Shield volcanoes are large, slow forming volcanoes that erupt fluid basaltic magma that cools to form the extrusive rock basalt. Basalt is composed of minerals readily available in the planet's crust, including feldspars and pyroxenes. Fissure volcanoes pour out low viscosity basaltic magma from fissure vents to form the extrusive rock basalt. Composite or stratovolcanoes often have andesitic magma and typically form the extrusive rock andesite.
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Andesitic magma is composed of many gases and melted mantle rocks. Cinder or scoria cones violently expel lava with high gas content, and due to the vapor bubbles in this mafic lava, the extrusive basalt scoria is formed. Lava domes are formed by high viscosity lava that piles up, forming a dome shape. Domes typically solidify to form the rich in silica extrusive rock obsidian and sometimes dacite domes form the extrusive rock dacite, like in the case of Mount St. Helens.
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Formation of igneous rock In terms of modes of occurrence, igneous rocks can be either intrusive (plutonic and hypabyssal) or extrusive (volcanic).
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Other magmatism in Borneo during the Late Cenozoic include intrusive and extrusive in Sarawak, the Semporna Volcanics of Eastern Sabah and in Kalimantan.
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The extrusive rocks scoria and pumice have a vesicular, bubble-like, texture due to the presence of vapor bubbles trapped in the magma.
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It is considered within the Tertiary Period; The subsoil is made up of limestone, extrusive igneous rocks, rhyolite, andesite, basalt, tuff and volcanic gap.
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Intrusions are one of the two ways igneous rock can form; the other is extrusive rock, that is, a volcanic eruption or similar event. Technically speaking, an intrusion is any formation of intrusive igneous rock; rock formed from magma that cools and solidifies within the crust of the planet. In contrast, an extrusion consists of extrusive rock; rock formed above the surface of the crust.
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Calderas are volcanic depressions formed after an erupted volcano collapses. Resurgent calderas can refill with an eruption of rhyolitic magma to form the extrusive rock rhyolite like the Yellowstone Caldera. Submarine volcanoes erupt on the ocean floor and produce the extrusive rock pumice. Pumice is a light-weight, glass with a vesicular texture that differs from scoria in its silicic composition and therefore floats.
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Boulder, Colo.: Geological Society of America, 2007. The extrusive rock is composed of breccia and conglomerate. The intrusive rock has formed numerous dikes, sills, and plugs.
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A sample of rhyodacite from Slovakia Rhyodacite is an extrusive volcanic rock intermediate in composition between dacite and rhyolite. It is the extrusive equivalent of granodiorite. Phenocrysts of sodium-rich plagioclase, sanidine, quartz, and biotite or hornblende are typically set in an aphanitic to glassy light to intermediate-colored matrix. Rhyodacite is a high silica rock containing 20% to 60% quartz with the remaining constituents being mostly feldspar.
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It is commonly produced in volcanic arcs, and in cordilleran mountain building, such as in the Andes Mountains, as large batholiths. The extrusive volcanic equivalent rock type is andesite.
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The degree to which these practices took place was based on the two modes of social death, intrusive and extrusive. In the intrusive mode, rituals were developed for the incorporation of an external enemy into the culture as a slave. In the extrusive mode, traditions evolved for including those who have "fallen into slavery" from within society into the slave status. Both of these modes provided a process for the institutionalization of socially dead individuals.
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Obsidian is a naturally occurring volcanic glass formed as an extrusive igneous rock.John P. Rafferty (August 2011). Rocks. The Rosen Publishing Group. pp. 97–. .I-science I' 2006 Ed. Rex Bookstore, Inc. pp. 127–. .
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In igneous petrology, eutaxitic texture describes the layered or banded texture in some extrusive rock bodies. It is often caused by the compaction and flattening of glass shards and pumice fragments around undeformed crystals.
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Seismic volcanostratigraphy of the extrusive breakup complexes in the northeast Atlantic: implications from ODP/DSDP drilling. In Larsen, H.C., Duncan, R.A., Allan, J.F., Brooks, K. (Eds.), Proc. ODP, Sci. Results, 163, 3–16 [Online.
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The Group comprises siltstones, slates and a variety of extrusive igneous rocks from the Croaghmarin, Drom Point, Mill Cove, Clogher Head, Ferriter's Cove, Foilnamahagh and Coosglass Slate formations of Silurian age. The siltstones are frequently fossiliferous.
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A Health Emergency was declared in the capital by the Central Government of India to cope with the extrusive amount of polluted air. The day was declared as a holiday for schools, offices and other government centres.
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The dyke trends at approximately 65 degrees. Dolerite is intrusive and is relative to basalt (extrusive). There is a significant alteration about the contact between the two rocks. The dolerite dyke was emplaced into the Uriconian Rhyolite.
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These studies also concluded that the sill was emplaced in a position nearly identical to its current one (10-to-15-degree dip); this is further confirmed by the still-vertical orientation of the columnar jointing. It has been proposed that the Watchung basalt flows of the Watchung Mountains are extrusive eruptions of the same magma that created the Palisades Sill. Magnetic and gravity measurements have indicated the presence of a large subsurface dike between the Palisades intrusion and the Ladentown basalt, an extrusive body of Watchung basalt north of Suffern, New York.Kodama, K.P., 1983.
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Auvergne, France, used as building stone, forming part of the walls of Clermont-Ferrand Cathedral, France Trachyandesite is field S3 in the TAS diagram Trachyandesite is an extrusive igneous rock with a composition between trachyte and andesite. It has little or no free quartz, but is dominated by sodic plagioclase and alkali feldspar. It is formed from the cooling of lava enriched in alkali metals and with an intermediate content of silica. The term trachyandesite had begun to fall into disfavor by 1985 but was revived to describe extrusive igneous rocks falling into the S3 field of the TAS classification.
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External signals of unknown origin are detected by the membrane receptors located at the top of the organism. The consequent activation of the adenylate cyclase-cAMP system triggers the ejection of the extrusive apparatus, with the formation of a hollow tube, about 40 μm long, terminating in a head mainly consisting of the apical portion of the epixenosome (the region containing DNA). The extrusive apparatus is surrounded by a basket of tubules. Experiments with antitubulin drugs and immunocytochemical analyses at the optical and electron microscopical level suggested that these tubules consist of tubulin, which is a eukaryotic protein.
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It was named for Richard Penrose (1863–1931), an economic geologist. Penroseite is a rare mineral found in the Pacajake mines in Bolivia. It was discovered in 1925. It used to be found in fissure veins in the extrusive igneous rhyolite rock.
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Nepheline syenite is a holocrystalline plutonic rock that consists largely of nepheline and alkali feldspar. The rocks are mostly pale colored, grey or pink, and in general appearance they are not unlike granites, but dark green varieties are also known. Phonolite is the fine-grained extrusive equivalent.
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He became inspector-general of mines, and director of the Geological Survey of France. He was distinguished for his researches on extrusive rocks and their microscopic structure and origins. He employed the polarizing microscope early on for the identification of minerals.Auguste MICHEL-LEVY (1844-1911) Annales.
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In Precambrian section was made up of felsic-intermediate granite with the inclusion of greenstones and ophiolites, where the Paleozoic section consists of mainly potassium- and sodium-deficient extrusive rocks. The basalts in the basement which indicated trapped late Paleozoic oceanic crust that came from the mantle.
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J. China Univ. Geosci. 37: 20–27. The youngest rocks are 23-million-year-old extrusive igneous rocks, which are located in Sanyitang (in Hebei) in the orogenic belt across the block. The sedimentary rocks distribute predominantly in the Ordos Basin located in the south of the Western Block.
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In When did plate tectonics begin on planet Earth (Vol. 440, pp. 281-294). Geological Society of America Special Papers. It is also noted that Archean TTGs were intrusive rocks while the modern adakite is extrusive in nature, thus their magma should differ in composition, especially in water content.
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In the range are volcanic intrusions. They can be seen in "intrusive and extrusive igneous rocks which clearly pre-date the Great Escarpment." The Gibraltar Range receives much rain. There is a surface water measurement station found in the range at Dandahra Creek that was opened on 10 May 1972.
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The other major rock types are sedimentary, metamorphics, ultrabasic rock complex and the extrusive igneous group that include basalt, andesite, and rhyolite. The metamorphic rocks are primarily in the northern part and the southern area is made up of volcanic and sedimentary rocks. The Wenatchee Mountains are mostly composed of peridotite.
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Tephriphonolite is a mafic to intermediate extrusive igneous rock in composition between phonotephrite and phonolite. It contains 9 to 14% alkali content and 48 to 57% silica content (see TAS diagram). Tephriphonolite has been found, for example, at Colli Albani volcano in Italy and in the Asunción Rift of Paraguay.
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Minette makes up the two highest points, Roof Butte and Matthews Peak. A maar complex, containing pyroclastic and extrusive minette, is exposed along New Mexico Highway 134 in Narbona Pass (Brand et al., 2008). Argon-argon dating of four minette samples at Narbona Pass yielded consistent ages of 25 million years.
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Its mix of granitic, sedimentary, metamorphic, and extrusive rocks contrasts with the predominantly volcanic rocks of the Cascades ecoregion to the northeast. The mild, subhumid climate of the region is characterized by a lengthy summer drought. It supports a mosaic of both northern Californian and Pacific Northwestern conifers and hardwoods.
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Glacial activity has shaped the park's landscape above mean sea level, leaving U-shaped valleys and moraines behind. Extrusive igneous rock is dominant above on the eastern slope sand on the western slopes. The Otún Lake, which lies in an extinct volcano crater, and the Green Lake are located in the area.
