. It averaged more than and in some places was as much as thick.

Based upon findings during the Apollo 16 mission, some of the floors of these craters were covered with glass similar to that found at the Taurus-Littrow landing site on Apollo 17. According to Apollo 16 commander John Young, the arrangement of the glass gave it the appearance of dried mud. Before Apollo 16 sampled the Descartes Highlands, it was believed that volcanic material would be abundant in the area after visual analysis of the features there. It was thought that the formations in the area were formed by lavas more viscous than the lavas that formed the Lunar mare.

These volcanoes are observed to approximate features observed elsewhere on Mars, including Hecates Tholus on the Elysium Rise; Tyrrhena Patera; Hadriaca Patera; and Apollinaris Patera. Later volcanic activity on the Thaumasia Plateau occurred in the Hesperian in association with a profusion of sheet lavas covering Syria Planum, Solis Planum, Sinai Planum, and Thaumasia Planum, emanating from the eastern flanks of the Arsia Mons region. In Thaumasia Planum and against the Coprates Rise, these sheet lavas were observed to onlap underlying plains materials and their associated ridged morphologies. Further volcanism occurred to the south of the Thaumasia highlands in Daedalia Planum.

An age of 5.3±1.9 mya on lavas in the northern part of the volcanic complex is the oldest obtained date. Other dating has resulted in ages of 3.9±1.3 mya for Pico Laco's dome, 3.8±0.9 mya for lavas beneath San Vicente Bayo, 3.7±0.9 mya for a lava front next to Laco Norte, 2.6±0.6 for Crystales Grandes, 2.1±0.4 for Hueso Chico, and 1.6±0.5 for "Volcano 5009". Cordon de Puntas Negras has younger dates. Another date from Pico Laco is 2.0±0.3 mya; one study suggested four separate episodes of volcano development.

The variety of mafic igneous rocks that contain varioles are, with rare exceptions, no longer classified as variolites, which is not recommended for usage. Instead, they are designated using the modifier variolitic in conjunction with the major lithology. The major varieties of variolites are variolitic basalts, variolitic pillow lavas and variolitic komatiites. Variolitic pillow lavas, that have been previously identified as variolites and also classified as spilites, are found in the Durance, France; on Mont Genvre, France; in Devonian rocks of Germany; and as cobbles on the beaches of the Strait of Juan de Fuca along the northern edge of the Olympic Peninsula.

Zola Turn officially disbanded in 2002. In 2005, the three remaining members formed The Lavas, a new band with a heavier sound than Zola Turn. Their 2007 album Wall to Wall, was recorded entirely on their own at their studio the Bottling Company.

Sierra de Gorbea is a large lava field in the Chilean Andes that has been dated 4.7±0.5 Ma and 5.2±0.5 Ma by potassium argon dating. The lavas are dacitic to basaltic andesite with rhyolitic inclusions and no vent is evident.

The cones have volumes of less than and lava flows are thin and branch out dendritically. Lava flows are up to thick and overlie the Salín Formation. The origin of the more basic lavas of this field has been explained with olivine differentiation.

It has a diameter of . Eruptive activity here probably coincided with glacier activity during the Pliocene, as evidenced by moraines in the area. Ages of 5.3 to 1.6 mya have been estimated via potassium-argon dating of the andesite lavas and subvolcanic rocks.

Surface exposure dating has indicated ages of 226 and 287 ka for some ice-affected lavas. Further, andesitic volcanism in neighbouring volcanoes has blanketed El Laco. Reports exist of continuing fumarolic activity and hot springs with the deposition of clay and other minerals.

The floor of the Caloris Basin is filled by a geologically distinct flat plain, broken up by ridges and fractures in a roughly polygonal pattern. It is not clear whether they are volcanic lavas induced by the impact, or a large sheet of impact melt.

Taftan has erupted lavas ranging from basaltic andesite to dacite. The dominant rock is andesite, with content ranging from 49.8 to 63.5%. Grey andesites form the youngest rocks on the main summit and contain chlorite schist and biotite gneiss inclusions. The andesites are vesicular.

The Cameron River Volcanic Belt is a Neoarchean volcanic belt near the Cameron River in the Northwest Territories, Canada. It contains pillow lavas about 2,600 million years old, indicating that great oceanic volcanoes existed during the early stages of the formation of the Earth's crust.

The isolated San Martin Tuxtla volcano is a shield volcano which rises above the Gulf of Mexico. It has had eruptions in historical times. It occurs in the Tuxtla volcanic field in Veracruz, Mexico. Lavas from San Martin vary between basanite and alkali basalt.

The Sifton Range volcanic complex is an early Cenozoic volcanic complex in southwestern Yukon, Canada. It is the northernmost volcanic center of the Skukum Group and is made of a 700 m thick, shallow-dipping, volcanic sequence dominated by middle lavas and pyroclastic deposits.

Taumako is the largest of the Duff Islands, in the Solomon Islands. This island has steep sides and rises to a height of above sea level. It is composed of basaltic lavas and pyroclastics like the other islands in the Duffs. Taumako seen from space.

These flood basalts reach a thickness of . Just southeast of the Queen Maud Gulf, the Ekalulia Formation flood basalts remain to thick. They appear green in colour and contain the magnesium iron silicate mineral olivine. Minor pillow lavas also exist in the Ekalulia flood basalts.

Cerro Nicholson is a scoria cone in Peru. It is constructed on top of the 1.65 mya Arequipa Airport Ignimbrite and is well preserved with a summit crater. It is located west-southwest of Chachani volcano. Lavas erupted from this centre are dark in colour.

Along with the alkaline character of the plagiogranites it can be assumed that the spreading ridge of the Troodos was situated above a subduction zone, but the mantle from which lavas were extruded was that of mantle that had recently lost a melt fraction.

Trident lavas are andesitic to dacitic in composition. The dominant phenocrysts are zoned plagioclase, hypersthene, calcic clinopyroxene, titanomagnetite, and rimmed olivine. The five flows which erupted from the new vent during the period from 1953 to 1963 are olivine-bearing, two pyroxene, high-silica andesite.

A crystal growing in a magma adopts a habit (see crystallography) which best reflects its environment and cooling rate. The usual phenocryst habit is the ones commonly observed. This may imply a 'normal' cooling rate. Abnormal cooling rates occur in supercooled magmas, particularly komatiite lavas.

Escalante and Sairecabur have erupted dark andesites, and later also dacites. Mafic enclaves are found in the post- caldera lavas. The colour of the rocks is black, brown or gray. Minerals include amphibole, biotite, bronzite, -containing augite, clinopyroxene, hornblende, magnetite, orthopyroxene, plagioclase, pyroxene and quartz.

Silicate lavas can be classified into three chemical types: felsic, intermediate, and mafic (four if one includes the super-heated ultramafic). These classes are primarily chemical; however, the chemistry of lava also tends to correlate with the magma temperature, viscosity and mode of eruption.

The older basalts contain phenocrysts of olivine, titanaugite, titano-magnetite and plagioclase, with a matrix of smaller crystals of all of the same minerals except for olivine. The younger lavas are somewhat different with nepheline, alkali feldspar and apatite phenocrysts. In the south and center of the island, these younger basalts are overlain by tristanite, phonolite and trachyphonolite lavas. The phonolite has a variety of phenocrysts including nepheline, augite, barkevicite, titanite, magnetite, augite, sanidine, aegirine and possibly small amounts of plagioclase and sodalite Potassium-argon dating of the tholeiitic basalts in the basement breccia of the island gives an age of 30.9 million years ago for the oldest rocks.

The western margins of Madagascar include Mesozoic and Tertiary limestones. These outcrop in the Ankarana and Bemaraha Massifs, Namoroka, Analamerana, and Ankara Plateau (172-162 million years in age), and the Mahafaly Plateau (54-38 million years in age) respectively. Flood basalts that ring Madagascar include the Mahajanga lavas (87.6 to 88.5 million years in age), the Toliara lavas and Ejeda-Bekily dike swarm (84.5-84.8 million years old), and the Androy lava flow (84.4 million years in age). These igneous rocks were emplaced during the interval when India and Madagascar were together (91 million years ago), and when apart (84 million years ago).

This last fact was first pushed by Akiho Miyashiro in 1973 who challenged the common conception of Troodos Ophiolite and proposed an island arc origin for it. This was done arguing that numerous lavas and dykes in the ophiolite had calc-alkaline chemistries. In the early 1980s the term supra-subduction zone was coined to infer the formation of lavas above a subducting lithospheric slab, with no specification of where in relation to the subducting slab they form. From subsequent studies of other ophiolites it has been found that these generally have a similar geochemical signature, and so it is inferred that most are supra-subduction zone related.

Among the products of this volcanism are the 58.1 ± 0.6 million year old northerly Khastor domes and stratovolcano, the 68.4 ± 0.6 million year old eastern centres (Cerro Alcoak, Cerro Salle, Bayo dome and the Vilama and Toloma lavas) and the less than 8.4 million years old Mesada Negra lavas on the resurgent dome. The Vitichi domes are of Pliocene age. At Cerro Vilama volcanic activity continued into the Pleistocene, with potassium-argon dating yielding dates of 1.2 ± 0.1 and 900,000 ± 30,000 years ago. Magnetotelluric imaging of the area has identified a low electrical conductivity anomaly beneath the caldera, which may be a solidified magma body.

This volcano was active around 23 million years agoKnesel K. M., Cohen B.E., Vasconcelos P. M., and Thiede D.S. (2008) Rapid change in drift of the Australian plate records collision with Ontong Java Plateau, Nature vol 454, pages 754–757. when this part of Australia was above a hotspot in the mantle. Both basaltic and rhyolitic lavas were erupted, and erosion of these lavas from rain and running water has formed the many spectacular landforms including cliffs, now observed in the park. Under these layers is a layer of tuff made from volcanic ash and fine rock which is up to thick in some places.

Although the locality of Vulcanodon itself cannot be dated radiometrically because of weathering of the lavas, it would roughly be a contemporary to Karoo lavas from other localities, as the entire sequence of volcanic eruptions was finished within one million years. Vulcanodon is the only named dinosaur from the Vulcanodon beds. Cooper (1984) noted that the habitat was desert-like, as indicated by aeolian (wind-blown) sands of the Forest Sandstone Formation, which underlies the "Vulcanodon beds". The sediments in which Vulcanodon was found may represent distal alluvial fan deposits which levelled off into a desert landscape, which may have contained lakes during the wet season.

Analysis of the radioactive isotopes of the lavas on the islands of the Galapagos archipelago and on the Carnegie Ridge shows that there are four major reservoirs of magma that mix in varying combinations to form the volcanic province.Mantleplumes.org The four types are: PLUME – this is magma associated with the plume itself and is similar to magmas from other ocean islands within the Pacific. It has the characteristics of intermediate Strontium (Sr), Neodymium (Nd) and Lead (Pb) ratios. The PLUME lavas are found predominately in the west of the islands, around Ferdinandina and Isabela Islands, which is near to the current position of the hotspot.

Eruptive activity at Newberry Volcano began about 600,000 years ago and has continued into the Holocene, the last eruption taking place 1,300 years ago. Unlike other shield-shaped volcanoes, which often erupt basaltic lavas only, Newberry Volcano has also erupted andesitic and rhyolitic lavas. A popular destination for hiking, fishing, boating, and other recreational activities, the volcano lies within of 16,400 people and within of nearly 200,000 people, and it continues to pose a threat to life. Still considered an active volcano, it could erupt and produce lava flows, pyroclastic flows, lahars (volcanically induced mudslides, landslides, and debris flows), ashfall, earthquakes, avalanches, and floods.

The ancestral and modern stages differ primarily in the composition of the erupted lavas; ancestral lavas consisted of a characteristic mixture of dacite and andesite, while modern lava is very diverse (ranging from olivine basalt to andesite and dacite). St. Helens started its growth in the Pleistocene 37,600 years ago, during the Ape Canyon stage, with dacite and andesite eruptions of hot pumice and ash. Thirty-six thousand years ago a large mudflow cascaded down the volcano; mudflows were significant forces in all of St. Helens' eruptive cycles. The Ape Canyon eruptive period ended around 35,000 years ago and was followed by 17,000 years of relative quiet.

The outer magmatic arc, of which the South Shetland Islands are a part, is a westward migration of the inner magmatic arc. Similar to the inner magmatic arc, the outer is composed of subduction-related acidic volcanism. A study on Alexander Island that focused on the conditions required for the generation of andesitic lavas postulated that the source for the andesitic lavas could be either the development of a slab-window due to the subduction of a spreading ridge or the breakup of the subducted slab beneath the fore-arc basin. The South Shetland Islands are bissected by two systems of strike-slip faults.

The coast, constituted by a sub-zone of more recent materials, Quaternary or Neogenic in age. These deposits came to rest over sand-stones and marls that comprise the coastal Mesocenozoic, a young relief, that is little accented, aided by a platform that includes superficial lavas.

The magma of Taftan volcano is very oxidized, as can be inferred from the composition of the surrounding ignimbrite and fumarole gases. The lavas of Taftan are porphyritic. Mineral components include biotite, clinopyroxene, hornblende, orthopyroxene, plagioclase and quartz. Other components are chalcopyrite, haematite, ilmenite, magnetite and pyrite.

Rocks assigned to the Cheviot Volcanic Formation, itself within the Reston Group, straddle the border with Scotland. This thick pile (over 1000m) of andesitic lavas was erupted during the early Devonian. The sequence includes rhyolites, agglomerates and tuff. The Cheviot Pluton is a mass of Devonian granite.

The andesites described in the 1920s were mapped as early Tertiary age, long before Level Mountain formed. Hamilton recognized the four sequences of alkali basalt flows and tuffs in the lava plateau as well as the overlying bimodal package of alkali basalt and peralkaline lavas and tuffs.

Sediments left by the lake cover an area of 50 square miles (about 130 square km). Of the artefacts, 99% were made from locally derived lavas, particularly trachyte, although small amounts of quartzite and obsidian have been found, indicating a transport over 16 to 40 km.

Göllüdağ Crater Lake, Niğde Göllü is a lava dome located in central Turkey. The volcano has produced rhyolite, dacite and basalt. The lavas have been dated at 1.33 to 0.84 million years by fission track dating of obsidian. The dome lies above the Tertiary Derinkuyu caldera.

The formation is dissected by fluvial and glacial erosion. The formation is made up of tuff, volcanic breccia and volcanic agglomerate. The lavas are made up of andesite, trachyandesite, trachyte, basaltic andesite and basalt. Volcanic rocks of Cola de Zorro Formation belong to two magma series.

Quinchilca is a volcano in Chile. It is situated south of Villarrica volcano and consists of a caldera and lava domes. The volcano has a semicircular form constructed by layers of lavas and volcaniclastic rocks, with an eroded core. Volcanic rocks include basalt and basaltic andesite.

The Mekong River which transported the eroded material may have followed a different course because sediments are primarily shallow and Holocene in age beneath the present course of the river. Thick basalt lavas extruded onto Mesozoic sandstone at the Bolovens Plateau east of Pakse during the Pleistocene.

It consists as is usual for such subglacially formed volcanoes, of pillow lavas under a layer of phreatomagmatic tephra (hyaloclastite). Pedersen and her coworkers think that the Ice Age glacier which was covering it at time of formation had a thickness between 70 and 400 m.

Lloyd studied in detail the variation in crystal sizes from the edge pristine pillow lava, which could have derived from nearby Pillow Ridge which last erupted during the Pleistocene period. Courtney Haynes, another student of Dickinson College, focused on mathematics of the pillow lavas in 2007.

In addition, apatite, ilmenite, iron oxides and zirconia are found. At least one lava erupted after the caldera-forming eruption contains olivine. Lavas erupted before the caldera-forming eruption of Sairecabur contain glass and have a microlithic texture. The magmas are calc-alkaline with medium-high content.

Rocks assigned to the Cheviot Volcanic Formation, itself within the Reston Group, straddle the border with Scotland. This thick pile (over 1000m) of andesitic lavas was erupted during the early Devonian. The sequence includes rhyolites, agglomerates and tuff. The Cheviot Pluton is a mass of Devonian granite.

Both before and after the magnetite lavas, layers of magnetite- containing pyroclastics were erupted. A aureole separates the magnetite rocks from the host rocks. The magnetite lava flows are thick, the pyroclastics and respectively. The pyroclastic-like deposits are porous and fragile and show traces of stratification.

The summit of the fell is representative of the Birker Fell Formation. This is composed of plagioclase-phyric andesite lavas and subordinate sills. To the south en route to High Seat are garnet-bearing porphyric andesite. Much of the northern section is overlain by peat and till.

The quickly cooled lavas that make nearly ideal samples for K–Ar dating also preserve a record of the direction and intensity of the local magnetic field as the sample cooled past the Curie temperature of iron. The geomagnetic polarity time scale was calibrated largely using K–Ar dating.

Malleco Formation () is a geological formation of volcanic origin in the Andes of Araucanía Region (38–39° S), Chile. The formation is made up by volcaniclastic rocks, including tuffs, lahars and lavas of Pliocene–Early Pleistocene age.Suárez, M. and Emparan, C. (1997). Hoja Curacautín, Carta geológica de Chile.

The similarity between the geochemical data of Rajmahal volcanos and lavas of the Kerguelen Plateau confirms this. According to plate tectonics, the Indian subcontinent was over this hot spot during the Cretaceous Period. The original lava flow covered an area of nearly . Below the Bengal basin the flows cover .

The characteristic volcanic rock of Baja California are magnesium-rich basaltic andesite and andesite which are known as bajaite. While San Borja lavas are calc-alkaline, there is a noticeable difference between volcanites erupted at San Borja over 11 years ago and those erupted about 4 million years ago.

Their thicknesses and widths range , increasing on gentler slopes. Especially on the upper slopes, old colluvium conceals the surface of Vinta Loma lava flows. The texture of the lavas ranges from porphyritic to seriate. Two-pyroxene andesite is the dominant component but dacite has been found as well.

The Group represents an assemblage of both volcanic rocks - lavas, tuffs, breccias - and volcaniclastic sediments - mudstones, siltstones sandstones and conglomerates. It comprises (in descending order i.e. youngest first) the Yoke House Formation, the Carneddol Rhyolitic Tuff Formation, the Foel Ddu Formation and, at its base, the Penmaen Formation.

Both feature wide pit craters. Other vents are known as Tabanka, Batuku, Mandora, De Saude and Koladera. Vents in the Charles Darwin volcanic field include cones with pahoehoe, pillow lavas, scoria and have erupted basalts with xenoliths. Unusually for volcanoes at such depths, they show evidence of explosive eruptions.

In the top region of Þorbjörn, there is also a rather eroded crater, but probably because of the erosion, no trace of subaerial lavas has been found. The tuya is slightly elongated in the direction of the volcanic fissure systems of Reykjanes, i.e. southwest to northeast.See maps, eg.

Augitite, potassic limburgite, pyroxene trachybasalts and trachyte-andesite are found in the Pliocene layers. Potassic basanite and limburgite are found in the Pleistocene layers. Holocene layers contain augitite, leucite basanite, potassic hawaiite and leucite tephrite. Horgo/Khorgo is constructed from phonolitic tephrite and its lavas range alkali basalt-basanite.

The lavas erupted from the cone are porphyric trachyandesite-basalt of shoshonitic composition. They contain pyroxene and olivine phenocrysts with subordinate microphenocrysts of plagioclase and phlogopite and inclusions of gray minerals. The magmas generating this volcanism are primitive and may be oceanic crust-derived melts with some crustal contamination.

There are around hundred cones in the field. Some volcanic rocks have been affected by faulting; buried faults are also found. The San Luis-Tepehuanes fault system is associated with the field. The whole field is covered by lavas, which are about thick and reach a total volume of .

Combined with the extensive lava flows at the termination of the rift, this may reveal areas that drained the caldera lavas and contributed to the collapse. The northwest flank of the volcano is significantly different and rougher than the southeast flank, and the features may represent evidence of glaciers.

Subglacial volcanoes develop underneath icecaps. They are made up of flat lava which flows at the top of extensive pillow lavas and palagonite. When the icecap melts, the lava on top collapses, leaving a flat-topped mountain. These volcanoes are also called table mountains, tuyas, or (uncommonly) mobergs.

As the lavas cool they are, in most instances, modified chemically by seawater.H. Elderfield (2006). The Oceans and Marine Geochemistry. Elsevier. pp. 182–. . These eruptions occur mostly at mid-ocean ridges, but also at scattered hotspots, and also in rare but powerful occurrences known as flood basalt eruptions.

Purely pyroxene-bearing volcanic rocks are rare, restricted to spinifex-textured sills, lava tubes and thick flows in the Archaean greenstone belts. Here, the pyroxenite lavas are created by in-situ crystallisation and accumulation of pyroxene at the base of a lava flow, creating the distinctive spinifex texture, but also occasionally mesocumulate and orthocumulate segregations. This is in essence similar to the formation of olivine spinifex textures in komatiite lava flows, the chemistry of the magma differing only to favor crystallisation of pyroxene. A type locality is the Gullewa Greenstone Belt, in the Murchison region of Western Australia, and the Duketon Belt near Laverton, where pyroxene spinifex lavas are closely associated with gold deposits.

Lava flows on Io, tens or hundreds of kilometres long, have primarily basaltic composition, similar to lavas seen on Earth at shield volcanoes such as Kīlauea in Hawaii. Although most of the lava on Io is made of basalt, a few lava flows consisting of sulfur and sulfur dioxide have been seen. In addition, eruption temperatures as high as were detected, which can be explained by the eruption of high-temperature ultramafic silicate lavas. As a result of the presence of significant quantities of sulfurous materials in Io's crust and on its surface, some eruptions propel sulfur, sulfur dioxide gas, and pyroclastic material up to into space, producing large, umbrella- shaped volcanic plumes.

Lavas from Nintoku Seamount have similar composition to lava erupted during the post-shield stage of Hawaiian volcanoes such as Mauna Kea. Slight differences in trace element composition between lavas from Nintoku Seamount and active Hawaiian volcanoes probably result from differences in source composition or variations in the degree of melting. All of the recovered lava flows had been altered very little by erosion or other lava flows, except for thin flow tops. Sparse veining indicates that there is only small-scale fluid circulation within the rocks, in contrast with some of the data collected from Detroit Seamount. Rock magnetic data obtained suggest that the lava flows from Site 1205 carry a remnant magnetization suitable for scientific analysis.

These are the youngest stages of Tuzgle volcanism and are well preserved. Radiating away from the central summit of the volcano, another lava flow unit forms the so-called Azufre synthem; these lava flows reach maximum thicknesses of and are gray to brownish-red with some evidence of hydrothermal alteration. On the northwestern and southern flanks, lava emission from one emission area down steep slopes form the San Antonio synthem (unconformity bounded unit), with lava flows up to thick. These San Antonio stage lavas have been cut by a long fault scarp trending NNE-SSW that may have been formed by a mass failure of the Tuzgle edifice, which was then rebuilt by the Azufre stage lavas.

The Divisadero Group is a group of geological formations in the Magallanes Basin (Chile) or Austral Basin (Argentina) of northwestern Patagonia. It overlies the Coihaique Group. The group is chiefly made up of pyroclastic rocks and lavas of the calc-alkaline magma series. Rocks are of andesite and rhyolite composition.

These lavas are primarily aphyric basalts, are grayish in color, trachytic in texture and composed of olivine. Other basalts contain olivine and pyroxene phenocrysts. To the west are a few mafic porphyritic basalts and possibly older Miocene basalts cut by dykes and faults. Olivine nephelinite has been collected near these basalts.

The characteristic rocks of obducted oceanic lithosphere are the ophiolites. Ophiolites are an assemblage of oceanic lithosphere rocks that have been emplaced onto a continent. This assemblage consists of deep-marine sedimentary rock (chert, limestone, clastic sediments), volcanic rocks (pillow lavas, glass, ash, sheeted dykes and gabbros) and peridotite (mantle rock).

Martinique has eight different centres of volcanic activity. The oldest rocks are andesitic lavas dated to about 24 million years ago, mixed with tholeiitic magma containing iron and magnesium. Mount Pelée, the island's most dramatic feature, formed about 400,000 years ago. Pelée erupted in 1792, 1851, and twice in 1902.

It forms vesicle fillings and linings in altered basaltic lavas. It was first described in 1847 on Monte Baldo, near Verona, Italy. The name is from the French celadon, for sea-green. It is one of two minerals, along with glauconite, used in making the pigment known as green earth.

The Azufrera stage lavas are blocky dacites with large clasts and flow fronts up to high. These flows are moderately altered and have oxidation rinds. There is little evidence of explosive activity, but it may have been obscured by glacial erosion. The total volume is , indicating a flux rate of .

Like all volcanic rocks, the Alaji Basalts originate from initial melting of the Earth's mantle. After extrusion, the magmatic structures form at the surface. Common volcanic structures such as lava tubes or ropy lavas are absent in the Alaji Basalts, but (columnar joints) are omnipresent. The basalts comprise successive flows.

Marcaillou, B. P. Charvis, and J.-Y. Collot (2006) Structure of the Malpelo Ridge (Colombia) from seismic and gravity modeling. Marine Geophysical Research. 27:289–300. Malpelo Island is composed of Miocene pillow lavas, volcanic breccias, and basaltic dikes that have been dated as being 16 to 17 million years old.

Basalt lava flows may extend more than from their vent. Dacite and rhyolite lavas produce short, thick flows that rarely extend more than from their vent. Mound-shaped features called lava domes are often created from these flows. Rock fragments thrown from a growing lava dome may reach from the dome.

The lavas contain phenocrysts of augite, olivine, plagioclase and sanidine. The cones in Trou au Natron are andesitic. Yirrigué conversely has erupted peralkaline rhyolite, while Ehi Timi erupted rhyolite and trachyte and Ehi Sosso only rhyolite. The formation of Trou au Natron has been accompanied by the eruption of bedrock material.

Kunlun Volcanic Group (), also known as Ashikule, is a volcanic field in northwestern Tibet. Eight other volcanic fields are also in the area. The field is within a basin that also contains three lakes. Volcanism in the field has produced lavas and cones, with rocks having varying compositions dominated by trachyandesite.

Fumarolically altered rocks are found on the eastern flanks of the chain. Desert patine covers post-caldera lavas. Based on crystal composition, the magmas of Sairecabur formed at temperatures of . The process started by partial melting of the mantle involving peridotite and subsequent interaction with the crust and fractional crystallization.

J. Patchett & J. Jocelyn U-Pb zircon ages for late Precambrian igneous rocks in South Wales., 1979, Journal of the Geological Society of London. 136 13-19 Both are cut by minor granitic intrusions. The Pebidian Supergroup is interbedded basic lavas and acid tuffs, is cut by the St David's Granophyre.

Third-stage lava flows run at the edge of one of these sites which was constructed on lavas from the previous two stages, suggesting that the site was affected by historical volcanic activity. There is also evidence of strong earthquake activity 6640±90 BP and between 782 and 773 BC.

Pillow lavas are commonly of basaltic composition, although pillows formed of komatiite, picrite, boninite, basaltic andesite, andesite, dacite or even rhyolite are known. In general, the more felsic the composition (richer in silica - resulting in an Intermediate composition), the larger the pillows, due to the increase in viscosity of the erupting lava.

The Egersund Basin has abundant fresh prophyritic Nephelinite lavas and dykes of lower Jurassic Age, with a composition nearly equal to those found on the clay pits. That reveals the translation of strata from the Continental margin by large fluvial channels, that ended on the sea deposits of the Ciechocinek Formation Green series.

In the Girvan area are the Blair and Straiton Beds. In Ireland, there is more rock of Wenlock age. In the Dingle Peninsula one finds the Ferriters Cove Beds, a thick series of shales, slates, and sandstones with lavas and tuffs. In County Tipperary and County Mayo are the Mweelrea Beds and others.

Spanning 50,000 years it ejected to of material and was followed by a third period. At least twelve periods of activity have taken place since Brokeoff formed, consisting of activity including pyroclastic flows, pasty lavas, and additional lava domes. Among the vents built by this activity include Lassen Peak.Lopes and Lopes, p. 114.

The 1600 kilometer Coastal Batholith of Peru formed in an ensialic marginal basin in the early Cretaceous, with the emplacement of pillow lavas, gabbro and volcaniclastic rocks. In the north, it formed as new continental crust with no older continental crust beneath it, while to the south it spans thick Precambrian rocks.

The lavas cover a surface area of and tend to have thicknesses . Many of these were erupted from fissures with no clear vents. Cinder cones have average heights of above basis. There is some geographical differentiation with the largest cones found on the western side and the cones concentrated on the easternmost edge.

Chalcopyrite in this environment is produced by concentration within a magmatic system. Chalcopyrite is an accessory mineral in Kambalda type komatiitic nickel ore deposits, formed from an immiscible sulfide liquid in sulfide-saturated ultramafic lavas. In this environment chalcopyrite is formed by a sulfide liquid stripping copper from an immiscible silicate liquid.

These volcanic mountains of the Permian period are composed of lavas, tuffs, rhyolites, andesites, dacites, diabases, and basalts. In places, they break through Permian and Triassic intrusions of granites, diorites, and gabbro. In the Eastern and Western part of Katutau there are two paleovolcano. The most common form is large lava domes.

Soil types found in the municipality are: Andosols and Regosols, Inceptisols and Entisols (phases of rolling to ALOM) and Regosols, reddish clay and Anaosoles, Latosols, Entisols, Alfisols and Inceptisols (phases rolling to rugged mountain). There are volcanic detrital sediments with pyroclastic material and lava flows interspersed, pyroclastic material and andesitic and basaltic lavas.

This geologic formation is divided into Lower Lupata Sandstones and Upper Lupata Series. Older sandstones consider to include also rhyolite and younger include alkaline rocks. Only the Upper Lupata Sandstones are developed in Monte Muambe region. The formation consists of two members: clastic, mostly feldspathic various grained sandstones, and volcano erupted - alkali lavas.

The Late Cretaceous strata is overlain by basaltic lavas ranging in age from Pliocene to Quaternary. The Quaternary volcanic rocks form volcanic cones.Kos’ko, M.K., B.G. Lopatin, and V.G. Ganelin, 1990, Major geological features of the islands of the East Siberian and Chukchi Seas and the Northern Coast of Chukotka. Marine Geology. vol.

The cones are vegetated, which contrast with the relatively scarce vegetation of the Cretaceous surrounding terrain. The total surface covered by lavas is about . The Rio Mascota and Rio Talpa cross the field. Aside from the town of Mascota, Talpa de Allende is another settlement in the southwestern part of the field.

Grande Comore is the youngest island and is still volcanically active. Karthala, a shield volcano occupying some two thirds of the island, rises to 2361 meters. The summit caldera is quite large, being approximately 3 x 4 km (1.9 x 2.5 miles) in size at the rim (2007).GlobalVolcanism Program: Karthala Esson J., M.F.J., Flower, D.F. Strong, B.G.J. Upton, and W.J. Wadsworth, Geology of the Comores archipelago western Indian Ocean Geological Magazine 107 (6) 549-557 1970 Flower, M.F.J., Evidence for the role of phlogopite in the genesis of alkali basalts Contrib. Mineral. Petrol. 32 (2) 126-137 1971 Flower, M.F.J., Rare earth element distribution in lavas and ultramafic xenoliths from the Comores archipelago, western Indian Ocean Contributions to Mineralogy and Petrology 31 (4) 335-346 1971 Flower, M.F.J., R N Thompson, One-atmosphere melting and crystallization relations of lavas from Anjouan Comores Archipelago western Indian Ocean Earth and Planetary Science Letters 12 (1) 97-107 1971 Flower, M.F.J., Petrology of volcanic rocks from Anjouan Comores archipelago, Bull, volcanol., 36 (1) 238-250 1973 Flower, M.F.J., Evolution of basaltic and differentiated lavas from Anjouan Comores Archipelago, Contrib. Mineral. Petrol.

At least four basaltic flows comprise the sequence and were deposited during periods of volcanic activity from an unknown vent between 0.01 and 1.6 million years ago. Pillow lava is abundant along the bases the flows, some of which are underlain by hyaloclastite breccia. In 1958, Canadian volcanologist Bill Mathews suggested that the lava flows were erupted during periods of subglacial activity and traveled through trenches or tunnels melted in glacial ice of the Fraser Glaciation. Mathews based this on the age of the underlying glacial till, the existence of pillow lava close to the bottom of some lavas, indicating subaqueous volcanism, the columnar jointing at the edges of the lavas, indicating rapid cooling, and the absence of apparent palaeogeography.

The volcanic cones at Olallie Butte and Mount Jefferson were erupted over deposits from the Minto lava group, which have been deeply eroded to create non-conforming surfaces. As a result, Olallie Butte has a relatively steeper slope, but there are lithologic similarities between the Olallie lavas and Minto lavas. Whereas Minto volcanoes follow a narrow, nearly linear arrangement south of Olallie Butte, north of Olallie the local volcanoes exhibit a scattered distribution across the plateau of the High Cascades. There are also transitional volcanoes not easily classified into either the Minto or Olallie group; their acidic composition suggests that they differentiated during the Minto eruptive phase, but progressive differentiation has been observed in the region, making definite conclusions about their categorization difficult.

At their peak rates, the crustal extension and depression of the Cascades area caused eruption of the Minto Lavas, made of basalt, followed by the Santiam basalts, named for their movement into the North Santiam River valley, which they filled to depths of . Though the Jefferson vicinity has produced andesitic and dacitic lavas for the past 5 to 6 million years, major volcanoes more than south of the area have erupted basaltic andesite. The central Oregon Cascades are made up of Eocene to Quaternary volcanic, volcaniclastic, igneous, and sedimentary rock. Miocene and Pliocene volcanic and sedimentary rocks have been exposed in the Jefferson area, which also sits above lava flows, cinder material, and breccia from the High Cascades that formed during and after the Pliocene.

Between Bogoslof, the other Aleutian island north of the main arc, and Amak, Amak's lavas are more alkalic and silicic. Glaciation took place around the volcano roughly 6700 years BP, carving out U-shaped valleys. At the southwest flank of the island, a crater, likely a maar, can be found amid an alluvial plain.

Surface features can be distinguished from atmospheric features by comparing emission and reflection spectroscopy with transmission spectroscopy. Mid-infrared spectroscopy of exoplanets may detect rocky surfaces, and near-infrared may identify magma oceans or high- temperature lavas, hydrated silicate surfaces and water ice, giving an unambiguous method to distinguish between rocky and gaseous exoplanets.

The youngest stage, known as Angulo, lasted from 0.66 to 0.24 mya. It was centered between the Azufrera and Rodado stage edifices 0.35–0.23 mya. Most lava flows from this stage originate on a long ridge that includes Aucanquilcha's highest summit. One crater on the northeast side of the ridge fed lavas to the north.

Lavas of modern volcanoes, like Antuco, unconformbly overlies the formations and dykes associated to modern volcanoes intrude it. In some localities the formation is covered by moraines. The Cola de Zorro Formation is largely undeformed except from some minor tilting caused by block tectonics. The strata of Cola de Zorro Formation are sub-horizontal.

At least two eruptions of Pumayacu occurred during the Holocene; one dated 4400 years ago and another's lapilli deposits overlie a cultural horizon 2000 years old. Older eruptions have been dated at 1.15 ± 0.07 Ma and are of high-potassium types. They compromise typical arc-derived lavas with fractional crystallization and other differentiation processes.

The lavas flow out, then sink back to their vents. A possible vent is located in the southernmost portion of the patera, which migrated from the north. Migration patterns can be concluded from changes in pictures from the Voyager to the Galileo. This agrees with the hot spot that has been found here as well.

Río Murta is a volcano in Chile. The volcano consists of a complex of lava flows along the valleys at the Río Murta. These flows display columnar joints, lava tubes and pillow lavas, and have volumes of less than . These landforms along with the presence of palagonite indicate that the eruptions happened beneath glaciers.

The geology of Montserrat formed from the Pliocene into recent times with five major and three parasitic volcanoes. For the most part, the volcanoes only erupted andesite, pyroclastic flows and dome lavas and the Montserrat series is dominantly calc-alkaline. The only exception is South Soufriere Hill with basalt lava flows and pyroclastic flows.

Letha Taung is located near Nweyon, Singu Township, Pyinoolwin District, Mandalay Division, about 3 km west of National Highway 31. The lavas that form the plateau originally came from fissure vents during the Holocene, although the date of the last eruption is unknown. The active Sagaing Fault, a transform boundary runs under this structure.

The butte is about in diameter at the base.Pahvant Butte North, Utah and Pahvant Butte South, Utah, 7.5 Minute Topographic Quadrangles, USGS, 1971 It formed in an active area of volcanism on top of pahoehoe and aa lavas. Originally a subaqueous volcano, it erupted out of the floor of Lake Bonneville approximately 15,500 years ago.

Small bursts were occurring at one end of an erupting fissure ~ 5 m long at a depth of 1,208 m, while pillow lavas were being extruded from the other end. By the next night (7 May) the activity had become more vigorous, sometimes blowing glowing bubbles as much as a meter across from the fissure.

Namarunu is located in the Suguta Valley, a section of the Kenyan Rift Valley just south of Lake Turkana. It extends from the western side of the rift past the center. The mountain forms a broad shield. The large basal part is about deep, made up of outward-dipping trachytic lavas, breccias and tuffs.

175 Specific information on the output of the ship's engine has not survived, but it ranged between for all the ships of this class. During Lavas sea trials on 12 July 1865, she reached a maximum speed of . She carried a maximum of of coal, which gave her a theoretical endurance of at .McLaughlin, p.

These lavas came 2000 years ago from some craters near Bláfjallavegur (Road 407) which have since been destroyed by quarrying. The name Óbrinnishólar means that there was no “fire” in them during further eruptions in the region in historical time. Parts of Hafnarfjörður (midtown and Vallahverfi) are located on top of this lava field.

Later volcanic activity from other volcanoes in the region led to the emplacement of extraneous volcanic rocks in the Vilama caldera, such as the Bonanza, Cienago and Panizos ignimbrites and the Loromayu lavas. In terms of tectonics, during the Cenozoic the region was substantially uplifted, forming a high plateau with an average elevation of about .

Pillow lavas are created due to rapid cooling of lava which forms a skin. As more magma is forced into this the skin expands creating a lobe. When this fractures then lava seeps through the gap exposing hot lava to the water and again a skin forms over this: this process is then repeated.

Aa lava presents a rough texture in the shape of broken blocks (clinkers). Pāhoehoe lava is recognized by its pillowy or ropy appearance. Rough surfaces appear bright in radar images, which can be used to determine the differences between aa and pāhoehoe lavas. These variations can also reflect differences in lava age and preservation.

The fissure eruptions resulted in lava flowing from the fissure. There was also an eruption within the caldera. A second fissure opened lower down the slope in early June. Analysis of the lavas on Cerro Azul show a range of tholeiitic to alkalic basalts that are unlike the neighbouring Sierra Negra or Alcedo volcanoes.

Geochemical provinciality in the Cretaceous basaltic magmatism of Northern Madagascar: mantle source implications. Journal of the Geological Society, 160(3), 477–488. doi: 10.1144/0016-764902-060Melluso, L., Morra, V., Brotzu, P., & Mahoney, J. J. (2001). The Cretaceous Igneous Province of Madagascar: Geochemistry and Petrogenesis of Lavas and Dykes from the Central–Western Sector.

The lava domes which were erupted from the ground after the Tuzgle ignimbrite have volumes of , while the Platform and subsequent units have volumes of . The lava domes and San Antonio lava flows have porphyritic surfaces. San Antonio lavas contain large plagioclase xenocrystals and xenoliths. The ignimbrite contains Ordovician lithic fragments and 1020% pumice.

Quartz is found only in the most strongly peralkaline rocks. Mafic minerals may include aegirine, fayalite, aenigmatite, ilmenite, and sodic amphibole (often arfvedsonite or ferrorichterite).White, J.C., Ren, M., and Parker, D.F., 2005, "Variation in mineralogy, temperature, and oxygen fugacity in a suite of strongly peralkaline lavas and tuffs, Pantelleria, Italy." The Canadian Mineralogist, vol.

Accessory phase controls on the geochemistry of crustal melts and restites produced during water-undersaturated partial melting. Contributions to Mineralogy and Petrology, 114(4), 550–566. It is commonly formed from magmatism involving carbonatic melts but not mafic plutons or lavas. Those rocks usually host economic REE ore deposits, making monazite geochronology important in mining exploration.

Aside from these lapilli deposits, scoriaceous lava flows are exposed on the edifice as well. Farther down, lava flow fronts form scarps which become particularly noticeable at depths of , except on the northern flank. Even deeper, pillow lavas predominate. Below the summit area, the slopes fall down steeply to a depth of and then flatten out.

The line of the shallower continental shelf area, to the south-east, ran approximately from the Long Mynd (in Shropshire) to Haverfordwest in Pembrokeshire. Some volcanic action also occurred. This thick sedimentary deposition continued into the Silurian period (444-416 million years old). Silurian volcanicity led to production of lavas at localised sites such as Skomer Island.

The San Juan volcanic field experienced two phases of volcanism. The earlier volcanism took place during the Oligocene age of the Paleogene Period. It produced largely intermediate composition lavas and breccias, together with ash flow tuffs reflecting differentiation of the original magma. The precaldera intermediate volcanic rocks include the Conejos Formation in the southeastern part of the field.

Its central crater was eroded and a glacier formed inside. The volcano itself is formed by three groups of andesite lavas which variously contain pyroxene or hornblende; these groups are known as the Lower Group, the Middle Group and the Summit Group. Cerro paniri and volcan san pablo chile ii region.jpg San Pablo volcano (left) and Cerro Paniri (center).

They occur as tightly folded, lightly metamorphosed (greenschist) preserved in easterly trending, elongate to irregular, structural basins known as greenstone belts. The most abundant volcanic rock is metamorphosed basalts that exhibit primary structures, e.g. pillow lavas, indicative of underwater volcanic eruptions. The metamorphosed sedimentary strata consist largely of interbedded mudstones and sandstones exhibiting sedimentary structures indicative of turbidites.

The Anadyr Plateau is formed from igneous rocks. The Mongolian Plateau has an area of basaltic lavas and volcanic cones. The Angara Shield also underlies the lowlands of the Ob River, but to the south and east in the Central Asian mountains and in the East Siberian Mountains there are folded and faulted mountains of Lower Palaeozoic rocks.

The green color is due to the large development of chlorite. Among the crystalline schists of many regions, green beds or green schists occur, which consist of quartz, hornblende, chlorite or biotite, iron oxides, feldspar, etc., and are probably recrystallized or metamorphosed tuffs. They often accompany masses of epidiorite and hornblende – schists which are the corresponding lavas and sills.

Sierra Nevada is a stratovolcano located in the La Araucanía Region of Chile, near the Llaima volcano. Its last certain eruptions were in the Pleistocene period, but its activity may extend into the Holocene. Its primary lavas are andesitic and basaltic flows, although it has also produced pyroclastic flows. Lahars are also a hazard of this volcano.

The high plateau, with a crustal thickness estimated to at least but probably closer to , has a volume of more than . The maximum extent of the event can, however, be much larger since lavas in several surrounding basins are closely related to the OJP event and probably represent dike swarms associated with the emplacement of the OJP.

The Noreán Formation (, J1-2n, J1n)González Iregui et al., 2015, p.56 is a geological formation of the Eastern Ranges of the Colombian Andes, the Serranía de San Lucas and as basement underlying the southernmost Lower and northern Middle Magdalena Valleys. The formation consists of volcanic and pyroclastic lavas that range from andesites to rhyolites.

