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65-494: A caldera ( / k ɔː l ˈ d ɛr ə , k æ l -/ kawl- DERR -ə, kal- ) is a large cauldron -like hollow that forms shortly after the emptying of a magma chamber in a volcanic eruption . An eruption that ejects large volumes of magma over a short period of time can cause significant detriment to the structural integrity of such a chamber, greatly diminishing its capacity to support its own roof, and any substrate or rock resting above. The ground surface then collapses into

130-407: A caldera, possibly an ash-flow caldera. The volcanic activity of Mars is concentrated in two major provinces: Tharsis and Elysium . Each province contains a series of giant shield volcanoes that are similar to what we see on Earth and likely are the result of mantle hot spots . The surfaces are dominated by lava flows, and all have one or more collapse calderas. Mars has the tallest volcano in

195-661: A cauldron is made of cast iron and is used to burn loose incense on a charcoal disc, to make black salt (used in banishing rituals), for mixing herbs, or to burn petitions (paper with words of power or wishes written on them). Cauldrons symbolize not only the Goddess but also represent the womb (because it holds something) and on an altar, it represents earth because it is a working tool. Cauldrons are often sold in New Age or "metaphysical" stores and may have various symbols of power inscribed on them. The Holy Grail of Arthurian legend

260-514: A cauldron. Also, in Irish folklore , a cauldron is purported to be where leprechauns keep their gold and treasure . In some forms of Wicca , appropriating aspects of Celtic mythology , the cauldron is associated with the goddess Cerridwen . Welsh legend also tells of cauldrons that were useful to warring armies. In the second branch of the Mabinogi in the tale of Branwen, Daughter of Llŷr ,

325-399: A diameter of 290 km (180 mi). The average caldera diameter on Mars is 48 km (30 mi), smaller than Venus. Calderas on Earth are the smallest of all planetary bodies and vary from 1.6–80 km (1–50 mi) as a maximum. The Moon has an outer shell of low-density crystalline rock that is a few hundred kilometers thick, which formed due to a rapid creation. The craters of

390-407: A glass with no true melting point, can be used as a glass fibre for fibreglass. Silicon dioxide is mostly obtained by mining, including sand mining and purification of quartz . Quartz is suitable for many purposes, while chemical processing is required to make a purer or otherwise more suitable (e.g. more reactive or fine-grained) product. Precipitated silica or amorphous silica is produced by

455-494: A heat capacity minimum. Its density decreases from 2.08 g/cm at 1950 °C to 2.03 g/cm at 2200 °C. The molecular SiO 2 has a linear structure like CO 2 . It has been produced by combining silicon monoxide (SiO) with oxygen in an argon matrix. The dimeric silicon dioxide, (SiO 2 ) 2 has been obtained by reacting O 2 with matrix isolated dimeric silicon monoxide, (Si 2 O 2 ). In dimeric silicon dioxide there are two oxygen atoms bridging between

520-450: A low value of 140° in α-tridymite, up to 180° in β-tridymite. In α-quartz, the Si–O–Si angle is 144°. Alpha quartz is the most stable form of solid SiO 2 at room temperature. The high-temperature minerals, cristobalite and tridymite, have both lower densities and indices of refraction than quartz. The transformation from α-quartz to beta-quartz takes place abruptly at 573 °C. Since

585-468: A magma chamber whose magma is rich in silica . Silica-rich magma has a high viscosity , and therefore does not flow easily like basalt . The magma typically also contains a large amount of dissolved gases, up to 7 wt% for the most silica-rich magmas. When the magma approaches the surface of the Earth, the drop in confining pressure causes the trapped gases to rapidly bubble out of the magma, fragmenting

650-601: A noticeable drop in temperature around the world. Large calderas may have even greater effects. The ecological effects of the eruption of a large caldera can be seen in the record of the Lake Toba eruption in Indonesia . At some points in geological time , rhyolitic calderas have appeared in distinct clusters. The remnants of such clusters may be found in places such as the Eocene Rum Complex of Scotland,

715-410: A silicon wafer enables it to overcome the surface states that otherwise prevent electricity from reaching the semiconducting layer. The process of silicon surface passivation by thermal oxidation (silicon dioxide) is critical to the semiconductor industry . It is commonly used to manufacture metal–oxide–semiconductor field-effect transistors (MOSFETs) and silicon integrated circuit chips (with

