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58-418: The Yellowstone Plateau Volcanic Field began forming around 2 Ma (million years ago). It has had over 110 different eruptions and has created mostly rhyolitic plains, with over 6000 km of rhyolitic material formed. Scientists have discovered three major eruptions that formed calderas . They used methods of geological mapping , with both satellites and field work, and potassium-argon dating , to discover

116-701: A magnitude of 4, but acoustic waves travel well in water and over long periods of time. A system in the North Pacific , maintained by the United States Navy and originally intended for the detection of submarines , has detected an event on average every 2 to 3 years. The most common underwater flow is pillow lava , a rounded lava flow named for its unusual shape. Less common are glassy , marginal sheet flows, indicative of larger-scale flows. Volcaniclastic sedimentary rocks are common in shallow-water environments. As plate movement starts to carry

174-498: A Peléan eruption are very similar to that of a Vulcanian eruption, except that in Peléan eruptions the volcano's structure is able to withstand more pressure, hence the eruption occurs as one large explosion rather than several smaller ones. Volcanoes known to have Peléan activity include: Plinian eruptions (or Vesuvian eruptions) are a type of volcanic eruption named for the historical eruption of Mount Vesuvius in 79 AD that buried

232-420: A Plinian eruption, and reach up 2 to 45 km (1 to 28 mi) into the atmosphere . The densest part of the plume, directly above the volcano, is driven internally by gas expansion . As it reaches higher into the air the plume expands and becomes less dense, convection and thermal expansion of volcanic ash drive it even further up into the stratosphere . At the top of the plume, powerful winds may drive

290-406: A coming eruption is the growth of a so-called Peléan or lava spine , a bulge in the volcano's summit preempting its total collapse. The material collapses upon itself, forming a fast-moving pyroclastic flow (known as a block -and- ash flow) that moves down the side of the mountain at tremendous speeds, often over 150 km (93 mi) per hour. These landslides make Peléan eruptions one of

348-482: A location in Wyoming is a stub . You can help Misplaced Pages by expanding it . Eruptions Several types of volcanic eruptions —during which material is expelled from a volcanic vent or fissure —have been distinguished by volcanologists . These are often named after famous volcanoes where that type of behavior has been observed. Some volcanoes may exhibit only one characteristic type of eruption during

406-401: A period of activity, while others may display an entire sequence of types all in one eruptive series. There are three main types of volcanic eruption: Within these broad eruptive types are several subtypes. The weakest are Hawaiian and submarine , then Strombolian , followed by Vulcanian and Surtseyan . The stronger eruptive types are Pelean eruptions , followed by Plinian eruptions ;

464-401: A probable cause for higher levels of volcanism. The technology for studying seamount eruptions did not exist until advancements in hydrophone technology made it possible to "listen" to acoustic waves , known as T-waves, released by submarine earthquakes associated with submarine volcanic eruptions. The reason for this is that land-based seismometers cannot detect sea-based earthquakes below

522-435: A single eruptive cycle. Volcanoes do not always erupt vertically from a single crater near their peak, either. Some volcanoes exhibit lateral and fissure eruptions . Notably, many Hawaiian eruptions start from rift zones . Scientists believed that pulses of magma mixed together in the magma chamber before climbing upward—a process estimated to take several thousands of years. Columbia University volcanologists found that

580-410: A stable height of around 2,500 m (8,200 ft) for 18 minutes, briefly peaking at a height of 3,400 m (11,000 ft). Volcanoes known to have Hawaiian activity include: Strombolian eruptions are a type of volcanic eruption named after the volcano Stromboli , which has been erupting nearly continuously for centuries. Strombolian eruptions are driven by the bursting of gas bubbles within

638-542: A type of volcanic eruption characterized by interactions between lava and ice , often under a glacier . The nature of glaciovolcanism dictates that it occurs at areas of high latitude and high altitude . It has been suggested that subglacial volcanoes that are not actively erupting often dump heat into the ice covering them, producing meltwater . This meltwater mix means that subglacial eruptions often generate dangerous jökulhlaups ( floods ) and lahars . Lateral eruption A lateral eruption or lateral blast

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696-490: A type of volcanic eruption named after the volcano Mount Pelée in Martinique , the site of a Peléan eruption in 1902 that is one of the worst natural disasters in history. In Peléan eruptions, a large amount of gas, dust, ash, and lava fragments are blown out the volcano's central crater, driven by the collapse of rhyolite , dacite , and andesite lava domes that often creates large eruptive columns . An early sign of