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C8-10 Hughes Mountain is formed of extrusive rhyolite which fractured into vertical joints when it cooled, creating polygonal columns. These columns have from four to six sides and are up to three feet (0.91 m) tall. When viewed from above they resemble a honeycomb. Columnar jointing is not limited to rhyolite formations.
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It is characterized by dominant analcime phenocrysts in a matrix of analcime, sanidine and alkalic pyroxene with accessory titanite, melanite and nepheline. It is a leucocratic variety of analcimite (a foidite). Blairmorite has also been described as an analcime-rich variety of phonolite. This extrusive igneous rock is known from only two geological formations worldwide.
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Its center consists of a siliceous breccia covering an area that is at least in diameter.Woolley, A. R. (2001) Alkaline Rocks and Carbonatites of the World, Part 3: Africa. London, United Kingdom, The Geological Society of London. Exposed within the interior of the Richat Structure are a variety of intrusive and extrusive igneous rocks.
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Tomichi Dome is a prominent igneous mountain formed during the Tertiary. The predominate rock is rhyolite, but microgranite, breccia, and tuff have been cited as present. Surrounding the mountain, on the valley floor, is Mancos Shale, a Mesozoic sedimentary rock. Tomchi Dome has been described as an intrusion and also as an extrusive, volcanic feature.
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Example of a cinder, found at Amboy Crater Volcanic eruptions such as this one can create cinders. Volcanic cinder in the Mount Cayley volcanic field, British Columbia, Canada A cinder is a pyroclastic material. Cinders are extrusive igneous rocks; they are fragments of solidified lava. Cinders are typically brown, black, or red depending on chemical composition and weathering.
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The UK Centre for Ecology & Hydrology, (part of UK's Natural Environment Research Council, NERC) describes the catchment area thus: "Headwaters are steep; lower valley is broad and very flat. Bedrock extrusive igneous rocks, 50% overlain by superficial deposits. Land use arable in the valley; grassland in headwaters, some forest." The catchment covers an area of 181 km2.
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Healy attended Massachusetts Institute of Technology in 1947 and finished his senior thesis in 1951. His thesis was based on geological field work conducted in 1949 in Nova Scotia supervised by Professor Walter L. Whitehead and Professor Robert. R Shrock. The thesis argued that a suite of rocks that had been identified as intrusive was actually extrusive in origin.
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Extrusive advances begin once the diapir reaches the ground's surface and the salt is exposed. The salt then spreads from the feeder under gravitational pressure alone. This flowing has two consequences that form the structure. First, as the top of the salt flows faster than the bottom, there is a frontal roll along the leading edge.
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The uppermost 80 m were deposited after the inundation of the Judith River equivalent sediments by the Bearpaw Sea. They are thought to have been deposited in only 500,000 years. Bentonitic ash is common in the Two Medicine. To the south extrusive volcanic activity occurred in association with the Boulder Batholith collectively called the Elkhorn Volcanics.
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A nematocyst is a subcellular structure or organelle containing extrusive filaments found in two families of athecate dinoflagellates (a group of unicellular eukaryotes), the Warnowiaceae and Polykrikaceae. It is distinct from the similar subcellular structures found in the cnidocyte cells of cnidarians, a group of multicellular organisms including jellyfish and corals; such structures are also often called nematocysts (alternatively, cnidocysts or cnidae), and cnidocytes are sometimes referred to as nematocytes. It is unclear whether the relationship between dinoflagellate and cnidarian nematocysts is a case of convergent evolution or common descent, although molecular evidence has been interpreted as supporting an endosymbiotic origin for cnidarian nematocysts. In polykrikoids the nematocyst is found associated with another extrusive organelle called the taeniocyst, a complex that has been described as synapomorphic for the genus Polykrikos.
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Metamorphic facies are defined by the pressure-temperature fields in which particular minerals form. Additional metamorphic rock names exist: greenstone (metamorphosed basalt and other extrusive igneous rock) is a classification based on composition and being located Precambrian terranes, while quartzite is based only on composition, as quartz is too stable and homogeneous to change phase at typical metamorphic temperatures and pressures.
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Pitchstone has a resinous lustre, or silky in some cases, and a variable composition. Its colour may be mottled, streaked, or uniform brown, red, green, gray, or black. It is an extrusive rock that is very resistant to erosion. The pitchstone ridge of An Sgùrr on the Isle of Eigg, Scotland, was possibly formed as a lava flow in a valley.
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Kaiserstuhl in Germany. Amygdules or amygdales form when the gas bubbles or vesicles in volcanic lava (or other extrusive igneous rocks) are infilled with a secondary mineral such as calcite, quartz, chlorite or one of the zeolites. Amygdules usually form after the rock has been emplaced, and are often associated with low-temperature alteration. Amygdules may often be concentrically zoned.
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Planet Mars – volatile gases (Curiosity rover, October 2012) The most common form of volcanism on the Earth is basaltic. Basalts are extrusive igneous rocks derived from the partial melting of the upper mantle. They are rich in iron and magnesium (mafic) minerals and commonly dark gray in color. The principal type of volcanism on Mars is almost certainly basaltic too.
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Associated with the transition between these two types of terrains (at about 15°50'N and 14°30'N respectively) are V-shaped, south-propagating structures. These transitional structures disappear away from the ridge. Within the rugged terrain serpentinized peridotite and gabbro are capped with a thin layer of extrusive basalt. In the smooth areas the lithosphere is more magmatic in composition.
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Alternatively, Tomichi Dome has been described as an extrusive, volcanic feature where the initial eruptions deposited breccia and tuff that is over thick. A flow or dome of topaz rhyolite overlies the tuff. Whether plutonic or volcanic, Tomichi Dome is possibly one of a string of igneous structures associated with the Rio Grande Rift, which stretches from Mexico to Colorado.
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Lava flow on Hawaii. Lava is the extrusive equivalent of magma. Magma (from Ancient Greek μάγμα (mágma) meaning "thick unguent") is the molten or semi- molten natural material from which all igneous rocks are formed. Magma is found beneath the surface of the Earth, and evidence of magmatism has also been discovered on other terrestrial planets and some natural satellites.
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Both Colpodella and Perkinsus species have open sided truncated conoids (sometimes called pseudoconoids), rhoptries that occupy the length of the cell and smaller micronemes. Both the rhoptries and micronemes arise at the anterior portion of the cell. A three-layered pellicle lies beneath the plasma membrane and is otherwise composed of the alveolar membranes and widely separated microtubules that arise subapically. Some species have extrusive organelles (trichocysts).
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To the south near Lake Superior, rock strata of the Duluth and Beaver Bay complexes are interspersed with and underlie the extrusive rock of the North Shore Volcanic Group.Ojakangas & Matsch (1982), pp. 52, 56. The Beaver Bay Complex occupies the center of the North Shore Volcanics, and is slightly younger in age than the other mafic rocks of the Duluth Complex, dating from c.
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Rocks containing quartz (silica in composition) are silica- oversaturated. Rocks with feldspathoids are silica-undersaturated, because feldspathoids cannot coexist in a stable association with quartz. Igneous rocks that have crystals large enough to be seen by the naked eye are called phaneritic; those with crystals too small to be seen are called aphanitic. Generally speaking, phaneritic implies an intrusive origin; aphanitic an extrusive one.
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The footwall to the Widgiemooltha Komatiite is the Mt Edwards Basalt, which is a low to medium MgO mafic extrusive rock, metamorphosed to upper greenschist facies. Mineralogy is chlorite, actinolite, rare epidote, quartz and albite. The Mt Edwards Basalt has uncommon interflow sedimentary intervals and some well developed pillow basalt flow tops which give regional facing directions. The true thickness of the Mt Edwards Basalt is unknown.
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The Bronson Hill Arc is a bimodal volcanic arc and associated sediments that formed over a west (?) dipping subduction zone during the Ordovician period (c. 475 - 450 million years ago (Ma)) as part of the Taconic Orogeny. These rocks are presently well exposed along the Connecticut River Valley of Vermont and New Hampshire. The arc is evidenced by plutonism and extrusive volcanicsm, including the Ammonoosuc Formation (c.
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Verrucomicrobia is a phylum of bacteria that contains only a few described species. The species identified have been isolated from fresh water, marine and soil environments and human faeces. A number of as-yet uncultivated species have been identified in association with eukaryotic hosts including extrusive explosive ectosymbionts of protists and endosymbionts of nematodes residing in their gametes. Verrucomicrobia are abundant within the environment.
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It is the high viscosity of the lava that prevents it from flowing far from the vent from which it extrudes, creating a dome-like shape of sticky lava that then cools slowly in-situ. Spines and lava flows are common extrusive products of lava domes. Domes may reach heights of several hundred meters, and can grow slowly and steadily for months (e.g. Unzen volcano), years (e.g.
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The Chiapanecan Central highlands constitute a portion of the Central American highlands, that run from the Tehuantepec Isthmus in Mexico to the lowlands of Nicaragua.(Enciclopedia Britanica, 2013) The Chiapas highlands comprise a limestone mass with extrusive volcanic rocks at the highest peaks, extending for over 11 000 km2, ca. 160 km along a northwest–southeast axis, and ca. 70 km at its widest.
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The basaltic and andesitic dikes and sills that occur within the strata underlying the Cardenas Basalt are similar in mineralogy and chemistry to the Cardenas volcanic rocks. This suggests that these intrusive and extrusive rocks are coeval and share a common source. The sills range in thickness from a few tens of meters to as thick as 300 m. The dikes typically are much thinner and locally follow fault planes.
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The geology of Snowdonia is largely characterized by a succession of sedimentary and extrusive igneous rocks of Cambrian, Ordovician and Silurian age which were faulted and folded during the Caledonian Orogeny. West of Harlech is an area of much younger rocks though these are wholly concealed by superficial deposits. Mining and quarrying have played a significant part in the economy of the area, notably for slate around Llanberis, Bethesda and Ffestiniog.