The Rodado stage edifice has several moraine stages on its southern slopes. Another small cirque with a moraine has been found in the northeastern side of the Cerro Cumbre Negra summit next to an Azufrera stage lava flow. A small moraine lies on the south side of the Angulo edifice; some lavas from that edifice overlie glacial deposits.

The structure of Papa Stour is largely made up of ashes and lavas from volcanic activity associated with this period, including bands of solidified volcanic ash and lava (rhyolite), but there is also a Devonian fish bed at Lamba Banks. There are numerous large boulders deposited by Pleistocene glaciation."The Devonian Period" Scottishgeology.com Retrieved 15 August 2007.

Information about the structure of Earth's deep interior can be acquired only indirectly by geophysical and geochemical methods. For the investigation of postulated plumes, gravimetric, geoid and in particular seismological methods along with geochemical analyses of erupted lavas have proven especially useful. Numerical models of the geodynamical processes attempt to merge these observations into a consistent general picture.

Moraines are also found and reflect the past occurrence of glaciation on the mountain; they lie at around elevation. The volcano has erupted dacitic lavas containing andesitic mafic inclusions. These inclusions resemble those from the Soncor flow of neighbouring Lascar to the northeast. Some rocks may have been influenced by the interaction with calcium carbonate in the magma chambers.

The regolith, referred to often as "soil", resembled those produced from the weathering of basaltic lavas. The tested soil contained abundant silicon and iron, along with significant amounts of magnesium, aluminum, sulfur, calcium, and titanium. Trace elements, strontium and yttrium, were detected. The amount of potassium was one fifth of the average for the Earth's crust.

The most recent volcanic activity produced a series of lava flows that were erupted when the vent area was not covered by glacial ice. However, the flows show evidence of interaction with glacial ice in their lower units. This indicates that the lavas were erupted about 10,000 years ago during the waning stages of the Fraser Glaciation.

It was first described in 1957 for an occurrence in nephelinite lavas and tephra on Mt. Nyiragongo, Goma, Kivu, Democratic Republic of Congo (then Zaïre).Combeite on Mindat.org It has also been reported from the Bellerberg volcano in Ettringen, Germany and the Oldoinyo Lengai volcano, Tanzania. It was named for Arthur Delmar Combe of the Geological Survey of Uganda.

The Widgiemooltha Komatiite is host to no less than 15 individual channelised kambalda type komatiitic nickel ore deposits of which 5 have been mined, the remaining ten being of too low grade and low tenor to be economic at present. These features correlate with thickened komatiitic sequences, thick basal flows, trough like structural features and high magnesium lavas.

The seamount is part of a group of seamounts about away from Pitcairn Island, which includes several small seamounts and the large Adams Seamount. These seamounts were discovered in 1989. Bounty has a conical shape, with three summit cones and several rift zones. Pillow lavas and hyaloclastite cover its slopes, and parasitic vents can be observed as well.

Animation of eruption from Tvashtar Paterae (Io), taken from imagery from the New Horizons probe in 2007 Lava flow at Tvashtar Paterae Io, a moon of the planet Jupiter, is the most volcanically active body in the Solar System. Its volcanoes are believed to eject sulfur and sulfur dioxide, as well as basaltic and ultramafic silicate lavas.

Today, sulfurous gases reach the surface via two fumarole pathways: Dorr Fumarole, northeast of the summit, and Sherman Crater, south of the summit. Both are sites of hydrothermal alteration, converting lavas to weak, white-to-yellow clays; sulfur is a common mineral around these fumaroles. At Sherman Crater, collapses of this weakened rock generated lahars in the 1840s.

It also contains xenoliths both from Agua Dulce lavas and Paleozoic sediments. The Kumurana intrusion has a composition between granodiorite and quartz monzonite. Overall, the Kari-Kari rocks are peraluminous and originated from the amphibolite-granulite segment of the crust under the influence of magmatic underplating. Differentiation along mafic and peraluminous phases formed the eventual magma.

The block and ash flows and Crater lavas consist of solely trachyandesitic rocks. Overall, these rocks belong to the potassium-rich calc-alkaline series typical of CVZ volcanoes. The magmas are formed by plagioclase and clinopyroxene crystallization with some mixing. Irruputuncu's rocks show minor evidence of crustal contamination, similar to other CVZ volcanoes located within transition zones.

Like much of nearby Mull and Ulva, Gometra is formed almost entirely from basalt lavas erupted during the early Palaeogene period. A couple of dykes are mapped cutting, and hence younger than, the basalt. In common with other such igneous intrusions assigned to the ‘Mull Swarm’, they are aligned northwest-southeast. Pipe-amygdales are present in some locations.

The terrain around Llullaillaco consists of andesite and dacite lavas and pyroclastics of Miocene to Pliocene age. Some Oligocene-Miocene layers are exposed in the Quebrada de las Zorritas. Dates obtained by argon- argon dating range between 11.94 ± 0.13 and 5.48 ± 0.07 million years ago. west of Llullaillaco do Paleozoic granites and volcanite rocks crop out.

The La Pacana caldera is buried beneath Puntas Negras. Both the 3.2 ± 0.3 Patao ignimbrite and the 2.4 ± 0.4 mya Pampa Chamaca or Tuyajto ignimbrite from La Pacana may have been erupted from beneath Puntas Negras. the Tuyajto ignimbrite is 530,000 ± 170,000 years old. Biotites in andesitic lavas have been dated 0.7 ± 0.3 to 0.3 ± 0.2 million years ago.

Slower cooling forms microscopic crystals in the lava and results in textures such as flow foliations, spherulitic, nodular, and lithophysal structures. Some rhyolite is highly vesicular pumice. Many eruptions of rhyolite are highly explosive and the deposits may consist of fallout tephra/tuff or of ignimbrites. Eruptions of rhyolite are relatively rare compared to eruptions of less felsic lavas.

A cluster of 14 volcanic plugs are exposed that were originally under the central part of Maitland Volcano. These form steep-sided, isolated monoliths that reach heights of above the surrounding eroded terrain. They are circular to elliptical in shape, ranging in diameter from . The plugs represent the principal feeders through which the Maitland lavas reached the surface.

About in area, the island has a domed shape, and is high. It is composed of andesite – dactic lavas and numerous explosion craters dot the volcano. A cone makes up the south part of the island, with its central crater filled by a lava dome. A -deep crater is located on the north-west side of the island.

Vesuvianite, also known as idocrase, is a green, brown, yellow, or blue silicate mineral. Vesuvianite occurs as tetragonal crystals in skarn deposits and limestones that have been subjected to contact metamorphism. It was first discovered within included blocks or adjacent to lavas on Mount Vesuvius, hence its name. Attractive-looking crystals are sometimes cut as gemstones.

This fault may represent the source of the Arsia lavas. The rift area to the southwest has been imaged in significant detail by the European Space Agency probe Mars Express. In 2004, a 3D map of this region was created at high resolution. Cliffs, landslides, and numerous collapse features can be seen in this detailed image.

These are the youngest mountains of the Sala y Gómez Ridge, which was formed by the Nazca Plate floating over the Easter hotspot.Haase, Karsten & Stoffers, P & Garbe-Schönberg, Dieter. (1997). The Petrogenetic Evolution of Lavas from Easter Island and Neighbouring Seamounts, Near-ridge Hotspot Volcanoes in the SE Pacific. Journal of Petrology - J PETROL. 38. 785–813. .

Casablanca () is a holocene stratovolcano in the Andes of Los Lagos Region, Chile. It is located about 90 km east of the city of Osorno and host on its slopes the Antillanca ski resort. The complex erupted lavas with composition between basalt and andesite and has no recorded historical eruptions. Several scoria cones formed after the last ice age.

The Neumayer Channel Tectonic Block is bounded by the Neumayer Fault and the Fournier Fault, which are parallel SW-NE trending strike-slip faults. The block consists of an Early Tertiary granite-granodiorite pluton intruded by a system of Early of Late Tertiary vertical dykes. These intrusive rocks are overlain by basaltic- trachyandesitic lavas and tuffs.

Podiform deposits are seen to occur within the ophiolite sequences. The stratigraphy of the ophiolite sequence is deep-ocean sediments, pillow lavas, sheeted dykes, gabbros and ultramafic tectonites. These deposits are found in ultramafic rocks, most notably in tectonites. It can be seen that the abundance of podiform deposits increase towards the top of the tectonites.

It forms a volcanic chain with Llullaillaco that extends towards Antofalla and Galán. This lineament is known as "Archibarca lineament". Cerro Corrida de Cori and Cerro Negro are associated with the intersections between this lineament and ENE lineaments. Fault zones on the area have controlled the magma ascent, probably facilitating the eruption of fairly primitive basaltic lavas.

Moorea consists of at least 16 flows of shield-stage basalt and post-shield lavas from 2.15 to 1.36 Ma. The area was first settled by early Polynesians during the early 4th century. Then Charles Darwin explored the area. After many years the area became very populated. Then people made trails and then it became a park.

These are matched by the Murton Formation (grey slates and thin sandstones) and the Kirkland Formation (mudstones with tuffs and lavas) at Cross Fell. The Buttermere Formation is interpreted as an olistostrome. The Tarn Moor and Kirkland Formations contain some volcaniclastic rocks. The inlier to the south at Black Combe contains the wackes of the Knott Hill Formation.

Map of Aubrac Souveyrols lake and a typical landscape of the Aubrac plateau around it. Aubrac is a volcanic and granitic plateau that extends over an area of 1,500 km2. The volcanic eruptions occurred between 6 and 9 million year ago and were of Hawaiian type with fluid lavas. There are therefore no individual volcanic cones.

Lastarria is composed of andesite–dacite, both rich in potassium and characteristic of calc-alkaline magmas of the Central Volcanic Zone. The appearance of Lastarria lavas is porphyritic. Some rocks display "banding" features, implicating the mixing of different magmas during their formation. Phenocrysts include plagioclase in andesite with smaller amounts of amphibole, biotite, clinopyroxene, and orthopyroxene.

The basalt lavas of the San Quintín field have the same composition as ocean island basalts found in Hawaii and the Azores, where they are associated with mantle plumes.Storey, M., Rogers, G., Saunders, A.D. and Terrell, D.J. 1989. San Quintín volcanic field, Baja California, Mexico: ‘within-plate’ magmatism following ridge subduction. Terra Nova 1: 195–202.

Leucogranites and anatectic granites have been derived from sediments melting. East Brittany and Lower Normandy contains the Mancellian batholith which consists of intrusions of granodiorite and granite. These other plutons are derived from fractionally crystallized mantle melts. At the Baie de St Brieuc and near Coutances in Manche and Trégor region there are pillow lavas, basalt erupted under water.

Between 51°S and 52°S the mid- ocean ridge basalts (MORBs) of the Mid-Atlantic Ridge have a composition that is associated with hotspots. Based on anomalously high Nb/Zr ratios in the southern end of the ridge, le Roex in 1987 suggested that the plume interacts with the ridge. Furthermore, inflated bathymetry and gravity coupled with increase in (La/Sm)n ratios (ratio of light rare-earth elements in MORBs) are indications that the plume is interacting with the ridge. analysed lavas dredged from the Shona Ridge System, the hotspot track formed by the Shona Rise, Meteor Rise, Agulhas Ridge, and Cape Rise, and concluded that those lavas are geochemically enriched compared to the MORBs, an indication that the Mid-Atlantic Ridge is interacting with a plume.

The formation is a volcanic unit, consisting mainly of high- titanium, low-potassium tholeiitic basalt flows, Pillow lavas in Batoka Basalt, Siyakobvu, Kariba District, Zimbabwe The lavas are dark, vesicular and porphyritic or massive basalts, with occasional pillows, although rare dacites and rhyolites have been reported from some areas of north-eastern Botswana. The vesicular and massive basalts occur in alternating bands, with the vesicular bands usually being the top and base of each flow. The basalt mineralogy consists of mainly of plagioclase, augite, magnetite, some ilmenite and volcanic glass. In the Hwange area, vesicles consist mostly of quartz, chalcedony or calcite, though zeolites, such as stilbite, mesolite and laumontite, are dominant towards Victoria Falls and in the lower Deka valley, and are common in north-eastern Botswana.

Rainbow and volcanic ash with sulfur dioxide emissions from Halemaʻumaʻu Geologists have dated and documented dozens of major eruptions over the volcano's long history, bridging the long gap between Kīlauea's oldest known rock and only extremely recent written records and historical observation. Historical lava flows from the volcano are generally recovered by scientists in one of three ways. The oldest flows, dating back 275,000 to 225,000 years, have been recovered from Kīlauea's submerged southern slope by ship-towed remotely operated vehicles. These lavas exhibit forms characteristic of early, submerged preshield-stage eruptive episodes, from when the volcano was still a rising seamount that had not yet breached the ocean surface, and their surface exposure is unusual, as in most other volcanoes such lavas would have since been buried by more recent flows.

Abetti is a lunar impact crater that has been completely submerged by mare lavas. It forms a 'ghost crater' in the surface, showing only a curved rise where the rim is located. Abetti is located near the southeast edge of Mare Serenitatis, to the west of the Mons Argaeus. This crater is generally visible only at low angles of illumination.

These formations are not visible in the Lascar area, but they crop out close to the Salar de Atacama. Tertiary sediment and volcanic rocks can also be found. The presence of Mesozoic limestone is indicated by xenoliths in Lascar's lavas; the only place they crop out farther east is in Argentina. This limestone formation has been identified as the Yacoraite formation.

The only large, accessible portion of Cape Purvis is at its southwest. It is composed of recently-formed volcanic rock of the James Ross Island Volcanic Group. Cape Purvis is described as a basalt tuya in the Encyclopedia of Quaternary Science. The basalts on Cape Purvis have similar composition to lavas on Paulet Island, which is 5 kilometers east of it.

Journal of the Geological Society, 153: 451-466. The age and stratigraphic equivalents of the Hoy sandstone sequence are a matter of continuing debate. Traditionally the presence of an unconformity at the base of the lavas beneath these sandstones on southwestern Hoy has been interpreted to mark a major time break.Mykura, W. (with contributions by Flinn, D, & May, F.) 1976.

The volcano has a caldera that is across; there is a wide gap in the caldera wall to the east, formed by a collapse of the structure. There is an unvegetated stratovolcano rising about from inside the caldera, and this is the main seat of current volcanic activity. The lavas are andesitic. On March 30, 2007, the mountain ejected ash again.

Piton de la Fournaise has two semi-circular craters, surrounding older craters. The volcano experiences a mix of Hawaiian eruption and Strombolitian eruption types and typically has highly liquid lava flows. When cooled, Piton de la Fournaise lavas form basalt enriched in labradorite with almost no olivine. Historic evidence indicates that the volcano erupts on a 20 to 40-year cycle.

Los Patos is part of the Cordillera Sundt, a mountain chain containing stratovolcanoes with lava domes and lava flows. The chain is constructed by dacite and smaller amounts of andesite. Other volcanoes in the chain include Falso Azufre, Monte Pissis and Mulas Muertas. So-called "Pircas Negras" lavas with compositions similar to adakite have been found on the northern flanks of Los Patos.

The western Cascades make up the western two thirds of the watershed, generally below in elevation. Steep, rugged canyons are common in this region. The lower stretches of the watershed contain soils such as decomposed lavas, clay, and gravel. The High Cascades compose the eastern third of the watershed, including volcanoes such as Brown Mountain and Mount McLoughlin, and lava plateaus.

The formation of the caldera was influenced by the neighbouring Pedernales-Arizaro fault. The caldera is the source of the Salar Grande ignimbrite, as well as the San Andrés ignimbrite that overlies the former. The ignimbrites erupted by Salar Grande crop out mainly east of the caldera. They are yellow, white and gray and embedded within Miocene basaltic andesite, andesite and dacite lavas.

The Bravo Lake Formation in central Baffin Island is a rare alkaline suite that formed as a result of submarine rifting during the Paleoproterozoic period.Volcanology and geochemistry of the Bravo Lake Formation, Baffin Island, Nunavut . Retrieved on 2007-11-06 The lavas of the volcanic belt display geochemical characteristics similar to modern ocean-island-basalt groups. The range from moderately to intensely fractionated.

The majority of ultramafic rocks are exposed in orogenic belts, and predominate in Archaean and Proterozoic terranes. Ultramafic magmas in the Phanerozoic are rarer, and there are very few recognised true ultramafic lavas in the Phanerozoic. Many surface exposures of ultramafic rocks occur in ophiolite complexes where deep mantle-derived rocks have been obducted onto continental crust along and above subduction zones.

Wherever they occur they accompany leucite- and nepheline syenites. Leucite monchiquites are fine-grained dark rocks consisting of olivine, titaniferous augite and iron oxides, with a glassy ground mass in which small rounded crystals of leucite are scattered. They have been described from Czechoslovakia. By far the greater number of the rocks which contain leucite are lavas of Tertiary or recent geological age.

After a long period of dormancy and erosion of the surface, the volcano may become active again, entering a final stage of activity called the rejuvenated stage. During this stage, the volcano erupts small volumes of lava very infrequently. These eruptions are often spread out over several millions of years. The composition of the lavas erupted in this stage is usually alkalic.

Gabbroic clots embedded in the lavas probably formed from cumulates. Xenocrysts with large reaction rims testify to a strong crustal contamination of the forming magma. The overall magma temperatures ranged for the andesitic and dacitic magmas and in the basaltic andesite. The magmas became cooler over time, with the post-collapse magmas being colder than the pre-collapse eruptive products.

As indicated by the name, the ophiolite is defined by the presence of ultramafic rocks in the California Coast Ranges. Pillow lavas and oceanic basalts are among the most common rocks found within the formation. There are a number of exposures that straddle the ancient Mohorovičić discontinuity. Metamorphosed peridotite, in the form of a serpentine rock, is an indicator of the formation.

In the northern group these are primarily composed from feldspar with minor components of amphibole, biotite and quartz. The southern group rocks have similar petrologies, but are of rhyolitic composition and contain mafic components. They contain a rhyolitic core surrounded with andesitic lavas that contains primarily plagioclase phenocrysts. Temperatures of for dacitic lava and for rhyolite lava have been estimated.

View from Puyehue's summit into its crater Panorama of Puyehue's crater from near the summit. In the background, black lavas from the 1960 Cordón Caulle eruption. Only Puyehue and Cordón Caulle have erupted during the Holocene, and until 2011 only Cordón Caulle had recorded historical eruptions. In the interval between 7,000 and 5,000 years ago Puyehue had rhyolitic eruptions that produced lava domes.

This material is found in Chaac Patera and thought to mimic the Kilauea Caldera floor overall, which would form from low viscosity, dark lavas ranging from mafic to ultramafic composition. Hummocks or pits are thought to be from the effect of inflation or vent openings that are common in this type of lava flow. Dark colored materials are the source of more heat.

Lake Ngozi is the second largest crater lake in Africa. It can be found near Tukuyu, a small town in the highland Rungwe District, Mbeya Region, of southern Tanzania in East Africa. It is part of the Poroto Mountains and the northern rim of the caldera is the highest point in the range. The caldera mostly composed from trachytic and phonolitic lavas.

The compound slag cone of Azhdahak, figures as a large strewn structure up to 1600m in diameter and about 370m high. The total area of volcano lavas, partly eroded and overlapped by the streams of Tar is around 8 square km. The cone is formed with slags, lapilli, sands, ashes, debris, lava boulders, slag, twisting, composite and spindle-shaped volcanic bombs.

Breccia remains from volcanic eruptions 1.7 billion years ago in collapsed pits. Dikes, sills and pillow lavas near the Hart River formed in connection with crustal extension 1.32 billion years ago. The 2.5 kilometer thick Pinguicula Group sandstone, dolomite, siltstone and shale deposited 1.27 billion years ago. The sedimentary rock contains a 200 million year gap after the Pinguicula Group.

The Hornitos basin is the precursor of the caldera, and the Lavas de Sierra La Dichosa form a precaldera stage. During the Cretaceous- Paleocene a group of stratovolcanoes formed in the area. Their eruption products are basalt and trachybasalt containing olivine and pyroxene. Magmatic intrusion triggered the formation of ring faults which then allowed the eruption of pyroclastic flows during caldera collapse.

Observers in Talca away heard the eruption noises, and the sulfurous odors reached them the day after the eruption. None of the reports mention earthquakes or ash fall, though the crackling and banging sounds could be from block lavas (aā).Hildreth and Drake, pp. 97–98. This first recorded eruption of Cerro Azul was effusive, and formed the volcanic vent at Quizapu.

Stratovolcanoes erupting about 14.7 million years ago in the Miocene covered about of what later became Grant County with andesite lavas and mudflows.Bishop, pp. 152–53 The Strawberry Mountains are eroded remnants of the mountains created by those volcanoes and by intrusions of igneous rock. Strawberry Lake is the largest of the small glacial lakes found in the Strawberry Mountain Wilderness.

The Eycott Volcanic Group (EVG) forms the youngest part of the preserved Ordovician sequence in the northernmost part of the Lake District. This set of mainly andesitic lavas and tuffs, with related minor intrusions is of Caradocian (Sandbian to Early Katian) age. In terms of their chemistry the EVG are transitional between moderately potassic tholeiitic and calc-alkaline in type.

The name Mt. Rittmann is sometimes applied to a fumarolically active nunatak on the caldera rim. The base of the volcano crops out from the Pilot Glacier, which together with the caldera is one of the few parts of the otherwise snow- and ice-covered volcano that crop out from the ice. Outcrops consist of hyaloclastites, lava flows and pillow lavas.

There is a tiny, man-made cave near the ridge of the hills called Clutter's Cave (or Giant's Cave or Hermit's Cave or Waum's Cave, after Walm's Well which is located on the boundary of News Wood below). The cave has been excavated into pillow lavas. Some of the rounded 'pillow' shapes are still visible around the entrance to the cave.

Aerial photograph of Hellisheiði: Lambafell in the foreground, behind it to the left the valley with the low shield of Leitin, Leitahraun lavas and small craters of the Brennisteinsfjöll volcanic system Rauðhólar Within Raufarhólshellir lava tube In the lava tube of Raufarhólshellir (volcanogenic) tumulus in the foreground, Bláfjöll in the background Leitin is a small shield volcano in the southwest of Iceland.

Pillow lavas and breccia overlain with slabby pieces of sulfide formed from hydrothermal venting on the east side of the Southern Explorer Ridge. Bathymetry image showing the crest of Southern Explorer Ridge. Purple and dark blue colors indicate deepest depths. The Explorer Ridge is a mid- ocean ridge, a divergent tectonic plate boundary located about west of Vancouver Island, British Columbia, Canada.

Results show that the lava was highly fluid (low viscosity) with low yield strength, resembling Hawaiian and Icelandic basaltic lavas. Average effusion rates are about 185 m3/s. These rates are comparable to those seen in Hawaii and Iceland. Earth-based radar studies show that Ascraeus Mons has a higher radar echo strength than other volcanic structures on the planet.

On the other hand, there are many hyaloclastite ridges, actually most of them consisting of mixtures of pillow lavas, hyaloclastite and lapilli tuff. Edwards, B.R., Gudmundsson, M.T., Russell, J.K., 2015. Glaciovolcanism. In: Sigurdsson, H., Houghton, B., Rymer, H., Stix, J., McNutt, S. (Eds.), The Encyclopedia of Volcanoes, pp. 377–393. There are also elongated pillow structures, called pillow tindars by Pedersen.

The volcano has been affected by glaciation. Glacial U-shaped valleys are found on the northern and western flanks, giving the volcano some angular patterns. One valley with glacial features and a subglacial river channel at altitude is found on the northern flank. It extends down to the valley north of Aguas Calientes and intersects the youngest lavas of the volcano.

Individual volcanoes in the Azas Plateau volcanic field include the Derbi-Taiga tuya (), which is formed by several layers of hyaloclastite and lava flows and displays a prominent "winged" topography. The hyaloclastite layers were formerly considered to be tuffs and reach thicknesses of . Pillow lavas also exist. A system of ancient valleys formed by floods are found near to Derbi-Taiga.

Acamarachi is a steep-sided conical volcano, like several other volcanoes in the region. Such a shape is due to the relatively high viscosity of the lavas forming them. In the case of Acamarachi, the upper slopes reach a slope angle of 45°. On the volcano's northern flank there is a large lava dome while the rest of the edifice is symmetrical.

Tajumulco is composed of andesitic-dacitic lavas on the top of a large escarpment of uncertain origin. It has two summits, one of which has a crater wide. A lava flow from the north-western summit descends into a steep valley on the same side of the volcano. The volcano's eruptive history is unclear and the date of its last eruption is unknown.

Once the alkali olivine basalt flows cooled, they formed well-developed columnar joints. Feldspar-phyric, highly vesiculated hawaiites and benmoreites were later erupted from several vents on the summit of Itcha Mountain. In the northwestern and northeastern parts of the shield volcano, basanite lava flows were erupted and are volumetrically subordinate. These represent the youngest known lavas of the Itcha Range.

Later the main edifice was built by andesitic lavas. Another view treats lava domes formed 8.6±0.5 million years ago as the final activity. In this view, the last activity coincides with the cessation of large ignimbritic volcanism in the northern Puna and is probably linked to a steeper subduction of the Nazca plate. Thermal springs are still present however.

Later, a debris flow named Veladero (also known as Quebrada de Veladero Ignimbrite) occurred in a glacier valley south of the caldera. It is rich in lithics and pumice. These lithics are derived from Sierra de Veladero, Cerro Bonete Chico, and Pircas Negras lavas. The debris flow ranges from in thickness south of the caldera to farther south, the total volume being .

The magnetite lavas are primarily aa lava, but other surface features are also found, including pahoehoe features. Columnar morphologies are found on the magnetite, implying that they cooled quickly. There is only one other place in the world where columnar magnetite has been found – Kiirunavaara, in Sweden. Large tubes coated on the inside by magnetite were formed in the lava by escaping gas.

It also forms lava tubes where the minimal heat loss maintains low viscosity. The surface texture of pāhoehoe flows varies widely, displaying all kinds of bizarre shapes often referred to as lava sculpture. With increasing distance from the source, pāhoehoe flows may change into aā flows in response to heat loss and consequent increase in viscosity. Pahoehoe lavas typically have a temperature of .

The Hornillos Formation, deposited in the Algarrobal Basin,Abad, 1982, p. 5 comprises sandstones, limestones, conglomerates, and caliches, intercalated with lavas and andesitic breccias and various volcanic rocks. Between these last is a conspicuous layer of rhyo-dactitic lithic tuff, which reaches up to in thickness. Bones of indeterminate titanosaurs appear in a marly limestone stratum of thick with decimeter-sized calcareous concretions.

Afterwards, lava flows were generated. The Igwisi Hills are the only places in the world where possible kimberlite lava flows have been found, in form of calcite-olivine lavas. Kimberlite tuffs are also found, a rare species which is very susceptible to erosion. True kimberlites are usually very old eruptive rocks, consequently any subsurface volcanic structure has long since been eroded away.

In Iceland a broad stretch of these rocks, described as "the palagonite formation," is said to cross the island from south-west to north-east. Some of these tuffs are fossiliferous; others are intercalated with glacial deposits. The lavas with which they occur are mostly olivine- basalts. Palagonite tuffs are found in Sicily, the Eifel, Hungary, Canary Islands, and other places.

" (The experiments of M. de Drée, in which he melted various lavas in a crucible, proved that in such a fluid mass, crystals of feldspar should tend to precipitate to the bottom.) "M. de Drée" was Étienne-Marie-Gilbert, Marquis de Drée (1760–1848) [ Fr ], a French amateur geologist who in 1808 had presented to L'Institut national de France his paper "Mémoire sur un nouveau genre de liquéfaction ignée qui explique la formation des laves lithoïdes" (Memoir on a new type of igneous liquefaction that explains the formation of stony lavas). (Summarized (in French) in: Etienne-Marie-Gilbert Drée (1808 March 28) "Mémoire sur un nouveau genre de liquéfaction ignée qui explique la formation des laves lithoïdes," Nouveau Bulletin des Sciences, 1 : 137–142.) On pp. 16–17 of the memoir, Drée stated: "En plaçant le morceau de porphyre dans le creuset no.

Diadem Mountain at Sunset, Tahiti, John LaFarge, c.1891, Brooklyn Museum The Society archipelago is a hotspot volcanic chain consisting of ten islands and atolls. The chain is oriented along the N. 65° W. direction, parallel to the movement of the Pacific Plate. Due to the plate movement over the Society hotspot, the age of the islands decreases from 5 Ma at Maupiti to 0 Ma at Mehetia, where Mehetia is the inferred current location of the hotspot as evidenced by recent seismic activity. Maupiti, the oldest island in the chain, is a highly eroded shield volcano with at least 12 thin aa flows, which accumulated fairly rapidly between 4.79 and 4.05 Ma. Bora Bora is another highly eroded shield volcano consisting of basaltic lavas accumulated between 3.83 and 3.1 Ma. The lavas are intersected by post-shield dikes.

147–150 although the dating of the slot is uncertain, and could date to Hadrian's temple of Aphrodite, Lavas suggested that it could have been the site of the crucifixion, as it would be strong enough to hold in place a wooden trunk of up to in height (among other things).Hesemann 1999, pp. 171–172: "....Georg Lavas and ... Theo Mitropoulos, ... cleaned off a thick layer of rubble and building material from one to 45 cm thick that covered the actual limestone. The experts still argue whether this was the work of the architects of Hadrian, who aimed thereby to adapt the rock better to the temple plan, or whether it comes from 7th century cleaning....When the restorers progressed to the lime layer and the actual rock....they found they had removed a circular slot of 11.5 cm diameter".Vatican-magazin.

Progression of ages of rhyolitic (silicic) lavas and calderas from alt=The diagram displays the movement of the North American tectonic plate with an arrow moving from right to left, with ovular shapes indicating the age progression of centers of rhyolitic (silicic) lavas. From right to left, three major volcanic centers are indicated with concentric circles, Yellowstone Caldera to McDermitt Caldera to Newberry Caldera Overlapping with the northwestern corner of the Basin and Range Province, also known as the High Lava Plains, Newberry Volcano lies within a Cenozoic highland marked by normal faults known as the Brothers Fault Zone. It is situated at the intersection of the Brothers Fault Zone with the north–northwest-trending Sisters and northeast-trending Walker Rim fault zones. In the mantle under Newberry Volcano, P and S seismic waves exhibit an unusually low wave velocity.

A series of eruptions built up a broad plateau of lava, and extended over the area where Calabozos now lies. Locally, this plateau was composed of mafic andesite with olivine, which over time gathered to form to thick layers. Nearby volcanoes sit on top of two mya lavas that formed during this period, while the Loma Seca Tuff lies atop andesitic deposits from Descabezado Grande.

In these volcanoes alkaline lavas are erupted in the post-shield stage but Macdonald is clearly a developing volcano, and further research is needed to explain the chemical history of Macdonald. These magmas in the case of Macdonald were derived from the partial melting of spinel-lherzolite and further influenced by fractional crystallization and carbon dioxide, but with no influence of the overlying plate.

The Cardenas Basalt is about thick and is typically divided into lower and upper units. The lower unit ranges in thickness from and forms low, talus covered slopes. It consists of complexly interbedded, thin, and discontinuous beds of basalt, hyaloclastite, and sandstone. Within the lower part of the Cardenas Basalt, the basaltic lavas are highly fractured and weather into rubble that is about in diameter.

The Faroe- Shetland Basin is a SW-NE trending rift basin that is divided into several sub-basins with intervening ridges and highs. The geometry is less clear on the northwestern side of the basin due to the presence of thick Late Paleocene flood basalts. Even where the lavas are absent the development of large sill complexes makes seismic imaging at deeper levels difficult.

Unconformities mark both the base and, possibly, the top of the Nankoweap Formation. The red beds of the Nankoweap Formation unconformably overlie the Cardenas Lavas of the Unkar Group. At most places, the upper member of the Nankoweap Formation directly overlies the Cardenas Basalt. In Basalt Canyon, an angular discordance in this lower contact reflects the erosion of 60 m of Cardenas Basalt has been recognized.

Tsiteli Khati () is a summit of the Kharuli Range in Northern Georgia. The elevation of the peak is above sea level. The mountain is located within the Kheli Volcanic Region of Georgia, an area which is the largest source of volcanism on the southern slopes of the Greater Caucasus Mountain Range within Georgia's boundaries. Tsiteli Khati is built up of holocene age andesites and dacitic lavas.

Pillow basalts at Wadi Jizz, which is part of the Semail Ophiolite sequence. These were named the Geotimes Pillow Lavas after a photo of them was published on the cover of the Geotimes magazine in 1975. Oman's geological record is extremely valuable to geologists, and needs to be preserved. It contains the most complete ophiolite on Earth, of which it is most famous for among geologists.

The caldera most likely was not formed by a large explosive eruption, considering that no deposits from such an eruption have been found. The volcano is formed by lava flows, lava domes, scoria, pillow lavas as well as pumice falls, pyroclastics and other material. The edifice has a volume of about and covers a surface area of about . Radial valleys extend away from the top.

It is bounded by Þistilfjörður to the northwest and Bakkaflói to the southeast, while the terrain inland reaches elevations of 200–450 metres (600–1200 feet). The highest point is Gunnólfsvíkurfjall in the southeast of the peninsula, at 719 m. The peninsula is composed of late Pliocene-early Pleistocene lavas. Kistufjall (444 m) is the distinctive tuya (table mountain) volcano that resulted from subglacial eruptions.

Winthrop is the remnant of a lunar impact crater that has been flooded by lava from the Oceanus Procellarum. It was named after American astronomer John Winthrop. It lies across the western rim of the much larger crater Letronne, a much larger feature that has been nearly destroyed by the intruding mare lavas. All that survives of Winthrop are a few segments of the outer rim.

The northern sea floor drops steeply within of the shore. This drop-off is known as the "blue edge". On Curaçao, four major geological formations can be found: the lava formation, the Knip formation, the Mid- Curaçao formation and limestone formations. Curaçao lies within the Caribbean large igneous province (CLIP) with key exposures of those lavas existing on the island consisting of the Curaçao Lava Formation (CLF).

There are no visible water features. Davidof's exact composition is unknown, although studies conducted by W.H. Nelson of the United States Geological Survey (USGS) determined that the lava, at least, was layered over a base of red breccia. The lavas appeared to be differentiating, but stuck to gray color with either "glassy or fine-grained, compact or dikty- taxitic" composition.Nelson, W. H., page 11.

Level Mountain has experienced volcanic eruptions sporadically for the last 15 million years, making it the most persistent volcano of the NCVP. More than 20 eruptive centres are present on the summit and flanks of the complex. These have produced mainly felsic and mafic lavas, a chemical composition range typical of bimodal volcanism. Such volcanism commonly occurs at hotspots, continental rifts and leaky transform faults.

The Burnie Formation followed in the Tonian period south east of the lineament with greywacke and slaty mudstone, and also some basic pillow lavas. The Oonah Formation has even more varieties of rock than the Burnie formation, also including conglomerate, quartz sandstone, dolomite and chert. The Bowry Formation in the Cryogenian was intruded by granite (Bowry granitoids) . These have been metamorphosed to the blueschist level.

These are aligned parallel to magnetic anomalies in the underlying oceanic crust. It is very similar in shape and structure to the nearby Davidson Seamount, except that it is smaller, at approximately by . It rises about above the seafloor and sits at depth of . The lavas from Guide are mostly alkalic basalt, hawaiite, mugearite with some pyroclastic flows near the top of the summit.

Ceraunius Tholus is a volcano on Mars located in the Tharsis quadrangle at 24.25° north latitude and 262.75° east longitude, part of the Uranius group of volcanoes. It is across, approximately high and is named after a classical albedo feature name. It is generally believed to be a basaltic shield with the lower part buried beneath plain forming lavas. Earlier interpretations suggested that it is a stratovolcano.

Geologically, the range is considered a monocline; part of a rifted volcanic margin. The Lebombo monocline was aligned with the Explora Escarpment off-shore Dronning Maud Land, Antarctica, before the break-up of Gondwana. The Lebombo monocline strikes N-S and dips to the east. It is composed of a sequence of Jurassic age volcanic rock, both basaltic lavas and rhyolitic flows and tuffs.

Early Paleozoic, Middle Paleozoic, Cretaceous, and Neogene rocks have been mapped within the De Long Islands. The Early Paleozoic rocks are Cambrian and Ordovician sedimentary rocks interbedded with minor amounts of limestone. The Middle Paleozoic rocks consist of predominately folded and faulted basaltic, andesitic, and dioritic volcanoclastics, tuffs, lavas, dikes, and sills. Cretaceous rocks are composed of basalts and interbedded argillites, sandstones and minor coals.

Volcanism began in the Miocene and over three stages continued in the Holocene. It is associated with the presence of two neighbouring active (in 1969 last earthquake) graben structures. Most cones are of small size and one of them (Akcakoy Tepe) has its internal structure exposed. Total volume of the volcanic field extrusion is about 2,3 km3 and the lavas are rich in xenoliths.

The ophiolite formed in the Late Cretaceous and consists of a basal metamorphic sole (150–200 m), peridotite tectonic (8–12 km), igneous peridotite and gabbro (0.5–6.5 km), sheeted dikes (1–1.5 km), and lavas (0.5–2.0 km). The Batinah complex containing continental margin sediments came from beneath the ophiolite during late-stage extensional faulting and then slid into the ophiolite late in the emplacement history.

Blackstone Plain is a small plain just south of Harper Point at the north end of Saunders Island, South Sandwich Islands. This lowland feature is made up of dark basaltic lavas and, in 1964, personnel from HMS Protector found it to be the only area of the island free from ice and snow. The descriptive name was given by the UK Antarctic Place-Names Committee in 1971.

2, pp. 365–377. is characterized by ultramafic massive and pillow lavas, a trondhjemitic suite of silicified felsic intrusive and flow banded rocks, and sedimentary chert beds. Veins of felsic, chert and ultramafic material intrude the belt. The depositional environment is thought to be a shoaling shallow sea in which the Hooggenoeg Formation has been deposited in a west-block down, listric faulted, synsedimentary setting.

The formation overlies across an angular unconformity older sedimentary rocks of continental origin as well as dykes and plutons that intruded these sediments. The unconformity has an irregular form attesting to a topography that was flattened out by the deposition of the Cola de Zorro sediments. Cola de Zorro Formation was deposited in Pliocene and Pleistocene times. The formation interdigitates with lavas of old and eroded volcanoes.

One major lava tube lies in the Cima field and is accessible through a skylight; it is long and wide. In some places flows surrounded basement outcrops, forming kipukas. In accordance to the slope of the area, most lavas flowed westward. Younger flows often show crisp lava flow features while older flows are almost always mantled with younger material and have lost their original surface features.

In mid or late glacial times cordillera Nevada produced its last lavas which were andesitic to dacitic in composition. Cordón Caulle evolved during this time from being a shield volcano to a graben with fissure vents. This was accompanied by emission of ignimbrites and dacitic lava flows. Puyehue was characterized by eruption of basaltic andesites to dacites until its activity turned bimodal at around 34,000 years ago.

The closest major air route is about to the east. Volcanic ash reduces visibility and can cause jet engine failure, as well as damage to other aircraft systems. Lava flows emitted during future volcanic eruptions would likely be basaltic in nature based on the composition of its lavas produced during past volcanic activity. Basaltic lava flows are low in silica content and can have speeds extending from .

Marchena is Tower Island's nearest neighbor, about 45 miles due west. Like many of the Galápagos volcanos, Marchena has a caldera. Marchena's caldera is roughly elliptical and measures , within the range of caldera sizes of the large western volcanoes. Marchena's caldera is unusual, however, in that it has been almost completely filled with young lavas, some of which has spilled over and down the sides.

This structure is at least 150,000 years old. Little Mount Adams is a symmetrical cinder cone on top of the Ridge of Wonders on Adams' southeast flank. Potato Hill is a cinder cone on Adams' north side that was created in the late Pleistocene and stands above its lava plain. Lavas from its base flowed into the Cispus Valley where they were later modified by glaciers.

It forms a wide stratocone with a lava-filled crater, and layers of scoria and agglutinated lavas dip from it. Volcan Pabellón (4.14–4.12 mya) sits southwest of the Puquíos-Negro ridge. The Las Bolitas lava field (5.23–5.13 mya) is associated with the Gordo group but the vent locations are unknown. The total volume of this group is , indicating a flux rate of .

Strombolian eruptions at Llaima, Antuco, Villarrica, and elsewhere have been produced by basaltic to basaltic–andesitic activity. Dacitic to rhyolitic lavas have been linked to subplinian and Plinian eruptions, such as those at Quizapu (1932) and Hudson (1991). Because of this variability, volcanic hazards from Cerro Azul and the surrounding region could come in many different forms. Historical eruptions typically have produced lahars, lava flows, and ashfalls.

The submarine volcanoes produce glassy lavas ranging in compositions similar to what would be expected in arcs higher in large-ion lithophile elements to enriched mid-ocean ridge basalts. The Bransfield Basin is abnormal when it comes to the style of volcanism that can be observed within the basin. Undersea volcanoes experience what is called bimodal volcanism. Igneous rocks within the basin are Andesite and Basalt.

This indicates that the lavas were erupted about 10,000 years ago during the waning stages of the Fraser Glaciation. The ice-marginal lava flows reach thicknesses of up to . Pali Dome West consists of at least three andesite lava flows and small amounts of pyroclastic material; its vent is presently buried under glacial ice. At least three eruptions have occurred at Pali Dome East.

It is here that basaltic lavas gently flow out of rifts to build huge dome-shaped volcanic mountains whose eroded summits form island arcs, chains, and clusters. Outside the andesite line, volcanism is of the explosive type. The Pacific Ring of Fire runs parallel to the line and is the world's foremost belt of explosive volcanism. The term andesite line predates the geologic understanding of plate tectonics.

These magnesium rich lavas have been named "bajaites". Late Miocene adakites are also found in Jaraguay. These melts probably form from dehydration melting of the mantle modified by the previous subduction of the Farallon plate; another older theory attributed their formation to the attempted subduction of a spreading ridge. The basement of the field is formed by Mesozoic sedimentary sequences with Cretaceous intrusions and Tertiary volcanic rocks.

Lavas from the Tweed Volcano are recognised as part of the Lamington Volcanics.Geoscience Australia Lamington Volcanics Stratigraphy The volcanic stratigraphy of the Tweed Volcano is similar to many other hotspot volcanoes around the world. Eruptions of tholeiitic and some calc-alkaline basalts are the oldest recognised units derived from the volcano. These are named the Lismore Basalt and Beechmont Basalt in New South Wales and Queensland respectively.

This sequence reaches thicknesses of . In the Miocene-Pliocene a major lava plateau was formed on the eastern end of the Taryat depression, with a surface area of . The depression itself however does not appear to contain lavas from this plateau. Between 0.75 and 0.36 mya the Taryat–Chulutyn lava river was erupted from several Pleistocene-Holocene centres and grew to a length of .

Hawaiite is an olivine basalt with a composition between alkali basalt and mugearite. It was first used as a name for some lavas found on the island of Hawaii. In gemology, hawaiite is a colloquial term for Hawaii-originated peridot, which is a gem-quality olivine mineral. It occurs during the later stages of volcanic eruptions which happens to be when the alkaline metals are most present.

Scoria cones on the slopes are accompanied by lava flows. On the upper sectors of the volcano, lavas are crisscrossed by cracks, which are known as "lappiaz". Sandstone crops out on the terrain surrounding the volcano. North of Emi Koussi lie other volcanoes, such as Tarso Ahon and Tarso Emi Chi, the former of which is connected to Emi Koussi by a narrow ridge.

The clastic beds overlay the TPG sediments, and are separated by angular unconformities. Overlying the MFF clastic sequence are the acidic volcanics of the Kenny Glacier Formation (KGF). This volcanic sequence is a 215 m thick group of rhyolite-dacite lavas, ignimbrites, tuffs, and agglomerates. The acidic dikes and sills which intrude the MFF and TPG sediments may be due to the KGF stratovolcano.