754-446: A volcanic cone on Kilauea , erupted continuously for over 35 years. Another Hawaiian volcanic feature is the formation of active lava lakes , self-maintaining pools of raw lava with a thin crust of semi-cooled rock. Flows from Hawaiian eruptions are basaltic, and can be divided into two types by their structural characteristics. Pahoehoe lava is a relatively smooth lava flow that can be billowy or ropey. They can move as one sheet, by

812-416: Is a volcanic eruption which is directed laterally from a volcano rather than upwards from the summit . Lateral eruptions are caused by the outward expansion of flanks due to rising magma . Breaking occurs at the flanks of volcanoes making it easier for magma to flow outward. As magma is pushed upward towards the volcano it diverges towards the flanks before it has a chance to erupt from the crater . When

870-437: Is characterized by a series of short-lived explosions, lasting a few minutes to a few hours and typified by the ejection of volcanic bombs and blocks . These eruptions wear down the lava dome holding the magma down, and it disintegrates, leading to much more quiet and continuous eruptions. Thus an early sign of future Vulcanian activity is lava dome growth, and its collapse generates an outpouring of pyroclastic material down

928-502: Is generally in the form of episodic explosive eruptions accompanied by the distinctive loud blasts. During eruptions, these blasts occur as often as every few minutes. The term "Strombolian" has been used indiscriminately to describe a wide variety of volcanic eruptions, varying from small volcanic blasts to large eruptive columns . In reality, true Strombolian eruptions are characterized by short-lived and explosive eruptions of lavas with intermediate viscosity , often ejected high into

986-500: Is only moderately dispersed, and its abundance indicates a high degree of fragmentation , the result of high gas contents within the magma. In some cases these have been found to be the result of interaction with meteoric water , suggesting that Vulcanian eruptions are partially hydrovolcanic . Volcanoes that have exhibited Vulcanian activity include: Vulcanian eruptions are estimated to make up at least half of all known Holocene eruptions. Peléan eruptions (or nuée ardente ) are

1044-420: The 1886 eruption of Mount Tarawera . Littoral cones are another hydrovolcanic feature, generated by the explosive deposition of basaltic tephra (although they are not truly volcanic vents). They form when lava accumulates within cracks in lava, superheats and explodes in a steam explosion , breaking the rock apart and depositing it on the volcano's flank. Consecutive explosions of this type eventually generate

1102-521: The Roman towns of Pompeii and Herculaneum and, specifically, for its chronicler Pliny the Younger . The process powering Plinian eruptions starts in the magma chamber , where dissolved volatile gases are stored in the magma. The gases vesiculate and accumulate as they rise through the magma conduit . These bubbles agglutinate and once they reach a certain size (about 75% of the total volume of

1160-410: The effusive eruption of very fluid basalt -type lavas with low gaseous content . The volume of ejected material from Hawaiian eruptions is less than half of that found in other eruptive types. Steady production of small amounts of lava builds up the large, broad form of a shield volcano . Eruptions are not centralized at the main summit as with other volcanic types, and often occur at vents around

1218-428: The eruption column . Base surges are caused by the gravitational collapse of a vaporous eruptive column, one that is denser overall than a regular volcanic column. The densest part of the cloud is nearest to the vent, resulting in a wedge shape. Associated with these laterally moving rings are dune -shaped depositions of rock left behind by the lateral movement. These are occasionally disrupted by bomb sags , rock that

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1276-419: The magma . These gas bubbles within the magma accumulate and coalesce into large bubbles, called gas slugs . These grow large enough to rise through the lava column. Upon reaching the surface, the difference in air pressure causes the bubble to burst with a loud pop, throwing magma in the air in a way similar to a soap bubble . Because of the high gas pressures associated with the lavas, continued activity

1334-430: The magma chamber differentiates with upper portions rich in silicon dioxide , or if magma ascends rapidly. Plinian eruptions are similar to both Vulcanian and Strombolian eruptions, except that rather than creating discrete explosive events, Plinian eruptions form sustained eruptive columns. They are also similar to Hawaiian lava fountains in that both eruptive types produce sustained eruption columns maintained by