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See Pages 53, Union Hill Trap. Available via Google Books but extensive quarrying has since obliterated most of the hill except for the slopes of its perimeter. Like the Ladentown Outlier, Union Hill was once considered to be an extension of the Palisades. It was determined later in the 20th century that the hill was composed of extrusive basalt with a minimum thickness of 125 ft (38 m).
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The geological substrate of the municipality is primarily extrusive igneous rock, that is, volcanic in origin. These rocks are notable for the presence of basaltic lava flows, deposits of basaltic ash, slag, and pyroclastic rocks. Many of the older buildings in Jilotepec were built using these basaltic rocks. The soil is mostly luvisolic, comprises 75% of the municipality's soil, and is particularly suited to agricultural industry though susceptible to erosion.
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Carbonatite lava at Ol Doinyo Lengai volcano, Tanzania Carbonatite () is a type of intrusive or extrusive igneous rock defined by mineralogic composition consisting of greater than 50% carbonate minerals.Bell, Keith (editor) (1989) Carbonatites: Genesis and Evolution, London, Unwin Hyman. Carbonatites may be confused with marble and may require geochemical verification. Carbonatites usually occur as small plugs within zoned alkalic intrusive complexes, or as dikes, sills, breccias, and veins.
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Thorite in Prague national museum Small crystals of green thorite under magnification Specimens of thorite generally come from igneous pegmatites and volcanic extrusive rocks, hydrothermal veins and contact metamorphic rocks. It is also known to occur as small grains in detrital sands. Crystals are rare, but when found can produce nicely shaped short prismatic crystals with pyramidal terminations. It is commonly associated with zircon, monazite, gadolinite, fergusonite, uraninite, yttrialite and pyrochlore.
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Solidification into rock occurs either below the surface as intrusive rocks or on the surface as extrusive rocks. Igneous rock may form with crystallization to form granular, crystalline rocks, or without crystallization to form natural glasses. Igneous rocks occur in a wide range of geological settings: shields, platforms, orogens, basins, large igneous provinces, extended crust and oceanic crust. Volcanic eruptions of lava are major sources of igneous rocks.
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Well-known examples of outcropping trap rock include both intrusive sills and extrusive lava flows. They include the Palisades Sill, a Triassic, 200 Ma diabase intrusion that forms the Palisades along of the Hudson River in New York and New Jersey. Vast areas of trap rock in the form of thick lava flows and other volcanic rocks comprise the Deccan Traps of India and Siberian Traps of Russia.
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The southern and western parts of the Pentland Hills are formed from sandstones together with some conglomerates, all of Devonian age and assigned to the Old Red Sandstone. Within the sedimentary sequence are extrusive igneous rocks, principally of basaltic and andesitic composition. The sedimentary rocks are also intruded by dykes of porphyrite. The oldest rocks are a sequence of Silurian mudstones, siltstones and sandstones collected together as the North Esk Group.
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They contain an extrusive apparatus within a proteinaceous matrix, although apparently not membrane-bound, which differs from the remaining cytoplasm. A functional cell compartmentalization has also been evidenced. Their phylogenetic position was originally unclear, because they appeared to have both prokaryote-like traits, such as binary fission, and eukaryote-like traits, such as intracellular membranes. However, molecular phylogenetics showed that they are actually bacteria from the phylum Verrucomicrobia.
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Huamango, means "place where Wood is carved" in the Nahuatl language. This ancient settlement stands majestically in a geological formation known as the San Miguel Huamango Camaye Plateau, formed by AndesiteAndesite is an extrusive igneous, volcanic rock, of intermediate composition, with aphanitic to porphyritic texture. In a general sense, it is the intermediate type between basalt and dacite. The mineral assemblage is typically dominated by plagioclase plus pyroxene and/or hornblende.
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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.
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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.
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The supergroup is up to 10 kilometers thick with magnesite-bearing marble, mica schist and quartzite (quartzite units increase in thickness to the west). The western edge of the Machyollong Zone is known as the Iwon Mobile Belt and contains extrusive and intrusive igneous rocks. The late Proterozoic Sangwon Synthem is widespread in the Pyongnam Basin and other, smaller basins in North Korea and experienced deformation during orogenies in the Mesozoic.
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Along its trace it principally cuts Paleozoic metamorphic rocks of the Cajamarca Complex, the Jurassic age Ibagué Batholith (consisting of granodiorites, tonalites, granites, porphyrics of andesitic and dacitic composition and extrusive rocks as pyroclastic deposits and lava,Cuéllar Cárdenas et al., 2014, p.39 Paleogene and Neogene sedimentary rocks of the Gualanday and Honda Groups and displacing and deforming the Neogene to Quaternary Ibagué Fan (), which is of volcano-sedimentary origin.Montes et al.
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The Wrekin is a prominent hill near the town of Telford. The sedimentary rock types are varied around the area, but lava and volcanic ash (tuff) from various volcanic eruptions form this famous landmark. However, The Wrekin itself is not a volcano, and never was. The primary igneous rock on the Wrekin is rhyolite; this has a pinkish colour and is usually banded as it is a slow cooling viscous extrusive rock.
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Dolerite dykes intruded the extrusive volcanic rocks around 563 million years ago. A variety of the intrusive igneous rock granophyre, known as Ercallite forms the northeastern shoulder of the Ercall. It was put in place around 560 million years ago and is overlain by Cambrian rocks of sedimentary origin.Toghill, P. 2006 Geology of Shropshire 2nd edn Crowood Press The southeastern side of the ridge is largely formed from sandstones and shales of Cambrian age.
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The texture of extrusive rocks is characterized by fine-grained crystals indistinguishable to the human eye, described as aphantic. Crystals in aphantic rocks are small in size due to their rapid formation during eruption. Any larger crystals visible to the human eye, called phenocrysts, form earlier while slowly cooling in the magma reservoir. When igneous rocks contain two distinct grain sizes, the texture is porphyritic, and the finer crystals are called the groundmass.
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Dietrich, R. and Skinner, B. (1979). Rocks and Rock Minerals. See p. 108. Porphyritic rocks may be aphanites or extrusive rock, with large crystals or phenocrysts floating in a fine-grained groundmass of non-visible crystals, as in a porphyritic basalt, or phanerites or intrusive rock, with individual crystals of the groundmass easily distinguished with the eye, but one group of crystals clearly much bigger than the rest, as in a porphyritic granite.
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The wilderness encompasses two distinct mountain ranges, namely the Beartooth and Absaroka ranges. These ranges are completely distinct geologically speaking with the Absarokas composed primarily of volcanic (or extrusive) and metamorphic rock, while the Beartooths are made up almost entirely of granitic rocks. The Absarokas are noted for their dark and craggy appearance, lush and heavily forested valleys and abundant wildlife. The highest peak in the range, located in Wyoming, is Francs Peak at .
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Obsidian is formed from quickly cooled lava, which is the parent material.M E Malainey. Consumer's Guide to Archaeological Science: Analytical Techniques, Springer, 2010 Extrusive formation of obsidian may occur when felsic lava cools rapidly at the edges of a felsic lava flow or volcanic dome, or when lava cools during sudden contact with water or air. Intrusive formation of obsidian may occur when felsic lava cools along the edges of a dike.
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Ojakangas and Matsch, Minnesota's Geology, p. 24. Proterozoic formations created about 1,900 mya that gave the area most of its mineral riches; and more recent intrusive gabbro and extrusive basalts and rhyolites of the Duluth Complex and North Shore Volcanic Group, created by magma and lava which upwelled and hardened about 1,100 mya during the Midcontinent Rift.Sansome, Minnesota Underfoot: A Field Guide to Minnesota's Geology, pp. 19, 30, 36; Ojakagas and Matsch, Minnesota's Geology, pp.
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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.
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There is a pattern of gold distribution along the Archean Boulder-Lefroy shear zone. Extrusive komatiites (ultramafic volcanic rocks) occur along the Norseman-Wiluna Greenstone Belt. A change from volcanic-dominated to plutonic-dominated magmatism occurred in the Norseman- Wiluna Greenstone Belt approximately 2685–2675 Ma. Voluminous high-Ca granite intrusions occurred 2670–2655 Ma.Moresi, Louis, Peter van der Borgh, and Roberto F. Weinberg. (2003) "Timing of deformation in the Norseman-Wiluna Belt, Yilgarn Craton, Western Australia".
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The Duluth and Beaver Bay complexes are intrusive rocks formed about 1.1 billion years ago during the Midcontinent Rift; these adjoin and are interspersed with the extrusive rocks of the North Shore Volcanic Group produced during the same geologic event. These formations are part of the Superior Upland physiographic region of the United States, which is associated with the Laurentian Upland of the Canadian Shield,Tapestry of Time and Terrain (2003). the core of the North American Craton.
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Epixenosomes live on the dorsal surface of their hosts, marine ciliates in the genus Euplotidium. The name "epixenosomes" comes from the ancient Greek , meaning "external alien body", referring to their extracellular position on the host. The extrusive apparatus ejects its contents when triggered; this process helps to defend the ciliate host against predators. Although Euplotidium can grow and reproduce without epixenosomes, those with epixenosomes have much higher survival when exposed to predators such as the ciliate Litonotus.
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Relative alkali and silica contents are illustrated in TAS diagrams. extrusive igneous rocks. About the name Acambay, it is based on ancient documents that mention that this region was called, in Otomi language, Cambay o Cabaye, which may be translated as "God’s Rock" (okha= "God", mbaye= "Rock"). A different theory claims the name is from the Purépecha language, from the word Akamba that means maguey or agave and the "rhi" desinence that means; Akambari or "Place of Magueyes".