The West Antarctic Rift is a major geological feature in Antarctica and one of Earth's largest continental rifts. It is a region of active crustal extension and spreading, which may be ongoing today. Volcanic activity occurs at the rift and includes the McMurdo Volcanic Group, a long chain of volcanoes in Victoria Land. This volcanic group has erupted alkaline lavas during the course of the Cenozoic.

Some rock units at the foot of the volcano were emplaced underneath ice or water and feature hyaloclastite and pillow lavas. These units rise to about above the present-day ice level. Some of these units, such as Gill Bluff, Möll Spur and Stauffer Bluff, are "hydrovolcanic deltas" comparable to lava deltas. They crop out at the base of the volcano and are well preserved.

Their slopes are covered with their eruptive products and serve as the surface expressions of intrusions. As a result, they provide a unique opportunity to study the relationships between magma chambers and their lavas. The mafic (rich in magnesium and iron), intermediate (between mafic and felsic) and felsic (rich in feldspar and quartz) volcanic rocks of the massif were erupted from at least eight volcanic vents.

The tephra produced by its eruptions is high in fluorine, which is poisonous to animals. Hekla's basaltic andesite lava generally has a SiO2 content of over 54%, compared to the 45–50% of other nearby transitional alkaline basalt eruptions (see TAS classification). It is the only Icelandic volcano to produce calc-alkaline lavas. Phenocrysts in Hekla's lava can contain plagioclase, pyroxene, titanomagnetite, olivine, and apatite.

Chert or flint may become a finely crystalline quartz rock; sandstones lose their clastic structure and are converted into a mosaic of small close-fitting grains of quartz in a metamorphic rock called quartzite. If the rock was originally banded or foliated (as, for example, a laminated sandstone or a foliated calc-schist) this character may not be obliterated, and a banded hornfels is the product; fossils even may have their shapes preserved, though entirely recrystallized, and in many contact-altered lavas the vesicles are still visible, though their contents have usually entered into new combinations to form minerals that were not originally present. The minute structures, however, disappear, often completely, if the thermal alteration is very profound. Thus small grains of quartz in a shale are lost or blend with the surrounding particles of clay, and the fine ground-mass of lavas is entirely reconstructed.

Calabozos lies between two different types of volcanism—to its north, andesite and rhyolite are the primary constituents of lava while its southern neighbors are composed of more mafic andesite and basalt. It is mainly basaltic andesite and rhyodacite that make up Calabozos, forming a calcalkilic suite rich with potassium. Its lavas are dotted with phenocrysts, which vary from 2 to 25 percent of their mass.Grunder and Mahood (1988), p. 831.

Argon–argon dating has been used to date the rocks erupted by Palomo. The main summit yielded dates of 100,000 ± 40,000 years ago, while postglacial lavas of Andrés are dated at 40,000 ± 30,000 years ago, but volcanic activity at Palomo may have continued into pre-Hispanic times. Future activity at Palomo might generate lahars through the melting of ice, which could affect the valleys of the rivers draining the volcano.

The volcano itself is constructed from lava domes and flows on top of Miocene ignimbrites. Several stages of eruptive activity are recognized, some of them exposed through erosion. A northwestern debris avalanche has been found on Isluga, on top of which the recent volcano is constructed. The fumarolically active crater region has been buried with surge deposits from phreatomagmatic activity, and the northern ridge is covered by Holocene lavas.

Panorama of the Drakensberg in Giant's Castle region, on the KwaZulu-Natal/Lesotho border. The uppermost layer of this portion of the Great Escarpment is formed by the 1400 m thick Drakensberg Lavas, which rest on the Clarens Formation rocks. The magma welled up through long crack-like fissures, with occasional spatter cones, but typical volcanoes were rare. Each surface lava flow was between 10 and 20 meters thick.

Abra Granada is a volcanic complex in the Puna de Atacama in Bolivia. It is located approximately north of Pirquitas and is composed from a lava dome, lavas and dacitic ignimbrites centering on Cerro Granada () and are dated 9.8-7.8 Ma. Deposits erupted 7.9-5.0 mya by this volcano overlie the older Granada ignimbrite. Other peraluminous rocks were erupted 10 mya. The complex is the likely source of the Granada Ignimbrite.

Cerros Bravos may have collapsed towards the northeast in its history, ignimbrites may have formed during this collapse. The bulk of the surface area of the complex is formed by lavas; ignimbrites or tuffs and lava domes are subordinate. The Cerros Bravos Ignimbrite covers a surface of and other ignimbrites of . The Esperanza lava dome complex is associated with the volcanoes, it was constructed on the northeast flank of Cerros Bravos.

These volcanics consist of tholeiitic lavas and intrusive lamprophyric sheets. Scientists have long considered the Bermuda Pedestal to be the remains of a large extinct shield volcano that formed between 45 and 35 million years ago. A number of theories have been established to explain the origin of the Bermuda Pedestal. According to one of these theories, it was formed by the volcanic activity of the Bermuda hotspot.

2010 National Statistics (Abstract): climate, Table A.1. Central Statistical Agency website (accessed 18 March 2011) To the north is the village of Anige, while to the east is Bu'i. Mount Gurage is described as part of an upwarped massif, which overlooks the Rift Valley. This massif is composed of layers of silicic lavas and tuffs, except for the summit line which is hidden by the Rift Valley tuffs.

The Variscan fracture zones were active during the entire Upper Cretaceous and decisively influenced the sedimentary facies distributions. This activity was further underlined by alkaline magmatism lasting from the Middle Albian until the end of the Coniacian; thus in the west of the North Pyrenean Zone, submarine basaltic lavas extruded, while farther east in the Béarn and in the Bigorre, different magmatic rock types intruded the Upper Cretaceous strata.

The formation is made up of volcaniclastic rocks, and non- volcaniclastic rocks such as andesite, basalt, basaltic andesites and some lesser amounts of dacite. The non-volcaniclastic rocks correspond variously to lava flows with autobrecciated parts, lava domes, cryptodomes and pillow lavas. The volcaniclastic rocks of the formation include hyaloclastite breccias, peperites and felsic ignimbrites. This last rock type forms at some locations the lowermost parts of the formation.

La Luna has a lava dome surrounded by a glaciated but unaltered lava table. Cerro Tres Monos (3.4–2.78 mya) forms a northbound long ridge with at least six vents. Hydrothermal alteration has affected some lavas and pyroclastics from Tres Monos, and the western side has lateral and terminal moraines. The Aucanquilcha platform (3.6–2.7 mya) sits underneath the main Aucanquilcha volcano, and its lava mostly flowed north.

Volcanic ultramafic rocks are rare outside of the Archaean and are essentially restricted to the Neoproterozoic or earlier, although some boninite lavas currently erupted within back-arc basins (Manus Trough, New Guinea) verge on being ultramafic. Subvolcanic ultramafic rocks and dykes persist longer, but are also rare. There is evidence of ultramafic rocks elsewhere in the solar system. Examples include komatiiteHill R.E.T, Barnes S.J., Gole M.J., and Dowling S.E., 1990.

Although these never contain quartz, but feldspar is usually present, though there are certain groups of leucite lavas which are non-feldspathic. Many of them also contain nepheline, sodalite, hauyne and nosean; the much rarer mineral melilite appears also in some examples. The commonest ferromagnesian mineral is augite (sometimes rich in sodium), with olivine in the more basic varieties. Hornblende and biotite occur also, but are less common.

In the Silurian period, sandstones and mudstones were deposited in some parts of England. Volcanic ashes and lavas deposited during the period are still found in the Mendip Hills. Avalonia had now joined with the continent of Baltica, and the combined landmass collided with Laurentia around 425 million years ago, joining the southern and northern halves of the British Isles together. The resulting Caledonian Orogeny produced an Alpine-style mountain range.

Further detailed work on the geochemistry of the lavas from El Barú and other volcanoes in Panama was completed by Defant et al.Defant, M. J., Jackson, T. E., Drummond, M. S., de Boer, J. Z., Bellon, H., Feigenson, M. D., Maury, R. C., and Stewart, R.H., 1992, The geochemistry of young volcanism throughout western Panama and southeastern Costa Rica: An overview: J. Geol. Soc. Lond., v. 149, p. 569-579.

Together these volcanic fields have a larger surface than the islands of Hawaii and expand the area affected by Hawaiian volcanism to over width; they have been called "peripheral lavas" of the Hawaii hotspot. The South Arch volcanic field is located upstream of the Hawaiian hotspot and has been described as "precursory" although it does not appear to be an early stage of a typical Hawaiian shield volcano.

The northeasternmost volcano is Mount Rees, which reaches a summit height of at Tasch Peak. Volcanic rocks crop out at Trabucco Cliff on its northeastern flank. Glacial erosion has cut deep cirques into the eastern flank of Mount Rees, and volcanic outcrops indicate that volcanic rocks alternate between subglacial formations and subaerial formations. Outcrops consist of breccia and lavas, which in one case are intruded by a dike.

Alteration has formed chlorite, epidote and sericite. In the northern part of the volcanic field, lavas have a porphyritic (with a texture characterized by visible crystals) appearance. The magma appears to originate from a heterogeneous mantle and ponds and crystallizes underneath and inside the crust but without stalling in long- lived magma chambers, before rapidly rising to the surface. Each volcano was supplied by one batch of magma.

Such faulting is believed to be the surface manifestation of a deeper shear zone. Progression of ages of rhyolitic (silicic) lavas and calderas from McDermitt Caldera to Newberry and Yellowstone calderas (red circles: MC, NC, & YC). Numbers are ages in millions of years. KBML - Klamath–Blue Mountains Lineament, HLP - High Lava Plains, EDZ - Eugene—Denio Zone, BFZ - Brothers Fault Zone, SMF - Steens Mountain Fault, VF - Vale Fault, NNR - North Nevada Rift.

The age of the first volcanic eruption is unknown, but it could have occurred in the last 10,000 years. The second eruption produced a lava flow that was erupted when the vent area was not buried under glacial ice. However, the flow does show evidence of interaction with glacial ice at its lower unit. This indicates that the lavas were erupted during the waning stages of the Fraser Glaciation.

About 25% of the volcanics contain crystal content, including plagioclase, hornblende, orthopyroxene, orthoclase and sporadic quartz. The orthoclase crystals are interpreted to represent rock fragments that became enveloped during hardening of the dacitic lavas. A portion of the southwestern flank of Mount Fee comprises no volcanic glass, but rather composed of an abnormal cryptocrystalline matrix. This indicates that it might have developed as part of a subvolcanic intrusion.

The water surface of the maars lies between below their rim. Eight wide and deep crater-like depressions lie underwater in Devil Mountain Maar and similar but partly filled depressions are also found at the Killeak Maars. Layered volcanic deposits crop out in high cliffs around Devil Mountain Maar and within gullies around the other maars. The maars are emplaced in over thick lavas and sediments of Pleistocene age.

The fumaroles near the summit crater of Mount Damavand in May 2014 Mount Damavand first erupted in the Pleistocene almost 1.78 million years ago. After several known eruptions around 600,000 and 280,000 years ago, its last eruption was around 5300 BC in the Holocene. Its steep cone is formed of ash and lava flows mainly of trachyte, andesite, and basalt. The Quaternary lavas are directly on the Jurassic sediments.

Important examples noted include slates from the Upper Devonian period, several invertebrate species, predatory birds and grey seals. Pentire Head is formed of pillow lavas, a type of rock found nowhere else in Cornwall, while The Rumps consists of durable Greenstone. Naturally occurring Prehnite has also been found on the cliffs here. Other valuable minerals can be found and two mines have operated on the headland over the years.

There are numerous flows recorded which may have been erupted irregularly as fossil soil (Paleosol) profiles and lacustrine type rock units are occasionally found within the rock unit. Following eruption of the Lismore/Beechmont Basalt a period of eruption of rhyolite lavas took place. Eruptions occurred in lava and some pyroclastic forms. These rhyolites are known in New South Wales as the Nimbin Rhyolite and Queensland as the Binna Burra Rhyolite.

The Deccan Traps shown as a dark purple spot on the geologic map of India Crystals of epistilbite and calcite in a vug in Deccan Traps basalt lava from Jalgaon District, MaharashtraWithin the Deccan Traps at least 95% of the lavas are tholeiitic basalts. Other rock types present include: alkali basalt, nephelinite, lamprophyre, and carbonatite. Mantle xenoliths have been described from Kachchh (northwestern India) and elsewhere in the western Deccan.

Volcanism and a rift system developed in the central North Sea area where basaltic lavas were extruded. The mantle warped upwards creating a dome in the middle of the North Sea where the Iapetus Suture intersected the Tornquist-Teisseyre fault system. The dome area was amidst the Viking Graben, Central Graben and Moray Firth Basin. The Scotland rifting and the extrusive centre of the Forties were associated with the uplifted area.

Llullaillaco has mostly erupted dacites with medium potassium content, with rocks becoming more felsic the younger they are. Rock samples taken from Llullaillaco are mostly porphyritic or vitrophyric, with a glassy or microcrystalline matrix. Phenocrysts are mostly plagioclase, with mafic phenocrysts being dominated by orthopyroxene and smaller amounts of biotite, clinopyroxene, and hornblende. Ilmenite, magnetite, and sulfide minerals are also present, magnetite especially in the more oxidized older lavas.

Active volcanic areas and systems in Iceland The stratovolcano, whose vents follow an east–west trend, is composed of basalt to andesite lavas. Most of its historical eruptions have been explosive. However, fissure vents occur on both (mainly the west) sides of the volcano. The volcano is fed by a magma chamber under the mountain, which in turn derives from the tectonic divergence of the Mid-Atlantic Ridge.

They were recognized as fragments of oceanic lithosphere, and dykes were viewed as the result of extensional tectonics at mid-ocean ridges. The plutonic rocks found in ophiolites were understood as remnants of former magma chambers. In 1973, Akiho Miyashiro revolutionized common conceptions of ophiolites and proposed an island arc origin for the famous Troodos Ophiolite in Cyprus, arguing that numerous lavas and dykes in the ophiolite had calc-alkaline chemistries.

Rhyolite can be considered as the extrusive equivalent to the plutonic granite rock, and consequently, outcrops of rhyolite may bear a resemblance to granite. Due to their high content of silica and low iron and magnesium contents, rhyolitic magmas form highly viscous lavas. They also occur as breccias or in volcanic plugs and dikes. Rhyolites that cool too quickly to grow crystals form a natural glass or vitrophyre, also called obsidian.

P. Press, 1993); Penmanship and Other Stories (Cacho, 1995); The Island (Ayala Foundation, 1996); Pagsabog ng Liwanag/Aninag, Anino (U.P. Press, 1996); Mac Malicsi, TNT/Ang Butihing Babae ng Timog (U.P. Press, 1997); The Lavas: A Filipino Family (Anvil, 1999); The Best of Barfly (Anvil, 1997); The Filipino Flag (Inquirer Publications, 2004); Man Overboard (Milflores, 2005); Journeys with Light: The Vision of Jaime Zobel (Ayala Foundation, 2005); Selected Stories (U.

Poike and Rano Kau exist on the east and south slopes of Terevaka, respectively. Rano Kau developed between 0.78 and 0.46 Ma from tholeiitic to alkalic basalts. This volcano possesses a clearly defined summit caldera. Benmoreitic lavas extruded about the rim from 0.35 to 0.34 Ma. Finally, between 0.24 and 0.11 Ma, a 6.5 km fissure developed along a NE-SW trend, forming monogenetic vents and rhyolitic intrusions.

Mount Talagabodas or Mount Telagabodas (which means Mount of White Lake (refer to white crater lake) in Sundanese) is a stratovolcano in West Java, Indonesia. The volcano is about 25 km to the east of the town of Garut and is built up of andesitic lavas and pyroclastics. Fumaroles, mud pots and hot springs are found around the crater lake. Changes of the lake color occurred in 1913 and 1921.

Pyroclastic eruptions then started to pile tephra into cones in the northern area of the park. Mount Tehama (also known as Brokeoff Volcano) rose as a stratovolcano in the southwestern corner of the park during the Pleistocene. It was made of roughly alternating layers of andesitic lavas and tephra (volcanic ash, breccia, and pumice) with increasing amounts of tephra with elevation. At its height, Tehama was probably about high.

In response to major shifts in US and international policies toward the Vietnamese boat people, they moved our headquarters to Northern Virginia to concentrate on advocacy. Rising to the new challenge of saving the last boat people, BPSOS sent lawyers to asylum countries through its Legal Assistance for Vietnamese Asylum Seekers (LAVAS) project and successfully advocated for policy changes, which resulted in resettlement of 18,000 former boat people after repatriation.

Sturgeon Lake Caldera is a large extinct caldera complex in Kenora District of Northwestern Ontario, Canada. It is one of the world's best preserved mineralized Neoarchean caldera complexes, containing well-preserved mafic- intermediate pillow lavas, pillow breccias, hyaloclastite and peperites, submarine lava domes and dome-associated breccia deposits. The complex is some 2.7 billion years oldCaldera Volcanoes Retrieved on 2007-07-20 with a minimum strike length of .

This plug is made of micronorite with a diameter of . There are dikes exposed throughout the summit cone, mostly oriented from north to south, with another dike swarm trending north from the central plug. The summit formed over a platform of basaltic andesite lavas from early eruptions at Mount Washington, made of thinner flows combined with pyroclastic rock. The volcano has a mafic composition, with subalkaline basalt and basaltic andesite.

The Kashmir Valley is noted for its bakery tradition. On the Dal Lake in Kashmir or in downtown Srinagar, bakery shops are elaborately laid out. Bakers sell various kinds of breads with golden brown crusts topped with sesame and poppy seeds. Tsot and tsochvor are small round breads topped with poppy and sesame seeds, which are crisp and flaky, sheermal, baqerkhayn (puff pastry), lavas (unleavened bread) and kulcha are also popular.

The northern parts of Buckbarrow, blending into the slopes of Seatallan, are overlain by drift deposits, much peat being in evidence around Glade How. The summit area shows outcropping of the Birker Fell Formation, an undivided sequence of generally plagioclase-phyric andesite lavas with subordinate sills. At the bottom of the slope are examples of granophyric microgranite, representative of the Ennerdale Intrusion. Dykes of basalt and dolerite run through both formations.

This age range fits well with a radiometric analysis (48.1 Ma) reported for a dredged rock from Koko Seamount from the 1973 expedition. Although shell fragments had been recovered from the sediment cover in 1973, none of these deposits contained microfossils. Lava flows dominate the lithology of the main body, with a small proportion of calcarenite. Many lavas were pahoehoe flows laced with a'a, evidence of subaerial eruptions.

Examination of Newberry lavas with olivine-plagioclase hygrometry shows that tholeiites are anhydrous (less than ) and thus distinct from calc-alkaline deposits ); both have different fractional crystallization sequences that derive from primitive magmas, which had their compositions influenced by equilibrium with peridotite in the mantle. By volume, basaltic andesite is the principal lava type at Newberry Volcano, with large volumes of silicic lava among older ash flow tuff deposits.

The district's land surface mainly consists of gently undulating sandveld which lies between 1,100 and 1,230 meters above sea level. The Kalahari is the largest continuous stretch of sand in the world, covering some 2,500 km2. Karoo sediments, covered by younger basaltic lavas, underlie most of the Kalahari sands and about half of the country of Botswana. The sands of the Kalahari vary in depth from 5m to 200m.

Silicic lava domes are also found. The Ashikule basin is covered by - of lava from this field. Various kinds of rock coatings have developed on these lavas, some of biogenic origin. Xi Shan is the westernmost volcano with a diameter of and a height of With a summit height of and a height of above base, Dahei Shan volcano is the highest volcano at Ashikule and features a V-shaped crater.

Mount Tavkvetili () is a volcanic mountain in the northern part of the Abul- Samsari Range in the Samtskhe-Javakheti region of Southern Georgia. It is also known as Gora Tavk'vetili and Mta Tavk'vetili. The elevation of the mountain is above sea level and is the 323rd highest mountain in Georgia. The mountain has the shape of a decapitated cone and is composed of young andesitic and andesitic-dacitic lavas.

The district is located within a Middle Jurassic volcano-plutonic complex composed of basaltic lavas and volcaniclastics underlain and intruded by gabbroic rocks. Mafic dikes are abundant and form sheeted dike swarms. Deposition of iron was not associated with silicification or sulfidation. Host rocks contain veins and large accumulations of pure magnetite in structural or breccia zones, or are impregnated with clots of magnetite in all size ranges.

These are overlain by thick mafic alkaline lava flows and at least 30 small cinder cones. Hawaiite is the dominant rock type, but alkali olivine basalt and spinel lherzolite-bearing basanite is also present. They merge laterally with lavas of the much older Chilcotin Group, which surrounds the Anahim Volcanic Belt. However, the exact nature of the relationship between the Anahim Volcanic Belt and the Chilcotin Group is unknown.

Like other volcanic landforms in British Columbia, Black Dome Mountain is part of the Pacific Ring of Fire which includes over 160 active volcanoes. There are obsidian deposits and other deposits around the volcano. It has produced olivine basalt dykes, lavas, and agglomerate. Black Dome Mountain is thought to have formed as a result of extension of the crust behind the Cascadia subduction zone and last erupted during the Pliocene.

Less common are pillow lavas; their arrangement along the caldera walls suggests that they were an important component in the volcano's early growth. There are several dome-like structures within the caldera with heights of . There are several small craters within the region, the largest of which, nicknamed the D.D. Cone, is in diameter and in relief. However, most of the features do not range over deep and across.

The late Early Miocene-early Middle Miocene reefal Kennon Limestone overlays the Zigzag. The Late Oligocene-Early Miocene Agno Batholith intrudes the Pugo and Zigzag. The Middle-Late Miocene Klondyke Formation was deposited during Central Cordillera geologic uplift, consisting of coarse clastics, polymictic conglomerates, sandstones, and vitric (glassy) tuffs, with minor shales and siltstones. Gold mineralization occurred with dioritic and gabbroic intrusions, and basaltic to andesitic lavas, including the Monglo adakite.

Their activity began 16million years ago, when the Chile Rise collided with the Peru-Chile Trench and thus caused a tear in the subducting slab and the formation of a slab window beneath Patagonia; later it was suggested that slab rollback might instead be the mechanism by which volcanism is triggered in the Pali-Aike region. The age trends of volcanism has been interpreted as indicating either a southward migration or a northeastward one in the case of the plateau lavas, following the movement of the triple junction to the north; in that case Pali-Aike would be an exception, probably due to local tectonic effects. However, some older plateau lavas in the north formed in response to an earlier ridge subduction event in the Eocene and Paleocene. farther west from Pali-Aike lies the actual Andean volcanic arc in the form of the Austral Volcanic Zone, a chain of stratovolcanoes and one volcanic field (Fueguino) which is South America's southernmost volcano.

In 2006, Jeff Hungerford, a student of the University of Pittsburgh in Carlisle, Pennsylvania, United States, focused on fieldwork on the region surrounding Edziza's Tennena Cone, located immediately west of Ice Peak which formed subglacially during the early Holocene period when this area had remnants of glacial ice from the last ice age. Hungerford's studies in 2006 focused on subglacial volcanism, sampling pillow lavas to be used for degassing studies aimed at determining ice thicknesses during a subglacial eruption, and describing coeval glaciogenic sediments immediately underlying pillow lavas at the distal end of the lava flows. Hungerford also worked on describing glaciogenic sediments immediately underlying lava flows from Ice Peak adjacent to Tennena Cone, which may preserve a record of a one-million-year-old ice sheet. Satellite image of the Mount Edziza volcanic complex Kristen LaMoreaux, another student of the University of Pittsburgh, focused on the emplacement of trachyte lava flows and domes.

Lucchitta, I, and JD Hendricks (1983) Characteristics, depositional environment and tectonic interpretations of the Proterozoic Cardenas Lavas, eastern Grand Canyon, Arizona. Geology. 11(3): 177–81. Deep reddish, (and dipping), Dox Formation overlain by Cardenas Basalt, in contact above with multi-banded, horizontal Nankoweap Formation-(Grand Canyon Supergroup), downstream from Tanner Canyon, Tanner Rapid, and Tanner Graben. The Cardenas Basalt is composed mainly of thin discontinuous beds of pahoehoe lava flows of olivine-rich basalt.

It features well developed levees and a flow front. Its rocks have a pale gray-blue colour, and their composition resembles the Soncor flow, despite more mafic lavas and pyroclastics being erupted in the time period between the emplacement of the Soncor flow and the Capricorn Lava. An early pyroclastic flow, the Saltar Flow, is exposed on the eastern flank. It was emplaced after the collapse of the oldest edifice, covering Aguas Calientes' western slopes.

It has small circular and elongated features in the mare plains that probably mark impact craters buried by less than 1000 to 1700 feet (300 to 500 m) of lava. Further, Mare Marginis is not centered on any clear, large impact basin. Thus, Mare Marginis seems to mark a low-lying region of the highlands where mare lavas were just able to reach the surface. Several large mare-floored craters also occur nearby.

In these craters, the crater floors lie below the surrounding highland surface. Thus, they mark sites around Mare Marginis where lavas were close to the lunar surface. The major crater to the north of Marginis is Al-Biruni, with Ibn Yunus to the southeast and Goddard to the northwest. The surface of this mare displays some lunar swirls; higher albedo deposits that are similar to the Reiner Gamma feature on the Oceanus Procellarum.

The age of the Orientale basin has not been directly determined, though it must be older than 3.72 Ga (based on Upper Imbrian ages of mare basalts) and could be as old as 3.84 Ga based on the size-frequency distributions of craters superposed on Orientale ejecta. About two-thirds of the Moon's mare basalts erupted within the Upper Imbrian Series, with many of these lavas filling the depressions associated with older impact basins.

The volcanism in the Agua Poca area began as fissure eruptions that released large amounts of liquid lavas, forming Agua Poca, El Escorial, Payun Matru and other volcanoes. The volcano is located east of the Peru–Chile Trench, in the back-arc region. Agua Poca has erupted basalt lava. Bisceglia (1977) assumed that Agua Poca, together with the neighbouring volcanoes Del Nido and Escorial/Amarillo, is the origin of the El Puente basalt formation.

They reach thicknesses of and contain small amounts of hyaloclastite. The feeder of their origins has not been discovered but is likely located at the summit of the mound. These lavas form ice- marginal edifies, suggesting that every lava flow was erupted about 10,000 years ago when the vast Cordilleran Ice Sheet was retreating and remains of glacial ice were sparse. Exposed along the Cheakamus River and its tributaries are the Cheakamus Valley basalts.

Generally, above basement unit is the Columbia River basalt unit, consisting of flood-basalt lavas. In this unit, water is stored in the region between two lava flows, where weather has created porosity in the rock unit. Because of this, water is able to flow horizontally through the unit, but generally has very low vertical permeability. Above the Columbia River Basalt is the lower sedimentary unit, which also sometimes directly overlays the basement unit.

The dacite and rhyodacite rocks comprising Mount Fee contain up to 70% brown volcanic glass and up to 15% vesicles. About 25% of the rocks contain crystal content, including plagioclase, hornblende, orthopyroxene, orthoclase and sporadic quartz. The orthoclase crystals are interpreted to represent rock fragments that became enveloped during hardening of the dacitic lavas. A portion of the southwestern flank of Mount Fee comprises no volcanic glass, but rather composed of an abnormal cryptocrystalline matrix.

This stage of activity is characterized by small volumes of more mafic lavas expressed as small cinder cones and capping flows. Dissection of the shield by stream erosion is also apparent, resulting in the creation of deeply incised radial valleys. Prolonged erosion eventually removes most if not all traces of the volcanoes to expose their underlying solidified magma systems. Such systems can be below the surface with rocks ranging from hypabyssal to plutonic.

The mountain began forming about 15 million years ago, with volcanism continuing up until geologically recent times. There have been four stages of activity throughout the long volcanic history of Level Mountain. The first stage commenced 14.9 million years ago with the eruption of voluminous lava flows; these lavas created a large shield volcano. The second stage began 7.1 million years ago to form a structurally complicated stratovolcano located centrally atop the shield.

The former partially embay the hummocky plains and are probably volcanic in origin. The latter are present mainly on a part of the floor between the peak ring and crater rim; they interpreted to be the original crater floor material not covered by the light colored lavas of smooth plains. The hummocky plains are slightly bluer than smooth plains. The areas outside Raditladi are covered by the dark relatively blue impact ejecta.

Glaciers that ran down to the Pacific Ocean sharpened the valley faces and eroded their bottoms. The Golden Hinde on Vancouver Island was formed by erosion carving into basalt. The Insular Mountains were formed when a large island arc, called the Insular Islands, collided against North America during the Mid-Cretaceous period. The mountains are made of turbidite and pillow lavas unlike the plutons of the Coast Plutonic Complex that make the Coast Mountains.

Both pahoehoe and aa lava types are common and the volcanic pile accumulated mostly by the quiet effusion of lavas. The pyroclastic lithologies become more common near the southern and eastern edges of the formation and represent lahars and beach to shallow marine reworked deposits. The formation contains flood basalts, which are found on western Axel Heiberg Island at Dragon Cliffs, tall. It contains columnar jointing units that are usually in diameter.

58 The volcanic and pyroclastic rocks of the Noreán Formation are composed of lavas that range from andesitic to rhyolitic, together with vitric, lithic and crystal tuffs. Mainly andesitic dikes and hypabyssal bodies are also present. Geochemically, the volcanic and pyroclastic rocks exhibit chemical similarities, belong to the calc-alkaline series and have negative anomalies of Nb, P and Ti and a positive anomaly of Pb, suggesting a subduction-related genesis.Correa Martínez et al.

Most kimberlite and lamproite occurrences occur as volcanic and subvolcanic diatremes and maars; lavas are virtually unknown. Vents of Proterozoic lamproite (Argyle diamond mine), and Cenozoic lamproite (Gaussberg, Antarctica) are known, as are vents of Devonian lamprophyre (Scotland). Kimberlite pipes in Canada, Russia and South Africa have incompletely preserved tephra and agglomerate facies. These are generally diatreme events and as such are not lava flows although tephra and ash deposits are partially preserved.

More recently our understanding has been aided by geophysical studies, offshore submersible studies, the advent of radioactive dating, advances in petrology and geochemistry, advanced surveillance and monitoring, and detailed geological studies.USGS, pg. 149 (digital pg. 167) The ratio of magnesium to silica in the lava is a sign of what stage the volcano is in, as over time the volcano's lavas shift from alkalic to tholeiitic lava, and then back to alkalic.

These sediments have yielded a fairly rich fossil fauna of brachiopods and trilobites indicating that they were deposited in a shallow marine sea into which the lavas were extruded. The rocks are quarried at Moons Hill near Stoke St Michael for aggregate. Coal measures appear in the Radstock district, and surrounding Somerset Coalfield (largely concealed by Triassic and newer rocks). There are two series of coal-bearing sandstones and shales separated by Pennant Sandstone.

Putana is a high volcano elongated from north to south. It is constructed by lavas and pyroclastic material, with effusive products such as lava domes and lava flows forming the bulk of the edifice. Most lava flows were viscous enough that they do not exceed of length, older flows are longer. Younger lava flows occur on the western slope, and some lava flows appear to be younger than the last glacial age.

Furthermore, some studies show that the amount of water dissolved in mantle minerals is two to six times higher in the Iceland region than in undisturbed parts of the mid-oceanic ridges, where it is regarded to lie at about 150 parts per million. The presence of such a large amount of water in the source of the lavas would tend to lower its melting point and make it more productive for a given temperature.

This lava is visible beside the Vilaflor–Chio road. Christopher Columbus reported seeing "a great fire in the Orotava Valley" as he sailed past Tenerife on his voyage to discover the New World in 1492. This was interpreted as indicating that he had witnessed an eruption there. Radiometric dating of possible lavas indicates that in 1492 no eruption occurred in the Orotava Valley, but one did occur from the Boca Cangrejo vent.

She was involved in the study of several moon rocks that had been retrieved during the Apollo missions. By studying these rocks she was able to determine that sometime in the moon's history large meteorites struck its surface causing flood lavas. The work she did with lunar rocks is still mentioned in lunar studies to this day. Later in her career she was involved in the ACCRETE study conducted in Alaska and British Columbia.

Mount Joyce, along with nearby nunataks, such as the Trio Nunataks, represents the remnants of a tableland of the Jurassic Ferrar Group, which consists of Kirkpatrick lavas and Ferrar dolerite sills, alternating with rafts of sandstone of the Paleozoic and Mesozoic Beacon Supergroup. The strata dip about 1-2 degrees (at most) to the west. On Mount Joyce only three major dolerite sills are observed, with two thin interleaving seams of Beacon sediments.

The northwestern part of the Lochmaben Basin also has lavas of the Carron Basalt Formation at the base of the sequence. These are overlain by interbedded silty sandstones and breccio-conglomerates of the Hartfield Formation. The Hartfield Formation passes up into the thick aeolian sandstones of the Corncockle Sandstone Formation. The uppermost part of the succession is the Lochmaben Formation formed of interbedded siltstones and fine-grained sandstones with layers of coarse-grained sandstone.

John C. Reed, Jr., "Ancient Lavas In Shenandoah National Park Near Luray, Virginia," Geological Survey Bulletin No. 1265 (1969). Little of West Virginia's ancient history can be seen at the surface. Only in the extreme eastern panhandle is the Precambrian core of the Blue Ridge Mountains exposed. Except for intrusives, all of the rocks occurring above the Catoctin and Swift Run formations are of sedimentary origin, and most date to the Paleozoic Era.

The main entrance was in Glenridding at Lucy's Tongue, but an exploratory level was driven into the cliffs at the top of Glencoyne, from just below the Miners' Balcony Path. In 1955 this was incorporated into an emergency back exit from the mine. Alfred Wainwright found the hole, but thought it was just a cave. Underlying the andesite lavas of the Borrowdale Volcanic Group are the mudstones of the Skiddaw Group of rocks.

The outcrop covers an area of about and an eruptive volume of roughly . The location is heavily forested and the BC Rail mainline passes through the lower portion of the outcrop about above sea level. It represents a feature in the Squamish volcanic field. Mount Garibaldi, one of the larger volcanoes in the southern Garibaldi Belt with a volume of , is composed of dacite lavas that were erupted in the past 300,000 years.

The threat from lava flows in the Garibaldi Belt is minor unless an eruption takes place in winter or under or adjacent to areas of glacial ice, such as ice fields. When lava flows over large areas of snow, it creates meltwater. This can produce lahars that could flow further than the associated lavas. If water were to enter a volcanic vent that is erupting basaltic lava, it may create a massive explosive eruption.

A pre-caldera lava structure in the south of the complex is known as Cerro Limitayoc, but it erupted lavas even after the Panizos ignimbrite was erupted. A depression is located just south of the lava dome group and may be a downsag caldera, likewise infilled by activity. The Panizos complex covers an area of and has a total volume of . The structure of the Panizos complex has been called an "ignimbrite shield".

A saddle at a depth of depth connects it to Ta'u. A high cone in the crater bears the name Nafanua, and formed in 2004 in the western half of the crater. Prior to the formation of the cone, the crater contained several pit craters; it is possible that the crater was once occupied by a higher cone, which might have risen to shallow depths. The Nafanua cone consists mostly of pillow lavas.

Nickel deposits are generally found in two forms, either as sulfide or laterite. Sulfide type nickel deposits are formed in essentially the same manner as platinum deposits. Nickel is a chalcophile element which prefers sulfides, so an ultramafic or mafic rock which has a sulfide phase in the magma may form nickel sulfides. The best nickel deposits are formed where sulfide accumulates in the base of lava tubes or volcanic flows -- especially komatiite lavas.

Since then, eruptions have become more explosive, with viscous andesitic lavas often generating lava domes. Dome collapse has often generated pyroclastic flows, and larger explosions, which have resulted in eruption columns, have also generated pyroclastic flows through column collapse. Typically, small eruptions occur every two to three years, and larger ones every 10–15 years or so. Notable eruptions, often causing many deaths, have occurred in 1006, 1786, 1822, 1872, and 1930.

Rhomb porphyry is a volcanic rock with gray-white large porphyritic rhombus-shaped phenocrysts embedded in a very fine-grained red-brown matrix. The composition of rhomb porphyry places it in the trachyte–latite classification of the QAPF diagram. Rhomb porphyry lavas are only known from three rift areas: the East African Rift (including Mount Kilimanjaro), Mount Erebus near the Ross Sea in Antarctica, and the Oslo graben in Norway. It is intrusive.

The Ocean Drilling Program provided most of the current knowledge about the drift. The 2001 expedition drilled six seamounts and tested the samples to determine their original latitude, and thus the characteristics and speed of the hotspot's drift pattern in total. Each successive volcano spends less time actively attached to the plume. The large difference between the youngest and oldest lavas between Emperor and Hawaiian volcanoes indicates that the hotspot's velocity is increasing.

Due to the remoteness of Alcedo historical eruptions are not well recorded. There was an eruption between 1946 and 1960, as determined from variation in photographs. Another eruption in 1954 is now believed to have taken place on neighbouring Sierra Negra. Even the 1993 eruption was not observed at the time and only recorded after an expedition discovered new craters in 1995 It is the only volcano in the Galapagos to have erupted Rhyolite lavas.

35, p 227–236. have ascribed these ridges to compression and a slight shortening of the crust of Mercury after formation of most of the present surface. Some ridges, however, may represent flow fronts, but their estimated heights of several hundred meters would require formation by extraordinarily viscous lavas. Numerous faint lineaments are visible within the quadrangle, especially in the area between the Tolstoj Basin and the large crater Zeami to the northeast.

Montes Carpatus has no shortage of volcanic landforms: lava flows, pyroclatic deposits, rilles, and more! Lavas are formed as the mantle begins to melt, so by sampling volcanic rocks of various ages from regions across the Moon scientists can reconstruct the range of compositions and processes over time. The Montes Carpatus formed as a result of the giant impact that formed the mighty Imbrium basin, the mountains are actually the raised rim of the basin.

The resulting breccia is uniform in rock type and chemical composition. Lavas may also pick up rock fragments, especially if flowing over unconsolidated rubble on the flanks of a volcano, and these form volcanic breccias, also called pillow breccias. Within the volcanic conduits of explosive volcanoes the volcanic breccia environment merges into the intrusive breccia environment. There the upwelling lava tends to solidify during quiescent intervals only to be shattered by ensuing eruptions.

The emissions probably did not include methane, but the Earth was probably free of molecular oxygen. The Late Heavy Bombardment was between 4.0 and 3.8 billion years ago (Ga). To start with, the Earth did not have a crust as it does today. Plate tectonics in its present form commenced about 2.5 Ga. Early sedimentary rocks formed under water date to 3.8 Ga. Pillow lavas dating from 3.5 Ga prove the existence of oceans.

The preserve contains a Pliocene epoch volcanic center that, about ten million years ago, produced most of the lavas that underlie the East Bay ridges from Inspiration Point in Tilden Regional Park to Moraga. Geologists refer to this local volcanism as the Moraga Volcanics.USGS.gov: "Upper Cretaceous and Lower Tertiary Rocks Berkeley and San Leandro Hills, California", by J. E. Case, GEOLOGICAL SURVEY BULLETIN 1251-J, 1968.Oakland Geology Blog: "Grizzly Peak and Moraga basalt"Geology.about.

Somewhat later, andesitic lavas poured out from what is now Reading Peak and mainly flowed to the south and east, reaching the head of Warner Valley. By this time, the park's eastern portion had been transformed into a relatively flat plain. The activity was followed by an eruption of the Eastern basalts from volcanoes east of the park. These thick flows have subsequently eroded to produce rugged hills that limit the park on the east.

Pillow lava on the slopes of Chenaillet. The Chenaillet is a geological curiosity, being an ancient submarine volcano as old as 155 million years, which was uplifted to its present location during the Alpine orogeny. On the slopes of the Chenaillet are well distinguishable pillow lavas and ophiolite rocks. These features are explained on a geological foothpath reaching the summit of the mountain by some didactic panels both in French and in Italian.

The Garleton Hills create an obvious ridge, from the top of the ridge there are wide views over the lower lying areas of East Lothian. The hills are made up of layers of igneous rocks from the Carboniferous which show differing resistance to erosion. In some places the volcanic rocks are both overlaid and underlaid with sandstones. In the volcanic sequence of the hills there is hard basalt lying over trachytic lavas.

Kokfelt et al. completed an isotopic examination of the mantle plume under Iceland and found that erupted mantle lavas incorporated lower crustal components, confirming crustal recycling at the local level. Some carbonatite units, which are associated with immiscible volatile-rich magmas and the mantle indicator mineral diamond, have shown isotopic signals for organic carbon, which could only have been introduced by subducted organic material. The work done on carbonatites by Walter et al.

The second eruptive period between 1,600,000 and 1,400,000 years ago produced rhyodacite tuff, breccia, lavas and domes of . This thick geological formation lies on the south and west flanks of Pylon Peak and Devastator Peak. Its western portion consists of roughly layered tephra while its eastern end represents the lava flows and subvolcanic intrusions of a partly preserved vent. Here, The Devastator Assemblage is massive and steeply truncates basal breccia from the first eruptive period.

Two more eruptive cycles took place approximately 1.6 and 1.25 million years ago. The first eruption created the Toledo Caldera, but this feature was largely obliterated by the later Valles eruption. Each eruption involved pyroclastic flows and produced some of the welded tuff now found west of the Rio Grande. There have been numerous eruptions of sticky lavas in the last 1.25 million years ago, but all have been within the Valles Caldera.

It was followed by a tour with Randy Crawford (1983), also contributing on the album Fire (1984). This is Lavas best-selling albums and it was awarded Spellemannsprisen (1984) in the class Pop. Later, the group released Prime Cuts (1985), Rhythm of Love (1990) and The Very Best of Lava (1996). On the next two albums Polarity (2003) and Alibi (2005), Geir Langslet was substituted by Stein Austrud (keyboards) Kåre Kolve contributed as saxophonist.

Colours indicate the age of oceanic crust, wherein red indicates the youngest age, and blue indicates the oldest age. The lines represent tectonic plate boundaries. Continental and oceanic crust on the upper earth mantle Oceanic crust is the uppermost layer of the oceanic portion of a tectonic plate. It is composed of the upper oceanic crust, with pillow lavas and a dike complex, and the lower oceanic crust, composed of troctolite, gabbro and ultramafic cumulates.

Also called "vertical tectonics" because structures move vertically due to gravity-driven instabilities. The deformation that occurs within the greenstone belts represents a dome-and-keel structure or the rise of diapiric plutons. This model provides an explanation for the dome-and-keel structure associated with greenstone belts. When dense basaltic lavas erupt on top of ductile, less dense TTGs they become weighed down by the overburden and squeeze out from areas with less stress.

In the area extending between Gümüşhane and Torul, there are extensive formations consisting of various types of extrusive, igneous rock, including andesitic and basaltic lavas, tuffs and agglomerates. The total thickness of these deposits reaches . These igneous strata are interleaved with sedimentary layers, varying in thickness between and consisting of limestone and certain other types of sedimentary rock. The Karaca Cave formed in one of these layers of highly fissured, massive limestone sandwiched between volcanics.

The stones are glacial erratic boulders composed of volcanic rock from the Borrowdale Volcanic Group. Both andesitic lavas and tuffs (volcanic ashes) are represented.Personal Observations by Rockhead9 Castle Rigg sits on a deposit of glacial till,British Geological Survey GeoIndex and it is likely that the boulders were originally part of this deposit. The stones are set in a flattened circle, measuring 32.6 m (107 ft) at its widest and 29.5 m (97 ft) at its narrowest.