1392-607: The mountain , and if a flank collapses, a lateral eruption occurs. The directed nature of the blast may cause damage at much greater distances from the peak than a summit eruption would have. Pyroclastic flows and lahars can affect areas originating from the volcano roughly in the shape of a cone that can span hundreds of square kilometers. Mount St. Helens is a stratovolcano located in Washington , USA . Volcanic activity beginning in March 1980 saw magma accumulating underneath

1450-417: The pyroclastic flows generated by material collapse, which move down the side of the mountain at extreme speeds of up to 700 km (435 mi) per hour and with the ability to extend the reach of the eruption hundreds of kilometers. The ejection of hot material from the volcano's summit melts snowbanks and ice deposits on the volcano, which mixes with tephra to form lahars , fast moving mudflows with

1508-568: The Hawaiian volcano deity). During especially high winds these chunks may even take the form of long drawn-out strands, known as Pele's hair . Sometimes basalt aerates into reticulite , the lowest density rock type on earth. Although Hawaiian eruptions are named after the volcanoes of Hawaii, they are not necessarily restricted to them; the highest lava fountain recorded was during the 23 November 2013 eruption of Mount Etna in Italy, which reached

1566-468: The advancement of "toes", or as a snaking lava column. A'a lava flows are denser and more viscous than pahoehoe, and tend to move slower. Flows can measure 2 to 20 m (7 to 66 ft) thick. A'a flows are so thick that the outside layers cools into a rubble-like mass, insulating the still-hot interior and preventing it from cooling. A'a lava moves in a peculiar way—the front of the flow steepens due to pressure from behind until it breaks off, after which

1624-427: The air before hitting the ground, resulting in the accumulation of cindery scoria fragments; when the air is especially thick with clasts , they cannot cool off fast enough due to the surrounding heat, and hit the ground still hot, the accumulation of which forms spatter cones . If eruptive rates are high enough, they may even form splatter-fed lava flows. Hawaiian eruptions are often extremely long lived; Puʻu ʻŌʻō ,

1682-1087: The air. Columns can measure hundreds of meters in height. The lavas formed by Strombolian eruptions are a form of relatively viscous basaltic lava, and its end product is mostly scoria . The relative passivity of Strombolian eruptions, and its non-damaging nature to its source vent allow Strombolian eruptions to continue unabated for thousands of years, and also makes it one of the least dangerous eruptive types. Strombolian eruptions eject volcanic bombs and lapilli fragments that travel in parabolic paths before landing around their source vent. The steady accumulation of small fragments builds cinder cones composed completely of basaltic pyroclasts . This form of accumulation tends to result in well-ordered rings of tephra . Strombolian eruptions are similar to Hawaiian eruptions , but there are differences. Strombolian eruptions are noisier, produce no sustained eruptive columns , do not produce some volcanic products associated with Hawaiian volcanism (specifically Pele's tears and Pele's hair ), and produce fewer molten lava flows (although

1740-606: The buildup of high gas pressure , eventually popping the cap holding the magma down and resulting in an explosive eruption. Unlike Strombolian eruptions, ejected lava fragments are not aerodynamic; this is due to the higher viscosity of Vulcanian magma and the greater incorporation of crystalline material broken off from the former cap. They are also more explosive than their Strombolian counterparts, with eruptive columns often reaching between 5 and 10 km (3 and 6 mi) high. Lastly, Vulcanian deposits are andesitic to dacitic rather than basaltic . Initial Vulcanian activity

1798-434: The cone. Volcanoes known to have Surtseyan activity include: Submarine eruptions occur underwater. An estimated 75% of volcanic eruptive volume is generated by submarine eruptions near mid ocean ridges alone. Problems detecting deep sea volcanic eruptions meant their details were virtually unknown until advances in the 1990s made it possible to observe them. Submarine eruptions may produce seamounts , which may break

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1856-422: The consistency of wet concrete that move at the speed of a river rapid . Major Plinian eruptive events include: Phreatomagmatic eruptions are eruptions that arise from interactions between water and magma . They are driven by thermal contraction of magma when it comes in contact with water (as distinguished from magmatic eruptions, which are driven by thermal expansion). This temperature difference between

1914-650: The eruption and formation of the island of Surtsey off the coast of Iceland in 1963. Surtseyan eruptions are the "wet" equivalent of ground-based Strombolian eruptions , but because they take place in water they are much more explosive. As water is heated by lava, it flashes into steam and expands violently, fragmenting the magma it contacts into fine-grained ash . Surtseyan eruptions are typical of shallow-water volcanic oceanic islands , but they are not confined to seamounts. They can happen on land as well, where rising magma that comes into contact with an aquifer (water-bearing rock formation) at shallow levels under