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The intrusive members are syenite and carbonatite. The complete sedimentary sequence is separated in Lupata region, about 10 km southeast of Monte Muambe, in Chincongolo area, near to Lupata Gorge, and consists of Upper Lupata Sandstones formation, intrusive rocks (syenite), carbonatites (intrusive and effusive products) and alkaline extrusive rocks. According to field findings geological units in the region as follows: 1\. Coarse-grained and conglomeratic sandstones which transressive overlain basalts, gently dipping to the south. 2\.
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The geologic occurrence of Iddingsite is limited to extrusive or hypabyssal rocks, and it is absent from deep-seated rocks. Iddingsite is an epimagmatic mineral derived during the final cooling of lava in which it occurs from a reaction between gases, water and olivine. The formation of iddingsite is not dependent on the original composition of the olivine. It is however dependent on oxidation conditions, hydration and the magma from which iddingsite forms must be rich in water vapor.
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Volcanism is the process that takes place at divergent boundaries by which one tectonic plate separates from another creating a rift in which molten rock (magma) erupts onto the surface of the Earth. This molten rock magma then cools and crystallizes, forming igneous rocks. If crystallization occurs at the Earth's surface, extrusive igneous rocks are formed; if crystallization occurs within the Earth's lithosphere, intrusive igneous rocks are formed which can then be brought to Earth's surface by denudation.
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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.
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Highwood, MT, 7.5 Minute Topographic Quadrangle, USGS, 1982 (access) The area has volcanic origins and is rich in potash. Many of the extrusive rocks and some of the dike rocks contain abundant phenocrysts of a clear analcime that appears to be primary. Pseudoleucite is an abundant constituent of many of the igneous rocks.Potash Analcime and Pseudoleucite from the Highwood Mountains of Montana, Esper S. Larson and Bennett Frank Buie The Shonkin Sag, a glacial meltwater channel, borders the Highwood Mountains to the north.
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Torfajökull (Icelandic for "Torfi's glacier") is a rhyolitic stratovolcano, caldera (central volcano) and complex of subglacial volcanoes, located north of Mýrdalsjökull and south of Þórisvatn Lake, Iceland. Torfajökull last erupted in 1477 and consists of the largest area of silicic extrusive rocks in Iceland. The volcano's eruption around 870, a combined bimodal eruption (rhyolite-basalt) with additional engagement of the Bárðarbunga-Veiðivötn volcanic system, has left a thin layer of easily recognized mixed tephra all over Iceland (Landnámslag).C.F. Zellmer, etal.
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The geology of Northumberland National Park in northeast England includes a mix of sedimentary, intrusive and extrusive igneous rocks from the Palaeozoic and Cenozoic eras. Devonian age volcanic rocks and a granite pluton form the Cheviot massif. The geology of the rest of the national park is characterised largely by a thick sequence of sedimentary rocks of Carboniferous age. These are intruded by Permian dykes and sills, of which the Whin Sill makes a significant impact in the south of the park.
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The ridge forming Mount Rose, Rocky Hill, and Ten Mile Run Mountain, is a continuation of the Palisades which connects to Pennington Mountain. South of Pennington Mountain the Palisades sill and Sourland Mountain's eastern ridge are essentially the same feature. Like the Palisades, Sourland Mountain exhibits volcanic dikes which extend away from the main ridge. One such dike extending northwest from Sourland Mountain has been determined to be responsible for the creation of Prospect Hill, an extrusive basalt peak near Flemington, New Jersey.
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FaultingTalcott Mountain is a high point on the Metacomet Ridge, a fault-block ridge that formed 200 million years ago during the Triassic and Jurassic periods. It is composed of trap rock, also known as basalt, an extrusive volcanic rock. Basalt is a dark colored rock, but the iron within it weathers to a rusty brown when exposed to the air, lending the ledges a distinct reddish appearance. Basalt frequently breaks into octagonal and pentagonal columns, creating a unique "postpile" appearance.
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New research indicates that the vicinity of Ladentown may have served as the primary vent from which the magma of the Palisades Sill erupted to the surface to form the Watchung flood basalts.Puffer, J.H., Block, K.A., Steiner, J.C., 2009. Transmission of Flood Basalts through a Shallow Crustal Sill and the Correlation of Sill Layers with Extrusive Flows: The Palisades Intrusive System and the Basalts of the Newark Basin, New Jersey, U.S.A. The Journal of Geology, volume 117, p. 139–155.
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Cushetunk Mountain, a ring- shaped volcanic mountain between Sourland Mountain and the Watchungs, is of the same geologic lineage. The Metacomet Mountains in the Connecticut River Basin, another aborted rift valley, came into existence around the same time as the Watchungs, also through extrusive eruptions. While non-contiguous, the two ranges may be considered geologic cousins, having formed under similar circumstances during the rifting of Pangaea. The same erosive and tectonic forces which elevated the Watchungs also served to raise the Metacomets.
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The Korean peninsula has been subject to archaeological excavations for establishing obsidian (a naturally occurring volcanic glass formed as an extrusive igneous rock) at many Paleolithic sites. One such site excavated is located in Hongcheon county, known as Hahwageri III. Several samples collected from the site have been subject to carbon dating. In the first cultural layer, out of the two layers established during the excavations, the finds consists of microliths of obsidian and quartz crystal which are embedded in microblade cores.
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Volcanic bombs are extrusive igneous rocks ranging from the size of books to small cars, that are explosively ejected from stratovolcanoes during their climactic eruptive phases. These "bombs" can travel over away from the volcano, and present a risk to buildings and living beings while shooting at very high speeds (hundreds of kilometers/miles per hour) through the air. Most bombs do not themselves explode on impact, but rather carry enough force so as to have destructive effects as if they exploded.
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Split Cinder Cone was created by magma that followed a fault plane. That same fault has since moved right laterally, tearing the small volcano in half. (Tom Bean, NPS image) Artist's Palette got its colors from volcanic deposits Igneous activity associated with the extension occurred from 12 to 4 Ma. Both intrusive (plutonic/solidified underground) and extrusive (volcanic/solidified above ground) igneous rocks were created. Basaltic magma followed fault lines to the surface and erupted as cinder cones and lava flows.
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Much of the exposed rock in Griffith Park is marine or non-marine sedimentary rock of Neogene and Quaternary formations, including the Lower, Middle and Upper Topanga, as well as the Monterey and Fernando. Both inclined bedding and fossil-bearing strata are common. Also present is late Miocene intrusive rock, generally strongly weathered and easily cleaved, as well as some dikes and purple and grey andesitic extrusive rock bodies. Faulting as well as clear contacts between rock bodies are also common.
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Typically the Deccan Plateau is made up of basalt extending up to Bhor Ghat near Karjat. This is an extrusive igneous rock. Also in certain sections of the region, we can find granite, which is an intrusive igneous rock. The difference between these two rock types is: basalt rock forms on eruption of lava, that is, on the surface (either out of a volcano, or through massive fissures—as in the Deccan basalts—in the ground), while granite forms deep within the Earth.
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Examples include the Medcalf Ultramafic Intrusion, a 3.5 km long, ~1 km thick pile of gabbroic to pyroxenitic cumulates which contain subeconomic stratiform vanadiferous magnetite deposits. The extrusive and intrusive igneous rocks are underlain and intruded by a series of I-type granite intrusions and granite domes of c. 2.65 Ga age. A late dyke swarm of Proterozoic age intrudes the belt, most notably the Jimberlana Dyke which attains a thickness of some 600m and transects the Emily Ann and Maggie Hays orebodies.
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When magma cools it begins to form solid mineral phases. Some of these settle at the bottom of the magma chamber forming cumulates that might form mafic layered intrusions. Magma that cools slowly within a magma chamber usually ends up forming bodies of plutonic rocks such as gabbro, diorite and granite, depending upon the composition of the magma. Alternatively, if the magma is erupted it forms volcanic rocks such as basalt, andesite and rhyolite (the extrusive equivalents of gabbro, diorite and granite, respectively).
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The highest parts of the Northumberland National Park are formed from a Devonian granite intrusion surrounded by a suite of extrusive igneous rocks from the Silurian and Devonian periods, between them creating the Cheviot Hills. The rest of the park is formed from gently dipping sedimentary rocks of Carboniferous age. The sedimentary rocks are intruded by the Great Whin Sill along the outcrop of which the Romans built sections of Hadrian's Wall. Zones of thermal metamorphism affect the sedimentary rocks adjacent to the igneous intrusions.
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Although Triton's crust is made of various ices, its subsurface processes are similar to those that produce volcanoes and rift valleys on Earth, but with water and ammonia as opposed to liquid rock. Triton's entire surface is cut by complex valleys and ridges, probably the result of tectonics and icy volcanism. The vast majority of surface features on Triton are endogenic—the result of internal geological processes rather than external processes such as impacts. Most are volcanic and extrusive in nature, rather than tectonic.
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The projecting, eroding edges of the flood basalts preserved in the syncline form the three ridges of the Watchung Mountains. Jurassic sedimentary rock layers between and above the ridges form the Feltville, Towaco and Boonton formations. Elsewhere in the Newark Basin, smaller synclines preserve the Watchung Outliers, additional fragments of the flood basalts and associated overlying sediments that have survived into the modern era. Because the majority of the Watchung Mountains are composed of extrusive igneous trap rock, they display characteristic columnar jointing and stacked lava flows.
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Klein, Cornelis and Hurlbut, Cornelius S. (1986), Manual of Mineralogy, Wiley, p. 484 The mass of the rock consists of a fine-grained matrix of felsic materials, particularly quartz, sodium and potassium feldspar, and may be termed a quartz felsite or quartz porphyry if the quartz phenocrysts are present. This rock is typically of extrusive origin, formed by compaction of fine volcanic ash, and may be found in association with obsidian and rhyolite. In some cases, it is sufficiently fine-grained for use in making stone tools.