By comparison with neighbouring basins both Paleozoic and Mesozoic sequences are expected to be present in the Hatton Basin. The proven Cenozoic sequence starts with Paleocene lavas, part of the North Atlantic Igneous Province, overlain by Eocene claystones. There is then a major hiatus, with the next youngest preserved strata above the unconformity (known regionally as C30) being of Upper Eocene to Lower Oligocene age. The remainder of the sequence consists of Miocene to Pleistocene calcareous oozes.

When lava flows were erupted from Tuber Hill, they interacted with the valley-filling glaciers on its southern flank and produced a glacial meltwater lake. Here, more than of stacked hyaloclastite, lahars and lacustrine tuff were deposited. A series of pillow lavas were also deposited during this eruptive period. The most recent volcanic activity in the Bridge River volcanic field produced a series of basaltic lava flows in the regional valleys that overlie till of the last glacial period.

The phosphine can be generated by geological process of weathering an olivine lavas containing inorganic phosphides, but this process requires an ongoing and massive volcanic activity. Therefore, detectable amounts of phosphine could indicate life. In a statement published on October 5, 2020 on the website of the International Astronomical Union's commission F3 on astrobiology, the authors of the September 2020 paper about phosphine were accused of unethical behaviour and criticized for being unscientific and misleading the public.

Basaltic over shoshonitic (both 25 and 21 m) to andesitic (post-Miocene) lavas are found in the southern Altiplano. Ignimbrites deposited during eruptions of APVC volcanoes are formed by "boiling over" eruptions, where magma chambers containing viscous crystal- rich volatile-poor magmas partially empty in tranquil, non-explosive fashion. As a result, the deposits are massive and homogeneous and show few size segregation or fluidization features. Such eruptions have been argued to require external triggers to occur.

Mare Desiderii was later found to be composed of a smaller mare, Mare Ingenii (Sea of Cleverness), and several other dark craters. The reason for this difference between the two sides of the Moon is still not fully understood, but it seems that most of the dark lavas that flowed out to produce the maria formed under the Earth-facing half. Luna 3 was followed by the United States with Ranger 7, Ranger 8, and Ranger 9.

Thanks to heavy erosion, lavas and eruption products are mostly found in peripheral parts of the edifice, while in the central area a deep-grounded crystalline core is exposed. A breach wide and long with an azimuth of 139° lies in the volcano, whose summit has a maximum slope of 25°. The volcano forms a lineament with Saxani and Isluga. The creeks named Qhamiña (Camiña) and on the western side Waywasi (Guayhuase) originate on the volcano.

Long belts of gabbroic intrusions are typically formed at proto-rift zones and around ancient rift zone margins, intruding into the rift flanks. Mantle plume hypotheses may rely on identifying mafic and ultramafic intrusions and coeval basalt volcanism. Nearly all gabbros are found in plutonic bodies, and the term (as the International Union of Geological Sciences recommends) is normally restricted just to plutonic rocks, although gabbro may be found as a coarse-grained interior facies of certain thick lavas.

The volcanic cluster was modestly glaciated during the Quaternary, as evidenced by glacial striations and moraines at elevations above , and shows evidence of glaciers both on the main volcano and its subsidiaries. At least two distinct glacier stages took place. The western Azufrera edifice was heavily glaciated in the past. At least three moraine stages have been mapped on that edifice, and on its southern side is found a modest cirque with glacially polished lavas on the floor.

Melanite is found in some of the lavas, as in the leucite syenites. Thin section of leucitophyre from Laacher See, Germany The rocks in which orthoclase (or sanidine) is present in considerable amount are leucite-trachytes, leucite- phonolites and leucitophvres. Of these groups the two former, which are not sharply distinguished from one another by most authors, are common in the neighborhood of Rome. They are of trachytic appearance, containing phenocysts of sanidine, leucite, augite and biotite.

These eroded areas exhibit pyroclastic rock in a matrix with lava flows, suggesting that blocky and ʻaʻā lavas formed an outer shell around Pelican Butte's fragmented interior. Glaciation has also lowered the overall volcano by tens of yards. Other volcanoes can be found within the Sky Lakes Wilderness area, including lava flows and mud flows at Big Bunchgrass Butte and Imagination Peak, in addition to more recent eruptive activity at Goosenest Mountain in the northeastern sector.

The lower slough nears Oregon Route 99E (Martin Luther King, Jr. Boulevard). Mount Hood is visible behind the levee at the left. The Columbia Slough is part of the roughly Portland Basin, which lies at the northern end of the Willamette Valley of Oregon and extends north into Clark County in the state of Washington. The region is underlain by solidified lavas of the Columbia River Basalt Group that are up to 16 million years old.

2016 60 cm orthophoto mosaic overlaid on 3 m slope map (derived from digital elevation model). Scale 1:50,000. About 593,000 years ago, andesitic lavas erupted in what is now Mount Shasta's western flank near McBride Spring. Over time, an ancestral Mount Shasta stratovolcano was built to a large but unknown height; sometime between 300,000 and 360,000 years ago the entire north side of the volcano collapsed, creating an enormous landslide or debris avalanche, in volume.

The final phases of mountain building occurred as Laurentia completed its collision with Gondwana and Europe to form the supercontinent Pangea. Beginning around 200 million years ago, rifting broke apart Pangea. Erupting basalt lavas formed the new oceanic crust of the Atlantic Ocean, wedging apart Africa, Europe and North America along the approximate lines where the continents collided. The Connecticut River Valley and the Middleton Basin formed as failed rifts, filling with sediment that preserve dinosaur footprints.

Lesser Antillean Iguana The reserve exhibits surface features which are considered the earliest phase of the geological history of the Lesser Antilles. Geological formations consists of basalt flows or pillow lavas with radiolarites which represent underwater volcanic activity. Radiolarites are intercalated with thin beds of siliceous sedimentary rocks in laminated forms, in colours of red, brown and green. It is also reported that these formations are a result of the accumulation of shells in deep ocean areas.

Divers observed that these hills are constructed mainly of pillow lavas that are without sediment cover, indicating they are new or young. Sediment covers most of the inner valley floor away from these hills indicating accretion is not taking place beyond the hills. Conceptual models suggest that volcanism within the valley floor is cyclic or episodic, with volcanic activity recurring every 5,000 to 10,000 years. The observed continuous background seismicity infers that faulting is continual and ongoing.

The second eruption produced a lava flow that was erupted when the vent area was not buried under glacial ice. However, the flow does show evidence of interaction with glacial ice at its lower unit. This indicates that the lavas were erupted during the waning stages of the Fraser Glaciation. The third and most recent eruption produced another lava flow that was largely erupted above glacial ice, but was probably constrained on its northern margin by a small glacier.

These (Armstrong Canyon/Division Creek/Taboose Creek) flows were erupted during the same episode, which created Armstrong Canyon cone, a series of scoria cones and the three lava flows along a long tract of the Sierra Nevada fault. This episode may have generated as much as of tephra, and lava flows interacted with water forming palagonite. The lavas from this event and the Blackrock Springs lava were later eroded by Owens Lake during its last glacial maximum highstand.

Recycling of existing primordial crust contributes to the production of secondary crust. Partial melting of the existing crust increases the mafic content of the melt producing basaltic secondary crust. A further method of formation due to the decay of radioactive elements within the Earth releasing heat energy and eventually causing the partial melting of upper mantle, also producing basaltic lavas. As a result, most secondary crust on Earth is formed at mid ocean ridges forming the oceanic crust.

Overhead view of the Marius Hills taken by Lunar Reconnaissance Orbiter. Oblique view of eastern Marius Hills and Marius crater (upper right) by Lunar Orbiter 2 Oblique view of Marius Hills by Apollo 12 The "hole" in Marius Hills The Marius Hills are a set of volcanic domes located in Oceanus Procellarum on Earth's Moon. The domes are thought to have formed from lavas fairly more viscous than those that formed lunar mares. These domes average approximately in height.

These rocks in western Graham Land include andesite lavas and granite from the magma, and indicate Graham Land was a continuation of the Andes. This line of volcanoes are associated with subduction of the Phoenix Plate. Metamorphism associated with this subduction is evident in the Scotia Metamorphic Complex, which outcrops on Elephant Island, along with Clarence and Smith Islands of the South Shetland Islands. The Drake Passage opened about 30 Ma as Antarctica separated from South America.

The Ochoa Point Member is thick and forms steep slopes and cliffs below the Cardenas Basalt. The Dox Formation that directly underlies the Cardenas Basalt consists of brick-red to vermilion well-bedded sandstone, with parallel bedding and shaly partings, forming smooth slopes. It also contains a thin, discontinuous basaltic lava flow.Lucchitta, I, and JD Hendricks (1983) Characteristics, depositional environment and tectonic interpretations of the Proterozoic Cardenas Lavas, eastern Grand Canyon, Arizona. Geology. 11(3):177–181.

Thus, the contact between the Cardenas Basalt and the Dox Formation is conformable and interfingering. This indicates that sands were still being deposited when the first lavas erupted and that deposition occurred during the transition from the accumulation of Dox Formation to Cardenas Basalt.Timmons, JM, J. Bloch, K. Fletcher, KE Karlstrom, M Heizler, and LJ Crossey (2012) The Grand Canyon Unkar Group: Mesoproterozoic basin formation in the continental interior during supercontinent assembly. In JM Timmons and KE Karlstrom, eds.

Some outflows are more than thick. Several different dates have been determined on the basis of argon-argon dating, including 3.55±0.01 on biotite and 3.49±0.01 mya on sanidine, which is the preferred age. The Chajnantor lavas and the Rio Guacha dome in the caldera have been K-Ar dated at 3.67±0.13 and 3.61±0.02 mya respectively. This ignimbrite ponded inside the Guacha caldera, and one particularly thick layer (>) is found beneath Zapaleri stratovolcano.

Lavas from Medicine Lake Volcano are estimated to be at least in volume, making Medicine Lake the largest volcano by volume in the Cascade Range (Newberry Volcano in Oregon has the second largest volume). Lava Beds National Monument lies on the northeast flank of the volcano. Medicine Lake Volcano has been active for 500,000 years. The eruptions were gentle rather than explosive like Mount St. Helens, coating the volcano's sides with flow after flow of basaltic lava.

These domes in clockwise direction are known as Cerro Lucho, Cerro Lucha, Cerro Agua Dulce and Cerro Pairique Chico and rise above the Bajo de Pairique, the centre of the wide semicircle. Most of these domes have been affected by lateral or centre-ward sector collapses. Eruption products associated with Pairique are the Pairique Chico block and ash flow, the Arco Jara ignimbrite and the Cerro Lucho lavas. All of these do not exceed of volume.

Another theory believes the Stariy and Treshina cones formed first in the whole field. The most recent model states that Staryi and Treshchina erupted in the first phase, their lavas being buried beneath more recent eruption products. Atkinson, Ostanets and Peretolchin shortly afterwards then filled the valley with lava. Kropotkin erupted in the third phase and Pogranichnyi in the fourth, both being accompanied by activity at additional vents and the latter taking place about 900 years ago.

Girekol is a volcano in Turkey. It is an alkaline shield volcano and the youngest activity goes back to 0.36 +/- 0.06 Ma. The volcano's eruption products are plagiophyric trachybasaltic lavas and is among the youngest eruption activities on the northern coast of Lake Van and overlie in part older volcanic products. The volcano is part of a volcanic province together with neighbouring Meydandag and Etrüsk volcanoes that is associated with a regional geological structure named "Lake Van dome".

The Keli (Qeli) Highland (, qelis zegani) is a volcanic field in Georgia on the western side of the Jvari Pass south to the Greater Caucasus range. More than thirty volcanic edifices on an area of 20x30km2 make up this volcanic field, which consists mostly of monogenetic volcanic structures. The lavas are rhyolites, trachyandesites and andesites. The rivers Tetri Aragvi, Patara Liakhvi, Ksani and Didi Liakhvi originate from the Keli volcanic area, and some peaks drain into the Terek river.

After the formation of the caldera, eruptions were localized to its edge and formed more than ten of small craters, mostly on the northern edge. The products were dominated by viscous trachyte and rhyolite lavas. Pyroclastic flow deposits were accumulating on the bottom of the caldera, forming ignimbrites and obsidian, and sometimes slag pumice. A cone-shaped crater Göltepe (height 2,485 m above sea level) formed at the bottom of the caldera, on the fault line.

The Crater lavas are 55.9 ± 26.8 ka old. The block and ash flow on the southwestern flank was formed 1570 ± 900 years BP. Historical activity of Irruputuncu is unclear. An unconfirmed eruption was reported in Bolivia in December 1989 and fumarolic activity in the crater was reported on 25 March 1990. Eruption plumes on Irruputuncu, which reached an altitude of and dispersed to the east, probably triggered by phreatomagmatic activity, were seen on 26 November 1995.

Igneous rocks can become foliated by alignment of cumulate crystals during convection in large magma chambers, especially ultramafic intrusions, and typically plagioclase laths. Granite may form foliation due to frictional drag on viscous magma by the wall rocks. Lavas may preserve a flow foliation, or even compressed eutaxitic texture, typically in highly viscous felsic agglomerate, welded tuff and pyroclastic surge deposits. Metamorphic differentiation, typical of gneisses, is caused by chemical and compositional banding within the metamorphic rock mass.

The sodium and potassium carbonate minerals of the lavas erupted at Ol Doinyo Lengai are unstable at the Earth's surface and susceptible to rapid weathering, the minerals are anhydrous and when they come into contact with the moisture of the atmosphere, they begin to react extremely quickly. The black or dark brown lava and ash erupted begins to turn white within a few hours. The resulting volcanic landscape is different from any other in the world.

Diagram of the remains of Maitland Volcano After Maitland Volcano became extinct, prolonged erosion destroyed the volcanic edifice. The reason why Maitland eroded away while its neighbour, Edziza, did not is twofold. With the cessation of volcanic activity, Maitland Volcano was unable to protect itself from erosion by providing a cover of younger lavas on top of the older shield. Another factor is that Maitland's basement was built entirely of soft, friable sedimentary rocks of the Bowser Lake Group.

The rocks of Montiferru are the remains of an extinct volcanic complex, covering an area of about , that was active 3.9 to 1.6 million years ago during the Pliocene and Pleistocene epochs of the Earth's geological history. The volcanic activity was at its most intense 3.6 million years ago. The volcano erupted a wide variety of lavas including basanite, hawaiite, phonolite, mugearite, benmoreite and trachyte, as well as small amounts of basaltic andesite and basaltic trachyandesite.

Izquierdo is a crater on Mercury located to the east of Beagle Rupes and Sveinsdóttir crater. The floor of Izquierdo is smooth, the result of having been partially filled with volcanic lava. Circular outlines of the rims of “ghost craters” – smaller, older craters that have been largely buried by the lavas that infilled the basin – are visible in a few places on Izquierdo’s floor. The remnants of a buried inner ring are also barely discernible in spots.

The hotspot is believed to be over 20 million years old and in that time there has been interaction between the hotspot, both of these plates, and the divergent plate boundary, at the Galapagos Spreading Centre. Lavas from the hotspot do not exhibit the homogeneous nature of many hotspots; instead there is evidence of four major reservoirs feeding the hotspot. These mix to varying degrees at different locations on the archipelago and also within the Galapagos Spreading Centre.

Rio Grande Gorge The Taos Plateau volcanic field is an area of extensive volcanism in Taos County, New Mexico, United States. It is the largest volcanic field in the Rio Grande Rift, spreading over 7,000 km2. The age of most of the vents and associated lava flows in the field is estimated to be between 1.8 and 4 million years, with a few 22-million-year-old vents. The composition of the lavas varies from tholeiitic basalt to rhyolite.

The summit area composes the plagioclase-phyric andesite lavas of the Birker Fell Formation. A band of volcaniclastic sandstone passes near to the actual top. Further south are outcroppings of the Whorneyside Formation (bedded tuff and sandstone with some breccias, interspersed with andesite sills.) The lower slopes are covered by drift.British Geological Survey: 1:50,000 series maps, England & Wales Sheet 29: BGS (1999) Dubs Quarry at the foot of the northern slope is an extensive slate working, now abandoned.

The north eastern flanks are overlain by drift deposits with the plagioclase-phyric andesite lavas of the Birker Fell Formation beneath. The rest of the fell exhibits rock of the Ennerdale Intrusion, granophyric granite.British Geological Survey: 1:50,000 series maps, England & Wales Sheet 29: BGS (1999) Iron Crag Mine operated below the crag of that name from around 1864 to 1896. 500 tons of haematite ore was raised in 1881, but the mine never proved a commercial success.

Harris, Stephen (2001). Fire Mountains of the West, page 75 Known as the Loomis Sequence, these pre-Lassen dacites are the black, glassy, columnar lavas that now encircle Lassen Peak. Sometime between 25,000 and 31,000 years ago, Lassen Peak, a Pelean lava dome volcano, was pushed up through the pre-Lassen dacites. Lassen grew past the normal maximum size of plug dome volcanoes, , and reached a height of above the surrounding plateau in as little as a few years.

In December 1878, after being ordained as a minister, Ward assumed the curacy of St. John's Church in Keswick. Early in 1880, Ward was appointed vicar of Rydal. Ward died on 15 April of the same year. Ward was among the first to appreciate the importance of Clifton Sorby's method of using the microscope for the study of the composition and structures of rocks, and applied it to the old lavas and ash-beds of the Lake district.

This formation integrated lavas, basaltic pyroclasts, tuff cones and trachyte domes into two layers (referred to as the Ponta Delgada and Penhal da Paz sub-depoists) and compiled to about 5,000 years ago. The peak area between Sete Cidades and Fogo is a monogenetic volcanic field composed of 270 volcanoes. They are primarily made up of basaltic cones which were formed during Strombolian and Hawaiian-style eruptions. This is the part of the island with most recent volcanic activity.

Scurdie Ness is a Geological Conservation Review (GCR) site. The Old Red Sandstone, lavas and associated sedimentary rocks found there are part of the Montrose Volcanic Formation. These rocks were formed around 410 million years ago from lava being erupted from a volcano lying to the north-east in the North Sea and known as the Montrose volcanic centre. Scurdie Ness is renowned for its agates formed by fluids flowing through the lava and depositing silica in cavities.

The highest point on the dominantly basaltic island reaches 550 m, about 190 m above the lake surface. An E-W-trending chain of small explosion craters cuts the eastern side of the 3-km-wide island. Several small islands to the SE represent partially submerged crater rims, and other cones and lava plugs lie beneath the lake surface near the island. The youngest Central Islands tuffs and lavas may be as young as Holocene (Karson and Curtis, 1992).

The Azas Plateau was affected by an ice sheet which formed on the East Sayan mountains during the Pleistocene. When volcanoes erupt into ice, the ice melts and volcanic structures named tuyas can form in meltwater lakes. Runny lavas can form such edifices, which tend to have steep slopes, only when trapped within ice. During tuya activity, the subaqueous activity forms hyaloclastite and when the activity occurs in the air lava flows are formed, including lava deltas.

Victory is dominantly Andesitic in origin, but also has traces of Basalt and Dacite, the lavas erupted have an unusually high level of Chromium and Nickel. The volcano is densely forested in all but the summit crater. On the sides of the volcano (near the summit) are four lava domes, two on the SW flank and two on the NE flank. The summit crater is breached to the SE and was probably created by a landslide.

Dikes, lava domes, lava flows and pyroclastic deposits are found in outcrops. Mason Spur also contains breccias from pillow lavas, while Gandalf Ridge features a diamictite and a cross-cutting fault. Owing to the lack of running water, the edifice is uneroded and parasitic vents have a young appearance. Glacial erosion has eroded some parts of the volcano, leaving volcanic necks in Pinnacle Valley, has etched glacial striations into exposed volcanic rocks and deposited glacial till.

Thus, the term depleted MORB mantle (DMM) is often used to describe the upper mantle that sources mid-ocean ridge volcanism. Ocean island basalts also sample geochemically depleted mantle domains. In fact, most ocean island basalts are geochemically depleted, and <10% of ocean island basalts have lavas that extend to geochemically enriched (i.e., 143Nd/144Nd lower than the Earth’s building blocks) compositions. There are two geochemically enriched domains, named enriched mantle 1 (EM1), and enriched mantle 2 (EM2).

The formation is interpreted as indicative of a Jurassic marine regression showing a successive shallowing of deep marine environments (pillow lavas, turbidites) to shallow marine environments (limestone) and culminating with an upper region displaying a continental environment (paleochannels). Tectonically, the formation is assumed to have deposited either in the westernmost fringes of Neuquén Basin or in an intra-arc basin. In both cases the formation must have been deposited very close to a volcanic arc, active in the Jurassic.

However, some sills do not usually have brecciated margins, and may show a weak metamorphic aureole on both the upper and lower surface, whereas a lava will only bake the substrate beneath it. However, it is often difficult in practice to identify these metamorphic phenomena because they are usually weak and restricted in size. Peperitic sills, intruded into wet sedimentary rocks, commonly do not bake upper margins and have upper and lower autobreccias, closely similar to lavas.

The site was unusual in being made of distinctive layers of different-colored lavas and ash. Although there was no way at that time of accurately dating the layers, they did indicate the relative age of the deposits. In December 1913 one of the workmen found a bone protruding from one of the oldest layers, Bed II, at a level where extinct animals from the Pleistocene had been found. He started to excavate, then told Reck of his find.

Foden, 1979, p. 49 Olivine is most present in the rocks with less than 53 percent SiO2, while it is absent in the more silica-rich volcanics, characterised by the presence of biotite phenocrysts.Foden, 1979, p. 50 The mafic series also contain titanium magnetite and the trachybasalts are dominated by anorthosite-rich plagioclase.Foden, 1979, p. 51 Rubidium, strontium and phosphorus pentoxide are especially rich in the lavas from Tambora, more than the comparable ones from Mount Rinjani.Foden, 1979, p. 56 The lavas of Tambora are slightly enriched in zircon compared to those of Rinjani.Foden, 1979, p.60 The magma involved in the 1815 eruption originated in the mantle and was further modified by melts derived from subducted sediments, fluids derived from the subducted crust and crystallization processes in magma chambers. 87Sr86Sr ratios of Mount Tambora are similar to those of Mount Rinjani, but lower than those measured at Sangeang Api. Potassium levels of Tambora volcanics exceed 3 weight percent, placing them in the shoshonite range for alkaline series.

With the widespread availability of geothermal power, and the harnessing of many rivers and waterfalls for hydroelectricity, most residents have access to inexpensive hot water, heating and electricity. The island is composed primarily of basalt, a low-silica lava associated with effusive volcanism as has occurred also in Hawaii. Iceland, however, has a variety of volcanic types (composite and fissure), many producing more evolved lavas such as rhyolite and andesite. Iceland has hundreds of volcanoes, with approximately 30 active volcanic systems.

The Bitiche lavas cover the 8.4 million years old Vilama ignimbrites and are in part covered by the 3.49 ± 0.01 million years old Tara ignimbrite, indicating that the field formed in the late Miocene- early Pliocene at the time where volcanism in the Altiplano-Puna volcanic complex reached its maximum. The volcanic activity that formed the scoria cones was probably mainly strombolian with some lava fountaining. The start of volcanic activity may have been preceded by hydrovolcanic processes that have left characteristic deposits.

The Cardenas Basalt, also known as either the Cardenas Lava or Cardenas Lavas, is a rock formation that outcrops over an area of about 310 km2 (120 mi2) in the eastern Grand Canyon, Coconino County, Arizona. The lower part of the Cardenas Basalt forms granular talus slopes. Its upper part forms nearly continuous low cliffs that are parallel to the general course of the Colorado River. The most complete, readily accessible, and easily studied exposure of the Cardenas Basalt lies in Basalt Canyon.

Contrary to rumors, Pinnacle Mountain is not a volcano. Despite its resemblance to a cinder cone, Pinnacle Mountain is composed of deep-water sedimentary rock, the Pennsylvanian Jackfork Sandstone. Named for Jackfork Mountain in Pittsburg and Pushmataha counties, Oklahoma, the Jackfork Sandstone at Pinnacle Mountain is massive, fine- to coarse-grained, mostly tan quartzitic sandstone of great hardness. Cinder cones, on the other hand, form from the eruption of mafic lavas and are composed of extrusive igneous rocks such as basalt.

The cliffs and rocky beach at Middle Hope At Middle Hope a sequence of carboniferous limestone is exposed, which includes thick volcanic tuffs and lavas, demonstrating Tournaisian carbonate sections. The site contains a Pleistocene-aged fossil cliff and shore platform. These features have led to the designation of Middle Hope as a regionally important geological site (RIGS). The raised beach of wave-cut platforms has been created by changes in sea level of the Bristol Channel since the Quaternary period.

100,000 years ago during the Valdivia Interglacial the ancestral Villarrica collapsed following an eruption and formed a large elliptical caldera of 6.5 and 4.2 km in diameter. During the Llanquihue glaciation Villarrica produced pyroclastic flow deposits, subglacial andesite lavas and dacite dykes. It collapsed once again 13,700 years ago forming a new smaller caldera, among other pyroclastic flows the Licán Ignimbrite has been related to this event. Beginning with the Licán Ignimbrite, generated just after the last deglaciation, activity continued in similar fashion.

This lava flow is joined by other lava flows from the , a small cone in the southwestern sector of the volcanic field; the lavas of this cone however are andesitic and basaltic. is a large lava flow of acidic rocks that is long in the northern sector of the volcanic field, close to the outlet of Laguna del Maule. It consists of two lobes with a volume of about and contains obsidian and vitrophyre. Crystals within the flow reflect the sunlight.

Some colleagues were skeptical of the hypothesis because of the numerous assumptions made—seafloor spreading, geomagnetic reversals, and remanent magnetism—all hypotheses that were still not widely accepted. The Vine–Matthews–Morley hypothesis describes the magnetic reversals of oceanic crust. Further evidence for this hypothesis came from Cox and colleagues (1964) when they measured the remanent magnetization of lavas from land sites. Walter C. Pitman and J.R. Heirtzler offered further evidence with a remarkably symmetric magnetic anomaly profile from the Pacific-Antarctic Ridge.

During the Maastrichtian, an alkali syenite dome near Saint Louis intruded sand deposits. By the early Cenozoic, the ocean retreated, except in the Casamance Gulf and by the Eocene, the region was experiencing intense, terrestrial weathering. The Cap-Vert experienced two peaks of volcanism, one in the Miocene and the other in the Quaternary, producing small occurrences of undersaturated, alkaline lavas. During the Quaternary, volcanism at the head of the Cap-Vert peninsula built the Mamelles volcano and its associated vents and flows.

Palagonite tuff and pillow lava, resulted from rapid cooling of lava in contact with seawater. São Tomé is the younger island and 15.7 million year old trachyte is the oldest rock type on the island from the time volcanic activity began. Most other lavas formed between 13.2 million years ago and the present. The basalts have alkaline lava mineralogy, with large augite, olivine and magnetite phenocryst crystals, surrounded by a matrix of smaller crystals such as bytownite, labradorite, augite, titanite and iron oxides.

During the Paleocene to Early Eocene Skye formed one of the main volcanic centres of the North Atlantic Igneous Province. Gently dipping lavas from the volcanoes cover most of northern Skye, giving a stepped trap type landscape. The dominant lava type is basalt, with subsidiary hawaiite and mugearite derived from silica-poor magma and minor amounts of trachyte from a silica-rich magma. Part of the magma chambers for the volcanoes are exposed at the surface as major intrusions of gabbro and granite.

Most of the dykes are basaltic in composition but a minority are trachytic. The dominant trend of the dykes is northwest-southeast although they are locally in part radial near the old volcanic centre. On the Trotternish peninsula, mafic magma was intruded along the bedding planes of the Jurassic sedimentary rocks beneath the lavas to form sills that are up to 90m thick. They commonly display columnar jointing, such as in the upper part of the Kilt Rock at Staffin.

This basin was formed by the subduction and orogenesis along the southern border of what eventually became Southern Africa, in southern Gondwana. Its sediments attain a maximum cumulative thickness of 12 km, with the overlying basaltic lavas (the Drakensberg Group) at least 1.4 km thick.Adelmann, D. and Kerstin Fiedler, (1996). Sedimentary development of the Upper Ecca and Lower Beaufort Groups (Karoo Supergroup) in the Laingsburg subbasin (SW Karoo Basin, Cape Province/South Africa) , Schriftenreihe der Deutschen Geologischen Gesellschaft, 1: 88–89, Bonn.

The Arnold Lava Tube System (or Arnold system) is series of lava tubes in Deschutes County, Oregon, in the United States. It is located several miles southeast of the city of Bend. The system starts in the Deschutes National Forest on the northern flank of Newberry Volcano, heads northeast onto BLM land before finally terminating on private property near Horse Ridge. The system acted as a conduit for the lavas from Lava Top Butte that later fed the Badlands rootless shield.

This is evidence of explosive eruptions during Fee's eruptive history, as well as its first volcanic event. The second volcanic event produced a sequence of volcanic rocks on Fee's eastern flank. This volcanic material was likely deposited when a sequence of lava flows and broken lava fragments erupted from a volcanic vent and moved down the flanks during the construction of the ancestral Mount Fee. Following extensive dissection, renewed volcanism produced a viscous series of lavas on its northern flank.

Layers of mafic and ultramafic intrusive rocks forming the mountain of Hallival The Rum layered intrusion is located in Scotland, on the island of Rùm (Inner Hebrides). It is a mass of intrusive rock, of mafic-ultramafic composition, the remains of the eroded, solidified magma chamber of an extinct volcano that was active during the Palaeogene Period. It is associated with the nearby Skye intrusion and Skye, Mull and Egg lavas. It was emplaced 60 million years ago above the Iceland hotspot.

A variety of trachybasalt from Yamalo-Nenets Autonomous Okrug in Russia, known there as enzorite Satellite image of Bayuda volcanic field in Sudan where nepheline-rich trachybasalt lavas have been erupted during the Holocene epoch Trachybasalt is a volcanic rock with a composition between trachyte and basalt. Minerals in trachybasalt include alkali feldspar, calcic plagioclase, olivine, clinopyroxene and likely very small amounts of leucite or analcime.Trachybasalt Trachybasalt is a basalt with high alkali content (5 to 7% Na2O + K2O, see TAS diagram).

A chemical analysis of the lavas of the volcanoes indicated that the materials erupted from the volcanoes are relatively primitive. With the exception of one, the volcanoes form a nearly linear chain of circular volcanic cones. The second volcano from the northwest is not discretely shaped like the rest, rather it is a rough structure of lava cones and flows, which cover an area of at least . The six conical volcanoes (not including the odd one) range from in volume, averaging .

The principal sector collapse occurred after the Ch'aska Urqu stage. It was followed by the eruption of andesitic lava flows and the compound lava dome in the summit region, all focused into the collapse scar; this focusing is a phenomenon noted at other volcanoes which underwent flank collapses such as Planchón-Peteroa. This formation has been named the Santa Cecilia series. The compound summit lava dome probably fills the collapse scar but young lavas and glacial erosion make this assessment difficult.

The basement beneath Ampato is formed by sedimentary and volcanic rocks of the Western Cordillera of Peru, and the rocks are of Mesozoic to Cenozoic age. A high plateau formed by ignimbrites and lavas of Pliocene to Miocene age rises above this basement. The terrain is cut by several different fault systems; one of these, the northeastward striking Sepina fault has been seismically active in the 20th and 21st centuries and seems to have controlled the development of the Ampato and Sabancaya volcanoes.

The Kaminak and Yathkyed belts are overlain by the Proterozoic (2.45 Ga) Hurwitz Group. Deformation of the Hurwitz Group occurred after the 2.11 Ga intrusion of gabbro sills, but prior to the intrusion of the 1.83 Ga lamprophyre dykes associated with the ultrapotassic lavas of the nearby Baker Lake Basin. Parallel to the Paleoproterozoic Hurwitz Group is massive veins of green biotite that are interpreted to have been emplaced there by a hydrothermal event accompanying a deformation along this contact area.

They were separated by an ocean, called the Iapetus Ocean by geologists. The line of joining, or suture, is approximately under the Solway Firth and Cheviot Hills. In the Lake District, the junction between the early Ordovician series, Skiddaw Slate, and the Borrowdale Volcanic that was forced under it, can be seen on the slopes of Fleetwith Pike. In the English Lake District, the Borrowdale Volcanic Group is composed of lavas (mainly andesites), tuffs and agglomerates, along with some major igneous intrusions.

Caldera Pico de Orizaba evolved in three stages, the most recent initiated about 16,000 years ago during the late Pleistocene and Holocene. Citlaltépetl consists of three superimposed stratovolcanoes and dome intrusions which are: Torrecillas (650–250 ka), Espolón de Oro (210– 16 ka), and Citlaltépetl (16 ka to present). The volcano was formed by thick andesitic and dacitic lavas that followed repetitive explosive eruptions and lava effusions which created the iconic cone structure. The volcano is currently dormant but not extinct.

Cerro Overo is a maar lying at the foot of Chiliques volcano and close to Laguna Lejía, in the Antofagasta Region of northern Chile over ignimbrites of Miocene-Pliocene age. It is the result of a phreatomagmatic eruption, its maximum diameter is and its depth is . The maar formed in postglacial times and erupted basalts that originated in the deep crust, with no magma chamber. The lavas are of lower crustal provenience and are among the least evolved of northern Chile.

The remaining product from Fee's earliest volcanic activity is a minor portion of pyroclastic rock. This is evidence of explosive volcanism from Fee's eruptive history, as well as its first volcanic event. The second volcanic event produced a sequence of lavas and breccias on the eastern flank of the main ridge. These volcanics were likely placed when a sequence of lava flows and broken lava fragments erupted from a volcanic vent and moved down the flanks during the construction of a large volcano.

Vífilsfell is part of a 10 km long mountain massif, the Bláfjöll, which are directed northeast to southwest. This corresponds well with the other mountain ranges and fissure systems of the region, the Reykjanes peninsula in Southwest Iceland. The subglacial mound even builds an escarpment reaching out the north, where mostly older lava fields are to be found, whereas to the south, younger Aa lavas form a landscape characterized by cragged ridges and fissures, with only some smoother Pahoehoe in between.

The remaining products from Fee's earliest volcanic activity is a minor portion of pyroclastic rock. This is evidence of explosive volcanism from Fee's eruptive history, as well as its first volcanic event. The second volcanic event produced a sequence of lavas and breccias on the eastern flank of the main ridge. These volcanics were likely deposited when a sequence of lava flows and broken lava fragments erupted from a volcanic vent and moved down the flanks during the construction of a large volcano.

Dacitic lapilli tuff of the Helvellyn Tuff Formation (Helvellyn Basin succession), on High Crag (Nethermost Pike) The Borrowdale Volcanic Group (BVG) lies unconformably above the Skiddaw Group, and is of Caradocian age. It is similar to, but distinct from, the Eycott Volcanic Group. It consists of a thick sequence of basaltic, andesitic, dacitic and rhyolitic lavas and pyroclastic rocks with interbedded volcaniclastic sediments. It is subdivided informally into two parts known as the Lower Borrowdale Volcanic Group and Upper Borrowdale Volcanic groups.

The northern terrane is dominated by tonalites and is the least metamorphosed section. It also contains zircon ages of approximately 3710-3690 million years old. The southern portion of the Isua Greenstone Belt contains approximately 3900-3810 million year old zircons with an abundance of amphibolite, schist, carbonate rock, volcanics, pillow lavas, and ultramafics. The northern portion makes up the area where many scientific studies have been conducted and offers up the evidence leading scientists to propose the following hypothesis.

A major subfeature of Hualālai is Puu Waawaa, Hawaiian for "many-furrowed hill", a volcanic cone standing tall and measuring over in diameter. It extends for , and has a prominence of , north of the summit at . The cone is constructed of trachyte, a type of volcanic lava that exists at no other volcano on Hawaii. Trachyte flows move more slowly than the typically "runny" Hawaiian lavas, a characteristic caused by its high (over 62%) silica composition (typical basalt is only 50% silica).

As early as the 18th century, it was noticed that compass needles deviated near strongly magnetized outcrops. In 1797, Von Humboldt attributed this magnetization to lightning strikes (and lightning strikes do often magnetize surface rocks). In the 19th century studies of the direction of magnetization in rocks showed that some recent lavas were magnetized parallel to the Earth's magnetic field. Early in the 20th century, work by David, Brunhes and Mercanton showed that many rocks were magnetized antiparallel to the field.

The thinning of the crust, which resulted from the impact, stimulated effusive volcanic activity. Light-colored lavas filled the inner part of Rembrandt causing it to subside, which led to the contraction of the basin's floor and formation of wrinkle ridges. The later floor uplift, which causes are not known, led to the extension and formation of troughs. The latest episode of tectonic activity led to the formation of the lobate scarp, which actually runs tangentially to the ring of wrinkle ridges.

It is a thick accumulation of volcanic rocks that were either erupted from or eroded from the slopes of two belts of Eocene stratovolcanoes. These rocks accumulated within an intermountain basin between these belts. Before they were destroyed by erosion, these volcanoes are estimated to have had peaks that rose about to above adjacent intermountain valleys. Depending on location, the Lamar River Formation unconformably overlies either older lavas, conglomerates, tuffs, volcanic breccias of the Sepulcher Formation; Mississippian limestones and dolomites; or Precambrian gneiss.

The volcano has erupted rocks ranging from andesite to rhyodacite, with the main stratovolcano formed by andesites that contain hornblende and pyroxene and phenocrysts of augite, biotite, iron oxide, olivine, orthopyroxene, pargasite, plagioclase, quartz and titanium oxide. Deposits of copper, gold, lead, silver and sulfur were reported as well. The volcanic rocks erupted by Sajama define a potassium-rich calc-alkaline suite and formed through various processes, including assimilation of country rock, fractional crystallization and magma mixing (particularly in the Sayara lavas).

While these lavas certainly contribute to the observed gravitational anomalies, uplift of the crust-mantle interface is also required to account for their magnitude. Indeed, some mascon basins on the Moon do not appear to be associated with any signs of volcanic activity. Theoretical considerations in either case indicate that all the lunar mascons are super-isostatic (that is, supported above their isostatic positions). The huge expanse of mare basaltic volcanism associated with Oceanus Procellarum does not possess a positive gravitational anomaly.

Fluid lavas are typically associated with the formation of broad shield volcanoes such as those of Hawaii, but Nyiragongo has very steep slopes down which lava can flow at up to . Lava flows could melt down ice and glaciers that accumulated on the volcano's crater and upper slopes, generating massive lahar flows. Rarely, generally fluid lava could also generate massive lava fountains, while lava of thicker viscosity can solidify within the vent, creating a block which can result in highly explosive eruptions.

East of the Jordan River Valley, the land surface eroded to a nearly flat peneplain and many Proterozoic sediments were eroded. Before Cambrian sediments began to accumulate quartz porphyry lavas erupted to the surface. Tectonic conditions favored the preservation of Proterozoic sediments in the Wadi al'Arabah as Cambrian sandstones began to form. The continental, marine and calcareous sandstones accumulated as the Tethys Ocean transgressed the region, followed by a late Cambrian marine regression marked by a return to more terrestrial sandstones.

Pyroxferroite is named from pyroxene and ferrum (Latin for iron), as the iron-rich analogue of pyroxmangite. The word pyroxene, in turn comes from the Greek words for fire (πυρ) and stranger (ξένος). Pyroxenes were named this way because of their presence in volcanic lavas, where they are sometimes seen as crystals embedded in volcanic glass; it was assumed they were impurities in the glass, hence the name "fire strangers". However, they are simply early-forming minerals that crystallized before the lava erupted.

The so-called Abancay deflection separates the CVZ in the north from the Peruvian flat subduction segment where no volcanic activity occurs, while the southern limit is marked by a seismic discontinuity around 27° S. Jotabeche is a high volcano with a caldera. A rhyolitic dome formed inside of the caldera. The Jotabeche complex reaches a thickness of when including ignimbrite, lava domes and lavas. The high and wide Jotabeche Norte stratovolcano is found northeast of Jotabeche and is surrounded by pyroclastic flows.

Fertile soils from weathered volcanic lavas have made it possible to sustain dense populations in the agriculturally productive highland areas. Central America has many mountain ranges; the longest are the Sierra Madre de Chiapas, the Cordillera Isabelia, and the Cordillera de Talamanca. Between the mountain ranges lie fertile valleys that are suitable for the people; in fact, most of the population of Honduras, Costa Rica, and Guatemala live in valleys. Valleys are also suitable for the production of coffee, beans, and other crops.

Dana's work was followed up by geologist C. E. Dutton's 1884 expedition, who refined and expanded Dana's ideas. Most notably, Dutton established that the island of Hawaii actually harbored five volcanoes, whereas Dana counted three. This is because Dana had originally regarded Kīlauea as a flank vent of Mauna Loa, and Kohala as part of Mauna Kea. Dutton also refined others of Dana's observations, and is credited with the naming of 'a'ā and pāhoehoe-type lavas, although Dana had noted a distinction.

Data demonstrate vertical variability in the amount of strontium present in both the alkalic (early stages) and tholeiitic (later stages) lavas. The systematic increase slows drastically at the time of the bend. Almost all magma created by the hotspot is igneous basalt; the volcanoes are constructed almost entirely of this or the similar in composition but coarser-grained gabbro and diabase. Other igneous rocks such as nephelinite are present in small quantities; these occur often on the older volcanoes, most prominently Detroit Seamount.

Apollinaris Patera parallels many of the volcanic terrains on Mars, including most of the Elysium and Tharsis Rises, in that they are demagnetized terrains that conspicuously predate the shutdown of the Martian dynamo. The mechanism of its deactivation has been compared to that of Hadriacus Mons. Researchers observing this noted that the deposition of lavas atop an older, more magnetized terrain might have led to the region's demagnetization. Its existence thus does not challenge hypotheses about the timing of the dynamo shutdown.

The only real separate volcanic peak associated with the Rainbow Range is Anahim Peak which sits on its northeast flank. Other peaks in the range are other high eroded remnants of the shield, including Beef Peak, TaiaTaeszi Peak, Mount MacKenzie and Tsitsutl Peak , which is the highest summit of the Rainbow Range. The range gets its name from the intense and varied colours of its terrains' volcanic lavas and sands from heavy mineralization, like the Spectrum Range in the Spatsizi Plateau.

Due to a strong tidal heating, Io is very geologically active and is volcanically resurfaced by lavas and plume deposits at a high rate (about per year). Several models have been proposed to related this resurfacing process to accumulation of stress in the lithosphere. Many mountains higher than have been observed on Io. This implies that Io has a thick crust. In O'Reilly and Davies' 1981 paper, they proposed that part of the heat in Io is transported by advection.

Salisbury, M.H., and Christensen, N.I., (1978) The observations that follow support this conclusion. Rocks originating on the seafloor show chemical composition comparable to unaltered ophiolite layers, from primary composition elements such as silicon and titanium to trace elements. Seafloor and ophiolitic rocks share a low occurrence of silica-rich rocks; those present have a high sodium and low potassium content.Mason, R., (1985) The temperature gradients of the metamorphosis of ophiolitic pillow lavas and dykes are similar to those found beneath ocean ridges today.

Portezuelo Maricunga The whole complex has been active for 1.5 mya and has generated two large scale pyroclastic eruptions, a first one 1.5 mya occurred on the western side of the volcano. It is fairly thin and covers Pliocene lavas. Otherwise, rhyodacitic lava flows, lava domes and various ash and tephra deposits also belong to this volcano. The three main volcanoes of the massif - Tres Cruces Sur (), Tres Cruces Centro () and Tres Cruces Norte () formed along a local fault zone.