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780-477: A very shallow layer of about 1 nm or 10 Å of so-called native oxide. Higher temperatures and alternative environments are used to grow well-controlled layers of silicon dioxide on silicon, for example at temperatures between 600 and 1200 °C, using so-called dry oxidation with O 2 or wet oxidation with H 2 O. The native oxide layer is beneficial in microelectronics , where it acts as electric insulator with high chemical stability. It can protect

845-524: A white powder with extremely low bulk density (0.03-0.15 g/cm ) and thus high surface area. The particles act as a thixotropic thickening agent, or as an anti-caking agent, and can be treated to make them hydrophilic or hydrophobic for either water or organic liquid applications. Silica fume is an ultrafine powder collected as a by-product of the silicon and ferrosilicon alloy production. It consists of amorphous (non-crystalline) spherical particles with an average particle diameter of 150 nm, without

910-691: Is a borrowing of the Old Norse variant ketill "cauldron". Cauldrons can be found from the late Bronze Age period; these include vast ones with a volume of 60–70 litres (16–18  US gal ). Cauldrons have largely fallen out of use in the developed world as cooking vessels. While still used for practical purposes, a more common association in Western culture is the cauldron's use in witchcraft —a cliché popularized by various works of fiction , such as William Shakespeare 's play Macbeth . In fiction, witches often prepare their potions in

975-439: Is also the primary component of rice husk ash , which is used, for example, in filtration and as supplementary cementitious material (SCM) in cement and concrete manufacturing. Silicification in and by cells has been common in the biological world and it occurs in bacteria, protists, plants, and animals (invertebrates and vertebrates). Prominent examples include: About 95% of the commercial use of silicon dioxide (sand)

1040-399: Is an oxide of silicon with the chemical formula SiO 2 , commonly found in nature as quartz . In many parts of the world, silica is the major constituent of sand . Silica is one of the most complex and abundant families of materials , existing as a compound of several minerals and as a synthetic product. Examples include fused quartz , fumed silica , opal , and aerogels . It

1105-604: Is covalently bonded in a tetrahedral manner to 4 oxygen atoms. In contrast, CO 2 is a linear molecule. The starkly different structures of the dioxides of carbon and silicon are a manifestation of the double bond rule . Based on the crystal structural differences, silicon dioxide can be divided into two categories: crystalline and non-crystalline (amorphous). In crystalline form, this substance can be found naturally occurring as quartz , tridymite (high-temperature form), cristobalite (high-temperature form), stishovite (high-pressure form), and coesite (high-pressure form). On

1170-402: Is ejected, the emptied chamber is unable to support the weight of the volcanic edifice above it. A roughly circular fracture , the "ring fault", develops around the edge of the chamber. Ring fractures serve as feeders for fault intrusions which are also known as ring dikes . Secondary volcanic vents may form above the ring fracture. As the magma chamber empties, the center of the volcano within

1235-600: Is first recorded in Middle English as caudroun (13th century). It was borrowed from Norman caudron ( Picard caudron , French : chaudron ). It represents the phonetical evolution of Vulgar Latin *caldario for Classical Latin caldārium "hot bath", that derives from cal(i)dus "hot". The Norman-French word replaces the Old English ċetel (German (Koch)Kessel "cauldron", Dutch (kook)ketel "cauldron"), Middle English chetel . The word "kettle"

1300-558: Is heated by solid flexing due to the tidal influence of Jupiter and Io's orbital resonance with neighboring large moons Europa and Ganymede , which keep its orbit slightly eccentric . Unlike any of the planets mentioned, Io is continuously volcanically active. For example, the NASA Voyager 1 and Voyager 2 spacecraft detected nine erupting volcanoes while passing Io in 1979. Io has many calderas with diameters tens of kilometers across. Cauldron The word cauldron

1365-465: Is in the construction industry, e.g. in the production of concrete ( Portland cement concrete ). Certain deposits of silica sand, with desirable particle size and shape and desirable clay and other mineral content, were important for sand casting of metallic products. The high melting point of silica enables it to be used in such applications such as iron casting; modern sand casting sometimes uses other minerals for other reasons. Crystalline silica