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Rocks of the CCVF host base- and precious metal deposits, including the volcanic diatreme at Cripple Creek, the site of a notable gold rush beginning in 1890. By 1900, more than 500 mines had been established in the Cripple Creek district, and the population exceeded 35,000. Open-pit gold mining continues today. Outcrops of Wall Mountain Tuff, one of the most widespread extrusive units of the CCVF, may be found near the town of Castle Rock, more than from the presumed eruptive source of the tuff.
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Like many rifts worldwide, the Canadian Arctic Rift System was a site of magmatic activity during active tectonism. This activity was associated with seafloor spreading in the Baffin and Labrador basins as well as continental rifting within the Arctic Archipelago. Several episodes of intrusive and extrusive activity took place from the Paleozoic to Cenozoic with the emplacement of dikes, sills, lava flows and pyroclastic rocks. The Sverdrup Basin Magmatic Province in the east- central Sverdrup Basin is an Early Cretaceous to Paleogene large igneous province.
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There are four major phases in this orogenic event. First phase known as the Bretonian reflected in changes in the sediment input and the reactivation of a south plunging subduction zone. The second phase, the Sudetian, was of volcanic event and extrusive metamorphic and igneous rocks with uplift and mild folding of grabens in the vicinity which lead to inversion. The Asturian tectonic phase created fragmentation of the Variscans and its foreland due to the complex fault system of conjugate shear faults and secondary extensional faults.
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The trap rock cliffs of East Rock East Rock is a fault-block ridge formed 200 million years ago during the Triassic and Jurassic periods and is composed of trap rock, known as basalt, if extrusive, or diabase, if intrusive. East Rock, being intrusive, is diabase. Diabase is a dark colored rock, but the iron within it weathers to a rusty brown when exposed to the air, lending the ledges a distinct reddish appearance. Diabase frequently breaks into octagonal and pentagonal columns, creating a unique "postpile" appearance.
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The southern domes are somewhat different in nature, comprising intrusive and extrusive phases of cream colored porphyries. The Sax Dome contains an upper portion of cream coloured, aphanitic to fine quartz porphyry felsite with abnormal green glass filled fractures, and a lower unit of microsyenite with red and green glassy zenocrysts. The Intra Caldera Assemblage is best exposed on the north edge of the caldera. The lower unit, indicative of caldera formation, is an epiclastic boulder-landslide deposit, roughly bedded and dipping into the caldera.
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Bedrock geology. Purple=basalt; surrounding brown & blue-grey=sedimentary rock The ridge of the Mount Tom Range was formed 200 million years ago during the late Triassic and early Jurassic periods and is composed of traprock, also known as basalt, an extrusive volcanic rock. Basalt is a dark colored rock, but the iron within it weathers to a rusty brown when exposed to the air, lending the ledges a distinct reddish appearance. Basalt frequently breaks into octagonal and pentagonal columns, creating a unique "postpile" appearance.
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Hydrocarbon generation commenced about 50 million years ago (Ma) in the deeper basins, about 40 Ma in many other areas, and may continue to the present day. Geothermal gradients generally range from to ; horsts and grabens generally have roughly equivalent thermal regimes relative to the primary source rock. Along the southwest and west margins of the province are extrusive igneous deposits that tend to diminish the hydrocarbon potential of these areas. The Gialo High is a relatively small horst block in the eastern Sirte Basin.
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This is an extrusive rock porphyritic rock, as the pink (and black) phenocrysts are clearly visible, in contrast to the grey groundmass with its microscopic crystals. intrusive porphyritic rock. The white, square feldspar phenocrysts are much larger than crystals in the surrounding matrix; eastern Sierra Nevada, Rock Creek Canyon, California. Porphyritic is an adjective used in geology, specifically for igneous rocks, for a rock that has a distinct difference in the size of the crystals, with at least one group of crystals obviously larger than another group.
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The northern and southern shores of the bay are mainly rocky in nature, backed by cliffs up to high. Its eastern shore comprises a series of large and small sandy beaches between rocky sections. The geological exposures around the bay reveal great complexity with considerable folding and faulting of the strata. The cliffs of its southern shore are formed from sandstones of Ordovician and Devonian age together with a suite of both intrusive and extrusive igneous rocks, some of which are Precambrian in age.
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It is the intrusive igneous equivalent of the extrusive igneous dacite. It contains a large amount of sodium (Na) and calcium (Ca) rich plagioclase, potassium feldspar, quartz, and minor amounts of muscovite mica as the lighter colored mineral components. Biotite and amphiboles often in the form of hornblende are more abundant in granodiorite than in granite, giving it a more distinct two- toned or overall darker appearance. Mica may be present in well-formed hexagonal crystals, and hornblende may appear as needle-like crystals.
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If extension at the surface exceeds about 50 percent, decompression melting may permit magmas to form; these will deform the footwall, resulting in a complex associated with intrusive and extrusive igneous rocks. Rocks above the detachment fault form normal faults and, at the same time, shear in a "layer-parallel" motion. This action creates a series of fault blocks, which are progressively tilted as the detachment fault progresses. The fracturing of the fault blocks can occur in a similar time frame or develop progressively.
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More recently, the various Watchung flows have been correlated to geochemically distinct layers within the Palisades sill, bolstering the theory that eruptions of the Palisades magma were responsible for the episodic flood basalts of the Newark Basin.Puffer, J.H., Block, K.A., Steiner, J.C., 2009. Transmission of Flood Basalts through a Shallow Crustal Sill and the Correlation of Sill Layers with Extrusive Flows: The Palisades Intrusive System and the Basalts of the Newark Basin, New Jersey, U.S.A. The Journal of Geology, volume 117, p. 139–155.
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Norman William Kingsley was the first person to try to move the maxillary teeth backwards in 1892 by means of headgear. Albin Oppenheim later advocated for the use of occipital anchorage to move the maxillary teeth backwards. Earlier into the field of orthodontics, molar teeth would be distalized with the use of headgears. Straight Pull (Combination) Headgear for translation of molar distally, Cervical Pull Headgear for extrusive and distalization of teeth in deep bite Class 2 patients and High Pull Headgear for intrusive and distalization of teeth in an open bite patient.
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Unlike the Sacramento Mountains, the neighboring Sierra Blanca is an extrusive igneous complex. Most of the main section of the Sacramento Mountains are part of the Lincoln National Forest, though the northern part of the range is included in the Mescalero Apache Indian Reservation. Evidence of Apache presence dates back to the fifteenth century.Butterfield, Mike, and Greene, Peter, Mike Butterfield's Guide to the Mountains of New Mexico, New Mexico Magazine Press, 2006, The range includes the town of Cloudcroft, a popular resort; the town of Ruidoso, also popular for recreation, lies on its northern edge.
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Sedimentary (those formed by the deposition of sediment) and extrusive (those formed by magma cooling at the Earth's surface) rocks largely underlay the Dry, Partly Wooded Mountains ecoregion. Granitics are less likely to be found here than in any other part of the Idaho Batholith ecoregion, which is uncharacteristic. This region is on the leeward (or downwind) side of the mountains, meaning it is dry and receives very little precipitation. Unlike any other parts of the Idaho Batholith ecoregion, there is a mosaic of shrubland, open Douglas-fir forests, and aspen occurs.
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The island has an area of about 237 square kilometers, making it the second-largest island in the archipelago. Togean and the other islands in the archipelago were formed by volcanic activity. It is separated from the islands of Batudaka to its southwest and Talatako to its east by narrow channels, which are believed to have originated from ancient riverbeds scoured by recent currents. Geology of the island varies, with reefal limestones in the extreme northwest, followed by sedimentary sandstones, extrusive volcaniclastic rocks and intrusive rocks further east.
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Weathering and oxidation, together with UV light interacting with metallic oxides and chemicals in the glass and seawater are all factors affecting the color of sea glass over long exposure and time frames. In texture and color black sea glass resembles black beach rock, very much resembling the extrusive igneous rock basalt, or weathered black obsidian, a natural black volcanic glass. Gas bubbles are often trapped in old glass, impurities and irregularities in the original bottles were common and one indicator of age. Early examples were hand blown, later ones utilized a mold.
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Ordovician rocks from the Northern and Southern Hainan Island show different characteristics. Rocks in the southern areas were sedimentary rocks deposited at the landward side of a coast, with distinctive features of having different grain sizes from black shale, lithic sandstone to conglomerate, as well as having both siliciclastic sedimentary rocks and limestones. On the other hand, Ordovician rocks found in the northern areas were interlayers of fine-grained siliciclastic rocks deposited in marine environment, extrusive igneous and pyroclastic rocks. The volcaniclastic rocks were exhibiting low-grade metamorphism.
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This collision caused subduction and volcanism in the Proto-Antillean area and likely resulted in continental uplift of the Bahama Platform and changes in sea level. The Greater Antilles have continuously been exposed since the start of the Paleocene or at least since the Middle Eocene (66-40 million years ago), but which areas were above sea level throughout the history of the islands remains unresolved. The oldest rocks in the Greater Antilles are located in Cuba. They consist of metamorphosed graywacke, argillite, tuff, mafic igneous extrusive flows, and carbonate rock.
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Unlike its larger neighbour, Little Cumbrae is formed almost entirely from extrusive igneous rocks. These are a mix of Carboniferous age basalts, mugearite and hawaiite lava flows cut by a similarly aged WSW-ENE aligned dyke of alkali olivine diorite. A later northwest-southeast aligned swarm of dykes of Palaeogene age intrude these rocks whilst several geological faults run generally NW-SE. There are limited outcrops of sedimentary rock in the east, these being of the Eileans Sandstone assigned to the Clyde Sandstone Formation of the Carboniferous age Inverclyde Group.