The earliest report on the Araguainha structure was published by Northfleet et al. (1969), who interpreted it as an uplift of the Phanerozoic sediments caused by a Cretaceous syenite intrusion. A geological reconnaissance survey by Silveira Filho and Ribeiro (1971) noted the occurrence of lavas, breccias, and tuffs around the central core and deduced that Araguainha was a crypto-volcanic structure. Dietz and French (1973) reported the occurrence of impact breccias and shocked quartz, and recognized the structure as an impact crater.

The PLUME lavas erupted on Fernandina and Isabela are relatively cool. Analysis shows that they are as much as 100 degrees Celsius cooler than those in Hawaii. The cause of this is not fully understood but may be due to cooling in the lithosphere or being relatively cool at formation in the mantle. They are then found in lower quantities in a horseshoe pattern north and south of the central islands mixing with the other reservoirs as it progresses east.

At Level Mountain, lava tubes reach diameters of to . These owed their origin to highly fluid lavas with temperatures of at least . In Nisga'a Memorial Lava Beds Provincial Park of northwestern British Columbia, lava tubes are present that were formed during one of Canada's most recent volcanic eruptions in the 18th century. Lava Fork at the British Columbia-Alaska border is influenced by lava flows from a recent volcanic eruption that later collapsed into underlying lava tubes after the lava solidified.

Stunning views of Paisley and the lower Clyde Valley to Ben Lomond are offered from the park, specifically from Robertson car park (aka car park in the sky). The area is situated on the edge of the Clyde plateau lavas, an interesting feature is Gleniffer gorge situated along the Tannahill walkway. It reaches some 50 feet deep in places and is eroded by the Gleniffer burn. Another feature is the Craigielinn waterfall in Glen park, where icicles can be seen hanging in winter.

North of Pinhead Buttes, the volcanoes in this region are older and less tall, usually between in elevation. South of Pinhead Buttes, the Cascades becomes younger Pleistocene volcanoes, which often have glaciers. Mount Jefferson may form part of a long- lasting intracrustal melting and magma storage area that encompasses an area of , where relatively little mafic eruptive activity has occurred. The melting of the metamorphic rocks amphibolite and at deeper strata, granulite, have both produced intermediate and silicic lavas at Jefferson.

The David S. and Ruth L. Gottesman Hall of Planet Earth is a permanent hall devoted to the history of Earth, from accretion to the origin of life and contemporary human impacts on the planet. Several sections also discuss the studies of Earth systems, including geology, glaciology, atmospheric sciences, and volcanology. The exhibit is famous for its large, touchable rock specimens. The hall features striking samples of banded iron and deformed conglomerate rocks, as well as granites, sandstones, lavas, and three black smokers.

A principal focus of Neptunism that provoked almost immediate controversy involved the origin of basalt. Basalts, particularly formed as sills, were differentiated from surface lava flows, and the two were not recognized as the same rock type by Werner and his students during this period. Lavas and volcanoes of obviously igneous origin were treated as very recent phenomena unrelated to the universal ocean that formed the layers of the Earth. Werner believed that volcanoes only occurred in proximity to coal beds.

Mount Melbourne is surrounded by a volcanic field consisting of 60 exposed volcanoes, which have the form of scoria cones and tuff rings with hyaloclastite deposits, lava flows and pillow lavas. Some of these volcanoes formed under ice. The volcanic field forms a peninsula which is separated by steep faults from the Transantarctic Mountains to the north. Among these volcanoes is Shield Nunatak southwest from Mount Melbourne, a subglacial volcano, now exposed, that may have formed during the latest Pleistocene.

Such lavas contain greater amounts of silica, and are more viscous than basalt. These eruptions created most of the highest peaks in the Jemez Mountains, including Chicoma Mountain (11,561 feet), and Polvadera Peak and Pajarito Mountain. Weathering of the igneous rocks resulted in alluvial fans, which spread eastward into the Rio Grande Rift. By 2 million years ago, the sediments had displaced the Rio Grande eastward from an earlier location near Los Alamos to its current location in White Rock Canyon.

This suggests that parental magmas may have been derived by increasingly smaller degrees of partial melting with time. If volcanic activity of the Itcha Range is related to a hotspot, this temporal and spatial evolution would suggest a waning heat source. The main body of the shield erupted over an area of about . Volcanic activity associated with the Itcha Range extended south to the Satah Mountain area where lavas erupted along a north-northwest trending fault system and covered an additional area of .

Temperatures estimated for the erupted rocks cover a wide range, with some exceeding . These rocks are of enigmatic origin, which may be geothermal or magmatic, with the presence of lava bombs of magnetite lava and other evidence supporting the magmatic origin theory. Other viewpoints consider the texture and chemical composition of the rocks as evidence that metasomatism of andesitic rocks formed the magnetite "lavas". The role of a post-magmatic fluid phase, which was inferred from inclusions in crystals, has also been suggested.

Iceland monitor With the widespread availability of geothermal power, and the harnessing of many rivers and waterfalls for hydroelectricity, most residents have access to inexpensive hot water, heating, and electricity. The island is composed primarily of basalt, a low-silica lava associated with effusive volcanism as has occurred also in Hawaii. Iceland, however, has a variety of volcanic types (composite and fissure), many producing more evolved lavas such as rhyolite and andesite. Iceland has hundreds of volcanoes with about 30 active volcanic systems.

Under the microscope they prove to be nearly completely glassy with small circular air vesicles sometimes drawn out to long tubes. Only in the Hawaiian Islands are glassy basaltic lavas of this kind at all common. KILAUEA VOLCANO (MT. KILAUEA), James St. John, OSU- Newark, Geology A small outcrop at Spring Hill in Victoria, Australia'Unusual Newer Volcanics trachyandesite cones in the Gisborne-Woodend and Kyneton- Trentham areas' has tachylite which has been exploited as a material for making Aboriginal flaked stone implements.

Cerro Bitiche is part of a number of mafic volcanic centres associated with the Altiplano-Puna volcanic complex. The two major calderas La Pacana and Cerro Guacha are close to Cerro Bitiche, the eastern margin of Guacha's oldest caldera is located just east of Bitiche. Ordovician marine sequences form the tectonic basement of the area, but most of it is covered by ignimbrites and lavas between 8.5-4 million years old. The volcanic field covers a surface area of , including lava flows and scoria cones.

About five different active eruption periods have been discovered at Taftan volcano. Activity first involved lava and pyroclastics of dacitic to rhyodacitic composition. Later, upper Pliocene lavas were erupted along with agglomerates. These can be found up to away from the cone. Three phases have been dated at 6.95 ± 0.72, 6.01 ± 0.15 and 0.71 ± 0.03 million years ago; an even older phase west-northwest of the current volcano occurred 8 million years ago, while a Quaternary ignimbrite has produced an age of 404,000 ± 82,000 years before present.

Usually littoral cones are formed by aa lava as their fragmented nature allows ideal water-lava interactions, but pahoehoe and intermediary lavas can also form littoral cones. Other properties such as the speed of the lava flow and the structure of the flow front also influence the formation of littoral cones. Larger lava flow rates generate larger cones. In some littoral cones on Hawaii that were formed by pahoehoe lava flows, the collapse of a lava bench and subsequent steam explosions formed the cones instead.

The postglacial activity appears to originate from a shallow silicic magma chamber beneath the caldera. Research published in 2017 indicates that this system is somewhat heterogeneous with distinct compositions of magmas erupted in the northwesterly and southeasterly parts of the volcanic field. The early post-glacial rhyodacites contain mafic inclusions implying that mafic lavas exist but do not reach the surface. From isotope ratios it has been inferred that the magma is of deep origin, and the rare-earth element composition shows no evidence of crustal contamination.

The Precambrian basement rock biotite-gniesses that form the underlying structure of Loriu were exposed during the plateau's formation through up faulting and tilting of the basement rock. These layers are clearly visible and form a major part of the stratigraphy of the Mugor scarp on the eastern edge of the plateau. Because of the gradual slope of the western plateau, Loriu is most likely not a horst. Lavas capping Loriu are dated to the Pliocene, according to the East African Geological Research Unit.

Sandstones, siltstones and mudstones of the St Mellion Formation occur in the Holne area and to its northeast. Its relationship to other units of the Teign Valley Group are uncertain since all contacts are tectonic. Brent Tor in the extreme west of the park is formed from basaltic lavas and tuffs of the Milton Abbot Formation, erupted between 347-329 million years ago though its lower western slopes are formed from a microgabbro which locally intrudes the rocks of the Brendon (formerly Greystone) Formation.

The Okete Volcanics erupted over short periods, between 1.8 and 3 Ma ago, from at least 27 tuff rings, or scoria mounds, surrounded by lava flows. At Maungatawhiri the initial eruption was of fine-grained volcanic tuffs, thought to be comminuted by water interacting with magma, followed by strombolian activity and lava flows. North of Papanui Point violent phreatomagmatic eruptions have formed tuff rings of airfall and pyroclastic surge deposits. The Okete Volcanics include basanites, alkali olivine basalts, hawaiites, and lavas with ultramafic xenoliths.

The sequence continues with the Lower to Middle Jurassic Bearreraig Sandstone Formation followed by Middle Jurassic Great Estuarine Group, comprising the Cullaidh Shale Formation, Elgol Sandstone Formation, Lealt Shale Formation, Valtos Sandstone Formation, Duntulm Formation, Kilmaluag Formation and the Skudiburgh Formation. The Upper Jurassic is represented by the Staffin Shale Formation. The only Cretaceous unit exposed on Skye is the Strathaird Limestone Formation, thought to be either Turonian or Campanian in age, which lies unconformably on the Jurassic and is overlain unconformably by Palaeocene lavas.

During the eruption, the heat of the lava from the subglacial volcano melts the overlying ice. The water quickly cools the lava, resulting in pillow lava shapes similar to those of underwater volcanoes. When the pillow lavas break off and roll down the volcano slopes, pillow breccia, tuff breccia, and hyaloclastite form. The meltwater may be released from below the ice as happened in Iceland in 1996 when the Grímsvötn caldera erupted, melting 3 km3 of ice and giving rise to a large glacial lake outburst flood.

The larger part of the bedrock of Seil is provided by the Neoproterozoic age Easdale Slate Formation, a pyritic, graphitic pelite belonging to the Easdale Subgroup of the Dalradian Argyll Group. Zones of metamorphosed intrusive igneous rocks occur within the southeast of the island. Andesitic lavas of the Lorn Plateau Lava Formation dominate the west of the island. Seil is cut by numerous NW-SE aligned basalt and microgabbro dykes which form a part of the ‘Mull Swarm’ which is of early Palaeogene age.

The floodplain of Johnson Creek is a remnant of large glacial floods known as the Missoula Floods that deposited thick sediments between 18,000 and 13,000 years ago in the Columbia River Basin, including much of the Willamette Valley. Underlying the sediments are substantial thicknesses of basalt lavas from the Columbia River Basalt Group. The lava, exposed mainly in the uplands, has been folded and faulted to form a series of sub-basins, including the Johnson Creek watershed. The watershed is a roughly rectangular area of about .

The Barrier is part of a thick lava flow that erupted from Clinker Peak between 15,000 and 12,000 years ago. Person in middle of image for scale During the Middle Pleistocene about 300,000 years ago, volcanism shifted westward and constructed the nearly symmetrical stratovolcano of Mount Price. Episodic eruptions produced andesite and dacite lavas, as well as pyroclastic flows from Peléan activity. Later, the volcano was overridden by the Cordilleran Ice Sheet, which covered a large area of North America during glacial periods of the Quaternary.

This geological formation formed 140,000 to less than 90,000 years ago when porphyritic plagioclase- augite-olivine basalt and trachybasalt was erupted in valleys and on mountain ridges. These volcanic rocks form scoriaceous lava flows, breccias, volcanic bombs and pillow lavas. The location of the Mosaic Assemblage is sparse, being present just north of the Lillooet River, south of and in upper Meager Creek and between Job Creek and Mosaic Creek. Because these four areas are well apart, each area probably has its own volcanic vents.

Precise dating methods performed on the southeastern flank have found ages of 3.65±0.15 mya and 3.81±0.30 for lavas and scoria. The snowline altitude in the area is Four moraine stages are found on the mountain, with the lowest moraines on the southern flank at altitude. Nowadays, block glaciers have been identified in the area, one of which is found at . The mountain is also one of the headwaters of the Loa River, and water was transferred from Palpana to Antofagasta by pipeline.

It was first recognized and described by J.B. Dawson from the Ol Doinyo Lengai carbonatite lavas in 1963 and named in honor of the president of Tanzania, Julius Nyerere (1922-1999). In the carbonatite lava it is associated with the potassium-bearing gregoryite. It has also been reported from the Afrikanda alkaline intrusive complex, in the Kola Peninsula, Russia. Anatoly N Zaitsev and Anton R Chakhmouradian, Calcite – amphibole – clinopyroxene rock from the Afrikanda Complex, Kola Peninsula, Russia: mineralogy and a possible link to carbonatites.

The Cape Sorell Block is a region of metamorphosed sediments from the Mesoproterozoic, to the south of the west end of Macquarie Harbour. It is separated from Neoproterozoic rocks by a low angle thrust fault. The Neoproterozoic rocks contain greywacke, mudstone and pillow lavas of the Lucas Creek Volcanics (matching the Crimson Creek Formation), mudstone, siltstone (matching the Success Creek Group) and dolomite (correlating with the Togari Group). South east of this is a metamorphosed belt of dolomite rich sediments correlated with the Oonah Formation.

Yucamane is constructed on a basement formed by the Paleozoic Tacaza Group (lavas of the lower Tacaza formation), the Jurassic Yura Group (sediments of the Hualhuani formation) and the Neogene volcanic Huaylillas formation; parts of this basement crop out on the southern side of Yucamane. This basement in turn consists of two major tectonic blocks, the southern Arequipa terrane and the northern Paracas massif; both are formed by igneous and metamorphic rocks such as gneiss and are covered by Mesozoic sedimentary and Cenozoic volcanic rocks.

Lake Turkana is an East African Rift feature.A good introduction is stated in the Regions of Kenya site. A rift is a weak place in the Earth's crust due to the separation of two tectonic plates, often accompanied by a graben, or trough, in which lake water can collect. The rift began when East Africa, impelled by currents in the mantle,For the mantle currents, or "plumes", see the abstract of Tertiary Mafic Lavas of Turkana ..., Journal of Petrology Volume 47, Number 6 Pp. 1221–1244.

Dale Head stands at the junction of the two main Lakeland geological systems, the Skiddaw slates to the north and the Borrowdale Volcanics to the south. On the northern flanks are outcrops of the Buttermere Formation, olistostrome of disrupted sheared mudstone, siltstone and sandstone. Southward march the Borrowdale series beginning with the plagioclase-phyric andesite lavas of the Birker Fell Formation, visible near the summit.British Geological Survey: 1:50,000 series maps, England & Wales Sheet 29: BGS (1999) The fell has seen extensive mining history.

Only six eruptions outside of the caldera have been recorded, most recently in 1986. The village of Piton-Sainte-Rose was evacuated in 1977 before it was inundated by a lava flow which destroyed several buildings. The lava flow crossed the highway and surrounded the local church, entered the front door, then stopped without destroying the building. The front entrance was later cleared out, and the church was brought back into service under the name of Notre-Dame des Laves ("Our Lady of the Lavas").

Inside the caldera is a high lava shield named Dolomieu. At the top of this lava shield are Bory Crater (Cratère Bory) and Dolomieu Crater (Cratère Dolomieu), which is by far the wider of the two and named for French geologist Déodat Gratet de Dolomieu. Topographic map showing the volcano and surrounding terrain Many craters and spatter cones can be found inside the caldera and on the higher flanks of the volcano. Lavas with high concentrations of iridium are routinely ejected through these vents.

Lava flows contain andesite and dacite of relatively uniform composition, the former containing amphibole. The morphology of the two long lava flows from Volcan Paruma implies that they were formed by lavas more mafic than is typical for the region, perhaps by andesite-andesite. Fumarolic alteration is widespread on the volcanic complex, being conspicuous on the ridge between Olca and Volcan Paruma and on the northern and southeastern flanks. Sulfur is present on the volcano, mainly around Olca, and was mined into the 1980s.

The lavas show no evidence of ponding in crustal magma chambers, suggesting that the large volatile content of the magma was sufficient to quickly transport it through the crust. Magma temperatures have been estimated at higher than . The cones are constructed by reddish lapilli and lava bombs up to wide with subordinate amounts of ash-like material, concentrated in the talus deposits that have been formed by erosion at the basis of the cones. Arenite of sedimentary origin and dacite are found as xenoliths.

Some flows are older and covered with soil while younger ones are not. Such young lava flows also have surface features including lava tunnels, hornitos, tumuli and a rugose surface. Some of these are heavily eroded while the southeastern part of the field features fresh-looking centres, where they form the "Basaltos del Diablo". The individual volcanoes are subdivided into three groups which are referred to as "U2" (the older centres) and "U3" (for the more recent vents); the plateau lavas are hence called "U1".

Based on geothermometric data, the highest temperatures occurred during phases of high activity and lower temperatures are associated with low output periods. It is likely that crustal feedback and increased deep crustal influx of mantle-derived basalts drive increased magmatic flux. During the time of the Polan eruption on the west flank, magma output was spatially segregated with the peripheral Miño Volcano generating andesite lavas and the more central volcanos generating dacites. Various parts of the main volcano have been subjected to hydrothermal alteration.

Buried within the ignimbrites and lavas, some orbs contain layers of biotite, bronzite, ilmenite and plagioclase around a centimetre- sized xenolith or orthopyroxene core. The layering is not disturbed by irregular shapes of the cores. These orbs most likely formed from material crystallizing around pre-existent cores during rapid changes in magma temperature that occurred shortly before the end of the first phase of the Cerro Panizos eruption through changes in magma water content. Opening of ring vents then delivered the orb-containing magma to the surface.

The Vema, a ship of the Lamont-Doherty Earth Observatory of Columbia University, traversed the Atlantic Ocean, recording echo sounder data on the depth of the ocean floor. A team led by Marie Tharp and Bruce Heezen concluded that there was an enormous mountain chain with a rift valley at its crest, running up the middle of the Atlantic Ocean. Scientists named it the 'Mid-Atlantic Ridge'. Other research showed that the ridge crest was seismically active and fresh lavas were found in the rift valley.

This layer of rock was pushed up and over sedimentary rocks during tectonic plate movement. "As the allochthon was moving, shales underneath it were broken up and mixed with sedimentary, volcanic and ocean crust rocks (ophiolite) from the slice itself, to form material known as mélange". In addition, rounded, bulbous masses—dark green and red basalt pillow lavas—thought to have been extruded under water can be seen at low tide. The sea has carved these sedimentary, mélange and lava rocks into curious and intriguing shapes.

The section at Rua do Paim is approximately long, with an internal cavity that is at its maximum extent high and wide. Along the cavern walls are speleological structures such as lateral benches, lava bridges, branching galleries, lava balls, stalactites, stalagmites, columns, spongy lavas, glaze and tree moulds. Apart from several cracks, the walls and ceiling are multi-coloured (orange to yellowish) due to the basalt oxidization. There are also conical-shaped stalactites, secondary mineral deposits of silica and earthen deposits covering the walls and ceiling.

Between 1,200 and 740 million years ago, a series of flood basalt eruptions took place. At the northern portion of the Mackenzie Large Igneous Province, vast volumes of basaltic lava paved over a large area of the northwestern Canadian Shield. This extensive volcanism constructed a large lava plateau with an area of , representing a volume of lavas of at least . This extensive area of flood basalt lava flows has been termed the Coppermine River flood basalts hence given the location of the flood basalt sequence.

In 1965, Canadian geologist John Oliver Wheeler foresaw the need for a volcanological program in Canada's western Cordillera. Souther was given the job of working on the Mount Edziza complex with the able assistance of Maurice Lambert. By 1970, the two geologists had established that eruptions of alkali basalt, followed by extrusion of silicic peralkaline lavas, had occurred episodically at Edziza for the past 10 million years and that volcanism was accompanied by east-west extension and incipient rifting. However, the regional tectonic context was still unresolved.

It is this molten lithosphere that becomes the basalt lavas that gush onto the surface to form the Columbia River and Snake River Plain basalts. The track of this hot spot starts in the west and sweeps up to Yellowstone National Park. The steaming fumaroles and explosive geysers are ample evidence of a concentration of heat beneath the surface. The hot spot is stationary, but the North American plate is moving over it, creating a record of the rate and direction of plate motion.

As an analogy, one should remember that there are two high tides per day on Earth, and not one. #Since mare basaltic magmas are denser than upper crustal anorthositic materials, basaltic eruptions might be favored at locations of low elevation where the crust is thin. However, the far side South Pole-Aitken basin contains the lowest elevations of the Moon and yet is only sparingly filled by basaltic lavas. In addition, the crustal thickness beneath this basin is predicted to be much smaller than beneath Oceanus Procellarum.

View on Sandskeið airfield and Vífilsfell from the Hringvegur Quarries at Vífilsfell in 2019 Winterly road conditions on the Hringvegur near Vífilsfell Bláfjöll with Vífilsfell to the left, seen from lake Rauðavatn in the outskirts of Reykjavík Vífilsfell is a hyaloclastite ridge in southwestern Iceland (Weichselian).Cromwell, G., L. Tauxe, and S. A. Halldórsson (2015), New paleointensity results from rapidly cooled Icelandic lavas: Implications for Arctic geomagnetic field strength, J. Geophys. Res. Solid Earth, 120, 2913–2934, doi:10.1002/2014JB011828. Retrieved 26 July 2020.

Tittivilla underwent an edifice collapse that triggered a long debris avalanche. The avalanche descended an altitude of with an azimuth 68° and covered a surface area of . The slide left a wide amphitheatre on the east-northeast side of the volcano that cut through older lava flows, the amphitheatre was originally interpreted to be an explosion crater. The northern side of the avalanche has large blocks up to several kilometres of length that are hard to distinguish from eroded lavas from the neighbouring Cerro Grande.

Significant deposits of fine material are restricted to but a few locales: Bancroft, Ontario, and Mont-Saint- Hilaire, Quebec, in Canada; and Litchfield, Maine, and Magnet Cove, Arkansas, in the US. The Ice River complex, near Golden, British Columbia, contains sodalite.Ice River deposit on Mindat Smaller deposits are found in South America (Brazil and Bolivia), Portugal, Romania, Burma and Russia. Hackmanite is found principally in Mont-Saint-Hilaire and Greenland. Euhedral, transparent crystals are found in northern Namibia and in the lavas of Vesuvius, Italy.

The stratovolcano consists of lava flows and pyroclastic material which radiate away from the centre of the volcano. Some parasitic vents occur southeast of Sajama and their location appears to be controlled by radial dikes; the whole complex is a compound volcano. Two later volcanic units are known as the Colquen Wilqui lavas and the Jacha Khala tuff. The Sajama volcano rises within a caldera that has been buried by later volcanic activity so that it is only recognizable on its eastern-northeastern side.

The Fish Canyon Tuff, made of dacite, is uniform in its petrological composition and forms a single cooling unit despite the huge volume. Dacite is a silicic volcanic rock common in explosive eruptions, lava domes and short thick lava flows. There are also large intracaldera lavas composed of andesite, a volcanic rock compositionally intermediate between basalt (poor in silica content) and dacite (higher silica content) in the La Garita Caldera. The caldera itself, like the eruption of Fish Canyon Tuff, is quite large in scale.

It is thought that this reservoir came from subducted ocean crust that has been entrained by the mantle plume. It has enriched Sr and Pb ratios and is enriched with trace elements. FLO is associated principally with the island of Floreana and shows up on the mixing of lavas within the Galapagos along the southern side archipelago and is diluted to the east and north of there. WD – (Wolf Darwin) is unique in the Pacific and resembles material from an Indian Ocean Ridge system.

Active lava flows in volcanic region Tvashtar Paterae (blank region represents saturated areas in the original data). Images taken by Galileo in November 1999 and February 2000. The tidal heating produced by Io's forced orbital eccentricity has made it the most volcanically active world in the Solar System, with hundreds of volcanic centres and extensive lava flows. During a major eruption, lava flows tens or even hundreds of kilometres long can be produced, consisting mostly of basalt silicate lavas with either mafic or ultramafic (magnesium-rich) compositions.

Between the layers of the basaltic plateau lavas in Iceland, there is an abundance of clay rich reddish silt- and sandstone layers. These layers are formed from ancient soil wherein are preserved the fossilized remains of plants. It is estimated that about five to ten thousand years passed on average between the formation of two adjacent layers that make up the basaltic plateau. Volcanic eruptions with frequency of one in every few years facilitated soil formation and thus enabled plants to gain a foothold.

Wright, I.C. and Gamble, J.A. (1999) Southern Kermadec Submarine caldera arc volcanoes (South West Pacific): caldera formation by effusive and pyroclastic eruption, Marine Geology, 161:207-277 This activity is thought to be common at subduction zones due to recycling of the lithosphere. It is not exclusive to these plate margins, occurring at hotspots and ocean ridges. An example is Loihi near Hawaii where both effusive and explosive activity occurs at 2000 m depth. Two formations associated with submarine eruptions are seamounts and pillow lavas.

The lavas erupted in 1669 define a sodic hawaiite suite with two distinct acidic and mafic members that were erupted before and after 20 March, respectively. These two magmas formed through fractional crystallization processes in different parts of Mount Etna's plumbing system. It appears that prior to the 1669 eruption, a batch of more acidic magma was residing underneath Etna. A batch of new, more mafic magma that was more buoyant than the residing magma penetrated and traversed the magmatic system, and reached the surface.

Vilevolodon is known from the Tiaojishan Formation and is placed within the Oxfordian age of the Late Jurassic, estimated to be 161 – 160 million years old, as based upon stratigraphic correlation to a regional index fossil, Qaidamestheria, a genus of Jurassic Clam Shrimp. The Tiaojishan Formation has also yielded holotypes of other euharamiyids, including Shenshou and Maiopatagium. The geology of the Tiaojishan Formation is characterized by high levels of pyroclastic and volcanic rock, including high levels andesitic breccias, tuffs, and various other brecciated lavas.

The varying geochemical signatures of a suite of Ethiopian lavas suggest multiple plume sources: at least one of deep mantle origin, and one from within the subcontinental lithosphere. In accordance, a study of Halldórsson et al. in 2014 compare the geochemical signature of rare Earth's isotopes from xenoliths and lava samples collected in the EAR. The results corroborate the coexistence of a superplume “common to the entire rift” with another mantle material source being either of subcontinental type or of mid-ocean ridge type.

Xenomorph of quartz crystals (grey) in granite In geology, a xenomorph or allotriomorph is a mineral that did not develop its otherwise typical external crystal form because of late crystallization between earlier formed crystals. Xenomorphs are typical of matrix minerals in rapidly crystallizing volcanic lavas and shallow igneous intrusions. It is also typical of the interstitial or cementing minerals formed during the diagenesis of sedimentary rocks. The opposite is an idiomorph in which the external form is controlled only by the internal crystal structure.

One of its tephras overlies an older formation that was erupted 1400 BP. Lavas from this cone form a peninsula in Lake Epulafquen and modified the local hydrography. Another cinder cone La Angostura formed a peninsula separating the lakes Epulafquen and Huechulafquen. This cone has three craters. A tephra layer of black trachyandesite has been linked to Huanquihue and is dated 4028-4212 BP. Varve count dating has indicated that tephras in Lake Villarrica and Lake Calafquen erupted presumably in 1591 are compositionally similar to Huanquihue scorias.

All basement rocks beneath the Wellington Region belong to the Torlesse Composite Terrane. They are largely composed of Greywacke (hardened sandstone and mudstone), but also contain Chert, and Pillow lavas. In the Wellington Region, the Torlesse Composite Terrane is composed of two subterranes, the Rakaia Terrane (late Triassic to early Jurassic, 230-180 Ma), to the west of the Ruahine Ranges, and the Pahau Terrane (late Jurassic to early Cretaceous, 180-100 Ma), to the east. Major faults such as the Wellington Fault and Wairarapa Fault lie close to the boundary between the terranes.

Locally, the contact is a low relief erosional surface associated with a thin weathering zone developed in the lavas of the Cardenas Basalt. Along the length of the outcrop of this unconformity, it cuts as much as down into the Cardenas Basalt. The lowest part of the Nankoweap Formation consists of a basal conglomerate that is composed chiefly of gravel derived from the Cardenas Basalt. The contact between the Tapeats Sandstone and the Cardenas Basalt and rest of the folded and faulted Unkar Group is a prominent angular unconformity.

Each group comprises psammites and pelites, that's to say sandstones and mudstones which have been subjected to low grade metamorphism. Lavas, tuffs and volcaniclastics also occur through the Southern Highland Group whilst meta-limestone and quartzites are to be found within the Argyll Group. The Southern Highland Group consists of the Pitlochry Schist Formation overlain by the Loch Katrine Volcanic (or Volcaniclastic) Formation which is in turn overlain by the Ben Ledi Grit Formation. Ben Lomond, Ben Venue and Ben Ledi are all formed from the Ben Ledi grit.

The Smartville Ophiolite is divided into sections based on lithology that describe the origin of the rocks it is made up of. In order of increasing depth: the top most unit is called the upper volcanic unit, then the lower volcanic unit, followed by the dike complex, and the plutonic suite at the bottom. The upper volcanic unit consists mainly of pillow lava and massive lavas with turbidites also being common. The turbidites of the upper volcanic unit are made of a siliceous rock type and have sandstones and conglomerate tops.

The Derwentwater fault runs along the valley of Broadslack Gill, the higher ground to the north west being mainly composed of the Birker Fell Formation. These are plagioclase-phyric andesite lavas and subordinate sills. By contrast Castle Crag shows outcropping of the Eagle Crag Member, a mixture of siltstone, sandstone, conglomerate and tuff with frequent andesite sills.British Geological Survey: 1:50,000 series maps, England & Wales Sheet 29: BGS (1999) The slopes of Castle Crag are extensively quarried with pits and levels on the northern and south eastern flanks.

Pillow lavas can be used as a way-up indicator in geology; that is, study of their shape reveals the attitude, or position, in which they were originally formed. Pillow lava shows it is still in its original orientation when: # Vesicles are found towards the top of a pillow (because the gas trapped as part of the rock is less dense than its solid surroundings). # The pillow structures show a convex (rounded) upper surface. # The pillows might have a tapered base downwards, as they may have molded themselves to any underlying pillows during their formation.

Mare lavas apparently could reach the surface more often and more easily there. The basin material is of the Nectarian epoch, while the mare material is of the Upper Imbrian epoch. Following the SELENE mission, scientists proposed that volcanism in Mare Moscoviense was active for at least ~1.5 Ga following the formation of the Moscoviense basin, but the formation of the mare as the result of a meteorite cluster impact, rather than from volcanism, has also been proposed based on the energy required to melt the lava in Mare Moscoviense.Morota, T., et al.

Barker 1958, p.10 but with lesser amounts of many other rock types, including metaconglomerate, phyllite, gneiss, and muscovite schist. Feldspathic schist and banded iron formation are also present. The banded iron is of the Algoma variety, formed by local volcanism rather than in the Great Oxidation Event.Fulp and Lee 1981 Pillow lavas can be discerned at some locationsBauer and Williams 1989, p.47 and the overall composition of the chlorite schist is that of altered basalt.Barker 1958, p.16 Major element and oxygen isotope ratios suggest the protolith was tholeiite.

The isotopic composition of volcanic rocks in Saint Helena and nearby Ascension Island and Tristan da Cunha are very different from the Mid-Atlantic Ridge basalts. Many of the lavas on the island display a hawaiite geochemistry and share a characteristic niobium enrichment with basalts from Ascension and Bouvet Island. Some geochemists have proposed that small amounts of 1.5 to 2 billion year old pelagic sediments contaminated the magma source of the island, as a means of explaining the differing trace element ratios relative to Tristan da Cunha.

Golden Hinde, the highest peak on Vancouver Island. The Karmutsen Formation is a Late Triassic volcanic sequence of tholeiitic pillow basalts and breccias on Vancouver Island, British Columbia, Canada. It is perhaps the thickest accreted section of an oceanic plateau worldwide, exposing up to 6000 m of basal sediment-sill complexes, basaltic to picritic pillow lavas, pillow breccia, and thick, massive basalt flows. The widespread succession of basalts and breccias are part of the Insular Mountains, a large volcanic mountain range that forms Vancouver Island and Haida Gwaii.

Mount Price and one of the Battleship Islands reflected in the clear water of Garibaldi Lake Mount Price, one of the three principal volcanoes in the southern segment, formed during three periods of eruptive activity. The first eruptive period 1.2 million years ago constructed a hornblende andesite stratovolcano on the floor of a cirque-like basin. During the Middle Pleistocene about 300,000 years ago, volcanism shifted westward and constructed the nearly symmetrical stratovolcano of Mount Price. Episodic eruptions produced andesite and dacite lavas, as well as pyroclastic flows from Peléan activity.

Lustrino, M.; Gomes, C.B; Melluso, L.; Morbidelli, L.; Muzio, R.; Ruberti, E. and Tassinari, C.C.G. Early Cretaceous Magmatic Activity in Southeast Uruguay: Trace Elements and Sr-Nd Isotopic Constraints Although volcanic rocks of the Paraná volcanism underlies more than half of Uruguay, they have in many areas been covered by younger sediments so that the lavas only crop out as a geological province in the Uruguayan northwest.David S. Thiede and Paulo M. Vasconcelos. 2010. Paraná flood basalts: Rapid extrusion hypothesis confirmed by new 40Ar/39Ar results. Geology vol 38.

Shallow subduction of young, buoyant slabs can result in the production of adakitic lavas via partial melting. Alternatively, metasomatised mantle wedges can produce highly oxidized conditions that results in sulfide minerals releasing ore minerals (copper, gold, molybdenum), which are then able to be transported to upper crustal levels. Mantle melting can also be induced by transitions from convergent to transform margins, as well as the steepening and trenchward retreat of the subducted slab. However, the latest belief is that dehydration that occurs at the blueschist-eclogite transition affects most subducted slabs, rather than partial melting.

While volcanic activity is reported as formation of a group of small islands, erosion has created the depressions which have a permeable base of "light grey, broken lava rocks, with harder rocks and grey or dark grey lavas overlying". Sandy soils resulting from sedimentation dominates the reserve with formation of parallel bars in the coastal area. The depressions are subject to filling by ephemeral floods; estuary lakes, grass marshes and wooded swamps caused by very heavy rainfall. Small tides of about height have also affected the coastal zone.

They are black, dark green, or red in colour; vary greatly in coarseness, some being full of round spongy bombs a foot or more in diameter; and being often submarine, may contain shale, sandstone, grit, and other sedimentary material, and are occasionally fossiliferous. Recent basaltic tuffs are found in Iceland, the Faroe Islands, Jan Mayen, Sicily, the Hawaiian Islands, Samoa, etc. When weathered, they are filled with calcite, chlorite, serpentine, and especially where the lavas contain nepheline or leucite, are often rich in zeolites, such as analcite, prehnite, natrolite, scolecite, chabazite, heulandite, etc.

Some authors have noted a series of large, km-wide fractured plates that appear southwest of the debouchment of the Athabasca Valles into the Cerberus Palus plains region. Some authors have interpreted these features as analogous to lava rafts expelled downstream from the Athabasca Valles system during its formation. Such rafts have been observed in the pahoehoe lavas of Hawaii which have stagnated, forming a surface that hardens and then cracks. Gas escapes from lava around the peripheries of the resulting polygons, collapsing their edges and causing the centers of the polygons to bulge.

Other lava flows from Trout Creek Hill are also embedded with till from Salmon Springs and Fraser Glaciation, but their exact age is unknown. Basaltic lavas from Trout Creek Hill show a lithology of pāhoehoe to blocky olivine, with pyroxene, breccia, scoria, and cinder deposits. Within the Marble Mountain–Trout Creek Hill field, there have been three eruptions during the Holocene epoch: at West Crater, another cone near Hackamore Creek, and a phreatic vent (producing steam and rock fragments) near Bare Mountain. These all took place about 8,000 years ago.

Most of the surrounding volcanoes consist of mafic (basaltic) lavas; only South and Middle Sister have an abundance of silicic rocks such as andesite, dacite, and rhyodacite. Mafic magma is less viscous; it produces lava flows and is less prone to explosive eruptions than silicic magma. The region was active in the Pleistocene, with eruptions between about 650,000 and about 250,000 years ago from an explosively active complex known as the Tumalo volcanic center. This area features andesitic and mafic cinder cones such as Lava Butte, as well as rhyolite domes.

This included new geochemical and geochronometric data for the Baldface Mountain and Satah Mountain volcanic fields, as well as for Nazko Cone. The data obtained indicated that volcanism in the two volcanic fields were contemporaneous with the Itcha Range shield volcano and that both fields agree with the vector of the North American Plate motion over a hotspot in the British Columbia Interior. It was also noted that the trace and rare-earth element patterns of mafic lavas in the Anahim Volcanic Belt are similar to ocean island basalts, providing more evidence for a hotspot.

However, past geologic field mapping and geochemical studies suggest massive plutons could be present in the offshore continental shelf. These suspected bodies are aligned with the northeast-trending Anahim Volcanic Belt, whose age progression suggests these suspected offshore plutons could be of Miocene age. An earlier displaced portion of the hotspot track might exist on Haida Gwaii as part of the Masset Formation. However, further analyses of Masset volcanic rocks are still required to determine if they are compositionally and istopically similar to alkalic lavas found on the mainland.

No large effusive eruptions have occurred since the 250,000 ± 5,000 eruption, and Holocene or recent eruptions have not been reported. While it was at first proposed that postglacial lavas existed it is now known that the volcano has been dormant since 271,000 years ago and glaciation has affected the youngest lava flows. The volcano is considered to be dormant. Fumaroles on Uturuncu Active fumaroles occur in two fields below the summit, with a number of tiny vents located between the two summit peaks; vapour emissions are visible from close distance.

The Kangaroo Point Cliffs were created by convicts mining the volcanic rock or ignimbrite or welded tuff which form the cliffs. These lavas and pyroclastic rocks were deposited in the Triassic Period about 230 million years ago and filled an ancient river valley. These rocks were known as porphyry and later became known as the geological unit called the Brisbane tuff. Records indicate that it was Captain Patrick Logan, commandant of the Moreton Bay penal settlement, who first opened a quarry to supply stone to his building works as early as 1826.

This county is an agglomeration of several distinct geologic terranes, as is most of the greater San Francisco Bay Area, which is one of the most geologically complex regions in the world. The great local mountain Mount Diablo has been formed and continues to be elevated by compressive forces resulting from the action of plate tectonics and at its upper reaches presents ancient seabed rocks scraped from distant oceanic sedimentation locations and accumulated and lifted by these great forces. Younger deposits at middle altitudes include pillow lavas, the product of undersea volcanic eruptions.

Geologists know that beneath Hawaii and Iceland, a temperature instability develops (for reasons not yet well understood) at the boundary between the core and mantle. The concentrated heat triggers a plume hundreds of kilometers in diameter that ascends directly through to the surface of the Earth. When the hot plume arrives at the base of the lithosphere, some of the lighter rock of the lithosphere rapidly melts. It is this molten lithosphere that becomes the basalt lavas that gush onto the surface to form the Columbia River and Snake River Plain basalts.

Over the next billion years, erosion exposed a number of the quartz-filled, banded vesicles—agates—were freed by running water and chemical disintegration of the lavas, since these vesicles were now harder than the lava rocks that contained them. The vast majority, however, remained lodged in the lava flows until the next major geologic event that changed them and Minnesota. During the ensuing ice ages a lobe of glacial ice, the Superior lobe, moved into Minnesota through the agate-filled Superior trough. The glacier picked up surface agates and transported them south.

The 3.6–2.3 mya Polan group, with ten dispersed volcanoes including Miño Volcano, is the largest group in the cluster and includes Tres Monos, La Luna, Cerro Polan, Chaihuiri, Miño Volcano and the lavas of the Aucanquilcha platform. Cerro Polan's (3.5–3 mya) eastern side is deeply dissected, and the exposed materials are heavily altered in the deeper sections. Lava fields to Polan's west and southwest (2.6 mya on one western field) are associated with it. La Luna (2.97–2.57) lies just east of Polan; these two volcanoes were probably one volcano in the past.

Leucite lavas from which feldspar is absent are divided into the leucitites and leucite basalts. The latter contain olivine, the former do not. Pyroxene is the usual ferromagnesian mineral, and resembles that of the tephrites and basanites. Sanidine, melanite, hauyne and perovskite are frequent accessory minerals in these rocks, and many of them contain melilite in some quantity, The well-known leucitite of the Capo di Bove, near, Rome, is rich in this mineral, which forms irregular plates, yellow in the hand specimen, enclosing many small rounded crystals of leucite.

The third stage of development consisted of floods of blocky lava erupting from below the summit and more fluid lavas erupting from basal fissures, mostly confined to the south slope. North Squaw Tip and South Squaw Tip on McLoughlin's west flank now mark the site of the two major blocky flow vents. There are two smaller vents as well. The entire third stage is thought to have happened after the last Pleistocene glaciers in the area had melted, due to a general lack of weathering and fresh appearance of the solidified lava.

By the trailhead of the summit path there lies a small noteworthy crater called Formica Leo, named for its resemblance to the sand pit trap of an antlion. Located outside of the main caldera is Commerson Crater, an extinct caldera notable for receiving intense rainfall, particularly during tropical storms. During Cyclone Hyacinthe in January 1980, it received of rainfall in 15 days, the most precipitation produced by a tropical cyclone in a single location. Some beaches in the proximity of the volcano are greenish in color, due to olivine sand derived from picrite basalt lavas.

The lower pressure, high temperature, and now volatile rich material in this wedge melts and the resulting buoyant magma rises through the overlying rock to produce island arc or continental margin volcanism. This volcanism includes more silicic lavas the further from the edge of the island arc or continental margin, indicating a deeper source and a more differentiated magma. At times some of the metamorphosed downgoing slab may be thrust up or obducted onto the continental margin. These blocks of mantle peridotite and the metamorphic eclogites are exposed as ophiolite complexes.

During late Miocene- Pliocene time (~10 to ~4 million years) the area was attended by volcanism (Late Miocene Tolay Volcanics and Late Miocene - Pliocene Sonoma Volcanics) which are interbedded with the late Miocene-Pliocene Petaluma Formation. The (~9 to 4 million year old) Petaluma Formation was a fresh-water river system flowing from east to west and through the volcanics. At that time, volcanic lava flows and river sands and gravels were actively deposited together, hence "interbedded lavas and gravels". The volcanoes may have been similar to island arcs.

San Pedro formed in two stages, which are known as the Old Cone and the Young Cone. The Old Cone was formed by lava and scoria and later largely buried by glacial, mudflows and volcanic deposits of the Young Cone; it forms about 80% of the volume of the present-day San Pedro edifice. One date has been obtained on Old Cone lavas by argon-argon dating: 160,000 years ago. After activity of the Old Cone ceased, glacial and fluvial erosion dissected San Pedro until the large sector collapse occurred.

The Barberton Mountain is a well preserved pre-3.0 Ga granite-greenstone terrane. The greenstone belt consists of a sequence of mafic to ultramafic lavas and metasedimentary rocks emplaced and deposited between 3.5 and 3.2 Ga. The granitoid rocks were emplaced over a 500 million year time span and can be divided into two suites. The TTG suite (emplaced approximately 3.5–3.2 Ga) contains tonalites, trondhjemites and granodiorites; and the GMS suite (emplaced approximately 3.2–3.1 Ga) includes granites, monzogranites and a small syenite–granite complex. According to a study by Yearron et al.