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1430-651: Is obtained by the dealumination of a low-sodium, ultra-stable Y zeolite with combined acid and thermal treatment. The resulting product contains over 99% silica, and has high crystallinity and specific surface area (over 800 m /g). Faujasite-silica has very high thermal and acid stability. For example, it maintains a high degree of long-range molecular order or crystallinity even after boiling in concentrated hydrochloric acid . Molten silica exhibits several peculiar physical characteristics that are similar to those observed in liquid water : negative temperature expansion, density maximum at temperatures ~5000 °C, and

1495-711: Is often associated with power and dominion over the land. Therefore, the ding is often used as an implicit symbolism for power. The term "inquiring of the ding" (Chinese: 问鼎; pinyin: wèn dǐng) is often used to symbolize the use of divination or for the quest for power. One example of the ding cauldron and gaining power over the traditional provinces of China is the Nine Tripod Cauldrons (whether regarded as myth or history). Archeologically intact actual cauldrons with apparent cultural symbolism include: Cauldrons known only through myth and literature include: Silica Silicon dioxide , also known as silica ,

1560-421: Is rapidly cooled, it does not crystallize, but solidifies as a glass. Because of this, most ceramic glazes have silica as the main ingredient. The structural geometry of silicon and oxygen in glass is similar to that in quartz and most other crystalline forms of silicon and oxygen, with silicon surrounded by regular tetrahedra of oxygen centres. The difference between the glass and crystalline forms arises from

1625-537: Is relatively young (1.25 million years old) and unusually well preserved, and it remains one of the best studied examples of a resurgent caldera. The ash flow tuffs of the Valles caldera, such as the Bandelier Tuff , were among the first to be thoroughly characterized. About 74,000 years ago, this Indonesian volcano released about 2,800 cubic kilometres (670 cu mi) dense-rock equivalent of ejecta. This

1690-439: Is sometimes referred to as a "cauldron", although traditionally the grail is thought of as a hand-held cup rather than the large pot that the word "cauldron" usually is used to mean. This may have resulted from the combination of the grail legend with earlier Celtic myths of magical cauldrons. The common translation for ding is often referred to as a cauldron. In Chinese history and culture, possession of one or more ancient dings

1755-426: Is the major constituent of sand . Even though it is poorly soluble, silica occurs in many plants such as rice . Plant materials with high silica phytolith content appear to be of importance to grazing animals, from chewing insects to ungulates . Silica accelerates tooth wear, and high levels of silica in plants frequently eaten by herbivores may have developed as a defense mechanism against predation. Silica

1820-405: Is the only polymorph of silica stable at the Earth's surface. Metastable occurrences of the high-pressure forms coesite and stishovite have been found around impact structures and associated with eclogites formed during ultra-high-pressure metamorphism . The high-temperature forms of tridymite and cristobalite are known from silica-rich volcanic rocks . In many parts of the world, silica

1885-504: Is the process by which a semiconductor surface is rendered inert, and does not change semiconductor properties as a result of interaction with air or other materials in contact with the surface or edge of the crystal. The formation of a thermally grown silicon dioxide layer greatly reduces the concentration of electronic states at the silicon surface . SiO 2 films preserve the electrical characteristics of p–n junctions and prevent these electrical characteristics from deteriorating by

1950-436: Is used as a fining agent for wine, beer, and juice, with the E number reference E551 . In cosmetics, silica is useful for its light-diffusing properties and natural absorbency. Diatomaceous earth , a mined product, has been used in food and cosmetics for centuries. It consists of the silica shells of microscopic diatoms ; in a less processed form it was sold as "tooth powder". Manufactured or mined hydrated silica

2015-489: Is used as the hard abrasive in toothpaste . Silicon dioxide is widely used in the semiconductor technology: Because silicon dioxide is a native oxide of silicon it is more widely used compared to other semiconductors like gallium arsenide or indium phosphide . Silicon dioxide could be grown on a silicon semiconductor surface. Silicon oxide layers could protect silicon surfaces during diffusion processes , and could be used for diffusion masking. Surface passivation

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2080-418: Is used in hydraulic fracturing of formations which contain tight oil and shale gas . Silica is the primary ingredient in the production of most glass . As other minerals are melted with silica, the principle of freezing point depression lowers the melting point of the mixture and increases fluidity. The glass transition temperature of pure SiO 2 is about 1475 K. When molten silicon dioxide SiO 2