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Close-up of traprock on the Sleeping Giant Faulting Sleeping Giant, a fault-block ridge that formed 200 million years ago during the Triassic and Jurassic periods, is composed of traprock, also known as basalt, an extrusive volcanic rock. Minor earthquakes have also been measured by seismographs and reported by residents. Basalt is a dark colored rock, but the iron within it weathers to a rusty brown when exposed to the air, lending the ledges a distinct reddish appearance. Basalt frequently breaks into octagonal and pentagonal columns, creating a unique "postpile" appearance.
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Zhokhov Island consists of extrusive basalt lava flows and tuffs. The bulk of this island is made up of a thick stack of olivine basalt, olivine trachybasalt, and nepheline basalt lava flows. Overlying these lava flows is a layer of friable volcanic ash and tuff that is capped by a thick basalt lava flow. The total thickness of volcanic rocks exposed within Zhokhov Island is about 400 metersFujita, K., and D.B. Cook, 1990, The Arctic continental margin of eastern Siberia, in A. Grantz, L. Johnson, and J. F. Sweeney, eds.
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Late Neoarchean rocks spread over the whole Eastern Block. High to medium-grade gneiss and ultramafic extrusive rocks, especially komatiites occur in eastern Hebei, eastern Shandong, northern Liaoning and southern Jilin areas, whereas low to medium-grade granite-greenstone terranes are seen in western Shandong, southern Liaoning and Anshan areas. All rocks were formed in a geologically brief period, between 2.55 and 2.5 billion years ago. In this period, mafic and felsic lava erupted and granitoids intruded the whole Eastern Block, followed by a 2.5 billion-year-old regional metamorphism.
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Similarly, other actinosporeans were folded into the life cycles of various myxosporeans. Today, the myxozoans, previously thought to be multicellular protozoans, are considered animals by most scientists, though their status has not officially changed. Recent molecular studies suggest they are related to Bilateria or Cnidaria, with Cnidaria being closer morphologically because both groups have extrusive filaments,. Bilateria were somewhat closer in some genetic studies, but those were found to have used samples that were contaminated by material from the host organism, and a 2015 study confirms they are cnidarians.
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Ping Chau is unique in the fact that it is the only sizeable island in Hong Kong made up of sedimentary rock. Hong Kong is mostly formed of extrusive igneous rocks, after a series of major volcanoes erupted during the Jurassic Period. Following the volcanic activity, a basin formed in the northeast, with deposition in a brackish lake—producing the siltstones and chert of Tung Ping Chau, which have been dated from the early Paleogene period. It is also home to some spectacular cliffs and wave-cut platforms.
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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.
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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.
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Plate convergence along the continental margin produced a volcanic arc system throughout the Sierra Nevada and Mojave region roughly 250 million to about 60 million years ago. These massive belts of plutonic (intrusive) and volcanic (extrusive) regional belts and isolated centers developed as plate convergence and subduction took place farther west along the western continental margin. These igneous provinces shed vast quantities of sediment both eastward into the Western Interior Seaway and westward into Pacific margin basin. At the same time, older sedimentary materials and rocks were subjected to regional metamorphism throughout much of Baja and Southern California.
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A claystone, the finest-grained sedimentary rock, deposited in Glacial Lake Missoula, Montana In igneous and metamorphic rocks, grain size is a measure of the sizes of the crystals in the rock. In igneous rock, this is used to determine the rate at which the material cooled: large crystals typically indicate intrusive igneous rock, while small crystals indicate that the rock was extrusive. As metamorphic reactions progress, the grains in metamorphic rocks can often be broken down into smaller grains. In clastic sedimentary rocks, grain size is the diameter of the grains and/or clasts that constitute the rock.
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When rocks are pushed deep under the Earth's surface, they may melt into magma. If the conditions no longer exist for the magma to stay in its liquid state, it cools and solidifies into an igneous rock. A rock that cools within the Earth is called intrusive or plutonic and cools very slowly, producing a coarse-grained texture such as the rock granite. As a result of volcanic activity, magma (which is called lava when it reaches Earth's surface) may cool very rapidly while being on the Earth's surface exposed to the atmosphere and are called extrusive or volcanic rocks.
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The Organ Mountains is a botanically diverse mountain range in New Mexico, with approximately 870 vascular plant species. Several of these, including the Organ Mountains evening-primrose (Oenothera organensis) and smooth figwort (Scrophularia laevis), are endemic to the mountain range and occur only in small, scattered populations. The range also has a high diversity in ferns, with 30 of the 56 species reported for New Mexico occurring within it. The flora differs greatly between the three sections of the mountain range, with the two igneous sections (The Needles and the central extrusive portion) sharing relatively few species with the southern limestone portions.
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The Barberton greenstone belt (BGB) is located in the Kapvaal craton of southeastern Africa. It characterizes one of the most well-preserved and oldest pieces of continental crust today by containing rocks in the Barberton Granite Greenstone Terrain (3.55–3.22 Ga). The BGB is a small, cusp-shaped succession of volcanic and sedimentary rocks, surrounded on all sides by granitoid plutons which range in age from >3547 to <3225 Ma. It is commonly known as the type locality of the ultramafic, extrusive volcanic rock, the komatiite. Greenstone belts are geologic regions generally composed of mafic to ultramafic volcanic sequences that have undergone metamorphism.
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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.
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The Sahand-Bazman Volcanic and Plutonic Belt or the Sahand-Bazman Igneous Arc or the Central Iranian Range is a mountain range that is made by (both extrusive and intrusive) igneous and pyroclastic rocks. Located East and almost parallel to the Zagros Mountains, the Central Iranian Range is stretched in a north-west-southeast direction from Mount Sahand in Azerbaijan in the north-west to Mount Bazman in Baluchistan in the Southeastern part of Iran.Microsoft Encarta World Atlas, 2001, Microsoft Corporation This range was mainly formed during the Tertiary volcanic and orogenic phase and especially in the Eocene volcanism and plutonism.Geological Map of Iran, National Geoscience Database of Iran, www.ngdir.
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FaultingThe fault-block Hanging Hills were formed 200 million years ago during the Triassic and Jurassic periods and are composed of trap rock, also known as basalt, an extrusive volcanic rock. Basalt is a dark colored rock, but the iron within it weathers to a rusty brown when exposed to the air, lending the ledges a distinct reddish appearance. Basalt frequently breaks into octagonal and pentagonal columns, creating a unique "postpile" appearance. Huge slopes made of fractured basalt scree are visible beneath many of the ledges of the Hanging Hills; they are particularly visible along the base of East Peak where it plunges into Merimere Reservoir.
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Cerro Seguro, a large hill underlain by Cieneguilla Basanite and Ortiz quartz monzonite The younger intrusions in the belt are increasingly alkaline in composition, and include the 25-26 Ma Cieneguilla basanite. This is a small-volume extrusive unit exposed around the village of La Cienega that may represent the earliest stages of opening of the Rio Grande rift. The basanite is characterized by olivine phenocrysts in a matrix of clinopyroxene, magnetite, and nepheline, with a total silica content of 42.40-44.10 wt % and a high magnesium oxide content (11.50-13.50 wt %). This places the basanite among the most primitive magmas of the central Rio Grande rift.
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Rutile in quartz Within the igneous environment, rutile is a common accessory mineral in plutonic igneous rocks, though it is also found occasionally in extrusive igneous rocks, particularly those such as kimberlites and lamproites that have deep mantle sources. Anatase and brookite are found in the igneous environment particularly as products of autogenic alteration during the cooling of plutonic rocks; anatase is also found in placer deposits sourced from primary rutile. The occurrence of large specimen crystals is most common in pegmatites, skarns, and granite greisens. Rutile is found as an accessory mineral in some altered igneous rocks, and in certain gneisses and schists.
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200 million years ago, magma intruded into the Newark Basin, then an active rift basin associated with the breakup of the supercontinent Pangaea.U.S. Geological Survey - NYC Regional Geology, Mesozoic Basins The magma was initially contained within the sedimentary strata of the basin, forming large intrusions like the Palisades Sill, but it ultimately broke out to the surface through large, episodic eruptions.Puffer, J.H., Block, K.A., Steiner, J.C., 2009. Transmission of Flood Basalts through a Shallow Crustal Sill and the Correlation of Sill Layers with Extrusive Flows: The Palisades Intrusive System and the Basalts of the Newark Basin, New Jersey, U.S.A. The Journal of Geology, volume 117, p. 139–155.
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The water forming Saint Columb's Rill, rises through limestone, Limestone, Sedimentary Rock, (sedimentary rock) before passing through basalt, Basalt, Extrusive Igneous Rock, (igneous rock) on its way to the surface. The water acquires small quantities of the minerals, Minerals, A Definition, calcium and magnesium and this makes the water slightly hard, Dr. A.M. Helmenstine, Chemistry of Hard and Soft Water, (alkaline). The rock structure is typical of the geology of County Antrim Culture Northern Ireland, Geology of County Antrim, that was formed by volcanic activity throughout the region in a bygone age. This can be verified by travelling less than thirty miles (fifty kilometres) to the south east.
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The Grenadines are geologically older than St. Vincent and are situated on an extensive shallow bank of volcanic origin – known as the southern Lesser Antilles arc platform (SLAAP). The SLAAP is a product of Miocene uplift (23–16 Ma) and characterized by Eocene to Pliocene extrusive to intrusive igneous rocks along with sedimentary rocks such as limestone, marl, and chert, and epiclastic arc- derived volcaniclastic units composed of mudstone, sandstone, and conglomerate. The islands are composed of a variety of volcanic and sedimentary rocks. The area is an active subduction zone, and lies along the interface of the Caribbean and South American Tectonic plates.