At the time of its formation, Daiichi-Kashima was located between 7.6° northern and 1° southern latitude, with one proposed coordinate being . One proposal envisages that volcanism took place in two separate stages, between which the western flank of the volcano underwent a large-scale collapse. In the first stage, basalts formed a volcanic island that eventually erupted trachytes. In a second stage, the western flank of the volcano collapsed and subsequently chemically different lavas and pyroclastics were emplaced, covering the bulk of the volcano and giving it a paired appearance similar to Reunion.

The central portion of the volcano is surrounded by an incomplete ring of faults (graben) and fractures, called Alba Fossae on the volcano's western flank and Tantalus Fossae on the eastern flank. The volcano also has very long, well preserved lava flows that form a radiating pattern from the volcano's central region. The enormous lengths of some individual flows (>) implies that the lavas were very fluid (low viscosity) and of high volume. Many of the flows have distinctive morphologies, consisting of long, sinuous ridges with discontinuous central lava channels.

More than six lava domes and two major cones are part of this system and surrounded by a pyroclastic apron, which covers a surface area of and is formed from many pyroclastic flows with a total volume of . The pyroclastic flows contain pumice and large blocks, some of which show signs of deformation when they were still hot. The lava domes and lavas are grouped in three units. Presumably, the activity of Tumisa started with explosive eruptions that generated the ignimbrite apron, later degassed magma formed the lava domes and lava flows.

The last eruption at The Volcano 150 years ago had a large impact on fish, plant and animal inhabitants in the valley the lava flows travelled through to cross the Canada – United States border. Because of these circumstances, future eruptions may again block the flow of local water courses if the volume of the erupted lavas are significant enough. This would again have disastrous consequences for fish habitats and spawning grounds. However, there are neither records of any impacts on people during this eruption, nor evidence that it was even witnessed by people.

Mount Scott first erupted about 420,000 years ago and is one of the oldest volcanoes in the Mount Mazama complex. It erupted mainly andesitic lavas before becoming extinct in the late Pleistocene. Since it was relatively far away from the main flanks of Mount Mazama, it survived the mountain's massive explosion that occurred around 5700 BC. At tall, Mount Scott is the highest point in Crater Lake National Park. Most of the lower slopes are covered with ash, pumice, and loose gravel, while the summit is mostly covered with scoria.

Erosional remnants of sills form the prominent mesas of North Mesa, Peaked Hill and Round Hill, the latter two of which consist of tholeiitic basalt and alkali basalt respectively. A major episode of Tertiary magmatism related to the opening of Baffin Bay emplaced mafic intrusions and volcanic rocks on Baffin Island and in West Greenland. Basaltic breccias and lavas on Baffin Island are exposed mainly along a narrow coastal strip between Cape Dyer and Cape Searle. They have a total thickness of over and are bounded in the north by minor intrusions.

This area contains many small shield volcanoes and cinder cones of mainly alkalic intraplate basalt with fractionated intermediate alkalic products, subordinate subalkaline mafic lavas, and several rhyolites as secondary products. There are about 205 vents that were active between 4.2 million and 600 thousand years ago. Seismic activity around Adams is very low and it is one of the quietest volcanoes in Oregon and Washington. It is monitored by the Pacific Northwest Seismic Network and the Cascades Volcano Observatory via a seismic station on the southwest flank of the mountain.

A series of pillow lavas were also deposited during this eruptive period. The most recent volcanic activity in the Bridge River volcanic field produced a series of basaltic lava flows in the regional valleys that overlie till of the last glacial period. The age of these valley-filling lava flows is unknown but the presence of unconsolidated glacial till under the flows suggests that they are less than 1,500 years old. To the northwest, the Franklin Glacier Complex is a set of volcanic bedrock that encompasses an area long and wide.

After lava inflation ends and the eruption wanes, the molten interior of the sheet flow typically subsides leaving a series of "bathtub rings" along the sides of the pillars. These rings are formed as the crust on the subsiding lava repeatedly adheres to and then breaks off from the pillar's sides. Lava pillars may continue to act as fluid conduits for years after an eruption. In uncollapsed lobate terrain, diffuse hydrothermal venting is typically focused in the depressions within the lobate lavas, which are probably underlain by pillars.

A wide amphitheater in eastern Tutupaca, open to the northeast, was formed by a major collapse of the volcano. Lava domes from the younger Tutupaca, as well as highly altered lavas from the older complex, are exposed within the collapse scar, which is the origin of a long debris avalanche deposit. The deposit is mostly found within glacial valleys and is interlaid by the Paipatja pyroclastic flow which divides the debris into two units. The pyroclastic flow reaches both Lake Suches north of the volcano and the Callazas River east of it.

Pahvant Butte, May 2015 Part of the Black Rock Desert volcanic field of the Pleistocene-Holocene age, Pahvant Butte formed above older pahoehoe and aa lavas of the Pahvant field. The volcano was originally a subaqueous volcano formed under Lake Bonneville by a large eruption about 15,500 years ago. The water depth at the time of eruption is estimated to have been . This eruptive activity probably ejected steam, ash, and other materials out of the lake, enveloping the surrounding area with ash and spawning large waves in the lake.

Indonesia, the Philippines, Japan, New Guinea, and New Zealand lie outside the andesite line. Within the closed loop of the andesite line are most of the deep troughs, submerged volcanic mountains, and oceanic volcanic islands that characterize the Pacific basin. Here basaltic lavas gently flow out of rifts to build huge dome-shaped volcanic mountains whose eroded summits form island arcs, chains, and clusters. Outside the andesite line, volcanism is of the explosive type, and the Pacific Ring of Fire is the world's foremost belt of explosive volcanism.

Pleistocene non-marine sediments are found primarily in fluvial deposits, lakebeds, slope and loess deposits as well as in the large amounts of material moved about by glaciers. Less common are cave deposits, travertines and volcanic deposits (lavas, ashes). Pleistocene marine deposits are found primarily in shallow marine basins mostly (but with important exceptions) in areas within a few tens of kilometers of the modern shoreline. In a few geologically active areas such as the Southern California coast, Pleistocene marine deposits may be found at elevations of several hundred meters.

Jorge Muñoz Cristi was in 1957 the first to define the rocks of Farellones as distinct unit and not as a facies as previously thought. Carlos Klohn then established the Farellones unit as a formation in 1960. Rivano and co-workers define two sub-units of the formation: a lower member made up of rather fresh rhyolitic ignimbrite and tuff, and an upper member made up of lavas of basaltic and andesitic composition. The volcanic rocks of Farellones Formation have mostly a calc-alkaline character contrasting with the mostly tholeiitic Abanico Formation.

Table Mountain is composed of Table Mountain Latite, which formed from potassium- rich lavas erupted from a center of volcanism near modern-day Sonora Pass around 10.4 million years ago. The lava flows followed the course of the ancestral Stanislaus River, filling the river valley. As the Sierra Nevada Mountains were uplifted, the softer sediments surrounding the flows were eroded away, leaving behind an inverted river valley. Although the formation stretches for miles and rises hundreds feet above the surrounding landscape, its width rarely exceeds a few hundred feet.

North of this, incipient rifting is magmatically manifested by unusual, shoshonitic lavas of the Hiyoshi complex, Fukutoku-oka-no-ba (or Sin Iwo Jima), and Iwo Jima . Rifting and spreading are inferred to be propagating northward at a rate of 10 to 40 cm/year , so the variations in tectonic and magmatic style seen along-strike north of 18°N provide an example of the sequence of events that occur at any one section across the back-arc basin as the rift evolves from updoming through rifting to true spreading.

Tricouni Southeast, another volcanic sequence south of Tricouni Peak, consists of at least four andesite or dacite lava flows that outcrop as several small cliffs and bluffs on extensively vegetated flanks. They reach thicknesses of and contain small amounts of hyaloclastite. The feeder of their origins has not been discovered but is likely located at the summit of the mound. These lavas form ice- marginal edifies, suggesting that every lava flow was erupted about 10,000 years ago when the vast Cordilleran Ice Sheet was retreating and remains of glacial ice were sparse.

It is composed of at least four lava flows of the Cheakamus Valley basalts. They are exposed in cliffs compassing the falls with a narrow sequence of gravel lying above the oldest lava unit. These lava flows are interpreted to have been exposed by erosion during a period of catastrophic flooding and the valley these lavas are located in is significantly larger than the river within it. The massive flooding that shaped the valley has been a subject of geological studies by Catherine Hickson and Andree Blais-Stevens.

The lavas became more gas- charged, throwing fragmented lava into the air which built the numerous, small scoria cones, such as the Seven Sisters, near Yungaburra. Some of the rising magma interacted with groundwater, producing violent eruptions that led to the formation of maar volcanoes, such as Lake Eacham and Lake Barrine. Although all the volcanoes in the Atherton Basalt Province are regarded as being extinct and volcanism has been waning over time, given the relatively recent activity, it is possible that further eruptions could occur in the future.

Most of Rubers Law is made of red sandstones and other sediments which used to be known as the Upper Old Red Sandstone. These rocks, now assigned to the Stratheden or Inverclyde groups (undifferentiated), were formed during the late Devonian or early Carboniferous Periods from the sand and gravel deposits of ancient river systems. This sedimentary deposition was followed by a period of volcanic eruptions which produced a series of basaltic lavas, some of which are now found near Kelso. The summit rocks of Rubers Law were formed within a volcanic vent.

Recent research revealed that volcanic eruptions did occur in the Nova Iguaçu region. After the eruptions, an intense uplifting and consequent regional denudation took place. The cones, craters, lavas, pyroclastic flow deposits, and volcanic bombs have been washed away in the strong tropical erosion of this region, exposing the underlying geologic structure. The Municipal Park is underlain by the geologic bodies corresponding to the magma chamber (composed of syenite and trachyte) and subvolcanic conduit (made up of pyroclastic rocks) of a depth of 3 kilometers, such as pyroclastic dikes.

Lava flows from mid-ocean ridge and plate boundary seamounts are mostly basaltic (both tholeiitic and alkalic), whereas flows from subducting ridge volcanoes are mostly calc-alkaline lavas. Compared to mid-ocean ridge seamounts, subduction zone seamounts generally have more sodium, alkali, and volatile abundances, and less magnesium, resulting in more explosive, viscous eruptions. All volcanic seamounts follow a particular pattern of growth, activity, subsidence and eventual extinction. The first stage of a seamount's evolution is its early activity, building its flanks and core up from the sea floor.

Guyots show evidence of having once been above the surface, with gradual subsidence through stages from fringed reefed mountain, coral atoll, and finally a flat-topped submerged mountain. Seamounts are made by extrusion of lavas piped upward in stages from sources within the Earth's mantle, usually hotspots, to vents on the seafloor. The volcanism invariably ceases after a time, and other processes dominate. When an undersea volcano grows high enough to be near or breach the ocean surface, wave action and/or coral reef growth tend to create a flat-topped edifice.

Hoodoo Butte lies near the Santiam Pass area, in the eastern segment of the Cascade Range known as the High Cascades, which trends north–south. Constructed towards the end of the Pleistocene epoch, these mountains are underlain by more ancient volcanoes that subsided due to parallel north–south faulting in the surrounding region. In the region stretching south from Mount Jefferson to Santiam Pass, shield volcanoes dominate, forming a broad ridge with cinder cones. Eruptions at these vents have produced rocks with compositions ranging from basaltic andesite to andesite and basalt lavas.

Examples of mascon basins on Mars include the Argyre, Isidis, and Utopia basins. Theoretical considerations imply that a topographic low in isostatic equilibrium would exhibit a slight negative gravitational anomaly. Thus, the positive gravitational anomalies associated with these impact basins indicate that some form of positive density anomaly must exist within the crust or upper mantle that is currently supported by the lithosphere. One possibility is that these anomalies are due to dense mare basaltic lavas, which might reach up to 6 kilometers in thickness for the Moon.

The Campo de Calatrava volcanic field is a volcanic field in Spain. The volcanic field is in the centre of the province of Ciudad Real, in a region known as Campo de Calatrava. The volcanic field has an area of more than 5000 km2 and more than 300 individual structures and contains pyroclastic cones, lava domes and maars. The field erupted basaltic to foiditic lavas from the Pliocene to the Holocene in Columba volcano with phreatomagmatic activity, and fumaroles were observed in the 16th-18th centuries in the Sierra de Valenzuela territory.

When exposed to air studtite converts over a short time to the metastudtite UO4·2(H2O) form. Despite their apparent chemical simplicity, these two uranyl species are the only reported peroxide minerals. They may also be readily formed on the surface of nuclear waste under long-term storage and have been found on the surface of spent nuclear fuel stored at the Hanford, Washington nuclear site. It has also been reported that studtite has since formed on the corium lavas that were created during the course of the Chernobyl nuclear plant accident.

Rocks from the Moon have been measured by radiometric dating techniques. They range in age from about 3.16 billion years old for the basaltic samples derived from the lunar maria, up to about 4.44 billion years old for rocks derived from the highlands. Based on the age-dating technique of "crater counting," the youngest basaltic eruptions are believed to have occurred about 1.2 billion years ago, but scientists do not possess samples of these lavas. In contrast, the oldest ages of rocks from the Earth are between 3.8 and 4.28 billion years old.

Arabia Terra is a large upland region in the north of Mars that lies mostly in the Arabia quadrangle. Several irregularly shaped craters found within the region represent a type of highland volcanic construct which, all together, represent a martian igneous province. Low- relief paterae within the region possess a range of geomorphic features, including structural collapse, effusive volcanism and explosive eruptions, that are similar to terrestrial supervolcanoes. The enigmatic highland ridged plains in the region may have been formed, in part, by the related flow of lavas.

The area around Loch Na Fooey is known as the site of the ancient "Finny volcano" (490 million years ago), formed as the Iapetus Ocean closed to bring the two halves of Ireland together. The volcano's landform is now gone but some of volcanic rocks are preserved in the area, including pillow lavas, and breccia. There is a small funnel-shaped island close to the south-eastern shore known as Red Island (An tOileán Rua). The waters hold a range of fish including wild brown trout and pike.

The oldest rocks at Irruputuncu are lavas that have been dated by potassium-argon dating to 10.8 ± 0.6 mya. The oldest component clearly belonging to the volcano is the El Pozo ignimbrite that was erupted 258.2 ± 48.8 ka, forming a multi-layered ignimbrite that was probably generated by the injection of new, hot magma into older, cooler magma. A lava dome on the upper flank on the western side of the volcano is 0.14 ± 0.04 mya old. The block and ash flow between 55.9 ka and 140 ka old, but has not been precisely dated.

The Danco Coast Tectonic Block includes the Upper Permian-Triassic Trinity Peninsula Group, consisting of over 1000 m of metaturbidites folded during the Gondwanide orogeny. This group is overlain by the Lower Cretaceous Antarctic Peninsula Volcanic Group, with up to 2000 m of basaltic and andesitic lavas, tuffs and agglomerates, which were folded and faulted during the Tertiary. These two groups were intruded by the Berriasian-Cenomanian granite and gabbro sills of the Andean Instrusive Suite. A system of hypabbysal dykes intruded during the Late Cretaceous or Tertiary.

Analysis of igneous rock microstructure may complement descriptions on the hand specimen and outcrop scale. This is especially vital for describing phenocrysts and fragmental textures of tuffs, as often relationships between magma and phenocryst morphology are critical for analysing cooling, fractional crystallization and emplacement. Analysis of intrusive rock microstructures can provide information on source and genesis, including contamination of igneous rocks by wall rocks and identifying crystals which may have been accumulated or dropped out of the melt. This is especially critical for komatiite lavas and ultramafic intrusive rocks.

Volcanic pyroclastic rocks are formed by explosive eruption of lava and any rocks which are entrained within the eruptive column. This may include rocks plucked off the wall of the magma conduit, or physically picked up by the ensuing pyroclastic surge. Lavas, especially rhyolite and dacite flows, tend to form clastic volcanic rocks by a process known as autobrecciation. This occurs when the thick, nearly solid lava breaks up into blocks and these blocks are then reincorporated into the lava flow again and mixed in with the remaining liquid magma.

There is a small amount of andesite in the lavas from the field, mostly erupted from monogenetic vents or Larch Mountain. Sometimes, Boring Lava overlaps with volcaniclastic conglomerate from other Cascade eruptions in Multnomah County and the northern part of Clackamas County. The Boring Lava also contains tuff, cinder, and scoria; it is characterized by plagioclase laths that show a pilotaxitic texture with spaces between them that show a diktytaxitic texture. The Boring Lava exposures show aeromagnetic anomalies with short wavelengths and high amplitudes suggestive of their relatively young geological ages.

These interpretations were based on Viking orbiter imagery, MOC imagery, THEMIS thermal mapping, and MOLA elevation mapping. However, Spirit did not find any lacustrine deposits, instead Spirit found alkaline volcanic rocks, including olivine basalt, comminuted basaltic debris, lavas, and pyroclastic rocks, but no eruption centers. Panoramic photo taken by Spirit Rover on January 1, 2006 from the crater Gusev, looking up a slope and across rippled sand deposits in a dark field dubbed "El Dorado". More recently, satellite images showed the trails of dust devils on Gusev's floor.

The Eycott Volcanic Group is a group of volcanic rock formations of Ordovician age (Llandeilo to Caradoc epochs) named after the locality of Eycott Hill in the English Lake District.British Geological Survey 1997 Cockermouth England and Wales sheet 23 Solid 1:50,000 Keyworth, Nottingham, BGS The group overlies the Skiddaw Group and is unconformably overlain by a variety of different Devonian and Carboniferous age rocks. This rock sequence has previously been known as the Eycott Group. It consists largely of andesitic lavas and sills with tuffs, breccias and volcaniclastic sandstones.

Because of these mixing mechanisms, lavas may have different compositions but similar appearances, or similar compositions with different appearances. The eruption that produced the Chaos Crags consisted of more than 90% mixed magma, and likely resulted from the interaction of felsic and mafic magmas. The Eagle Peak sequence, which includes the Chaos Crags, consists of seven dacite and rhyodacite lava domes and lava flows, along with pyroclastic rock deposits. The Chaos Crags consist of five small lava domes, made of rhyodacite, which line up with the western edge of the Mount Tehama caldera.

This back-arc volcanism that Tunupa is part of has an uncertain origin; one proposed process is delamination, whereby the lowermost mafic section of the crust and lithosphere underneath separates itself from the above lying layers. This separation process then triggers volcanic activity through either decompression melting, dehydration melting, increases in temperature, or some combination of these processes. Back-arc volcanism in the region started about 25-30 million years ago. East of Tunupa lie the Huayrana lavas, which are much older (Potassium-argon dating has yielded an age of 11.1 ± 0.4 million years ago).

Ushas Mons is a 2-kilometer-high (1.25 mile) volcano in the southern hemisphere of Venus at 25 degrees south latitude, 323 degrees east longitude. Its name is derived from vedic goddess of dawn Ushas The volcano is marked by numerous bright lava flows and a set of north-south trending fractures, many of which appear to have formed after the lavas were erupted onto the surface. In the central summit area, however, younger flows remain unfractured. An impact crater can be seen among the fractures in the upper center of the image.

The behavior of Etna changed after the eruption, presumably due to the large volume of material erupted in the 1669 event and changes in the plumbing system it caused. After 1669, Etna's eruptions were smaller, shorter, and more sporadic with fewer flank eruptions, and mafic phenocrysts became more common in the lavas. The 1669 eruption has been defined as the starting point of a century-long cycle of activity that continues to this day and Etna's volcanic products are subdivided into pre-1669 and post-1669 formations in Italy's geological map.

Plutonic rocks around San Martín de los Andes crystallized from magma in the Devonian in connection to the onset of the Gondwanide orogeny. Plutonic rock types in the area are granodiorites, tonalites and less voluminous gabbros. Plutonic and metamorphic rocks make up the basement around San Martín de Los Andes, yet near Cerro Chapelco this basement is overlain by volcaniclastic and sedimentary rock belonging to Huitre Formation. The higher parts of Cerro Chapelco are made up of basaltic and andesitic lavas of Chapelco Formation which overlies Huitre Formation.

Animal remains from the cave show that its early inhabitants had a diet of bushpig, warthog, zebra and buffalo. Raw materials used in the making of artifacts include chert, rhyolite, quartz, and chalcedony, as well as bone, wood and ostrich egg shells. The west-facing cave, which is near Ingwavuma, is located about 100 m below the crest of the Lebombo range and commands sweeping views of the Swazi countryside below. It is semi-circular in horizontal section, some 40 m across, and formed in Jurassic lavas as a result of differential weathering.

Jacquemart Island consists of a stack with an area of , being about in length by in width and surrounded by precipitous cliffs at least high at their lowest. Its highest point is about asl. It is an eroded remnant of basaltic lavas originally laid down on a sedimentary base. Because of its inaccessibility from the sea, the first visit by humans to the island did not take place until 29 December 1980 when a small party of scientists was landed by helicopter on the summit ridge for a 90-minute survey.

Water is scarce in this karst landscape, especially during the dry months, resulting in the presence of a vegetation type adapted to seasonally drier conditions, and a seasonal migration of wildlife to the lowlands. Smaller streams that emerge as springs within the hill slopes then disappear underground again after flowing a short distance – a characteristic of this limestone topography. Only the Bladen, flowing over the porphrytic Bladen Volcanic Member (an area composed of lavas and associated extrusive volcanic sediments that lies between the Santa Rosa Group and the limestone hills), runs permanently throughout the year.

As a story-teller, educator and colleague, he was much-loved, supportive, inspirational to generations of students and considered his role more as a vocation than a job. Showing his great humour, he duped his students into believing in rats occupying lava tubes and that the principal danger to be encountered while working amongst rope-like Hawaiian pahoehoe lavas was a poisonous snake. He had a great talent for interpreting geology from morphology, even from photographs. Very inquisitive, he was fascinated by the international cultures and customs he encountered on his travels.

This quiescence was followed by a mafic capping stage between 2.2 and 0.8 million years ago, but renewed activity might have occurred in the last 340,000 years. Alkali olivine basalts of the mafic capping stage were derived from the fractionation of a clinopyroxene, olivine and oxide assemblage. However, the associated hawaiite lavas may have derived from an alkali olivine basalt parent by the fractionation of a clinopyroxene-dominated assemblage at higher pressures. As volcanic activity waned during the mafic capping stage, lava flows became more viscous and decreased in volume.

The mountain is part of the Tawau volcanic field which contributed to the prominent topographic features of the Semporna Peninsula in northeastern Borneo and the western side of a valley in its middle section. The low volcanic cone is north of Sebatik Island and has a roughly 300-m-wide crater breached to the south. Two young lava flows extend almost to the coastal plain. The flows are considered younger than a lava flow radiocarbon dated at about 27,000 years before present, and the extrusion of basaltic lavas possibly continued into the Holocene epoch.

Acid lavas are found in the area surrounding the High Island Reservoir and the south islands such as Kau Sai Chau, Tiu Chung Chau and Basalt Island, banded acid lava with some welded tuffs are found in the central and southern shore of Pak Tam Chung area. The most spectacular of all are the hexagonal columnar joints which are found near the east dam of the High Island Reservoir and Po Pin Chau area. They are the results of the uniform cooling of tuff. This natural landscape is complemented by the nearby gigantic water works.

Felsic or silicic lavas such as rhyolite and dacite typically form lava spines, lava domes or "coulees" (which are thick, short lava flows) and are associated with pyroclastic (fragmental) deposits. Most silicic lava flows are extremely viscous, and typically fragment as they extrude, producing blocky autobreccias. The high viscosity and strength are the result of their chemistry, which is high in silica, aluminium, potassium, sodium, and calcium, forming a polymerized liquid rich in feldspar and quartz, and thus has a higher viscosity than other magma types. Felsic magmas can erupt at temperatures as low as .

The rocks on either side of the fault have moved relative to one another with the western section transposed northward. West of the St. Magnus Bay Fault the rocks of Papa Stour and Esha Ness are Old Red Sandstone and lavas of Devonian age, which have produced spectacular cliffs at the latter location and numerous caves at the former and at nearby Brei Holm. Kirstan's Hole in the southwest of Papa Stour at has been described as the finest sea cave in Britain. Hole of Bordie further north penetrates the massive cliffs for nearly .

Pyroxenes that crystallize in the monoclinic system are known as clinopyroxenes and those that crystallize in the orthorhombic system are known as orthopyroxenes. The name pyroxene is derived from the Ancient Greek words for fire (πυρ) and stranger (ξένος). Pyroxenes were so named because of their presence in volcanic lavas, where they are sometimes seen as crystals embedded in volcanic glass; it was assumed they were impurities in the glass, hence the name "fire strangers". However, they are simply early-forming minerals that crystallized before the lava erupted.

Its lavas are made of basalt, a common grey to black or dark brown extrusive volcanic rock low in silica content (the lava is mafic) that is usually fine-grained due to rapid cooling of lava on the Earth's surface. Pāhoehoe is found at the volcano, which has a smooth, billowy, undulating, or ropy surface. A pāhoehoe flow typically advances as a series of small lodes and toes that continually break out from a cooled crust.Basaltic Lava Retrieved on 2008-02-13 It also forms lava tubes where the minimal heat loss maintains low viscosity.

Volcanic activity began less than one million years ago and occurred at between 40 and 30 separate volcanic vents, some of which are submarine. Sea level varied during the activity of the volcanic field, and some volcanic eruptions have been dated through correlation with individual sea level fluctuations. The field erupted various kinds of lavas of mostly basaltic type with a high content of xenoliths. During eruptions, ascending magma often underwent interactions with water and thus caused steam explosions and the formation of particular volcanic structures such as tuff cones.

The differences between these two deposits can be accounted for by a few factors, including time of eruption and placement. The material inside the caldera must be younger and erupted from a pool of magma that had larger crystals. Its extensive erosion can be explained by the presence of hydrothermal vents, and its high levels of lithics probably originate from either being exposed to the rocks after they were erupted, lying adjacent to them while they underwent subsidence, or is a result of long, slow formation. Any of these reasons would also effectively account for the poor mixing of the lavas.

Thick tuffs were deposited in the Pago caldera, and the southern rim was buried by lavas composed of picritic basalts, andesites, and trachytes. Subsequent erosion in Early to Middle Pleistocene enlarged the calderas, the Pago River in particular carved a deep canyon, the forerunner of today's Pago Pago Bay. A submarine shelf formed from the erosional runoff, allowing for the development of coral reefs before the island was submerged 600 to 2000 feet. Sea level fluctuations continued in the Middle to Late Pleistocene. A barrier reef formed, was submerged 200 feet, before emerging 50 feet, leaving sea caves above sea level.

West of Tanner Canyon, erosion has locally removed as much as 300 m of Cardenas Basalt before the deposition of the Nankoweap Formation. As demonstrated by a 10 m thick ferruginous weathered zone (paleosol), deep chemical weathering of the exposed lava flows of the Cardenas Basalt occurred before deposition of the Nankoweap Formation west of Tanner Canyon. The deeply weathered lavas retain their original textures but have been pervasively stained and altered to earthy hematite and siderite. The upper contact of the Nankoweap Formation with the base of the Galeros Formation of the Chuar Group appears to be quite sharp.

Volcanic activity would have started with volcaniclastic accumulations, like volcanic ash, quickly followed by vast outpourings of highly fluid basaltic lava during successive eruptions through multiple volcanic vents or in linear fissures. As mafic low viscosity lava reached the surface it rapidly cooled and solidified, successive flows built up layer upon layer, each time filling and covering existing landscapes. Hyaloclastites and pillow lavas were formed when the lava flowed into lakes, rivers and seas. Magma that did not make it to the surface as flows froze in conduits as dikes and volcanic plugs and large amounts spread laterally to form sills.

Although it is now well accepted that subducting slabs cross the mantle transition zone and descend into the lower mantle, debate about the existence and continuity of plumes persists, with important implications for the style of mantle convection. This debate is linked to the controversy regarding whether intraplate volcanism is caused by shallow, upper-mantle processes or by plumes from the lower mantle. Many geochemistry studies have argued that the lavas erupted in intraplate areas are different in composition from shallow-derived mid-ocean ridge basalts (MORB). Specifically, they typically have elevated Helium-3 – Helium-4 ratios.

The story of the Fundy Basin begins about 200 million years ago in the early Jurassic, when all land on earth was part of a supercontinent called Pangaea. At that time what is now The Maritimes was situated near the equator and had a warm tropical climate and lush vegetation. As continental drift reshaped the world, rift valleys formed, including the Cobequid-Chedabucto fault system. During the continental breakup, magma erupted as basaltic lavas and left igneous rock formations such as the columnar jointing which can be seen on Brier and Grand Manan islands, among other places around the bay.

These 2.5 to 2.8 million year-old basalt lavas, commonly known as trap rock, fractured during cooling into vertically standing, hexagonal basalt columns. These columns are locally known as the "organ pipes" for which this park is named. Over the last one to two million years, the slow cutting by Jackson Creek of its valley down into the basaltic plains and through the underlying trap rock exposed these geological structures. The bottom of the valley of Jackson Creek also exposes a prehistoric buried creek valley, which is cut into 400 million year-old (Silurian) mudstones and sandstones.

The area is mostly covered by a Pliocene blanket of pyroclastic rocks and calc-alkaline lavas, Quaternary lahar deposits and fluvio-glacial deposits. The Buesaco-Aranda Fault has a very well-defined fault trace, with strongly deformed landforms of Pleistocene- Holocene age, clear breaks in slope along eroded fault scarps, and fault scarps facing both to the southeast or the northwest, which is a characteristic of strike-slip faults. Systematic right lateral deflections of some stream gullies, river channels, and ridges are visible. Offset features in confined alluvial deposits and in recent alluvial fans have fresh scarp morphology.

Andesite lava is intermediate in silica content, indicating that it has a higher viscosity than basaltic lava, but less viscous than dacite and rhyolite lava. As a result, andesite lava flows typically move slower than basaltic lava flows and are less likely to travel far from their source. Dacite and rhyolite lavas are normally too viscous to flow far from a volcanic vent, resulting in the formation of lava domes. An exception is the long Ring Creek dacite lava flow from Opal Cone on the southeastern flank of Mount Garibaldi, a length that is normally attained by basaltic lava flows.

The frequent presence of rounded corroded quartz crystals, such as occur in rhyolitic lavas, helps to demonstrate their real nature. Welded ignimbrites can be highly voluminous, such as the Lava Creek Tuff erupted from Yellowstone Caldera in Wyoming 631,000 years ago. This tuff had an original volume of at least . Lava Creek tuff is known to be at least 1000 times as large as the deposits of the May 18, 1980 eruption of Mount St. Helens, and it had a Volcanic Explosivity Index (VEI) of 8, greater than any eruption known in the last 10,000 years.

Behn, M. D., Kelemen, P. B., Hirth, G., Hacker, B. R., and Massonne, H. J., 2011, Diapirs as the source of the sediment signature in arc lavas: Nature Geoscience, v. DOI: 10.1038/NGEO1214. Diapiric rise of a much larger subducted continental body has been invoked to explain the exhumation of the Papua New Guinea UHP terrain.Little, T. A., Hacker, B. R., Gordon, S. M., Baldwin, S. L., Fitzgerald, P. G., Ellis, S., and Korchinski, M., 2011, Diapiric Exhumation of Earth’s youngest (UHP) eclogites in the gneiss domes of the D'Entrecasteaux Islands, Papua New Guinea: Tectonophysics, v.

The central band is a mix of volcanic and sedimentary rocks of mid-to-late Ordovician age comprising the lavas and tuffs of the Borrowdale Volcanic Group, erupted as the former Iapetus Ocean was subducted beneath what is now the Scottish border during the Caledonian orogeny. The northern central peaks, such as Great Rigg, were produced by considerable lava flows. These lava eruptions were followed by a series of pyroclastic eruptions which produced a series of calderas, one of which includes present-day Scafell Pike. These pyroclastic rocks give rise to the craggy landscapes typical of the central fells.

Since nyerereite is very unstable when it reaches the surface it creates pseudomorphs,Hay, R.L., (1983) Carbonatite tuffs in the Laetolil Beds of Tanzania and the Kaiserstuhl in Germany. Contributions to Mineralogy and Petrology 82, 403-406 which is basically the process by which the rock appearance and dimensions remain constant but the main mineral component is replaced by another. McKie (1976) categorized nyerereite into two different categories, high and low nyerereite. There are two types because the Ol Doinyo Lengai lavas are very soluble and hygroscopic; when they come in contact with water or the atmosphere, the lava changes physically and chemically.

Ben Nevis is all that remains of a Devonian volcano that met a cataclysmic end in the Carboniferous period around 350 million years ago. Evidence near the summit shows light-coloured granite (which had cooled in subterranean chambers several kilometres beneath the surface) lies among dark basaltic lavas (that form only on the surface). The two lying side-by-side is evidence the huge volcano collapsed in on itself creating an explosion comparable to Thera (2nd millennium BC) or Krakatoa (1883). The mountain is now all that remains of the imploded inner dome of the volcano.

Its form has been extensively shaped by glaciation. Research has shown igneous rock from the Devonian period (around 400 million years ago) intrudes into the surrounding metamorphic schists; the intrusions take the form of a series of concentric ring dikes. The innermost of these, known as the Inner Granite, constitutes the southern bulk of the mountain above Lochan Meall an t-Suidhe, and also the neighbouring ridge of Càrn Mòr Dearg; Meall an t-Suidhe forms part of the Outer Granite, which is redder in colour. The summit dome itself, together with the steep northern cliffs, is composed of andesite and basaltic lavas.

Although Meiji is the oldest extant seamount in the Hawaii-Emperor chain, the question of whether there were older seamounts in the chain which have already been subducted into the trench remains open, and is the subject of ongoing scientific research. The Deep Sea Drilling Project (DSDP) Leg 19, Hole 192A, recovered of pillow lava from near the summit of Meiji. The lavas were initially classified as alkali basalts on the basis of their mineralogy, but subsequent microprobe analyses of glass and pyroxene suggested that they are tholeiitic in origin. At least five flows were found.

In the Smithton Synclinorium the Togari Group followed with conglomerate from the Sturtian and Marinoan glaciations and dolomite marking the end of Cryogenian and on into the Ediacaran and Cambrian. The Togari group contains greywacke, conglomerate, diamictite, mafic volcanic rocks, and quartz sandstone, and mudstone. The components of the Togari Group are called Forest Conglomerate and Quartzite, Black River Dolomite, Kanunnah subgroup (containing the lavas) and Smithton Dolomite. These rocks are important for determining the boundary between the Cryogenian and Ediacaran periods as they contain volcanics that can be dated and dolomites marking the end of glaciations and marking the period boundary.

The Insular Mountains have much seismic activity, with the Juan de Fuca Plate subducting at the Cascadia subduction zone and the Pacific Plate sliding along the Queen Charlotte Fault. Large earthquakes have led to collapsing mountains, landslides, and the development of fissures.Insular Mountains in the Canadian Mountain Encyclopedia. Retrieved on 2007-12-02 Flood basalts on Vancouver Island form a geologic formation called the Karmutsen Formation, which is perhaps the thickest accreted section of an oceanic plateau worldwide, exposing up to of basal sediment-sill complexes, basaltic to picritic pillow lavas, pillow breccia, and thick, massive basalt flows.

In total, throughout its 150,000 years of eruptive activity, Broken Top erupted between of lava. Though most of the material that forms Broken Top's volcanic cone originated from its main vent, the edifice was also built up by auxiliary vents on its flanks and parasitic cones that surrounded the main edifice. The side vents erupted to form fissure vents, producing basalt and andesite, while the parasitic vents erupted scoria. Broken Top's volcanic crater, now in diameter, was most likely created through subsidence, which created a depression that was filled with thick basaltic andesite lava flows topped by thin lavas.

Retrieved on 2007-10-18 The formation is a rare alkaline-suite that formed as a result of submarine rifting during the Paleoproterozoic period.Volcanology and geochemistry of the Bravo Lake Formation, Baffin Island, Nunavut. Retrieved on 2007-10-18 The Bravo Lake Formation is surprisingly undeformed by the Himalayan-scale forming event during the Trans- Hudsonian orogeny. The stratigraphy of the Bravo Lake Formation starts with a basic section of iron-oxide rich sandstones, psammites, and semi-pelites which cover a series of deformed pillow lavas which expand in viscosity towards the west, and volcanic/clastic deposits and ultramafic sills.

This supergroup is a sedimentary-volcanic sequence, in which the sedimentary Schumacherfjellet Formation and Högfonna Formation are intruded by the Grunehogna and Kullen mafic sills (838 Ma). The basaltic lavas of the Straumsnutane Formation (821 Ma) is the uppermost unit within the supergroup. To the east of the Ritscherflya Supergroup, lies the Proterozoic metamorphic terrane of H.U. Sverdrupfjella, which is composed of para- and orthogneisses. The Sør Rondane Mountains are underlain by Late Proterozoic metamorphic rocks of the Teltet-Vengen Group and the Nils Larsen Group gneisses, which are intruded by latest Proterozoic to Early Paleozoic plutonic rocks and dykes.

Map of the road to the lava tube The cones have given rise to about 60 lava flows. Lava flows reach lengths of , thicknesses of and have surface features similar to pahoehoe or aa lava depending on how steep the slopes they flowed down were. The lava flows display structures like levees, finger-like and lobe-like edges at the lava flow margins, spines and spires and material from the cones that was rafted away by the lavas. One can distinguish between long flows which dominate the field, and shorter rougher flows covered by blocks with sizes of up to .

Argaka () is a village in the Paphos District of Cyprus, located 7 km northeast of Polis Chrysochous. From a geological perspective, it is located upon the calcareous sandstones, the sands, and the marls of the Pleistocene period as well as the lavas and the magma rocks (northeast of the settlement). From a morphological aspect, what stand out are the coastal, alluvial plain, one or two marine terraces, and a slope that steadily ascends up to 500 metres. Several streams flow down from the slope toward the sea, indeed with a relatively large one flowing next to the village.

The volcanic field lies about south from Hawaiʻi Island, at a depth of around below sea level. It covers an area of . It consists of several metres thick lava flows that are surrounded by sediment-covered seafloor mainly to the north and east and by clusters of Cretaceous seamounts mainly to the west and southwest. In sidescan sonar images, young lava flows have a bright appearance while older ones are covered by sediments and thus appear darker, and structures identified as lava coils, lava rubble, lava tumuli, pillow lavas, polygons and sheet flows have been observed on young flows.

Only a few plant remains have been found between these lavas. The bedrock in this area, roughly from Skien to Oslo and Mjøsa, results in soil rich in nutrients important for plant growth. Since the Permian, erosion has removed the volcanic peaks and indeed most of the lava layer and laid bare the magma chambers and volcanic pipes deep below, allowing scientist a rare view of what goes on beneath a rift valley. Several of the old magma plumes are now quarried, the rich black larvikite (named from Larvik, a town south of Oslo) being one.

Older and more deeply eroded, the Western Cascades are a range of volcanoes lying west of and merging with the High Cascades. They consist of partly altered volcanic rock from vents in both volcanic provinces, including varied lavas and ash tuffs ranging in age from 0 to 40 million years. As the Cascades rose, the Rogue maintained its flow to the ocean by down-cutting, which created steep narrow gorges and rapids in many places. Bear Creek, a Rogue tributary that flows south to north, marks the boundary between the Western Cascades to the east and the Klamath Mountains to the west.

Wichhu Qullu (Aymara jichu, wichhu stipa ichu, qullu mountain, "ichu mountain", also named Wichukkollu Loma (Spanish loma hill) is a mountain in a volcanic field in the Cordillera Occidental of Bolivia northeast of the summit of the Chullkani volcano. It is located in the Oruro Department, Sajama Province, Turco Municipality, between Jach'a K'uchu in the northeast and Liyun Ikiña in the southwest. The peak of Wichhu Qullu reaches a height of approximately . The Wichhu Qullu lavas, named after the mountain, are lava flows whose outcrops are best visible in the Qhuyani (Khoyani), Liyun Ikiña and Wichhu Qullu valleys.

At the level on Adams' south flank is South Butte. The lavas associated with this structure are all younger than Suksdorf Ridge but were emplaced before the end of the last ice age. Trout Lake (Trout Lake Creek) reflecting Mount Adams near the small town of Trout Lake Several relatively young obvious lava flows exist in the area around Adams. Most of these flows are on the north side of the mountain and include the flow in the Mutton Creek area, Devils Garden, the Takh Takh Meadows Flow, and the much larger Muddy Fork Lava Flow to the north of Devils Garden.

The eruption is intriguing both in terms of the viscosity of the erupted lavas and its effusive nature. Conventional lava flows increase in viscosity with increasing crystal content; however Chao lava flows were erupted with similar viscosities and yield strengths as silicic domes. The formation of a lava flow instead of a lava dome may have been influenced by the formation of a carapace on the flow and the steep slopes the flows initially formed on; the late Chao III flow formed on the very gentle slope left by the previous Chao I and Chao II flows and shows some lava dome characteristics.

Aerial photo of Panum Crater Panum Crater is the northernmost volcano in the sequence and is a good example of both a tuff ring and a rhyolite dome. Its structure is twofold; an outer tuff ring (forming a classic crater) and an inner plug, or dome of rhyolite, pumice and obsidian created from lavas. In this case, heat from the magma feeding Panum flashed groundwater to steam to create the tuff ring before lava reached the surface. Other Mono Craters also were formed in this manner, but their plug domes grew larger than their tuff ring craters.

At the time that these tidal flats were covered by the initial eruption of the Cardenas Basalt, the eastern grand Canyon region was at or very near sea level. Features found in the lowermost part of the Cardenas Basalt indicate that the basaltic lavas outpoured over unconsolidated sandy and silty Dox sediments at the time they were wet. It is unknown whether these sediments were slightly above or slightly below water level at the time they were buried by lava. The high proportion of altered glass in and the pervasive fracturing (hyaloclastite) of the basal Cardenas Basalt support this interpretation.

Cenozoic sediments are unimportant except for volcanic ash and Asian loess deposited adjacent to Japan and carbonate sediment s associated with the relatively shallow Caroline Ridge and Caroline plate. Strong seafloor currents are probably responsible for this erosion or non-deposition. The compositions of sediments being subducted beneath the northern and southern parts of the IBM arc are significantly different, because of the Cretaceous off-ridge volcanic succession in the south that is missing in the north. Lavas and volcaniclastics associated with an intense episode of intraplate volcanism correspond in time closely to the Cretaceous Superchron.

During the most recent eruptive episode between 3000 and 900 years ago, eight eruptions produced approximately of lava ranging in composition from basalt to rhyolite. Late Holocene lava compositions include basalt and andesite, but silicic lavas dominate. Eruptive activity during Holocene time has included numerous rhyolite and dacite lava flows erupted at high elevations inside and outside the caldera; cinder cones and associated lava flows of basalt and basaltic andesite have resulted from eruptions at vents on the flanks of the shield. Most vents are aligned along zones of crustal weakness that trend northeast to northwest.

The eastern Snake River Plain is a topographic depression that cuts across Basin and Range Mountain structures, more or less parallel to North American plate motion. Beneath more recent basalts are rhyolite lavas and ignimbrites that erupted as the lithosphere passed over the hotspot. Younger volcanoes that erupted after passing over the hotspot covered the plain with young basalt lava flows in places, including Craters of the Moon National Monument and Preserve. The central Snake River plain is similar to the eastern plain, but differs by having thick sections of interbedded lacustrine (lake) and fluvial (stream) sediments, including the Hagerman Fossil Beds.

The authors refer to their experience from watching and researching the Gjálp eruption from 1996 which has had many similarities to the Helgafell formation. At Helgafell next an edifice was formed about 300 m high in an ice vault, meltwater drained away very fast through subglacial channels so that the explosive activity continued to the end, which seems to have been after some days. This explains the fact, that Helgafell is next to overall made from mafic hyaloclastite, whereas most other researched smaller subglacial volcanoes showed a basis of pillow lavas. Of these and some small intrusions, the researchers just found minimal quantities.

