"There never was any record of Neanderthals collecting pumices," said Dr. Villa.
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The team doesn't know what the Neanderthals used the pumices for, but one possibility is that they collected the rocks like we do today, to exfoliate dead skin from our feet and bodies.
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I like to think of the Amopé Pedi Perfect foot file as the sophisticated, diamond-wearing older cousin of all the archaic tools I was previously using to control calluses, which ran the gamut from large foot files to questionable shower pumices to dangerous metal graters (leave those for cheese, y'all).
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Outcrop of pumice at Kuthiny Baty, from the lake The idea that pumices around Kurile Lake were formed by an eruption in the area of the lake was first suggested by Boris Piip in 1947. Later research identified these pumices as the product of the caldera-forming eruption, although some scepticism remains, which considers these pumices as the product of fissure eruptions. An earlier Pleistocene caldera-forming eruption took place 41,500 years ago, ash deposits from this eruption are found as far away as Magadan, away from Kurile Lake, and possibly Lake El′gygytgyn. The Kurile Lake caldera forming eruption, also known as "KO", occurred in 6460-6414 BC. It is the largest known Holocene eruption in Kamchatka.
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It was followed by three pumice fallout episodes, with deposits over an area wider than was reached by any of the other eruption phases. These pumices fell up to to east, against the prevailing wind, in Sumbawa, where they are up to thick. The deposition of these pumices was followed by another stage of pyroclastic flow activity, probably caused by the collapse of the eruption column that generated the flows. At this time the eruption changed from an eruption-column-generating stage to a fountain-like stage and the caldera began to form.
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Outside of the caldera, the ignimbrite is formed by two different cooling units with distinct characteristics. The lower cooling unit is massive, poorly welded and contains lithics and pumices; the content of these varies at different sites and there are several different types of pumices. The thickness of the lower cooling unit varies between to exceeding , and pre-existent topography has controlled the emplacement of the unit; it crops out mainly in valleys. The upper cooling unit is thicker and covers a larger surface than the lower unit, although part of the latter may be buried beneath the upper cooling unit.
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The Toconao and Atana ignimbrites are formed by rhyolite and dacite-rhyodacite, respectively. They form a potassium-rich calc-alkaline suite. Both contain pumices, three different types of which are found in the Atana ignimbrite. Phenocrysts within the ignimbrite are chiefly formed by plagioclase.
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Volcanic ashes and pumices largely composed of volcanic glass are commonly used, as are deposits in which the volcanic glass has been altered to zeolites by interaction with alkaline waters. Deposits of sedimentary origin are less common. Diatomaceous earths, formed by the accumulation of siliceous diatom microskeletons, are a prominent source material here.
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To a more recent phase of volcanism belong andesitic centres, some of which lie on river terraces and form easily recognizable coulees. Explosive activity has also left ignimbrites and pumices; such explosive activity took place in the eastern part of the field towards Bazman volcano and was accompanied by the formation of nuee ardente breccia.
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There are vast resources of nonmetallic minerals and construction materials. These are salt, gypsum, zeolites, diatomites bentonitic clays, lithographic stone, abradants, mineral paints, cement raw materials, travertine, marbles, motley conglomerates, granites, basalts, perlites, slags, pumices and others. Tuffs and welded tuffs (ignimbrites) are of a special interest. They are pink, yellow, orange and black in color.
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The floor of Era Kohor is thus deep white. Three maars and several scoria cones are also nested within the combined caldera, along with lava domes and lava flows. Debris from explosive eruptions fills the calderas. The Kohor pumices and two sets of ignimbrites cover the flanks of Emi Koussi, which steepen as they approach the summit.
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There was no prior Plinian fallout. Orbs and two differently coloured pumices are located in the upper section of the lower unit, with some xenoliths. The upper cooling unit contains two types of pumice, one strongly welded and the other weakly so, and is much richer in lithic fragments. The upper unit was erupted in several discrete flows from the central complex.
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Both of these faults have caused activity within Kone's recent history. The calderas widths can range from 1.5 to 5 km. There are many rock types identified at Kone and they are divided into five main groups, trachytes, comenditic rhyolites, ignimbrites, pumices, syenite inclusions and basalts. Trachytes and comenditic rhyolites form the main volume of the rock in the Complex.
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Most of it is buried beneath the flow and only on the eastern side does some material emerge; its volume is estimated at . This deposit is formed from several layers of pumices separated by erosion surfaces; at least one layer may be derived from Paniri volcano. An overlapping pair of pyroclastic cones sits on top of the Chao flow and form its eruption vent. The cone has a dense rock equivalent volume of of lapilli and blocks.
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The ignimbrite features three facies, one rich in breccia, another rich in pumice, and a normal ignimbrite. Ignimbrite was channeled to the Salar de Atacama by the Quebrada de Chaile, Quebrada de Soncor and Quebrada de Talabre canyons and some smaller valleys, northeastwards by the Quebrada de Morro Blanco and as far as southeastwards over the Pampa Leija area. In these valleys, the ignimbrite can be as much as thick. Pumices are encased in the ignimbrite as lenses and levees and are also found in the terrain above the canyons.