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Okaite, an ultramafic rock found near the carbonatite of the Oka Carbonatite Complex, Oka, Quebec Overall, 527 carbonatite localities are known on Earth, and they are found on all continents and also on oceanic islands. Most of the carbonatites are shallow intrusive bodies of calcite-rich igneous rocks in form of volcanic necks, dykes, and cone-sheets. These generally occur in association with larger intrusions of alkali-rich silicate igneous rocks. The extrusive carbonatites are particularly rare, only 49 are known, and they appear to be restricted to a few continental rift zones, such as the Rhine valley and the East African rift system.
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Only a few of the largest large igneous provinces appear (coloured dark purple) on this geological map, which depicts crustal geologic provinces as seen in seismic refraction data. A large igneous province (LIP) is an extremely large accumulation of igneous rocks, including intrusive (sills, dikes) and extrusive (lava flows, tephra deposits), arising when magma travels through the crust towards the surface. The formation of LIPs is variously attributed to mantle plumes or to processes associated with divergent plate tectonics. The formation of some of the LIPs the past 500 million years coincide in time with mass extinctions and rapid climatic changes, which has led to numerous hypotheses about the causal relationships.
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The East Rock trap rock ridge overlooking New Haven, Connecticut, U.S. Trap rock forming a characteristic pavement, Giant's Causeway, Northern Ireland Trap rock cliff overlooking the Hudson River from an overlook on the Hudson Palisades in Bergen County, New Jersey, U.S. Trap rock forming a characteristic stockade wall, Giant's Causeway, Northern Ireland Trap rock, also known as either trapp or trap, is any dark-colored, fine-grained, non- granitic intrusive or extrusive igneous rock. Types of trap rock include basalt, peridotite, diabase, and gabbro.Neuendorf, K.K.E., J.P. Mehl, Jr., and J.A. Jackson, J.A., eds. (2005) Glossary of Geology (5th ed.) American Geological Institute, Alexandria, Virginia.
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Porcellanite layer is the black rock above the hammer, and below the brown layer higher up the slope at Tievebulliagh Porcellanite worked into Neolithic axes, Northern Ireland At Tievebulliagh, Northern Ireland, porcellanite is a tough contact metamorphosed hornfels formed from a lateritic soil horizon within a basaltic intrusive/extrusive sequence. The rock is black to dark grey in colour. Tievebulliagh is the site of a Neolithic axe or stone tool quarry, and there is another quarry on Rathlin Island. It is likely that roughouts or roughly-shaped prehistoric tools (celts) were chipped on site before transportation both within Ireland and over the Irish Sea to Britain.
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The volcanism in the area is triggered by the subduction of the Nazca plate beneath the South America plate; magmas formed from the subduction process trigger the melting of the crust. The large calderas are located east of the main volcanic arc of the Central Volcanic Zone, Panizos being east of the main arc. Volcanism in the area is heavily dominated by calderic silicic volcanics with volumes of contrasting to less than andesites. The volcano is part of the so- called Tin belt, a territory in the Andes where large tin mineral deposits are found in granitic and extrusive rocks, formed from sulfidation reactions involving the numerous volcanoes in the area.
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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.
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Talus slopes on Bare Mountain The ridge of the Holyoke Range was formed 200 million years ago during the late Triassic and early Jurassic periods and is composed of traprock, also known as basalt, an extrusive volcanic rock. Basalt is a dark colored rock, but the iron within it weathers to a rusty brown when exposed to the air, lending the ledges a distinct reddish appearance. Basalt frequently breaks into octagonal and pentagonal columns, creating a unique "postpile" appearance. Huge slopes made of fractured basalt talus are visible beneath many of the ledges; they are particularly visible along the Metacomet-Monadnock Trail on Bare Mountain.
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The morphology and structural relations of the scarps suggest that most result from thrust or reverse faults. However, an extrusive origin has been suggested by Dzurisin (1978) for a scarp more than 200 km long that extends from about lat 70° S. to the map border between long 45° and 52°; he based this interpretation on albedo differences between the two sides of the scarp and on partial burial of craters transected by it. Age relations among structural features are not readily apparent. In the Bach region, the youngest craters cut by a scarp are of c4 age; the oldest crater to superpose a scarp is a c3.
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Late Cretaceous paleogeographic map of the United States, showing Elkhorn volcanoes in the northwestThe rocks of the Elkhorns were formed about 74 to 81 million years ago (Late Cretaceous time) as a result of the Farallon tectonic plate subducting beneath western North America and allowing magma to rise to the surface. The Elkhorn Mountains Volcanics are extrusive rocks related to the plutonic granites of the Boulder Batholith. Volcanic flows, lahars, and ash falls from sources in the Elkhorn Mountains reach as far as Choteau, Montana, but the thickest deposits lie within a radius of about from the Elkhorns. The volcanics probably originally covered an area of about .
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However, disseminated and low tenor nickel mineralisation is known from the other ultramafic units, especially the Western Ultramafic Unit (WUU). The general stratigraphy of the belt is, from base upwards, a thick sequence of felsic orthogneiss composed of fragmental to glomerocrystic feldspar gneiss, known as the footwall felsic sequence; the ultramafic units of komatiite affinity, 'overlain' by grunerite-magnetite- quartz-amphibole banded iron formation of the Honman Formation, tholeiitic basalt and metasedimentary rocks. Regionally, several subvolcanic lopolithic layered intrusions have been identified from mapping and drilling. These are interpreted to represent the feeder conduits to extrusive ultramafic and mafic igneous rocks stratigraphically higher in the belt.
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União da Vitória lies on the south bank of Iguazu River and at 752 meters above the sea level. The city borders its interstate neighbour Porto União, Santa Catarina; both are known as "Gêmeas do Iguaçu" (Iguazu Twins). The city is 238 kilometers far from Curitiba, the capital of Paraná State and the municipality's area is of 720 square kilometers and the population density is of 72 people per square kilometer. Being located between the Second and the Third Plateaus, the city's topography is characterized by extrusive igneous mountains origined in the Paraná Flood Basalt; making this region full of waterfalls and creeks nationally known.
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1 Oct. 2016. In ore deposit geology, hypogene processes occur deep below the earth's surface, and tend to form deposits of primary minerals, as opposed to supergene processes that occur at or near the surface, and tend to form secondary minerals. White veins of gypsum (primary/secondary sulfate mineral) near Gunthorpe in Nottinghamshire, England, UK The elemental and mineralogical composition of primary rocks is determined by the chemical composition of the volcanic or magmatic flow from which it is formed. Extrusive rocks (such as basalt, rhyolite, andesite and obsidian) and intrusive rocks (such as granite, granodiorite, gabbro and peridotite) contain primary minerals including quartz, feldspar, plagioclase, muscovite, biotite, amphibole, pyroxene and olivine in varying concentrations.
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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.
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The basalt (also called traprock) crest of the Metacomet Ridge is the product of a series of massive lava flows hundreds of feet thick that welled up in faults created by the rifting apart of the North American continent from Eurasia and Africa. Essentially, the area now occupied by the Metacomet Ridge is a prehistoric rift valley which was once a branch of (or a parallel of) the major rift to the east that became the Atlantic Ocean. Basalt is a dark colored extrusive volcanic rock. The weathering of iron-bearing minerals within it results in a rusty brown color when exposed to air and water, lending it a distinct reddish or purple–red hue.
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The city lies within the Sidlaw-Ochil anticline, and the predominant bedrock type is Old Red Sandstone of the Arbuthnott-Garvock group.; Differential weathering of a series of igneous intrusions has yielded a number of prominent hills in the landscape, most notably the Dundee Law (a late Silurian/early Devonian Mafic rock intrusion) and Balgay hill (a Felsic rock intrusion of similar age). In the east of the city, in Craigie and Broughty Ferry, the bedrock geology is of extrusive rocks, including mafic lava and tuff. The land surrounding Dundee, particularly that in the lower lying areas to the west and east of the city, bears high quality soil that is particularly suitable for arable farming.
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The Organ Mountains are near the southern end of a long line of mountains on the east side of the Rio Grande's rift valley. The range is nearly contiguous with the San Andres Mountains to the north and the Franklin Mountains to the south, but is very different geologically. Whereas the San Andres and Franklin Mountains are both formed from west- dipping fault blocks of mostly sedimentary strata (with limestone most prominent), the Organ Mountains are made primarily of igneous rock (intrusive granite and extrusive rhyolite). Their name reflects their similarity in appearance (particularly the granite "needles" in the highest part of the range) with pipes that would be part of a pipe organ.
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In front of the block and above the subducting oceanic plate are volcanoes emitting a range of varied deposits that give a spectrum of signatures (basaltic eruption, intermediate eruptions and acidic eruptions, as the material melting and rising changes over the period of the subduction). These volcanic deposits get mixed up with the sediment from the continent (now in the form of a back arc basin). These are the volcaniclastic deposits that we can see today at places such as The Wrekin. During the formation of the volcanoes and their associated deposits of basalt and rhyolite there are melts that never reach the surface and these shallow level intrusions are notable in the forms of their non-extrusive equivalents such as granophyre and rhyolite.
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Mount Elden is one of five large peripheral silicic volcanic features within the greater San Francisco Peaks volcanic system (part of the San Francisco volcanic field) which include the nearby Dry Lake Hills, the Hochderffer and White Horse Hills to the northwest, and O'Leary Peak to the northeast. Because these features developed within close proximity of the San Francisco Mountain strato-volcano there is a strong likelihood that each is a geologic subsidiary of the larger mountain. Geologically, Mount Elden is a lava dome composed almost entirely of dacitic lava flows which emerged from several vents. These features emerged as intrusive emplacements within sedimentary blocks or as viscous extrusive flows in which the younger flows partially covered the older, lower flows.