It is located within the Australian marine park known as the South-west Corner Marine Park. The Naturaliste Plateau formed during the Early Cretaceous 136 Ma when Australia and India broke up and during the Late Cretaceous 83 Ma when Australia and Antarctica broke up. Lavas and intrusive rocks on the plateau flanks have ages of between 132-128 Ma. The eastern flank of the plateau slopes relatively gently, while the other three flanks are relatively steep. The southern flank formed during the Australia-Antarctica break-up, the other flanks during the rifting between India and Australia.

The western edge of the North American continent was later pushed against the oceanic plate under the adjacent ocean. An area of great compression called a subduction zone was formed in the early-to-mid Mesozoic, which replaced the quiet, sea-covered continental margin with erupting volcanoes and uplifting mountains. A chain of volcanoes pushed through the continental crust parallel to the deep trench, fed by magma rising from the subducting oceanic plate as it entered the Earth's hot interior. Thousands of feet (hundreds of meters) of lavas erupted, pushing the ocean over to the west.

Mead is classified as a multi-ring crater with its innermost, concentric scarp being interpreted as the rim of the original crater cavity. No inner peak-ring of mountain massifs is observed on Mead. The presence of hummocky, radar- bright crater ejecta crossing the radar-dark floor terrace and adjacent outer rim scarp suggests that the floor terrace is probably a giant rotated block that is concentric to, but lies outside, the original crater cavity. The flat, somewhat brighter inner floor of Mead is interpreted to result from considerable infilling of the original crater cavity by impact melt and/or by volcanic lavas.

The formation of Nemrut and the first stage of eruptions began about 1 million years ago with fissure eruptions that later localized in separate vents separated by 5–10 km. These eruptions resulted in a strong (thicker than 50 m) layer of successive pyroclastic deposits consisting mainly of trachyte. Their products covered an area of 500 km2, forming a plateau that hid the continental deposits of the Miocene period. The cone of Nemrut was further formed by mobile dark trachytic lavas, which gradually filled Bitlis gorge to a distance of 80 km from the volcanic center.

Lava flows reached a width of 200 m and had a thickness of 5–30 meters. Consequent deposits from basalt and trachytic lavas finalized a pronounced cone with a height of about 4400-4500 m. The next major eruption (volume 62.6 km3) created large voids inside the volcano, which led to the collapse of the apex and the formation of the caldera. Initially it was assumed that the caldera formed right after this eruption, about 310 thousand years ago; however, more recent studies suggest that the collapse happened with the next eruption, about 270 thousand years ago.

Some fiamme are formed from flattened hot, relatively low viscosity, high porosity fragments of volcanic glass or pumice. But this is not the only way they can form: they can also form when pumice lapilli are altered to clay and compact during diagenesis; and fiamme are also widely reported in viscous lavas (andesites to rhyolites) where they form by shear-induced autobrecciation of pumiceous or obsidian zones, followed by shear and annealing of the fragments. Fiamme can also result from patchy alteration and recrystalisation of volcanic rocks, or by patchy revesiculation of welded tuff matrix (especially in rheomorphic peralkaline tuffs).

The Minerva Hills National Park sits on the Oligocene Minerva Hills Volcanics. These volcanics have been broadly divided into a basal series of mafic lavas (some 70 m thick) overlain by a series of intercalated mafic volcanics, felsic volcanics ranging from trachyte to rhyolite and trachytic pyroclastics. The pyroclastics are related to plugs and domes. The lower sequence has been dated at approximately 33 -34 Ma (million years) and the upper sequence 28.5–27.5 Ma. View of Minerva Hills National Park The Minerva Hills Volcanics is a remnant of Oligocene hot spot volcanism known as the Cosgrove Hot Spot.

Both arcs show increased evidence for sediment recycling as the collision progressed, but for differing reasons. In Halmahera, this may represent an increased sediment flux through the arc front, while in Sangihe it may simply reflect a greater opportunity for melting of sediment-fluxed portions of the mantle wedge. In both cases the change in arc geochemistry can be related to the evolving architecture of that particular subduction zone. The Halmahera lavas also record a temporal change in the chemistry of the mantle component that resulted from induced convection above the falling Molucca Sea Plate drawing compositionally distinct peridotite into the mantle wedge.

A classic example of inverted relief is Table Mountain, Tuolumne County, California. Multiple lava flows filled an ancient fluvial valley that cut westward through the central Sierra Nevada range to the Central Valley about 10.5 million years ago. These Miocene lava flows filled this ancient river valley with a thick sequence of potassium-rich trachyandesite lavas that are significantly more resistant to erosion than the Mesozoic siltstone and other rock in which the valley was cut. Thus, subsequent differential erosion left these volcanic rocks as a sinuous ridge, which now stands well above landscape underlain by more deeply eroded Mesozoic rocks.

The variety of volcanic deposits at Heart Peaks indicates that it has a history of producing not only fluid and passive basaltic lava flows, but also more silica-rich trachyte and rhyolitic lavas and explosive eruptions. Phreatic breccias are found at the volcano, providing evidence that phreatic eruptions have occurred at least once throughout its eruptive history. Features created by subglacial eruptions are also present. The latest volcanic phase at Heart Peaks is largely Pleistocene (between 2.5 million and 10,000 years ago) in age and late-stage Holocene (10,000 years ago to present) activity is uncertain.

The Coso Volcanic Field is well known as a geothermal area. Fumaroles are present along faults bounding the rhyolite-capped horst and locally within the rhyolite field. A multi- disciplinary program of geothermal assessment carried out in the 1970s defined a potential resource of 650 megawatts electric with a nominal life span of 30 years. Judged by the youthfulness of the rhyolite lavas and by a zone of low seismic velocity crust roughly beneath the rhyolite, a magma body may be the source of thermal energy for the geothermal system. Commercial power development began in the 1980s.

Geological Journeys. pp. 300–311. Struik Publishers, Cape Town. Sediments eroded from these mountains provided the bulk of the 6 km thick Beaufort sediments in the Karoo Basin, but they also covered the Cape Fold Belt, thereby protecting them from erosion. At the end of the Karoo Period about 180 million years ago, the subcontinent was covered by a thick layer of Drakensberg lavas, an event that was accompanied by upliftment or bulging of Southern Africa, ushering in an almost uninterrupted period, continuing to the present, of erosion removing many kilometers of surface rocks from the entire subcontinent.

As a continuation of their work under Legal Assistance for Vietnamese Asylum Seekers (LAVAS) in the 1990s, BPSOS continues to defend Vietnamese victims of persecution including those still in Vietnam and hundreds of Vietnamese who successfully fled to neighboring countries. BPSOS currently collaborates with legal aid and human rights organizations, UN agencies, and US and other embassies in Southeast Asia to promote refugee protection policies, provide legal assistance to victims, and advocate for expeditious resettlement. High- profile cases successfully assisted by BPSOS include Pastor Nguyen Lap Ma, Pastor Nguyen Nhat Thong, Ven. Tim Sakhorn (Buddhist monk) and numerous dissidents.

Hildreth (2007) lists Belknap Crater's summit elevation at . McArthur and McArthur (1984) list its elevation at , while according to the U.S. National Geodetic Survey, Belknap reaches an elevation of , and has a "bald" appearance. The central Belknap shield volcano has a diameter of and a volume of , with a maximum thickness of . The shield has proximal and draping reliefs of and , which are the "difference between summit elevation and that of highest exposure of older rocks overlain by the edifice" and the "difference between summit elevation and that of lowest distal lavas of the edifice (not including distal pyroclastic or debris flows)," respectively.

However, unlike plains material of the lunar uplands, no source basin is evident for the mercurian smooth and very smooth plains units within the imaged part of the Bach region. Although such a source basin may lie within the part not imaged, intervening areas do not contain smooth or very smooth plains materials. For these reasons we tentatively ascribe a volcanic origin to most of the smooth and very smooth plains material. The ridges appear to be of volcano-tectonic origin; the fracturing may have provided the means by which lavas reached the surface to form these younger plains units.

It rises from the abyssal floor about in height. A prominent south-trending ridge extends about from the summit area in the direction of Kimmei Seamount, to the southeast. The base of the guyot is similar to a "pedestal," and is composed of consolidated lavas and extinct volcanic centers of the volcano's formally active history; it is similar to structure to the pedestal found at the base of most of the other, usually larger Emperor seamounts. However, a thick carbonate cap, similar to the one covering Detroit Seamount, makes it difficult to find the exact eruptive centers.

There was a large amount of variation in the density, structure, porosity, and grain size of the recovered volcanic rock, varying widely with depth. The bulk of the volcanic rock is basalt of aphyric to olivine-phyric lava, and tholeiitic or alkalic in composition. The basaltic lavas from Koko Seamount resemble those drilled during Leg 55, at Suiko Seamount. Studies suggested that the magnetic arrangement of the rock, used to determine its latitude at formation (magnets align to the North pole; also, the drift and position of the Hawaii hotspot at various times is important to hotspot studies), were relatively stable.

The Upper Mesozoic unit dominates in the southern and western parts, consisting of massive effusive rocks made up of basaltic sheets separated by volcanic ashes and tuffs, mixed with terrigenous rocks with layers of coal.Barr (1995): 22 The Mesozoic-Tertiary unit remains mostly on the sea floor and consist of marine quartz sandstones and shales. Plate tectonics of the Arctic Ocean created basalt lavas and dolerite sheets and dykes in the Upper Jurassic and Lower Cretaceous periods.Barr (1995): 23 The land is rising by per year, due to the melting of the Barents Sea Ice Sheet c.

The next eruptive period, the Castle Creek period, began about 400 BCE, and is characterized by a change in composition of St. Helens' lava, with the addition of olivine and basalt. The pre-1980 summit cone started to form during the Castle Creek period. Significant lava flows in addition to the previously much more common fragmented and pulverized lavas and rocks (tephra) distinguished this period. Large lava flows of andesite and basalt covered parts of the mountain, including one around the year 100 BCE that traveled all the way into the Lewis and Kalama river valleys.

The top of the formation is formed by an erosional unconformity at the base of the Late Oligocene to Early Miocene Blaubok Conglomerate. The fauna from the Black Crow Limestone, especially the arsinoithere Namatherium blackcrowense and the reithroparamyid rodent Namaparamys inexpectatus indicate a Late Ypresian or Early Lutetian age for the deposits. The limestones are likely to be older than 42.5 Ma on the basis of radio-isotopic dates obtained from phonolite cobbles reworked from lavas considered to have erupted later than the limestone deposition. The carbonates could be as old as 47 ± 1 Ma, i.e.

The stratigraphy can be divided into four major units, from young to old: #Syrtis Major lavas unit contains high-calcium pyroxene bearing material; #Layered sulfate-bearing unit, include poly-hydrated sulfates and jarosite; #Olivine unit, olivine-enriched unit variably altered to carbonate and serpentine; #Basement unit: The mixture of iron/magnesium (Fe/Mg) smectite and low-calcium pyroxene-bearing unit variably altered to Aluminium-clay bearing materials. The basement unit is one of newest units on Mars, recording early-stage evolution history of terrestrial planets. The change from carbonate to sulfate indicates a transition from alkaline-neutral to acid aqueous environments.

The Aleutian island arc formed ~50-55 ma as a result of Kula plate subduction under the North American Plate before the Pacific plate arrived. There are three stratigraphic units of the Aleutian island arc: volcanic rocks from ~55-33 ma, marine sedimentary rocks from ~23-33 ma, and sedimentary and igneous rocks from ~5 ma-present. Volcanic rocks from ~55-33 ma include sandstone, siltstone, conglomerate, and breccia that are all volcanic, and they are mixed with pillow lavas in a complex way. Debris flows and turbidity currents transported igneous materials from volcanic source to shallow marine basins.

The main volcanics at Hoodoo Mountain are phonolite and comendic trachyte lavas and hyaloclastites, although some pyroclastic rocks also exist. The trachyte and comendic magmas erupted from Hoodoo Mountain and other Northern Cordilleran volcanoes are thought to have been created by fractionation of primary alkali basaltic magma in crustal reservoirs. The estimated volume of erupted material from Hoodoo Mountain is , and at least six phases of eruptive activity are recognized at the volcano. The first phase of eruptive activity occurred 85,000 years ago in the Late Pleistocene stage of the Pleistocene epoch, producing lava flows, lava domes, and breccia deposits.

The Itcha Range as seen from the south During the mafic capping stage, basanite, alkali olivine basalt and hawaiite erupted mainly from small parasitic cones, tuff rings and fissures in the eastern half of the shield. Eruptions occurred subglacially, subaqueously and/or subaerially as shown by a wide range in the degree of vesicularity, freshness and glass content of the lavas. In most cases, each parasitic cone produced three or four lava flows from breaches in the cone walls. These were erupted as pāhoehoe and ʻaʻā, but the tops of the lava flows are commonly missing due to erosion.

Fantastic Lava Beds near Cinder Cone in Lassen Volcanic National Park Block lava flows are typical of andesitic lavas from stratovolcanoes. They behave in a similar manner to ʻaʻā flows but their more viscous nature causes the surface to be covered in smooth-sided angular fragments (blocks) of solidified lava instead of clinkers. Like in ʻaʻā flows, the molten interior of the flow, which is kept insulated by the solidified blocky surface, overrides the rubble that falls off the flow front. They also move much more slowly downhill and are thicker in depth than ʻaʻā flows.

The Malvern Hills represent another depositional environment for Late Neoproterozoic sedimentation with the Warren House Formation being in thrust contact with the Malvern Complex. The Warren House Formation is composed of pillow basalts, intermediate lavas, altered rhyolites and welded and non-welded acid tuffs with evidence to suggest that they are linked via fractional crystallisation. U-Pb zircon dating gives an age of 566 Ma+/-2 Ma. The geochemical signature from this sequence is contrasting to that of the rest of the Wrekin Terrane being of a volcanic arc formed on oceanic or on thin, immature continental crust.

The porphyry orebody consists of a stockwork (a network of narrow veins) of mineralised veinlets, mainly in andesitic lavas and tonalite, superimposed by a leached zone and a substantial zone of secondary enrichment, both of very variable thickness. It surrounds a narrow, almost circular ring of tourmaline breccia which in turn surrounds the Braden Chimney, an inverted cone of breccia which was emplaced after the main mineralisation. Reserves and resources are substantial. At the end of 2007 reserves and resources in the mining plan totalled 4,204 million tonnes grading 0.91% copper or 38.3 million tonnes of contained copper.

El Negrillar volcano just north of Socompa; the white area to the right is part of the Socompa landslide deposit Socompa forms a northeast-trending alignment with neighbouring volcanoes such as Pular and Pajonales, which reach elevations of about . Monogenetic volcanoes were active in the area as well during the Pliocene and Quaternary and generated lava flows. One of these centres is El Negrillar just north of the collapse deposit, which was active during the Pleistocene and formed andesite-basaltic andesite lavas unlike the eruption products of Socompa itself. A long lineament known as the Socompa Lineament is associated with the volcano.

Helmcken Falls and the deposits of volcanic rock The composition of some lava flows in the Wells Gray-Clearwater volcanic field is unusual because they include small, angular to rounded fragments of rock called nodules and crystals that come from the mantle. These green nodules are known as peridotites because they are mostly made of a magnesium iron silicate mineral called olivine. These lava flows also comprise large crystals of olivine, plagioclase, and pyroxene that crystallized deep within the Earth's crust and mantle. The lavas and nodules they contain are similar to those erupted at Volcano Mountain in the Yukon.

In allusion to the pock-marked appearance of weathered surfaces of variolite, this term is derived from the Latin word, variola, for smallpox. Varioles are millimeter- to centimeter-scale, light-colored, globular to spherical structures, that are conspicuously observable within aphanitic, mafic igneous rocks, such as basalt, komatiite, and tachylite, that comprise either pillow lavas, subaerial lava flows, or volcanic dykes. Typically, they are less resistant to weathering than the enclosing aphanitic rock and, as a result, form pock-marks on the weathered surfaces of mafic rocks.Arndt, N., and Fowler A.D. (2004) Textures in komatiites and variolitic basalts.

Roger Weller Lithophysae cluster These cavities are believed to be caused by expanding gases in tuffs and rhyolitic lavas before solidification. If it has become lined with crystals it may be referred to as a geode or filled partially or fully with agate, jasper or opal is a thunderegg. The term vug is also used for similar cavities although the meaning of vug is usually restricted to cavities in rocks formed by the removal of material such as soluble minerals. These cavities usually contain layers of various colors (red, pink, gray, etc.) composed by crystals of quartz, chalcedony, hematite, fluoriteMineralienatlas and various colored oxides or other minerals.

The northern segment overlaps the older Pemberton Volcanic Belt at a low angle near the Mount Meager massif where Garibaldi Belt lavas rest on uplifted and deeply eroded remnants of Pemberton Belt subvolcanic intrusions and combines to form a single belt. A few isolated volcanoes northwest of the Mount Meager massif, such as Silverthrone Caldera and Franklin Glacier Complex, are also grouped as part of the Garibaldi Volcanic Belt. However, their tectonic origins are largely unexplained and are a matter of going research. When the Farallon Plate ruptured to create the Nootka Fault between five and seven million years ago, there were some apparent changes along the Cascadia subduction zone.

More recent volcanic activity has created a northwest trending line of volcanic rocks called the Wrangell Volcanic Belt. This volcanic belt lies largely in the U.S. state of Alaska, but extends across the Alaska-Yukon border into southwestern Yukon where it contains scattered remnants of subaerial lavas and pyroclastic rocks which are preserved along the entire eastern fringe of the ice covered Saint Elias Mountains. The Wrangell Volcanic Belt formed as a result of arc volcanism related to subduction of the Pacific Plate under the northern portion of the North American Plate. Over large areas extrusive rocks lie in flat undisturbed piles on a Tertiary surface of moderate relief.

Two dating techniques were used to arrive at the approximate age of the beds that make up the ground layers at Laetoli: potassium-argon dating and analysis of stratigraphy. Based on these methods, the layers have been named as follows, starting with the deepest: Lower Laetolil Beds, Upper Laetolil Beds, Lower Ndolanya Beds, Upper Ndolanya Beds, Ogol lavas, Naibadad Beds, Olpiro Beds, and Ngaloba Beds; it is the ancient Laetolil Beds that contain the footprints trackway. The upper unit of the Laetolil Beds dated back 3.6 to 3.8 million years ago. The beds are dominantly tuffs and have a maximum thickness of 130 meters.

Mount Wrangell The majority of the volcanoes in the Wrangell volcanic field lie at the western end of the Wrangell Mountains. The western Wrangell volcanoes are unusual for subduction-related volcanoes, in their generally non-explosive nature. The majority of the volcanoes are unusually large shield volcanoes that built to their present size quickly from voluminous flows of andesite lavas which erupted from multiple centers.Winkler, p. 76. Their growth is associated with the arrival of the Yakutat terrane, with considerable activity until about 200,000 years ago, when movement along the Denali-Totchunda and Fairweather faults began to accommodate some of the Pacific Plate's motion.

Such a process is accompanied by uplift of the abovelying crust and often by volcanism of mainly small volume. Seismic imagery has been used to argue for the existence of delaminated crust in the mantle above the downgoing Nazca Plate slab beneath the Arizaro region. The age of the lavas has been determined by argon-argon dating. The northernmost lava flow has yielded an age of 80,000 ± 60,000 years before present, while a southern lava flow has been dated to 130,000 ± 10,000 years before present and a date of 2.52 ± 0.05 million years ago was found on a central lava flow; this last lava flow shows evidence of younger faulting.

Paralleling the Canadian Cascade Arc to the northeast is an area composed of minor basaltic lava flows. This zone, known as the Chilcotin Group, formed as a result of back-arc basin volcanism behind the Canadian Cascade Arc, in response to ongoing Cascadia subduction. Volcanic activity began 31 million years ago, but most of the volcanism occurred during two younger magmatic periods, the first between 6.0 and 10 million years ago and the other between 2.0 and 3.0 million years ago. This indicates that most Chilcotin Group volcanism corresponded with volcanism in the Pemberton Belt, although some of the younger Chilcotin lavas were erupted during early stages of Garibaldi Belt volcanism.

Nearly all of the Drakensberg lavas were eroded away, leaving a remnant in Lesotho, several small patches on the Springbok Flats in the north of the country, and in the Lebombo mountains along the Mozambique border. Once the layer of hard lava was eroded away, the softer Karoo sediments over the rest of the basin eroded even faster. However, the dolerite sills resisted erosion, protecting the softer Beaufort and Ecca shales beneath them. This created numerous and widespread flat topped hills, known as Karoo Koppies ("koppie" being the Afrikaans term for hill), which are iconic of the Karoo, and, by extension, the South African landscape.

The oldest rocks are of Silurian age (443–419 million years ago). They make up a sequence of lavas, tuffs (volcanic ash), shales and mudstones in a narrow outcrop to the northeast of Shepton Mallet in the eastern Mendip Hills. Rocks from the Devonian (419–359 million years ago) are found across much of Exmoor, the Quantocks, and in the cores of the folded masses that form the Mendip Hills. The Cheddar Gorge was carved by water Carboniferous Period (359–299 million years ago) rocks are represented by the Carboniferous Limestone that forms the Mendip Hills, rising abruptly out of the flat landscape of the Somerset Levels.

The Keilor Plains, where the geomorphological and geological features of heritage value are located, is part of the greater Western Volcanic Plains which cover a large part of western Victoria and extend into south-eastern South Australia and are stated to be the third largest lava plains in the world. These landforms were created by the incision of the Jacksons Creek into thick lava flows that erupted about 2.5 to 2.8 million years ago during the Pleistocene Period. These lavas overlie steeply dipping Silurian sedimentary rocks. Sedimentary rock and fossils found in the park are also dated back 400 million years, an indication that the area was once a sea.

The falls are located on Brandywine Creek, which has its origin in the Powder Mountain Icefield to the west, and are formed by the lip of a lava flow flanking the west bank of the Cheakamus River. Just downstream of the falls is Daisy Lake. At least four basaltic lava flows of Late Pleistocene age comprise the vertical walls surrounding Brandywine Falls.Floods, faults, and fire: Geological Field Trips in Washington State and Southwest British Columbia These Cheakamus Valley basalts are part of the Garibaldi Volcanic Belt, a northwest-southeast chain of volcanoes and related lavas that form the northern end of the Cascade Volcanic Arc.

Spatter cones and spatter ramparts are typically formed by lava fountaining associated with mafic, highly fluid lavas, such as those erupted in the Hawaiian Islands. As blobs of molten lava, spatter, are erupted into the air by a lava fountain, they can lack the time needed to cool completely before hitting the ground. Consequently, the spatter are not fully solid, like taffy, as they land and they bind to the underlying spatter as both often slowly ooze down the side of the cone. As a result, the spatter builds up a cone that is composed of spatter either agglutinated or welded to each other.

Rodrigues also began to sing her own poems ('Estranha Forma de Vida') on Amália Rodrigues, as well as poems written by other poets, such as Pedro Homem de Mello and David Mourão- Ferreira. This album also established her signature songs like 'Povo Que Lavas no Rio', 'Maria Lisboa' and 'Abandono'. Oulman, a left-wing intellectual, was arrested by Portugal's political police (known as PIDE) in 1966, and forced into exile, but he continued contributing for Amália. She resumed her stage- career singing in Israel, the UK, France, and returning to the US for Promenade Concerts at the Hollywood Bowl, and New York City, accompanied by Andre Kostelanetz, in 1966 and 1968.

In the Late Pliocene, andesitic lava and ash erupted from Magdalena-Lucia, Mount Andrassy, Mount Wullersdorf and Mount Pock, with these eruptions now forming the highest landform of the region. Rhyolite was later extruded from Mount Wullersdorf, Mount Andrassy and Glass Hill, and at the end of the Pliocene dacite was erupted from Mount Maria. The coastal platform was formed during the Quaternary period after series of eruptions of basaltic lavas. Basalt flows following eruptions from hills in the Table-Tiger area, Quoin Hill including in Mostyn caused much disruption of drainage and account for the upper alluvial valleys mentioned in the third region.

Island - seabirds and Les Eclaireurs Lighthouse in foreground with mountain rising in background Argentine Patagonia is for the most part a region of steppe-like plains, rising in a succession of 13 abrupt terraces about at a time, and covered with an enormous bed of shingle almost bare of vegetation.Patagonia: Natural History, Prehistory and Ethnography at the Uttermost End of the Earth, C. McEwan, L.A. and A. Prieto (eds), Princeton University Press with British Museum Press, 1997. In the hollows of the plains are ponds or lakes of fresh and brackish water. Towards Chilean territory, the shingle gives place to porphyry, granite, and basalt lavas, and animal life becomes more abundant.

Rangitoto Range from junction of red and white tracks The Range is formed of Late Jurassic to Early Cretaceous Manaia Hill Group greywacke (a form of sandstone, with little or no bedding, fine to medium grained, interbedded with siltstone and conglomerate, and with many quartz veins), buried in many places by Quaternary ignimbrites. The main ignimbrite is the Ongatiti Formation, up to 150 m thick of compound, weakly to strongly welded, vitrophyric (phenocrysts embedded in a glassy rock), including pumice-, andesite and rhyolite lavas. The ignimbrite forms round, flat-topped hills, edged by eroding banks, covered in blocks of ignimbrite, where the underlying greywacke has eroded.

There are hot springs at some volcanoes while 10 volcanoes in British Columbia appear related to seismic activity since 1975, including: Mount Silverthrone, Mount Meager massif, Wells Gray-Clearwater volcanic field, Mount Garibaldi, Mount Cayley massif, Castle Rock, The Volcano, Mount Edziza, Hoodoo Mountain and Crow Lagoon. Numerous shield volcanoes developed during the Tertiary period in north-central British Columbia and some were active intermittently to recent times. Mount Edziza and Level Mountain are most spectacular examples. Mount Edziza is a stratovolcano consisting of a basal shield of basaltic flows surmounted by a central vent and flanked by numerous satellite cones, ash beds and blocky lavas.

Uturuncu has formed about east of the main volcanic front in the Western Cordillera, in a terrain formed by various volcanic and sedimentary rocks of Miocene to Quaternary age. The region is characterized by the Altiplano high plateau, which reaches an elevation of and in terms of dimension is only exceeded by Tibet. The 8.41 million years old Vilama and 5.65 million years old Guacha ignimbrites underlie the volcano and crop out in the Quetena River valley, while the 4 million years old Vilama lavas are found southwest of Uturuncu and are partly buried by the volcano. The crust in the region is about thick.

The central and northern areas of Birker Fell are dominated by composite andesite lava flows. Within the andesitic lava flows, the Great Whinscale Dacite lava flow and the associated, underlying Little Stand Tuff form a marker band that runs northeast-southwest across the fell, but are best seen at Silver How () and Great Whinscale (). A small area of basaltic material occurs approximately 1 km north of Birkerthwaite, composed of plagioclase- and pyroxene-phyric andesite-basalt lavas (the Birkby Fell Member), and tuff and lapilli-tuffs (the Devoke Water Member). The main outcrop of the Devoke Water Member occurs to the south-west of Devoke Water itself, on Ulpha Fell.

A U-shaped valley of Level Mountain with extensive elevated plateau in the foreground After the basal shield volcano was constructed, several vents produced oversaturated, undersaturated, peralkaline and metaluminous lavas. This tremendous variation in the erupted magmas and influence of adjacent vents gave rise to a high and volumnous complex bimodal stratovolcano centrally located atop the shield. Mapping indicates that the headwaters of Kakuchuya Creek were the site of this large stratovolcano cap and that it grew over in elevation. Volcanic rocks of felsic composition, notably peralkaline trachyte and comendite, were the primary products comprising this edifice, forming more than 80% of its volume.

The project objective was detecting and mapping the sub- seafloor magma chamber that feeds lavas and igneous intrusions that create the oceanic crust and lithosphere in the process of seafloor spreading. The approach comprised many geophysical techniques including seismology, magnetism, crustal electrical properties, and gravity. The major experiment effort though, was seafloor observation and sample collection using the deep submergence submersible ALVIN on the crest of the EPR at depths of 2600 meters or more. RISE was part of the RITA (Rivera-Tamayo expeditions) project, which included submersible investigations (CYAMEX) at 21° N and at the Tamayo Fracture zone at the mouth of the Gulf of California.

Rabid, Jack. The Big Takeover Issue Vo. 70, Spring 2012 The record has earned positive reviews from publications such as The Big Takeover, GhettoBlaster magazine, and PowerPopaholic.Coleman, Gregg. Ghettoblaster Issue 31 May 2012 The record also features performances by guitarist, bassist, and arranger Gary Rand, keyboardists Dave Lieb (The Vinyl Skyway) and Peter Linnane (The Farewells), backing vocalists Alice Austin (The Lavas, Stark Raving Mad) and Amy Fairchild, keyboardist and 2012 Rock & Roll Hall of Fame inductee Ian McLagan (Small Faces, Faces, The Rolling Stones, Billy Bragg), singer/songwriter Amy Rigby (solo, Wreckless Eric), multi-instrumentalist Ian Kennedy (Reverse, Dennis Brennan), and cellist Aristides Rivas.

At the base of the lithosphere (the layer of crust and upper mantle that forms Earth's moving tectonic plates). In an effort to figure out why this area, far from a plate boundary, had such an enormous outpouring of lava, scientists established hardening dates for many of the individual lava flows. They found that the youngest volcanic rocks were clustered near the Yellowstone Plateau, and that the farther west they went, the older the lavas. Although scientists are still gathering evidence, a probable explanation is that a hot spot, an extremely hot plume of deep mantle material, is rising to the surface beneath the Columbia Plateau Province.

Most of the lavas appear to originate in fissure vents, under the influence of dykes and tectonic faults. In addition, there are about 150 individual volcanic massifs and more smaller volcanic cones, many of which form rows of cones and sometimes have large craters and which occur mainly in the Al Haruj al Abyad part of Haruj. Craters range from deep pits with steep inward walls to wide and shallow depressions, and the craters are often filled with material eroded from their flanks. Phreatomagmatic processes triggered by groundwater interacting with rising magma have generated some of these large craters, while others formed when lava lakes drained through gaps in their rims.

This lighthouse looks out over the Inner and Outer Bucks, two rocks that partially show at low water, and where in 1868 the SS Garonne was lost. They form a popular sub-aqua dive site. The nearest point for launching a dive-boat is Penzance, as Lamorna Cove just around the corner from The Bucks, does not allow launching from there. The coastal slope and cliffs around the lighthouse are designated the Tater–du SSSI (a Site of Special Scientific Interest) notified in 1992 because ″... it provides unique evidence of the geological history of SW England during the Variscan orogeny, in particular because of the occurrence of pillow lavas.

To the north and west of the Highland Boundary Fault lie hard Precambrian and Cambrian metamorphic rocks: marine deposits metamorphosed to schists, phyllites and slates, namely the Dalradian Supergroup and the Highland Border Ophiolite suite. To the south and east are Old Red Sandstone conglomerates and sandstones: softer, sedimentary rocks of the Devonian and Carboniferous periods. Between these areas lie the quite different rocks of the Highland Border Complex (at one time called the Highland Boundary Complex), a weakly metamorphosed sedimentary sequence of sandstones, lavas, limestones, mudstones and conglomerates. These make up a zone which is found discontinuously along the line of the fault and which is up to in width.

The so-called "white airfall" with a volume of as well as pyroclastic flows on the western summit may have been erupted during the collapse but this is uncertain. Activity of the Young Cone began after the collapse within the scar left by the failure of the edifice. This activity involved the extrusion of four groups of lavas of both andesitic and dacitic composition as well as lava domes and one pumice flow. Apparently, the emission of each lava unit was preceded by explosive eruptions which formed pyroclastic flows. Argon-argon dating on one of these units has yielded an age of 100,000 ± 35,000 years ago.

Fatutaka is one of numerous volcanic highs, islands and banks, in the north-western North Fiji Basin south of the fossil Vitiaz Trench (10°30'–19°S, 169°–174°E). These highs are, however, located up to from the Vitiaz Trench and do not form a continuous chain derived from the trench, but are a series of massifs aligned on north-south trending faults. Anuta and Fatutaka consist of basaltic lavas and andesitic breccias. In the 1970s the formation of Anuta and Fatutaka 2.2 was attributed to volcanism in the Vitiaz island arc during the initial back-arc opening of the North Fiji Basin.

In the Bronze Age copper could be found on the surface, but as these depleted, underground extraction methods were adopted. The northern slopes of the Troodos Mountains (in the Pillow Lavas Series of Troodos Ophiolite) contained vast amounts of copper bearing ores. The wastes of the metal extraction process, known as "ancient slug", lying outside the mines, contains slight traces of residual copper, but are inaccessible as the mines are currently legislatively protected monuments. During the Roman period Cyprus was able to satisfy almost all of the world's copper requirements, but after the downfall of the Roman Empire, copper mining went dormant until the 19th century.

The term "clastogenic" refers to volcanic eruptions which cause a particular type of ejecta. : _Illustrative sentence_ : "The complex features of this eruption can be explained by rapid deposition of coarse pyroclasts near the vent and the subsequent flowage of clastogenic lavas which were accompanied by a high eruption plume generating pumice falls and/or pyroclastic flows."Yasui, Maya and Takehiro Koyaguchi. "Sequence and eruptive style of the 1783 eruption of Asama Volcano, central Japan: a case study of an andesitic explosive eruption generating fountain-fed lava flow, pumice fall, scoria flow and forming a cone," Journal Bulletin of Volcanology (Kasan). Vol. 66, No. 3 (March 2004). pp. 243-262.

Jiang, C., Wan, J., Wang, Y., Wei, H., and Zhang, X (2006), Tectonic controls on the late Mioene-Holocene volcanic eruptions of the Tengchong volcanic field along the southeastern margin of the Tibetan plateau, Journal of Asian Earth Science, 2007, 275-389. The largest of rock distribution in the TVF is characterized by the rocks formed during the Pleistocene (2) indicating that volcanic activity was greatest during this phase. Andesitic lavas comprise the most recent volcanic rocks. The basement rocks are dominantly composed of Precambrian metamorphic rocks underlain by sedimentary and igneous rocks including limestones, sandstones, mudstones, and granitoids followed by volcanic-sedimentary sequences.

More recent volcanic activity has created a northwest trending line of volcanic rocks called the Wrangell Volcanic Belt. This volcanic belt lies largely in the U.S. state of Alaska, but extends across the Alaska-Yukon border into southwestern Yukon where it contains scattered remnants of subaerial lavas and pyroclastic rocks which are preserved along the entire eastern fringe of the ice covered Saint Elias Mountains. The Wrangell Volcanic Belt formed as a result of arc volcanism related to subduction of the Pacific Plate under the northern portion of the North American Plate. Over large areas extrusive rocks lie in flat undisturbed piles on a Tertiary surface of moderate relief.

These Insular Mountains are not yet fully emerged above sea level, and Vancouver Island and the Haida Gwaii are just the higher elevations of the range, which was in fact fully exposed during the last glacial period (maximum ice extent about 18,000 years ago) when the continental shelf in this area was a broad coastal plain. The Insular Mountains formed when a chain of active volcanic islands (the Insular Islands) collided against the North American continent during the mid Cretaceous period. The type of rocks that form the Insular Mountains are turbidites and pillow lavas. Granitic plutons seldom occur in the Insular Mountains, unlike the Coast Mountains.

The only eruption recognized to have produced ash flow tuff occurred in late Pleistocene time, and this eruption was too small to account for formation of the caldera. Later conclusions were that Medicine Lake caldera formed by collapse in response to repeated extrusions of mostly mafic lava beginning early in the history of the volcano (perhaps in a manner similar to the formation of Kilauea caldera in Hawaii). Several small differentiated magma bodies may have been fed by and interspersed among a plexus of dikes and sills. Late Holocene andesitic to rhyolitic lavas were derived by fractionation, assimilation, and mixing from high alumina basalt parental magma.

Johnson decided to follow a science career after enjoying studying science at King Edward VI High School for Girls during her teenage years. In 1998, Johnson obtained a BSc degree in Geology (1st class) from Durham University (Hatfield College). She then went on to complete a PhD in 2002, supervised by at Clare College, Cambridge, with a thesis on Magmatism of the Vitim Volcanic Field, Baikal Rift Zone, Siberia. The research consisted of using geochemical characteristics of lavas to study the composition and thickness of the lithosphere in the Baikal Rift Zone of Siberia, and to improve understanding of the melting regime beneath the region during the Cenozoic.

The trend of a seamount chain traces the direction of motion of the lithospheric plate over a more or less fixed heat source in the underlying asthenosphere, the part of the Earth's mantle beneath the lithosphere.Seamounts are made by extrusion of lavas piped upward in stages from sources within the Earth's mantle to vents on the seafloor. Seamounts provide data on movements of tectonic plates on which they ride, and on the rheology of the underlying lithosphere. The trend of a seamount chain traces the direction of motion of the lithospheric plate over a more or less fixed heat source in the underlying asthenosphere part of the Earth's mantle.

The lava field measures in the whole 18 km2 and is thought to have a volume of about 0,36 km3 as well as a length of about 12 km, one of the bigger lava fields on the Reykjanes peninsula. The lavas are today partially covered up by structures and another part of them lies under seawater in the fjords Skerjafjörður and Hafnarfjörður, as the sea water level at time of eruptions was lower than it is today. Whereas the geologic denomination is Búrfellshraun for all the lava of the eruption, the locals, depending on the region, use different names. The branches in direction of Skerjafjörður e.g.

This is also the age that has been attributed to the large northern lava flow; the crustal magma pond forming the flow may have formed during lithospheric unloading at the time of the Bolling-Allerod when glaciers in the East Sayan Mountains melted. The age of the Medvedev cone and flow are unknown. The eruptions at Jom-Bolok are the most voluminous Holocene eruptions of Central Asia; their volume has been estimated to be . The youngest lavas are even more recent in age, 682–779 CE. One hypothesis formulated in 2015 assumes that the Irkut-Oka plateau may be the Ergune-Kun locality referenced in Mongolian chronicles.

A circular structure around Sajama may be the origin of the 2.7 million years old Lauca-Perez Ignimbrite. Hot springs on the Junthuma River Argon-argon dating has yielded ages of 679,000 years ago from Sajama and of 80,900 to 25,000 years ago for the Kkota Kkotani lavas, which are unrelated to the main Sajama volcano. The date of the last eruption is not known, it may have occurred in the Pleistocene or Holocene. Hot springs occur on the Junthuma River and reflect the presence of geothermal heat with temperatures of about on the western foot of Sajama, and volcanic rocks of Sajama bear traces of fumarolic activity.

Exploration for Kambalda-style nickel ores focuses on identifying prospective elements of komatiite sequences via geochemistry, geophysical prospecting methods and stratigraphic analysis. Geochemically, the Kambalda Ratio Ni:Cr/Cu:Zn identifies areas of enriched Ni, Cu and depleted Cr and Zn. Cr is associated with fractionated, low-MgO rocks and Zn is a typical sediment contaminant. If the ratio is at around unity or greater than 1, the komatiite flow is considered fertile. Other geochemical trends sought include high MgO contents to identify the area with highest cumulate olivine contents; identifying low-Zn flows; tracking Al content to identify contaminated lavas and, chiefly, identifying anomalously enriched Ni (direct detection).

Entities found in these lake beds include fossil leaf impressions, petrified wood, fossil insects, and bones of vertebrate animals. Evidence suggests that some concentrated heat source is melting rock beneath the Columbia Plateau Province at the base of the lithosphere (the layer of crust and upper mantle that forms Earth's moving tectonic plates). In an effort to figure out why this area, far from a plate boundary, had such an enormous outpouring of lava, scientists established hardening dates for many of the individual lava flows. They found that the youngest volcanic rocks were clustered near the Yellowstone Plateau, and that the farther west they went, the older the lavas.

Seismic imaging shows the existence of a partially molten magma body in the crust beneath the Altiplano-Puna volcanic complex. The pre-caldera terrain at Vilama is formed by various sedimentary and volcanic formations, such as the Paleozoic Acoite Formation and the Cretaceous Salta Group; Ordovician sediments are the most important component of the basement while later units only sporadically crop out. Volcanic units of Oligocene-Miocene age predating the formation of the Vilama caldera include the 9.79.8 million years old Granada ignimbrite, the 10.25 ± 0.12 million years old Lagunillas ignimbrite, the 9.8 ± 0.7 million years old Ojo de Perico lavas and other volcanic units.

In the north of Germany and in the Netherlands, the Rotliegend is usually subdivided into two groups: a Lower Rotliegend Group (mostly volcanic rocks: tuffs and basaltic lavas) and an Upper Rotliegend Group (sandstones and siltstones). During the formation of the lower group the basin was still small and the deposition was restricted to the centre of the basin in the southeastern North Sea and northern Germany, this group is very limited in thickness in the Dutch subsurface. The upper group has a larger arial distribution since the basin had grown wider. In Dutch lithostratigraphy, the Rotliegend lies on top of the late Carboniferous Limburg Group and below the Zechstein Group.

The Gruta das Torres (), is a lava cave, a geological formation of volcanic origin formed from the flow and cooling of subterranean magma rivers. This formation is located outside the parish of Criação Velha, in the municipality of Madalena, on the western flanks of the island of Pico. The cave system formed from a series of pāhoehoe lava flows which originating from the Cabeço Bravo parasitic cone about 500 to 1500 years ago. The caves are a group of interconnected lava tubes between 0.5–22 metres (2–72 ft) width, created from both pāhoehoe and aā types of lavas generated during different geological periods.

The oldest volcanic rocks in the Meidob volcanic field have been dated by potassium-argon dating, yielding ages of 6.8 ± 0.2 and 6.5 ± 0.2 million years ago. The Jebel Sireif vent has yielded ages of 1.3 ± 0.4 to 0.6 ± 0.2 million years ago. Volcanism at first took the form of lava emissions. Later, during the Pliocene to Holocene, it was dominated by pyroclastics and lavas. The field has been active during the Holocene, with thermoluminescence and tephrochronology dating giving ages of 14,600 ± 6,600 - 12,200 ± 3,300, 10,100 ± 1,400 at Malha crater, 8,000 ± 1,600 - 7,200 ± 720, 4,150 ± 1,450 BCE, possibly 3,050 BCE and 3,000 BCE, and 4,900 ± 520 years ago for eruptions.

Armadillo Peak caldera The lava domes, calderas, stratovolcanoes, subglacial mounds and cinder cones forming the volcanic complex were constructed in five phases, each of which began with the effusion of dark olivine basalt which formed the flat-lying shield volcanoes and concluded with the eruption of light-coloured magma. This cyclical behavior is attributed to the episodic rise of basic, mantle-derived alkali basalt both to the surface and partly into crustal reservoirs where the light-coloured magmas with very little aluminum were created by prolonged crystal fractionation. The silica- rich trachyte and comendite lavas are similar to those associated with the most violent eruptions on Earth.

Endress attempted to determine if the sediments were deposited immediately before the lava flow was emplaced, or if they are likely to be much older. Endress has quantified the mineralogy of clasts and sand-sized particles from samples in the sediment, and has determined that the mineralogy of several of the trachytic clasts is very similar to that in the overlying lava flow, including the minerals clinopyroxene, magnetite, alkali feldspar, and aenigmatite. Endress has also found small lenses of pristine basaltic glass, which could have derived from the Pillow Ridge subglacial mound near Mount Edziza. Alexander S. Lloyd, a student of Dickinson College, focused on the cooling rates of pillow lavas.