2145-498: Is used in structural materials , microelectronics , and as components in the food and pharmaceutical industries. All forms are white or colorless, although impure samples can be colored. Silicon dioxide is a common fundamental constituent of glass . In the majority of silicon dioxides, the silicon atom shows tetrahedral coordination , with four oxygen atoms surrounding a central Si atom ( see 3-D Unit Cell ). Thus, SiO 2 forms 3-dimensional network solids in which each silicon atom

2210-538: Is used to produce elemental silicon . The process involves carbothermic reduction in an electric arc furnace : Fumed silica , also known as pyrogenic silica, is prepared by burning SiCl 4 in an oxygen-rich hydrogen flame to produce a "smoke" of SiO 2 . It can also be produced by vaporizing quartz sand in a 3000 °C electric arc. Both processes result in microscopic droplets of amorphous silica fused into branched, chainlike, three-dimensional secondary particles which then agglomerate into tertiary particles,

2275-472: The Pair Dadeni (Cauldron of Rebirth) is a magical cauldron in which dead warriors could be placed and then be returned to life, save that they lacked the power of speech. It was suspected that they lacked souls. These warriors could go back into battle until they were killed again. In Wicca and some other forms of neopagan or pagan belief systems, the cauldron is still used in magical practices. Most often

2340-503: The San Juan Mountains of Colorado , where the 5,000 cubic kilometres (1,200 cu mi) Fish Canyon Tuff was blasted out in eruptions about 27.8 million years ago. The caldera produced by such eruptions is typically filled in with tuff, rhyolite , and other igneous rocks . The caldera is surrounded by an outflow sheet of ash flow tuff (also called an ash flow sheet ). If magma continues to be injected into

2405-555: The planar process ). Hydrophobic silica is used as a defoamer component . In its capacity as a refractory , it is useful in fiber form as a high-temperature thermal protection fabric. Silica is used in the extraction of DNA and RNA due to its ability to bind to the nucleic acids under the presence of chaotropes . Silica aerogel was used in the Stardust spacecraft to collect extraterrestrial particles. Pure silica (silicon dioxide), when cooled as fused quartz into

2470-416: The Earth's volcanic activity (the other 40% is attributed to hotspot volcanism). Caldera structure is similar on all of these planetary bodies, though the size varies considerably. The average caldera diameter on Venus is 68 km (42 mi). The average caldera diameter on Io is close to 40 km (25 mi), and the mode is 6 km (3.7 mi); Tvashtar Paterae is likely the largest caldera with

2535-680: The English term cauldron is also used, though in more recent work the term cauldron refers to a caldera that has been deeply eroded to expose the beds under the caldera floor. The term caldera was introduced into the geological vocabulary by the German geologist Leopold von Buch when he published his memoirs of his 1815 visit to the Canary Islands , where he first saw the Las Cañadas caldera on Tenerife , with Mount Teide dominating

2600-514: The Moon have been well preserved through time and were once thought to have been the result of extreme volcanic activity, but are currently believed to have been formed by meteorites, nearly all of which took place in the first few hundred million years after the Moon formed. Around 500 million years afterward, the Moon's mantle was able to be extensively melted due to the decay of radioactive elements. Massive basaltic eruptions took place generally at

2665-675: The San Juan Mountains of Colorado (formed during the Oligocene , Miocene , and Pliocene epochs) or the Saint Francois Mountain Range of Missouri (erupted during the Proterozoic eon). For their 1968 paper that first introduced the concept of a resurgent caldera to geology, R.L. Smith and R.A. Bailey chose the Valles caldera as their model. Although the Valles caldera is not unusually large, it

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2730-724: The Solar System, Olympus Mons , which is more than three times the height of Mount Everest, with a diameter of 520 km (323 miles). The summit of the mountain has six nested calderas. Because there is no plate tectonics on Venus , heat is mainly lost by conduction through the lithosphere . This causes enormous lava flows, accounting for 80% of Venus' surface area. Many of the mountains are large shield volcanoes that range in size from 150–400 km (95–250 mi) in diameter and 2–4 km (1.2–2.5 mi) high. More than 80 of these large shield volcanoes have summit calderas averaging 60 km (37 mi) across. Io, unusually,

2795-496: The acidification of solutions of sodium silicate . The gelatinous precipitate or silica gel , is first washed and then dehydrated to produce colorless microporous silica. The idealized equation involving a trisilicate and sulfuric acid is: Approximately one billion kilograms/year (1999) of silica were produced in this manner, mainly for use for polymer composites – tires and shoe soles. Thin films of silica grow spontaneously on silicon wafers via thermal oxidation , producing