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The two submarine volcanoes are capped by hawaiite and are surrounded by numerous smaller vents, with a total edifice volume of about 12 km3. The lava emitted in eruptions at the Tuzo Wilson Seamounts is made of basalt, a common gray 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. Glassy pillow lava is found at the seamounts, a type of rock typically formed when basaltic lava emerges from a submarine volcanic vent. The viscous lava gains a solid crust on contact with the water, and this crust cracks and oozes additional large blobs or "pillows" as more lava emerges from the advancing flow.
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Basalt (, )American Heritage DictionaryMerriam-Webster DictionaryCollins English DictionaryOxford Living Dictionaries is a mafic extrusive igneous rock formed from the rapid cooling of lava rich in magnesium and iron exposed at or very near the surface of a terrestrial planet or a moon. More than 90% of all volcanic rock on Earth is basalt, and the eruption of basalt lava is observed by geologists at about 20 volcanoes per year. Molten basalt lava has a low viscosity due to its relatively low silica content (between 45% and 52%), resulting in rapidly moving lava flows that can spread over great areas before cooling and solidifying. Flood basalts are thick sequences of many such flows that can cover hundreds of thousands of square kilometers and constitute the most voluminous of all volcanic formations.
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The Paipa–Iza volcanic complex is a volcanic field of Late Pliocene to Early Pleistocene age on the Altiplano Cundiboyacense in the Eastern Ranges of the Colombian Andes. It is the northernmost volcanic complex of the Andean Volcanic Belt with Fueguino in Tierra del Fuego, Chile, at the opposite end of the Andean mountain belt. The complex, comprising mainly felsic extrusive volcanic rocks as rhyolites, also is the only confirmed volcanic province in the Eastern Ranges, with traces of probably contemporaneous explosive volcanic activity in the vicinity of Guatavita, Cundinamarca. The Paipa-Iza volcanic field is important as a touristic site with thermal baths in both Paipa and Iza and is being studied for the potential of geothermal energy production and for the extraction of uranium in the area.
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Snake Pond, a kettle pond along the M&M; Trail on trap rock East Mountain The ridge that forms the spine of the M&M; Trail across Provin Mountain, East Mountain, and the Mount Tom and Holyoke ranges was formed 200 million years ago during the late Triassic and early Jurassic periods and is composed of trap rock, also known as basalt, an extrusive volcanic rock. Basalt is a dark colored rock, but the iron within it weathers to a rusty brown when exposed to the air, lending the ledges a distinct reddish appearance. Basalt frequently breaks into octagonal and pentagonal columns, creating a unique "postpile" appearance. Huge slopes made of fractured basalt talus are visible beneath many of the ledges; they are particularly visible along the Metacomet- Monadnock Trail on Bare Mountain.
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Chronostratigraphy relies heavily upon isotope geology and geochronology to derive hard dating of known and well defined rock units which contain the specific fossil assemblages defined by the stratigraphic system. In practice, as it is very difficult to isotopically date most fossils and sedimentary rocks directly, inferences must be made in order to arrive at an age date which reflects the beginning of the interval. The methodology used is derived from the law of superposition and the principles of cross-cutting relationships. Because igneous rocks occur at specific intervals in time and are essentially instantaneous on a geologic time scale, and because they contain mineral assemblages which may be dated more accurately and precisely by isotopic methods, the construction of a chronostratigraphic column relies heavily upon intrusive and extrusive igneous rocks.
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Close-up view Acarospora socialis (bright cobblestone lichen) is a usually bright yellow aereolate to squamulose crustose lichen in the Acarosporaceae family that grows up to 10 cm wide, mostly on rock in western North America.Lichen Flora of the Greater Sonoran Desert Region, Vol 3, (2001), Nash, T.H., Ryan, B.D., Gries, C., Bugartz, F., (eds.) It is among the most common lichens in the deserts of Arizona and southern California.Joshua Tree Lichens Photo Gallery, National Park ServiceField Guide to California Lichens, Stephen Sharnoff, Yale University Press, 2014, It grows on sandstone, intrusive and extrusive igneous rock such as granitics, in all kinds of exposures to sunlight, including vertical rock walls. It is found in North America, including areas of the Mojave Desert and Sonoran Desert region, to Baja California Sur.
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Sandstone modal compositions and detrital zircon U‐Pb analyses of the Wilcox Group indicate long‐distance sediment transport from primarily volcanic and basement sources to the west, northwest, and southwest. The Wilcox Group represents the earliest series of major post‐Cretaceous pulses of sand deposition along the western margin of the Gulf of Mexico. Laramide basement uplifts have long been held to be the source of Wilcox sediments, implying that initiation of basement uplift was the driving factor for the transition from carbonate sedimentation to clastic deposition. Zircon age‐spectra for the sandstones of the Wilcox Group reveal a complex grain assemblage derived from Laramide uplifted crystalline blocks of the central and southern Rocky Mountains, the Cordilleran arc of western North America, and arc‐related extrusive and intrusive igneous rocks of northern Mexico.
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Roaring Brook Falls, a short distance from the Robert Frost Trail on Mount Toby Both the Holyoke Range and Mount Toby were formed 200 million years ago between the end of the Triassic period and the beginning of the Jurassic. The Holyoke Range, part of the Metacomet Ridge that extends south to Long Island Sound, are composed of basalt, an extrusive volcanic rock. This basalt ridge is the product of several massive lava flows hundreds of feet deep that welled up in faults created by the rifting apart of North America from Eurasia and Africa over a period of 20 million years. Basalt is a dark colored rock, but the iron within it weathers to a rusty brown when exposed to the air, lending it a distinct reddish appearance.
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The hypothesis that the Athabasca Valles were formed by a lava flow suggests that these RMLs are actually rootless cones, which form phreatomagmatically as steam is expelled through the solidifying lava flow. The RMLs strongly resemble rootless cones that have been analogously observed in Iceland in dimension and shape, and notably lack clear evidence of extrusive materials around the cones. Some proponents of the flood-formation hypothesis for the Athabasca Valles suggest that megaflood waters could have saturated the ground upon which lava could have later flowed, causing the phreatomagmatic effect, as they appear to have formed in depressions where water might have feasibly ponded. Because water ice was not stable in this region of Mars during the Amazonian, the lava flows that formed these rootless cones must have reached ponded areas very soon after the occurrence of a megaflood.
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A field of flowers in the Arbuckle foothillsGeologically the Arbuckles are an elongate anticline structure with an orientation or strike of west-northwest. The core of the structure consists of Proterozoic extrusive and intrusive rocks, the Colbert rhyolite porphyry and the Tishomingo granite (age dated at 1374 Ma),Bickford, M. E. and Richard D. Lewis, U-Pb geochronology of exposed basement rocks in Oklahoma, Geological Society of America Bulletin, 1979;90;540-544 which are overlain and flanked by early Paleozoic limestones and sandstones that are very steeply dipping to near vertical in orientation. Pennsylvanian to Permian conglomerates were deposited after the orogenic buckling had uplifted and deformed the older strata. The west trending structure of the Arbuckles and the parallel trending Wichita Mountains is at almost right angle to the regional tectonic trend of the mid- Paleozoic structure from the Ouachitas south to the Marathon Uplift.
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Variations in water depth over this time, related both to crustal extension and to the growth and decline of a south polar ice-sheet, gave rise to changes in conditions of deposition and hence a varying rock sequence. Volcanic activity began in the Ordovician period as ocean crust was subducted to the northwest of Snowdonia and continued into the early Silurian until continental collision had ceased. The nature of the volcanism and hence the character of both extrusive and intrusive igneous rocks varied over time. Most of Snowdonia is thought to have remained as land during the succeeding few hundred million years before being submerged during the Jurassic period though, with one marginal exception, no rocks dating from the Devonian onwards remain. Cardigan Bay developed as a depositional basin during the Mesozoic and some of those sediments are recorded within Snowdonia’s boundaries, albeit concealed at depth.
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Principle of Uniformitarianism: defined in the authoritative Glossary of Geology as "the fundamental principle or doctrine that geologic processes and natural laws now operating to modify the Earth's crust have acted in the same regular manner and with essentially the same intensity throughout geologic time, and that past geologic events can be explained by phenomena and forces observable today; the classical concept that 'the present is the key to the past'.". Law of Original Horizontality: sedimentary rocks are always deposited as horizontal, or nearly horizontal, strata, although these may be disturbed by later earth movements. This law was proposed by Nicolaus Steno in the mid-17th century. Law of Superposition: general law upon which all geologic chronology is based: In any sequence of layered rocks, sedimentary or extrusive volcanic, that has not been overturned, the youngest stratum is at the top and the oldest at the base; i.e.
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In the early time of its active development, from the Pennsylvanian on into the Lower Rotliegend (Glan Subgroup, Meisenheim Formation), fluviolacustrine sedimentation conditions prevailed in the Saar–Nahe Basin. The basin lay, according to palaeomagnetic investigation, just north of the equator in the tropics at this time, so that under warm and moist climatic conditions, the lacustrine deposits especially, with their heavy amounts of organic remnants, ended up forming many coal seams, especially in the Pennsylvanian. Towards the end of the Rotliegend (Disibodenberg Formation), the extensive, at times basinwide lakes were filled in by advancing deltas, and by the end of the Glan Subgroup (beginning with the Oberkirchen Formation), the predominant deposit conditions were fluvial in what were now dry-warm climatic conditions. Along with its attendant, sometimes heavy, intrusive and effusive-extrusive magmatism – involving lavas and tuffs being pushed up, their place taken by both acidic and basic intrusions – it lasted until the middle of the Nahe Subgroup, when it came to an end with the quartzite conglomerate deposition found in the Wadern Formation.
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