Sulphur Works Boiling mudpot, Sulphur Works As in many hydrothermally active areas, the rocks at Sulphur Works and Little Hot Springs Valley in Lassen Volcanic National Park have been chemically altered into bright-colored clays. Sulfurous acid and sulfuric acid have broken down hard, gray-green andesite lavas into red, yellow and buff clays and iron oxides. Many visitors pass through Sulphur Works on their way north on State Route 89 and sense the rotten-egg smell (hydrogen sulfide) when they pass by a hot vent to the east of the road. Sulphur Works is said to be the volcanic center of the ancestral Mount Tehama.

This, and other observations, have been interpreted as indicating that the distinct geochemical signature of ocean island basalts results from inclusion of a component of subducted slab material. This must have been recycled in the mantle, then re-melted and incorporated in the lavas erupted. In the context of the plume hypothesis, subducted slabs are postulated to have been subducted down as far as the core-mantle boundary, and transported back up to the surface in rising plumes. In the plate hypothesis, the slabs are postulated to have been recycled at shallower depths – in the upper few hundred kilometers that make up the upper mantle.

These phases are also known as the phase I or the Mason Spur Lineage, and as the phase II or the Riviera Ridge Lineage. The early phase produced mildly alkaline volcanic rocks, the late phase which makes up most of the outcrops strongly alkaline rocks. The older rocks have undergone significant glaciation, while the younger ones are largely uneroded and make up the present-day edifice. Volcanic activity mostly occurred under the atmosphere, with the exception of some lavas that may have been erupted in a subaqueous environment and hyaloclastites which have been used to infer that glaciers existed there 15.4 million years ago.

313 The Andean Central Volcanic Zone runs along the Western Cordillera of the Andes and along the Altiplano. During the Neogene, the position of this volcanic arc moved eastward and the arc became broader, probably due to a change in the tilt of the slab of the Nazca Plate. Volcanic activity during this time was heavily influenced by local strike-slip faults which acted to channel the magma flows. About 7 million years ago, tectonics and volcanic activity changed in the region probably in response to the delamination of the crust beneath the region: Large scale ignimbrites were erupted at Galán and small back-arc volcanoes erupted mafic basaltic andesite lavas.

The seamount is located in the Greenland Sea-Norwegian Sea, west of due north from Jan Mayen Island and in between Norway and Greenland. Vesteris Seamount is an isolated volcanic seamount that reaches a depth of below sea level and with two summits that rise from a plateau at depth; it is likely that the summit once emerged from the sea. The summit area of the seamount is flat, probably due to wave erosion during the Weichselian glaciation, and sediment cover is scarce. Lava flows extend from the summit area to depths of almost , and sheet flows, scarps, pillow lavas, lava tubes and lava debris have been observed on the seamount.

Arenal Volcano, Costa Rica, is a stratovolcano. Volcanoes are the primary landforms built by repeated eruptions of lava and ash over time. They range in shape from shield volcanoes with broad, shallow slopes formed from predominantly effusive eruptions of relatively fluid basaltic lava flows, to steeply-sided stratovolcanoes (also known as composite volcanoes) made of alternating layers of ash and more viscous lava flows typical of intermediate and felsic lavas. A caldera, which is a large subsidence crater, can form in a stratovolcano, if the magma chamber is partially or wholly emptied by large explosive eruptions; the summit cone no longer supports itself and thus collapses in on itself afterwards.

The southern end of the peninsula includes a series of mafic pillow lavas, volcanigenic sediments, shales and limestones, collectively known as the "Burin Group", as well as a 1500 m thick sill of gabbro about 760 million years old. The northern end of the peninsula is defined by the "Marystown Group", primarily carbon-lacking Silica-based sediments which span the Precambrian-Cambrian boundary. The sediments were probably deposited in shoreline environments along the former Iapetus Ocean. The global stratotype at Fortune Head is composed of the uppermost part of member 1 and all of member 2 of the Chapel Island Formation of the Marystown Group.

These kimberlites were erupted in a fairly nonexplosive fashion. Not all researchers agree that these lavas are kimberlites, however, with the low alkali content being cited as a difference although the Benfontein "kimberlites" share this property with the Igwisi hills ones. If the Igwisi Hills aren't true kimberlites, the next youngest would be the 32.3 ± 2.2 Ma Kundelungu plateau pipes in the Democratic Republic of Congo. These kimberlites are also the youngest kimberlites in the world by over thirty million years, cosmogenic helium-3 dates of olivine indicates they were erupted in the late Pleistocene-Holocene, some indicated ages being 11,200 ± 7,800 ± and 12,400 ± 4,800.

Lava dams are formed by lava flowing or spilling into a river valley in sufficient quantity and height to temporarily overcome the explosive nature (steam) of its contact with water, and the erosive force of flowing water to remove it. The latter depends on the quantity of water flow and stream gradient. The lava may flow during numerous successive or repetitive eruptions and may emanate from single or numerous vents or fissures. Lava of this nature, like basalt, is usually associated with less explosive eruptions; more viscous lavas with lower mafic content, like dacites and rhyolites, can also flow, but tend to be more closely associated with eruptions of greater explosiveness and the formation of pyroclastics.

The most important bedrock on the islands from a commercial point of view is the Neoproterozoic age Easdale Slate Formation, a pyritic, graphitic pelite belonging to the Easdale Subgroup of the Dalradian Argyll Group. Zones of metamorphosed intrusive igneous rocks occur within the southeast of Seil and andesitic lavas of the Lorn Plateau Lava Formation dominate the west of the island. There are numerous NW-SE aligned basalt and microgabbro dykes which form a part of the ‘Mull Swarm’ which is of early Palaeogene age. Raised marine deposits of sand and gravel occur widely around the margins of some of the islands, a legacy of late Quaternary changes in relative sea-level.

These gold-bearing rocks had furthermore been covered by a thick layer of Ventersdorp lavas and the Transvaal Supergroup of rocks before the meteor struck, and thus the gold did not actually arrive in the asteroid/meteorite. What the Vredefort impact achieved, however, was to distort the Witwatersrand basin in such a way that the gold-bearing rocks were brought to the present erosion surface in Johannesburg, on the Witwatersrand, just inside the rim of the original 300 km diameter crater caused by the meteor strike. The discovery of the deposit in 1886 launched the Witwatersrand Gold Rush. Some 22% of all the gold that is ascertained to exist today on Earth has been extracted from these Witwatersrand rocks.

The Ochils are formed from a thick wedge of Devonian age volcanic and volcano- sedimentary rocks, rising up from below the lower Old Red Sandstone sedimentary rocks to the north and terminated to the south by the major southerly downthrowing Ochil Fault. The Ochil Volcanic Formation, a sub-unit of the Arbuthnott-Garvock Group, consists of basaltic andesite and trachyandesite lavas and related rock types erupted during the Early Devonian epoch. Parts of the lower slopes on the northern side around Blackford and Auchterarder are formed from a volcanic conglomerate. It is intruded by numerous dykes of micridiorite of Silurian/Devonian age which form a part of the North Britain Siluro-Devonian Calc-alkaline Dyke Suite.

Tahaa consists of shield-stage basalt with an age of 3.39 Ma, followed by additional eruptions 1.2 Ma later. Raiatea consists of shield-stage basalt followed by post-shield trachytic lava flows, all occurring from 2.75 to 2.29 Ma. Huahine consists of two coalesced basalt shield volcanoes, Huahine Nui and Huahine Iti, with several flows followed by post-shield trachyphonolitic lava domes from 3.08 to 2.06 Ma. Moorea consists of at least 16 flows of shield-stage basalt and post-shield lavas from 2.15 to 1.36 Ma. Tahiti consists of two basalt shield volcanoes, Tahiti Nui and Tahiti Iti, with an age range of 1.67 to 0.25 Ma. Mount Aorai in northwestern part Tahiti.

The urban municipality of the city of Angra do Heroísmo Geological evidence points to the bay being formed by basaltic lavas, much eroded and covered by pyroclastic surges, tuffs of palagonite-like matter, material formed by the interaction of molten basalt and cold seawater, and consolidated volcanic ash ejected from vents during volcanic eruptions, all from the volcano that helped define the bay itself, the looming presence called Monte Brasil. These depositions originated under water and are very solid and compact. On top of these volcanic layers are sedimentary materials, sometimes of great thickness, formed mainly of sand, pebbles, and large blocks of rolled palagonite with abundant cavities. Consequently, there are many submarine springs that emit brackish water.

This is because the peralkaline content of these felsic lavas decreased the viscosity of the flows a minimum of 10–30 times over that of calc-alkaline felsic flows. Evidence for explosive volcanism exists in the form of pumice flows, bedded tuffs, intensely shattered basement rocks and the high content of coarse basement clasts in rhyolite breccias. Magma production of the Anahim hotspot has shifted from more felsic to more mafic compositions in the last 3.0 million years. For instance, much of the magma created between 3.0 and 0.33 million years ago was igneous phonolite, trachyte, trachyandesite, basalt and basanite; the volcanoes built during this period are almost entirely made of these rock types.

Floods, faults, and fire: Geological Field Trips in Washington States and Southwest British Columbia The latest basaltic eruption deposited wood in lacustrine sediments under the lava flows that have been dated years old. These youngest lavas form isolated ridges above the older glaciated Cheakamus Valley basalts and were described as "esker-like" by Canadian volcanologist Bill Mathews. Columnar jointing is present all through the most recent basalt lava flow and pillow basalts exist in the lowermost unit, portions of which are underlain by hyaloclastite breccia. Bill Mathews suggested that these esker-like lava flows were deposited during subglacial eruptions that traveled away from the vent inside tunnels or trenches melted in the overlying ice sheet.

The landscape in this parish is different from the rest of the landscape in County Limerick which is predominantly flat. This is because Kilteely-Dromkeen is situated in one of the most important Carboniferous Volcanic districts in either Great Britain or Ireland. A variety of igneous rocks from two volcanic phases of about 300 million years ago can be found here. The volcanic plugs of Knockderk 220 m (782 ft) and Kilteely Hill 176 m (580 ft) are both conical in appearance, while in the neighbouring parish of Pallasgreen stands the Hill of Nicker, where hardened lavas have formed a cliff of basalt hexagons, similar to those found at the Giant's Causeway.

The oldest rocks are of Silurian age (443–419 million years ago), the most southerly known outcrop of rocks of this age in Britain. They make up a sequence of lavas, tuffs (volcanic ash), shales and mudstones in a narrow outcrop to the northeast of Shepton Mallet, in the eastern Mendip Hills. Rocks from the Devonian (419–359 million years ago) are found across much of Exmoor, the Quantocks (including Hangman Sandstone and Cockercombe tuff), and in the cores of the folded masses of the Mendip Hills. Carboniferous Period (359–299 million years ago) rocks are represented by the Carboniferous Limestone that forms the Mendip Hills, rising abruptly out of the flat landscape of the Somerset Levels and Moors.

Volcanism in general has shifted southward over time, although more recent radiometric dating efforts indicate that volcanic activity in the fields was more contemporaneous than thought. The volcanic field overlies a high Tertiary surface between the Paleozoic to Tertiary Murzuk and Sirte Basins; the Syrte embayment during the Miocene reached into the Haruj mountains. A number of swells and tectonic lineaments, some of which are located at the margins between geologic blocks, characterize the basement beneath Haruj and have influenced the location of volcanic vents. The basement is of Eocene to Oligocene age and consists of conglomerate, dolomite, limestone, marl and sandstone, known as the Bishimah Formation; where the lavas of Haruj are thinner, it often forms white outcrops.

The fault zone penetrates the Chilean Coastal Cordillera through North-South striking elongate terranes of Jurassic to early Cretaceous igneous rocks. The region was formed through arc-magmatism and is composed of mostly andesitic tuffs and lavas with large diorite batholiths. Certain areas of these igneous provinces are overlain by terranes of continental clastic rocks and marine limestones. Past and recent fault activity has reworked some of the surrounding rock, producing regions of ductilely deformed rocks, which can be categorized into two types: Cretaceous plutonic rocks (tonalites) deformed under greenschist conditions and metamorphic rocks from Jurassic volcanics, which includes intrusive rocks (diorites, gabbros and tonalites), and Paleozoic greywackes formed in mid-amphibolite facies conditions.

Numerous studies have addressed the geochemical signature of the lavas present on Iceland and in the north Atlantic. The resulting picture is consistent in several important respects. For instance, it is not contested that the source of the volcanism in the mantle is chemically and petrologically heterogeneous: it contains not only peridotite, the principal mantle rock type, but also eclogite, a rock type that originates from the basalt in subducted slabs and is more easily fusible than peridotite. The origin of the latter is assumed to be metamorphosed, very old oceanic crust which sank into the mantle several hundreds of millions of years ago during the subduction of an ocean, then upwelled from deep within the mantle.

These basaltic lavas are intruded by narrow mafic and ultramafic sills. At least three different types of lava compositions exist in the Chukotat Group, including olivine phyric, pyroxene-phyric and plagioclase phyric. The upper unit of the Chukotat Group is 1,870 million years old whereas the lower unit is associated with the Katiniq Suite sills, which cut through the underlying Povungnituk Group. In 1989, the Katiniq Suite sills were thought to be 1,918 million years old, but more recent dating and a reinterpretation of the original age in 2004 suggests that the Katiniq Suite sills are closer to 1,880 million years old. Therefore, the age range for the Chutotat Group is 1,880 to 1,870 million years.

There is a connection between volcanism and crustal thickness on the subsurface of Io. Thinner crust produces dense, mafic, dark flows that cover larger areas and where secondary, more sulfurous flows occur. Conversely, in thicker crust regions, the more dense lavas do not occur as often. Crustal thickness is thought to be related to tidal flexing in the interior of Io. The shift from dark, freshly erupted material into bright plains material may support the notion that Io has strong crustal materials that can support the steep paterae walls. The lithosphere of Io is thought to be well-fractured, which is supported by the paterae hot spot migration between the times of the Voyager and the Galileo flybys.

The complex nature of the formation of the area has led to the debates as to origin but it is speculated that much of the modern geology of the area began with the development of a very large volcano of which little now remains. Volcanoes also erupted in the south of the area and as a result, remains of volcanic necks can be found in the hills around Forkhill. Along the contact zone between the Silurian rocks and the Newry granite a roughly circular fracture developed into which was intruded a series of acidic lavas. These cooled to form very hard granophyre and felsite rocks – in fact two 'rink dykes' or the "outer" and "inner" rings.

The history of the volcano has been identified with the early Pliocene age. However, the caldera of the volcano is dated to a comparatively recent history of 8000 years. The “Sugarloaf cone on the ENE flank, and a cluster of about a dozen explosion pits and cinder cones at Point Kadin on the WNW flank” is attributed to the Holocene age. According to the history recorded by the Alaska Volcano Observatory: “The first episode began in Pliocene or early Pleistocene time (the oldest known age of lavas is 0.93 Ma [Nye, 1990]) and produced extensive flows and subordinate pyroclastic deposits of basaltic and andesitic composition, which enlarged the island by several kilometers along the northwest coast.

The total volume of this group is , indicating a flux rate of . The Gordo group, which erupted 6–4 mya following a probable 2-million-year hiatus, is located in the southern and western parts of the cluster. Cerro Gordo itself (5.49 mya) has a crater that is breached westwards, exposing about twelve radial dykes but with no trace of a debris avalanche. One of the larger centres of the cluster, Gordo is associated with a lava field on its western side that is dated 4.9 mya. Cerro Puquíos and Cerro Negro (5.81–5.28 mya) lie on the southern side of the cluster, and glacial cirques cutting their northeastern flanks reveal layers of scoria and lavas.

The upper slopes and the floor of the caldera are covered by holly and juniper forests, almost all of which are protected in the Nature Reserve of Serra de Santa Barbara e dos Mistérios Negros. In 1761 a portion of the volcano erupted, and according to local religious lore, the villagers took a holy relic up to the erupting lava, and the lava stopped.Quando no sítio conhecido por "Entre o Pico e a Serra" rebentou um vulcão cujos fumos densos desceram da cumeada da Serra de Santa Bárbara, a coroa do Império do Outeiro foi levada ao local e as lavas não avançaram mais para além do sítio onde depois foi construído o Império.

Alteration of the lavas is related to both axial hydrothermal systems and crustal aging in a submarine environment. Fluid can be shown to have penetrated at least to the base of the plutonic sequence where high temperature and secondary phases in the plutonics and cumulates imply alteration close to the ridge axis. The presence of alteration in all of the extrusive levels but the very highest imply a succession of numerous hydrothermal convection cells active during eruption. As the crustal sequence gradually moved off of the spreading axis, there was cessation of the main metalliferous deposition and progressive restriction of water/rock action and eventually water interaction was restricted to within rock units as the crust was sealed off.

However, the focus of volcanism at Yellowstone in the Columbia Plateau Province is far inland from the subduction zone that lies along the Oregon and Washington coast. Evidence suggests that some concentrated heat source is melting rock beneath the Columbia Plateau Province, at the base of the lithosphere (the layer of crust and upper mantle that forms Earth's moving tectonic plates). In an effort to figure out why this area, far from a plate boundary, had such an enormous outpouring of lava, scientists established hardening dates for many of the individual lava flows. They found that the youngest volcanic rocks were clustered near the Yellowstone Plateau, and that the farther west they went, the older the lavas.

The lavas, intrusive volcanic rocks, and volcanic vents have largely gone unaltered by erosion or other geological processes besides sparse mineralization as a result of volcanic exhalative processes, though there are tiny amounts of specular hematite and malachite in cracks among lava flows. Heavily eroded by glaciers, which no longer exist on Diamond Peak, the mountain has several cirques from glacial erosion, some of which have talus deposits due to Holocene glacial motion. Glaciers also placed both lateral and ground moraines along the lower to middle elevations of the wilderness area, unlayered pebble deposits interbedded with sand and rock. These deposits have very few weathering rinds, corresponding to their production during the late Pleistocene.

A reconstruction of the origin of continental crust, which formed the greenstone belt, using geochemical, lithological, and structural clues, is predicated upon two assumptions: first, new Hadean crust formed laterally by the expelling and lateral accretion of mafic to ultramafic lavas. Then stabilization occurred through the re-melting of the crust. The reworked crust can be attributed to the burial, most likely through subduction, of hydrated materials, such as basalt, that were formed in the Hadean. Additionally, the source for tested rock samples came from a mantle depleted in titanium and niobium and enriched in lead, strontium, barium, rubidium, and light rare- earth elements, which, taken together, are indicative of arc-related basalts.

The Stirling Sill is an outcropping of a large quartz-dolerite intrusion or sill that underlies a large part of central Scotland, and may be contiguous at great depth. The sill is of very late Carboniferous age or more probably Permian, as it penetrates the coal measures, often in bedding planes between the various strata. In places, it rises through fractures in the strata to a new level, forming features that, at the surface, would be called dikes. At its outcrop on the west, the sill generally lies towards the base of the Carboniferous sequence, and just above the calciferous sandstone deposits and lavas, as can be seen in the upper part of the valley of the Bannock Burn.

Degassing of underlying volatile-rich alkali basalt may have transported enough alkali elements into the Amalia magma chamber to change the magma to a peralkaline composition. Fractional crystallization took place at an intermediate level of the crust before the final magma body formed at a relatively shallow level. Miocene lavas from the same region did not assimilate significant crust nor mix with primitive basalts, suggesting that these processes required large magma chambers fed by large flows of basaltic magma from the upper mantle. The Miocene magmas may reflect a time when the flow of basaltic magma had diminished or extensive faulting allowed the magma to erupt before it could pool in the subsurface.

The Sierra Negra like the other volcanoes on Isabela is believed to have been created from a mantle plume which has created the hotspot. The age of Sierra Negra and the other volcanoes on Isabela is hard to determine as they are in a North-South line to the east of the hotspot, which is believed to be under Fernandina volcano, and the Nazca plate is moving east. This puts the volcanoes perpendicular to the hotspot. The surface of Sierra Negra and its neighbouring volcanoes are also covered by young lavas, adding to the difficulty of aging them. An estimate based on volume (588 km3) and eruption rates suggest that Sierra Negra is approximately 535,000 years old.

One notable phenomena in and around the domes which host the majority of the komatiitic nickel ore deposits in Australia is the high degree of parallelism of the ore shoots, especially at the Kambalda Dome and Widgiemooltha Dome. Ore shoots continue, in essential parallelism, for several kilometres down plunge; furthermore in some ore trends at Widgiemooltha, ore trends and thickened basal flow channels are mirrored by low-tenor and low-grade 'flanking channels'. These flanking channels mimic the sinuous meandering ore shoots. Why extremely hot and superfluid komatiitic lavas and nickel sulfides would deposit themselves in parallel systems can only be described by Horst-Graben type faulting which is commonly seen at rift zones.

Satellite photo of the Ring Creek lava flow The hazard from lava flows would be low to moderate because the nature of the lavas would prevent them from travelling far from their source, even though the Ring Creek lava flow ends only from Squamish. Magma with high to intermediate levels of silica (as in andesite, dacite or rhyolite) commonly move slowly and typically cover small areas to form steep- sided mounds called lava domes. Lava domes often grow by the extrusion of many individual flows less than thick over a period of several months or years. Such flows will overlap one another and typically move less than a few meters per hour.

By the beginning of the Cenozoic era, 66 million years ago, the Blue Mountains province was uplifting (that is, was being pushed higher by tectonic forces), and the Pacific Ocean shoreline, formerly near Idaho, had shifted to the west. Volcanic eruptions about 44 million years ago during the Eocene deposited lavas accompanied by debris flows (lahars) atop the older rocks in the western part of the province. Containing fragments of shale, siltstone, conglomerates, and breccias, the debris flows entombed plants and animals caught in their paths; the remnants of these ancient flows comprise the rock formations exposed in the Clarno Unit. Preserved in the Clarno Nut Beds are fossils of tropical and subtropical nuts, fruits, roots, branches, and seeds.

The island is mainly composed of the Jurassic Lemaire Formation, composed of tuffs and lavas. The Islas Año Nuevo, Isla Observatoria, and the Caleta Lacroix region on the west coast, however, have exposures of the Jurassic-Cretaceous Beauvoir Formation, mainly composed of shales, mudstones, limestones, and graywacke, plus silt, clay, sand and gravel glacial fluvial deposits. There are at least 18 fjords, with associated glacial sediments such as moraines and till, especially prevalent at Cape San Antonio and Cape Colnett on the north coast. Key fjords on the north coast include Port Hoppner, Port Parry, Port Basil Hall, Port Año Nuevo, Port Cook, and Port San Juan Del Salvamento going east to west.

It is covered with volcanoes that erupt sulfur, sulfur dioxide and silicate rock, and as a result, Io is constantly being resurfaced. Its lavas are the hottest known anywhere in the solar system, with temperatures exceeding 1,800 K (1,500 °C). In February 2001, the largest recorded volcanic eruptions in the solar system occurred on Io. Europa, the smallest of Jupiter's Galilean moons, also appears to have an active volcanic system, except that its volcanic activity is entirely in the form of water, which freezes into ice on the frigid surface. This process is known as cryovolcanism, and is apparently most common on the moons of the outer planets of the solar system.

Although extensive rifting has not yet been recognized in the Northern Cordilleran Volcanic Province, volcanism throughout the past 1.6 million years is possibly due to repetitive upper mantle upwelling and adjacent transtension throughout the Queen Charlotte Fault, accommodated partly by numerous east-west trending fault zones that extend all through the Northern Cordilleran Volcanic Province. The volcanics comprising the Northern Cordilleran Volcanic Province are consistent with the rifting environment. Alkaline basalt, lesser hawaiite and basanite magmas from effusive eruptions create the massive shield volcanoes and small cinder cones throughout the volcanic province, several of which comprise lherzolite magma. Felsic magmas from more viscous eruptions create the massive central volcanoes and largely consist of trachyte, pantellerite and comendite lavas.

The shield-stage lavas that built the enormous main mass of the mountain are tholeiitic basalts, like those of Mauna Kea, created through the mixing of primary magma and subducted oceanic crust. Mauna Loa's summit hosts three overlapping pit craters arranged northeast-southwest, the first and last roughly in diameter and the second an oblong feature; together these three craters make up the summit caldera Mokuʻāweoweo, so named for the Hawaiian ʻāweoweo fish (Priacanthus meeki), purportedly due to the resemblance of its eruptive fires to the coloration of the fish. Mokuʻāweoweo's caldera floor lies between beneath its rim and it is only the latest of several calderas that have formed and reformed over the volcano's life.

The Stibnite Mining District sits atop the Idaho Batholith, one of the signature features of Idaho’s unique geology. The Idaho Batholith is nearly 14,000 square miles of granite, formed from the collision of the oceanic plate and the North American plate around 100 million years ago during the Cretaceous period. Continental drift pushed the denser oceanic plate under the North American plate, where immense heat, pressure and superheated water caused the rocks to melt, rise and then slowly cool, creating the vast expanse of crystalline granite underneath most of central Idaho. Some 50 million years later, an enormous volcanic complex erupted through the granite and left behind volcanic ash, lavas and crystalline rocks.

Mount Jefferson from above Scientists lack a comprehensive record of activity at Mount Jefferson, as important details have been obscured by the erosion of deposits by large glaciers. A few eruptions have been documented from the deposits that have been preserved, but the broad outline of Jefferson's eruptive history is understood, including that its activity has changed over time, producing both powerful explosive eruptions and lava flows. Historically, eruptive activity has alternated between andesitic and dacitic lavas. The volcano formed over the course of several eruptive episodes, beginning about 300,000 years ago with the formation of rocks on the western and southwestern flanks of the volcano, and lasting until roughly 15,000 years ago.

The mountain was created by the subduction of the Nazca Plate beneath the South American Plate. Aconcagua used to be an active stratovolcano (from the Late Cretaceous or Early Paleocene through the Miocene) and consisted of several volcanic complexes on the edge of a basin with a shallow sea. However, sometime in the Miocene, about 8 to 10 million years ago, the subduction angle started to decrease, resulting in a stop of the melting and more horizontal stresses between the oceanic plate and the continent, causing the thrust faults that lifted Aconcagua up off its volcanic root. The rocks found on Aconcagua's flanks are all volcanic and consist of lavas, breccias and pyroclastics.

The River Camel rises on Hendraburnick Down (UK Grid Reference SX135875) on the edge of Bodmin Moor, an area which forms part of the granite spine of Cornwall. The river's course is through sedimentary upper and middle Devonian rocks, predominantly the Upper Delabole Slates, Trevose Slates and Polzeath Slates that stretch to the coast, making a land which has shallow acidic soils. Other than sedimentary rocks, Igneous rocks can be found at Brea Hill and at Pentire Point which is composed mainly of pillow lavas. Across the mouth of the River Camel Stepper Point is composed of greenstone as is The Rumps, a promontary on the north side of Pentire point facing Port Quin Bay>.

Located at the northern and southern extensions of the Bárðarbunga and Askja fissure systems, respectively, the soil is mainly composed of lavas derived from these volcanoes, either in the form of flows or alluvial deposits of volcanic origin. The geological configuration, along with the presence of nearby subglacial volcanoes such as Bárðarbunga and Grímsvötn, is responsible for the risk of jökulhlaups, which have affected Holuhraun repeatedly. The eruption in Holuhraun on 4 September 2014 Lava fountains of the fissure eruption in Holuhraun on 13 September 2014 around 21:20. Until 2014, the surface of the lava field was of an older lava flow, which had erupted from a vent associated with Askja in 1797.

Bathymetric diagram of the Axial Seamount, showing the 1998 eruption and segmentation between the CoAxial, Axial, and Vance segments of the ridge The first documented eruption on the Juan de Fuca Ridge took place on the Cleft segment in 1986 and 1987. Hydrothermal megaplumes indicated a large rifting event, releasing hydrothermal fluids as a result of lavas being extruded from a dike. A majority of the eruptions along the ridge are dike injection events, where molten rock is extruded between cracks in the crust's sheeted dike layer. Typically eruptive events can be predicted, as they are preceded by large earthquake swarms in the region. A significant event took place in June 1993, lasting 24 days at the CoAxial segment.

Figure 1. Age-progression of volcanic islands and seamounts at the Hawaiian hotspot Ocean island basalt (OIB) is a volcanic rock, usually basaltic in composition, erupted in oceans away from tectonic plate boundaries. Although ocean island basaltic magma is mainly erupted as basalt lava, the basaltic magma is sometimes modified by igneous differentiation to produce a range of other volcanic rock types, for example, rhyolite in Iceland, and phonolite and trachyte at the intraplate volcano Fernando de Noronha. Unlike mid-ocean ridge basalts (MORBs), which erupt at spreading centers (divergent plate boundaries), and volcanic arc lavas, which erupt at subduction zones (convergent plate boundaries), ocean island basalts are the result of intraplate volcanism.

Other volcanoes such as Three Fingered Jack and Mount Washington lie about to the west. According to the U.S. National Geodetic Survey and scientists from the United States Geological Survey, Black Butte has an elevation of ; the Geographic Names Information System database lists its elevation as , while Oregon Geographic Names lists its elevation at . The butte has proximal and draping reliefs of and , which are the "difference between summit elevation and that of highest exposure of older rocks overlain by the edifice" and the "difference between summit elevation and that of lowest distal lavas of the edifice (not including distal pyroclastic or debris flows)," respectively. According to E. M. Taylor, Black Butte has a diameter of .

At the northern limit, the bedrock around the Cove is Devonian (419.2-358.9 mya) in age, beginning with conglomerate sandstone and siltstone of the Pointagare group, then the Ballydavid sandstone formation and further south the medium-grained Farran sandstone formation. Furthest south the igneous Silurian (443.8–419.2 mya) rocks of the Foilnamahagh Formation are dominant, with lavas and pyroclastic remnants. Between 2009 and 2017 (at Baile 'n Fheirtéaraigh), for January and July respectively, the mean temperatures are 8 C and 16C and the mean rainfall 207mm and 153mm; the highest and lowest mean wind speeds were 39.3 km/h (November 2009) and 14.3 km/h (July 2013) respectively, with the highest wind speeds generally in winter.

Oceanic crust is primarily composed of mafic rocks, or sima, which is rich in iron and magnesium. It is thinner than continental crust, or sial, generally less than 10 kilometers thick; however, it is denser, having a mean density of about 3.0 grams per cubic centimeter as opposed to continental crust which has a density of about 2.7 grams per cubic centimeter. The crust uppermost is the result of the cooling of magma derived from mantle material below the plate. The magma is injected into the spreading center, which consists mainly of a partly solidified crystal mush derived from earlier injections, forming magma lenses that are the source of the sheeted dikes that feed the overlying pillow lavas.

The central portion of the Anahim Volcanic Belt contains three complex shield volcanoes, known as the Rainbow, Ilgachuz, and Itcha ranges. These fairly dissected shield volcanoes lie on the northern end of the Chilcotin Group lava plateau and distal lava flows at the margins of the shield volcanoes merge imperceptibly with flat- lying lava flows comprising the Chilcotin Group lava plateau. Unlike the Chilcotin Group basalt, which is not associated with any felsic derivatives, the volcanoes of the central Anahim Volcanic Belt are markedly bimodal, comprising a mixed assemblage of basalt and peralkaline silicic rocks. While volcanoes of the Anahim Volcanic Belt appear to merge laterally with the Chilcotin Group lavas, the particular nature and connection between the Anahim Volcanic Belt and the Chilcotin Group is unknown.

Modern Elysium Planitia (including the Athabasca Valles) and the Elysium Rise were first extensively mapped in the 1970s and 1980s using orbital imagery from the Viking program. Initial geophysical and tectonic interpretations of this region were proposed in the 1980s by various authors. In 1990, Jeffrey B. Plescia of the Jet Propulsion Laboratory was among the first to examine the origin of central Elysium Planitia in detail; at the time of his publication, he referred to this region informally as the "Cerberus Plains", and was the first to critically examine the hypothesis that this region was largely formed through the eruption of low-viscosity flood lavas. This hypothesis - among other volcanic-aeolian and sedimentary hypotheses - ultimately received widespread acceptance in the Martian planetary geology community.

Pseudoleucite nepheline syenite of the Intrusive Complex of Morro de São João, State of Rio de Janeiro, Brazil (Motoki et al., 2011b) Nepheline syenites and phonolites occur, for example, in Canada, Norway, Greenland, Sweden, the Ural Mountains, the Pyrenees, Italy, Brazil, China, the Transvaal region, the mountains of the Central Montana Alkali Province, and Magnet Cove igneous complex of Arkansas, as well as on oceanic islands. Phonolite lavas formed in the East African rift in particularly large quantity, and the volume there may exceed the volume of all other phonolite occurrences combined, as discussed by Barker (1983). Nepheline-normative rocks occur in close association with the Bushveld Igneous Complex, possibly formed from partial melting of the wall rocks to that large ultramafic layered intrusion.

Part of the Cascade Volcanic Arc and the Cascade Range, each of the three volcanoes formed at different times from several variable magmatic sources. The amount of rhyolite present in the lavas of the younger two mountains is unusual relative to nearby peaks. The Three Sisters form the leading edge of a rhyolitic crustal-melting anomaly, which might be explained by a combination of mantle flow (movement of Earth's solid silicate mantle layer caused by convection currents) and decompression that has generated similar melting and rhyolitic volcanism nearby for the past 16 million years. Like other Cascade volcanoes, the Three Sisters were fed by magma chambers produced by the subduction of the Juan de Fuca tectonic plate under the western edge of the North American tectonic plate.

Crustal collision had occurred in the south between the North Palawan-Mindoro crustal block and perhaps sediment contamination was derived from this region. This substantiates preliminary early isotope and trace element studies on the central Luzon arc Further work was done on the northern Luzon arc by McDermott et al. who found systematic variations in an assortment of isotopes with latitude not only in the lavas analyzed over the 500 km section of the arc but also in sediments along the trench. The only way to explain the latitudinal variations was through the addition of an increasing input of terrigenous sediments toward the continental regions in the north China and Taiwan During the Middle Miocene, 16-15 Ma, activity started in Taiwan.

G. M. Dawson of the Geological Survey of Canada was able to demonstrate that on the Stikine River there were at least four flows of basalt. The basalts and andesites were considered to be younger than all the rocks they were observed in contact with, namely granitic intrusives, porphyries and greenstones. More definite evidence as to their age was obtained by W. A. Johnston and F. A. Kerr of the Geological Survey of Canada who placed them in the Tertiary with some of the most recent flows of the Stikine valley probably belonging to the Pleistocene. A 3D model of Level Mountain Level Mountain was demonstrated in the 1920s as a possible source for the extensive lavas in the neighbouring Tuya volcanic field.

For the presence of this mineral it is necessary that the silica percentage of the rock should be low, since leucite is incompatible with free quartz and reacts with it to form potassium feldspar. Because it weathers rapidly, leucite is most common in lavas of recent and Tertiary age, which have a fair amount of potassium, or at any rate have potassium equal to or greater than sodium; if sodium is abundant nepheline occurs rather than leucite. In pre-Tertiary rocks leucite readily decomposes and changes to zeolites, analcite and other secondary minerals. Leucite also is rare in plutonic rocks and dike rocks, but leucite syenite and leucite tinguaite bear witness to the possibility that it may occur in this manner.

The west coast looking from A' Bhrideanach point towards Bloodstone Hill The main range of hills on Rùm are the Cuillin, usually referred to as the "Rùm Cuillin", in order to distinguish them from the Cuillin of Skye. They are rocky peaks of gabbro, forming the Rum layered intrusion. Geologically, Rùm is the core of a deeply eroded volcano that was active in the Paleogene era some 60 million years ago,Hamilton MA, Pearson DG, Thompson RN, Kelly SP, Emeleus CH (1998) Rapid eruption of Skye lavas inferred from precise U-Pb and Ar-Ar dating of the Rum and Cuillin plutonic complexes. Nature 394: 260-263 and which developed on a pre-existing structure of Torridonian sandstone and shales resting on Lewisian gneiss.

When the Mount Edziza volcanic complex began to form 7.5 million years ago, volcanism rates in the Northern Cordilleran Volcanic Province increased again. Early volcanic activity of the Mount Edziza volcanic complex seven million years ago constructed Armadillo Peak, the oldest and most central of the four central volcanoes comprising the complex. Its summit is capped by thick fine-grained silica-rich trachyte lava flows that ponded inside the caldera to produce a lava lake six million years ago during its final stage of activity. A massive stratovolcano was also formed on top of the Level Mountain shield volcano 7.1 to 5.3 million years ago during this increased period of volcanism when viscous peralkaline trachyte and comendite lavas were erupted.

Some dredge samples might come from neighbouring Cretaceous seamounts rather than the South Arch volcanic field, however. The alkalic composition of the lavas resembles that of rejuvenated stage volcanics on Kauai, that of preshield volcanics at Loihi and that of the North Arch volcanic field; they share with the latter a high ratio of helium-3/helium-4 and a high carbon dioxide content. Mixing between mantle plume melts of the Hawaiian hotspot and components typical of mid-ocean ridge basalts may have given rise to the volcanics of the South Arch volcanic field, with metasomatism involved as well. The magmas of the South Arch volcanic field appear to have been unusually water-rich, perhaps because of an early melting of water-rich mantle.

The recognised summit is at 388m to the South of the hill, but the highest point, named Cerrig-y-Myllt on only the most detailed UK Ordnance Survey mapping, is at 463m above the two small lakes to the North of the hill. The craggy nature of the hill is due to the presence of lavas and tuffs (volcanic ash deposits) dating from the Ordovician period when Snowdonia was characterised by numerous volcanic eruptions; Yr Arddu is a particularly good location to see the record of Ordovician volcanism. The Yr Arddu Tuffs may be the earliest eruptive phase of the Lower Rhyolitic Tuff Formation. The whole hill is a site of special scientific interest designated by the Countryside Council for Wales.

Basaltic lavas were extruded 183 Mya to form the Karoo large igneous province; a volcanism caused by the Bouvet hotspot which is linked to the Gondwana break-up. The Bouvet hotspot was located in or near present-day South Africa from the late Triassic 220 mya and until the Africa-Antarctica breakup 120 mya. The Bouvet hotspot track stretches south-east from the African continent, near the South Africa-Mozambique border, and east of the AFFZ down to Bouvet Island/Bouvet Triple Junction in the South Atlantic. 100 Mya, the region where the triple junction was located passed over the hotspot, resulting in a continuous eruption that lasted to about 94 Mya and the seafloor spreading that still separates Antarctica, Africa, and South America.

The Peak is formed almost exclusively from sedimentary rocks dating from the Carboniferous period. They comprise the Carboniferous Limestone, overlying Gritstone and the Coal Measures which occur only on the extreme margins and infrequent outcrops of igneous rocks including lavas, tuffs and volcanic vent agglomerates.Gannon, Paul, Rock Trails Peak District:A Hillwalker's Guide to the Geology and Scenery, Pesda Press, 2011, The general geological structure is that of a broad dome, whose western margins have been most intensely faulted and folded. Uplift and erosion have effectively sliced the top off the Derbyshire Dome to reveal a concentric outcrop pattern with Coal Measures rocks on the eastern and western margins, Carboniferous Limestone at the core and with rocks of Millstone Grit outcropping between them.

The hills are formed largely from the Ordovician age marine mudstones and siltstones of the Penmaen Dewi Shales and Aber Mawr Shale formations which have been intruded by microgabbro (otherwise known as dolerite or diabase) of Ordovician age. The former slate quarries at Rosebush on the southern edge of the hills worked the Aber Mawr Formation rocks whilst it is the dolerite tors of Carnmenyn which have been postulated, amongst other localities, as the source of the Stonehenge ‘bluestones’. In contrast Foel Drygarn towards the eastern end of the range is formed from tuffs and lavas of the Fishguard Volcanic Group. Further east is Frenni Fawr which is formed from mudstones and sandstones of the Nantmel Mudstone Formation of late Ordovician Ashgill age.

In the Eastern Alborz Range, the far eastern section is formed by Mesozoic (chiefly Triassic and Jurassic) rocks, while the western part of the Eastern Alborz Range is made primarily of Paleozoic rocks. Precambrian rocks can be found chiefly south of the city of Gorgan situated in the southeast of the Caspian Sea and, in much smaller amounts, in the central and western parts of the Central Alborz Range. The central part of the Central Alborz Range is formed mainly of Triassic and Jurassic rocks, while the northwestern section of the range is mainly composed of Jurassic rocks. Very thick beds of Tertiary (mostly Eocene) green volcanic tuffs and lavas are found mainly in the southwestern and south-central parts of the range.

However, analysis of the chemical composition of lavas from the two volcanoes show that they have separate magma chambers, and are thus distinct. Nonetheless, their proximity has led to a historical trend in which high activity at one volcano roughly coincides with low activity at the other. When Kīlauea lay dormant between 1934 and 1952, Mauna Loa became active, and when the latter remained quiet from 1952 to 1974, the reverse was true. This is not always the case; the 1984 eruption of Mauna Loa started during an eruption at Kīlauea, but had no discernible effect on the Kīlauea eruption, and the ongoing inflation of Mauna Loa's summit, indicative of a future eruption, began the same day as new lava flows at Kīlauea's Puʻu ʻŌʻō crater.

These include cinder cones, lava domes, and various other lava edifices, with at least 25 vents on the volcano's flanks and summits becoming active within the past 10,000 years. Most of the cinder cones on the volcano's edifice vary from in elevation, though a number of them reach heights above with diameters greater than . Most of these exhibit saucer-like summit depression landforms, with notable exceptions at Lava Top and North Kawak Buttes, which have craters that are in depth. Basaltic and basaltic andesite lava flows have penetrated the bases of many of these cinder cones, forming a matrix of connected flows, and a veneer of pāhoehoe and ʻaʻā lavas can be found on Newberry volcano's northern and southern sides.

The places broad valleys contain deep alluvial and colluvial soils derived from a diversity of parent rocks. The northern Downey Creek sector of the TTA is geologically best described as being a deeply incised upland basalt plateau siting at around , and is flanked by granite and metamorphic ranges on its west and east respectively, and which extend into the southern portions of the place. The basalts were erupted during the Cainozoic era and the lavas flooded and partially filled the South Johnstone River and Downey Creek valleys in the northern part of the place to depths of hundreds of metres. Subsequent erosion has carved a spectacular sheer walled gorge as the South Johnstone River re-asserted its course and the basalts have been deeply weathered and eroded.

The extension in the Lau-Havre basin results in a higher rate of subduction than convergence along the Australian-Pacific plate boundary. The rates of extension, subduction, and convergence all increase northwards in this complex, subduction at a rate of and extension at a rate of . As a result, the Tonga-Kermadec Ridge moves independently of both tectonic plates and forms the Tonga-Kermadec Plate, in its turn fragmented into the Niuafo'ou, Tonga, and Kermadec microplates. The Samoa and Louisville mantle plumes both contribute to the lavas of two of the northern Tonga islands, Tafahi and Niuatoputapu; ocean island basalt (OIB) from the Samoa plume were introduced from 3-4 Ma when subduction in the Vitiaz Trench (north-west of Tonga) ceased.

Pillow Lava in lron ore belt at Nomira 2 km east of Nomira 18 km from 18 km south of Joda town, on the Keonjhar-Barbil-Lahunipada state highway, has been declared the National Geological Monuments of India by the Geological Survey of India (GSI), for their protection, maintenance, promotion and enhancement of geotourism.national geo-heritage of India, INTACH Pillow Lava, Iron ore belt of Nomira is an exposure of ellipsoidal pillow lava of a maximum thickness of 2m x 0.6m. The fine to medium grained, green to bluish green coloured with abundant Vesicular texture filled with quartz. The lavas and the associated pyroclastic rocks and tuffs are underlain by quartzite and overlain by shale, chart-shale and banded hematite jasper.