2860-410: The base of large impact craters. Also, eruptions may have taken place due to a magma reservoir at the base of the crust. This forms a dome, possibly the same morphology of a shield volcano where calderas universally are known to form. Although caldera-like structures are rare on the Moon, they are not completely absent. The Compton-Belkovich Volcanic Complex on the far side of the Moon is thought to be

2925-552: The branching of the pyrogenic product. The main use is as pozzolanic material for high performance concrete. Fumed silica nanoparticles can be successfully used as an anti-aging agent in asphalt binders. Silica, either colloidal, precipitated, or pyrogenic fumed, is a common additive in food production. It is used primarily as a flow or anti- caking agent in powdered foods such as spices and non-dairy coffee creamer, or powders to be formed into pharmaceutical tablets. It can adsorb water in hygroscopic applications. Colloidal silica

2990-586: The caldera atop Fernandina Island collapsed in 1968 when parts of the caldera floor dropped 350 metres (1,150 ft). Since the early 1960s, it has been known that volcanism has occurred on other planets and moons in the Solar System . Through the use of crewed and uncrewed spacecraft, volcanism has been discovered on Venus , Mars , the Moon , and Io , a satellite of Jupiter . None of these worlds have plate tectonics , which contributes approximately 60% of

3055-670: The collapsed magma chamber, the center of the caldera may be uplifted in the form of a resurgent dome such as is seen at the Valles Caldera , Lake Toba , the San Juan volcanic field, Cerro Galán , Yellowstone , and many other calderas. Because a silicic caldera may erupt hundreds or even thousands of cubic kilometers of material in a single event, it can cause catastrophic environmental effects. Even small caldera-forming eruptions, such as Krakatoa in 1883 or Mount Pinatubo in 1991, may result in significant local destruction and

3120-509: The connectivity of the tetrahedral units: Although there is no long-range periodicity in the glassy network, ordering remains at length scales well beyond the SiO bond length. One example of this ordering is the preference to form rings of 6-tetrahedra. The majority of optical fibers for telecommunications are also made from silica. It is a primary raw material for many ceramics such as earthenware , stoneware , and porcelain . Silicon dioxide

3185-488: The densest of the low-pressure forms, which has a density of 2.648 g/cm . The difference in density can be ascribed to the increase in coordination as the six shortest Si–O bond lengths in stishovite (four Si–O bond lengths of 176 pm and two others of 181 pm) are greater than the Si–O bond length (161 pm) in α-quartz. The change in the coordination increases the ionicity of the Si–O bond. Faujasite silica, another polymorph,

3250-402: The emptied or partially emptied magma chamber, leaving a large depression at the surface (from one to dozens of kilometers in diameter). Although sometimes described as a crater , the feature is actually a type of sinkhole , as it is formed through subsidence and collapse rather than an explosion or impact. Compared to the thousands of volcanic eruptions that occur over the course of a century,

3315-459: The formation of a caldera is a rare event, occurring only a few times within a given window of 100 years. Only eight caldera-forming collapses are known to have occurred between 1911 and 2018, with a caldera collapse at Kīlauea , Hawaii in 2018. Volcanoes that have formed a caldera are sometimes described as "caldera volcanoes". The term caldera comes from Spanish caldera , and Latin caldaria , meaning "cooking pot". In some texts

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3380-411: The gaseous ambient environment. Silicon oxide layers could be used to electrically stabilize silicon surfaces. The surface passivation process is an important method of semiconductor device fabrication that involves coating a silicon wafer with an insulating layer of silicon oxide so that electricity could reliably penetrate to the conducting silicon below. Growing a layer of silicon dioxide on top of

3445-464: The human species was reduced to approximately 5,000–10,000 people. There is no direct evidence, however, that either theory is correct, and there is no evidence for any other animal decline or extinction, even in environmentally sensitive species. There is evidence that human habitation continued in India after the eruption. Some volcanoes, such as the large shield volcanoes Kīlauea and Mauna Loa on

3510-429: The island of Hawaii , form calderas in a different fashion. The magma feeding these volcanoes is basalt , which is silica poor. As a result, the magma is much less viscous than the magma of a rhyolitic volcano, and the magma chamber is drained by large lava flows rather than by explosive events. The resulting calderas are also known as subsidence calderas and can form more gradually than explosive calderas. For instance,