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Andesite has also been found at Huaynaputina. The Huaynaputina pumices have a white colour. A large amount of sulfur appears to have been carried in a volatile phase associated with the magma rather than in the magma proper. An even larger amount of sulfur may have originated from a relic hydrothermal system that underpins the volcano, and whose accumulated sulfur would have been mobilized by the 1600 eruption; some contradictions between the sulfur yield inferred from ice core data and these inferred from the magma composition can be resolved this way.
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"Assessment of volcanological factors" in one scientific study reconstruct a minimum eruption time of 3 hours in which an initial explosion raised a column of and deposited about 0.32 km3 of white pumice ("the white pumice phase"), while a second, more intense explosion raised a column of depositing 1.25 km3 of grey pumice ("the grey pumice phase"). These pumices appearing in Apulian pottery can be used to establish relative chronology of pottery phases. A 2008 study of the lithofacies (deposits from the eruption) distinguishes three phases. Pyroclastic flows (PDC's) of Phases 1 and 2 were generated by "magmatic fragmentation" and had "small dispersal areas" mainly on the slopes of Vesuvius.
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Dredging has produced basaltic and carbonatic rocks that are partly covered by ferromanganese crusts or chemically altered by phosphate. In addition, shallow water calcarenites, conglomerates, coral debris, hemipelagic sediments, breccia, limestones, felsite, foraminiferal sand, pelagic ooze, reefal limestones and sediments have been recovered. The volcanic rocks include alkali basalts, basanite, hyaloclastite, palagonite, picrite, pumices, basaltic tuffs, trachybasalt and trachyte and define an alkaline ocean island basalt suite although the existence of tholeiites as in Hawaii is possible and substantial amounts of evolved volcanic rocks have been recovered; these were probably generated by basaltic melts in magma chambers. Minerals contained in the rocks include mafic clots, amphibole, apatite, clinopyroxene including augite, olivine, plagioclase, spinel and titanomagnetite.
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This ignimbrite has a volume of approximately and is formed by a lower un-indurated and an upper indurated subunit. Tube pumices are contained in the lower subunit and in a less than Plinian deposit that was emplaced beneath the Toconao ignimbrite. The formation of the caldera coincided with the eruption of the Atana ignimbrite; the eruption was still underway when the terrain subsided to a depth of beneath the previous surface in the northwestern segment of La Pacana. Dates obtained on the Atana ignimbrite are between 3.8 ± 0.1 and 4.2 ± 0.1 million years ago, which is not clearly distinguishable from the dates of the Toconao ignimbrite seeing as there is no indication that a pause occurred between the eruption of the two ignimbrites.
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The Romans used volcanic pumices and tuffs found in neighbouring territories, the most famous ones found in Pozzuoli (Naples), hence the name pozzolan, and in Segni (Latium). Preference was given to natural pozzolan sources such as German trass, but crushed ceramic waste was frequently used when natural deposits were not locally available. The exceptional lifetime and preservation conditions of some of the most famous Roman buildings such as the Pantheon or the Pont du Gard constructed using pozzolan-lime mortars and concrete testify both to the excellent workmanship achieved by Roman engineers and to the durable properties of the binders they used. Much of the practical skill and knowledge regarding the use of pozzolans was lost at the decline of the Roman empire.
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At Grotta dei Moscerini, about 24% of the shells were gathered alive from the seafloor, meaning these Neanderthals had to wade or dive into shallow waters to collect them. At Grotta di Santa Lucia, Italy, in the Campanian volcanic arc, Neanderthals collected the porous volcanic pumice, which, for contemporary humans, was probably used for polishing points and needles. The pumices are associated with shell tools. At Abri du Maras, France, twisted fibres and a 3-ply inner-bark-fibre cord fragment associated with Neanderthals show that they produced string and cordage, but it is unclear how widespread this technology was because the materials used to make them (such as animal hair, hide, sinew, or plant fibres) are biodegradable and preserve very poorly.
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The fine scoria ashes or "cinders" thrown out by basaltic volcanoes are often spongy masses of tachylite with only a few larger crystals or phenocrysts imbedded in black glass. Such tachylite volcanic bombs and scoria are frequent in Iceland, Auvergne, Stromboli and Etna, and are very common also in the ash beds or tuffs of older date, such as occur in Skye, Midlothian and Fife, Derbyshire, and elsewhere. Basic pumices of this kind are exceedingly widespread on the bottom of the sea, either dispersed in the pelagic red clay and other deposits or forming layers coated with oxides of manganese precipitated on them from the sea water. These tachylite fragments, which are usually much decomposed by the oxidation and hydration of their ferrous compounds, have taken on a dark red color.
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