3575-480: The landscape, and then the Caldera de Taburiente on La Palma . A collapse is triggered by the emptying of the magma chamber beneath the volcano, sometimes as the result of a large explosive volcanic eruption (see Tambora in 1815), but also during effusive eruptions on the flanks of a volcano (see Piton de la Fournaise in 2007) or in a connected fissure system (see Bárðarbunga in 2014–2015). If enough magma

3640-559: The magma to produce a mixture of volcanic ash and other tephra with the very hot gases. The mixture of ash and volcanic gases initially rises into the atmosphere as an eruption column . However, as the volume of erupted material increases, the eruption column is unable to entrain enough air to remain buoyant, and the eruption column collapses into a tephra fountain that falls back to the surface to form pyroclastic flows . Eruptions of this type can spread ash over vast areas, so that ash flow tuffs emplaced by silicic caldera eruptions are

3705-472: The only volcanic product with volumes rivaling those of flood basalts . For example, when Yellowstone Caldera last erupted some 650,000 years ago, it released about 1,000 km of material (as measured in dense rock equivalent (DRE)), covering a substantial part of North America in up to two metres of debris. Eruptions forming even larger calderas are known, such as the La Garita Caldera in

3770-400: The other hand, amorphous silica can be found in nature as opal and diatomaceous earth . Quartz glass is a form of intermediate state between these structures. All of these distinct crystalline forms always have the same local structure around Si and O. In α-quartz the Si–O bond length is 161 pm, whereas in α-tridymite it is in the range 154–171 pm. The Si–O–Si angle also varies between

3835-460: The ring fracture begins to collapse. The collapse may occur as the result of a single cataclysmic eruption, or it may occur in stages as the result of a series of eruptions. The total area that collapses may be hundreds of square kilometers. Some calderas are known to host rich ore deposits . Metal-rich fluids can circulate through the caldera, forming hydrothermal ore deposits of metals such as lead, silver, gold, mercury, lithium, and uranium. One of

3900-401: The silicon atoms with an Si–O–Si angle of 94° and bond length of 164.6 pm and the terminal Si–O bond length is 150.2 pm. The Si–O bond length is 148.3 pm, which compares with the length of 161 pm in α-quartz. The bond energy is estimated at 621.7 kJ/mol. SiO 2 is most commonly encountered in nature as quartz , which comprises more than 10% by mass of the Earth's crust. Quartz

3965-418: The silicon, store charge, block current, and even act as a controlled pathway to limit current flow. Many routes to silicon dioxide start with an organosilicon compound, e.g., HMDSO, TEOS. Synthesis of silica is illustrated below using tetraethyl orthosilicate (TEOS). Simply heating TEOS at 680–730 °C results in the oxide: Similarly TEOS combusts around 400 °C: TEOS undergoes hydrolysis via

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4030-492: The so-called sol-gel process . The course of the reaction and nature of the product are affected by catalysts, but the idealized equation is: Being highly stable, silicon dioxide arises from many methods. Conceptually simple, but of little practical value, combustion of silane gives silicon dioxide. This reaction is analogous to the combustion of methane: However the chemical vapor deposition of silicon dioxide onto crystal surface from silane had been used using nitrogen as

4095-446: The transformation is accompanied by a significant change in volume, it can easily induce fracturing of ceramics or rocks passing through this temperature limit. The high-pressure minerals, seifertite , stishovite, and coesite, though, have higher densities and indices of refraction than quartz. Stishovite has a rutile -like structure where silicon is 6-coordinate. The density of stishovite is 4.287 g/cm , which compares to α-quartz,

4160-650: The world's best-preserved mineralized calderas is the Sturgeon Lake Caldera in northwestern Ontario , Canada, which formed during the Neoarchean era about 2.7 billion years ago. In the San Juan volcanic field , ore veins were emplaced in fractures associated with several calderas, with the greatest mineralization taking place near the youngest and most silicic intrusions associated with each caldera. Explosive caldera eruptions are produced by

4225-463: Was the largest known eruption during the ongoing Quaternary period (the last 2.6 million years) and the largest known explosive eruption during the last 25 million years. In the late 1990s, anthropologist Stanley Ambrose proposed that a volcanic winter induced by this eruption reduced the human population to about 2,000–20,000 individuals, resulting in a population bottleneck . More recently, Lynn Jorde and Henry Harpending proposed that

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