1972-441: The eruption of Costa Rica's Irazú Volcano in 1963 was likely triggered by magma that took a nonstop route from the mantle over just a few months. It is important when studying the products of explosive eruptions to distinguish between...: George P. L. Walker , Quoted The volcanic explosivity index (commonly shortened to VEI) is a scale, from 0 to 8, for measuring the strength of eruptions but does not capture all of

2030-512: The eruptions. The three major eruptions are: The Yellowstone Caldera is a resurgent caldera and has experienced resurgent doming . The Yellowstone Caldera has two resurgent domes formed by magma upwelling called Sour Creek and Mallard Lakes. The magma chambers under the Yellowstone Caldera provides heat and energy for large hydrothermal systems. The Yellowstone Caldera has the greatest concentration of hydrothermal features in

2088-466: The eruptive material does tend to form small rivulets). Volcanoes known to have Strombolian activity include: Vulcanian eruptions are a type of volcanic eruption named after the volcano Vulcano . It was named so following Giuseppe Mercalli 's observations of its 1888–1890 eruptions. In Vulcanian eruptions, intermediate viscous magma within the volcano make it difficult for vesiculate gases to escape. Similar to Strombolian eruptions, this leads to

2146-441: The expanding flank finally gives it releases a flow of magma. More explosive lateral eruptions are referred to as lateral blasts. Some of the most notable examples of a lateral eruption include Mount St. Helens , Mount Pelée , and Mount Etna . Most eruptions are caused by the immediate decompression of a magma chamber near the flanks of the volcano. During an eruption, the rapid decompression of magma may cause subsidence of

2204-444: The explosive nature than thermal contraction. Fuel coolant reactions may fragment the volcanic material by propagating stress waves , widening cracks and increasing surface area that ultimately leads to rapid cooling and explosive contraction-driven eruptions. A Surtseyan (or hydrovolcanic) eruption is a type of volcanic eruption characterized by shallow-water interactions between water and lava, named after its most famous example,

2262-429: The general mass behind it moves forward. Pahoehoe lava can sometimes become A'a lava due to increasing viscosity or increasing rate of shear , but A'a lava never turns into pahoehoe flow. Hawaiian eruptions are responsible for several unique volcanological objects. Small volcanic particles are carried and formed by the wind, chilling quickly into teardrop-shaped glassy fragments known as Pele's tears (after Pele ,

2320-434: The growth of bubbles that move up at about the same speed as the magma surrounding them. Regions affected by Plinian eruptions are subjected to heavy pumice airfall affecting an area 0.5 to 50 km (0 to 12 cu mi) in size. The material in the ash plume eventually finds its way back to the ground, covering the landscape in a thick layer of many cubic kilometers of ash. The most dangerous eruptive feature are

2378-423: The magma conduit) they explode. The narrow confines of the conduit force the gases and associated magma up, forming an eruptive column . Eruption velocity is controlled by the gas contents of the column, and low-strength surface rocks commonly crack under the pressure of the eruption, forming a flared outgoing structure that pushes the gases even faster. These massive eruptive columns are the distinctive feature of

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2436-424: The most dangerous in the world, capable of tearing through populated areas and causing serious loss of life. The 1902 eruption of Mount Pelée caused tremendous destruction, killing more than 30,000 people and completely destroying St. Pierre , the worst volcanic event in the 20th century . Peléan eruptions are characterized most prominently by the incandescent pyroclastic flows that they drive. The mechanics of

2494-598: The mountain's north flank. On May 18, 1980 , an earthquake triggered the collapse of the flank and a lateral eruption which killed 57 people. It was the deadliest volcanic event in US history. Bezymianny is a stratovolcano located on the Kamchatka peninsula in Russia . On March 30, 1956, it erupted laterally after a flank collapse similar to that experienced by Mount St. Helens. No fatalities resulted from this eruption due to

2552-403: The one extreme there are effusive Hawaiian eruptions, which are characterized by lava fountains and fluid lava flows , which are typically not very dangerous. On the other extreme, Plinian eruptions are large, violent, and highly dangerous explosive events. Volcanoes are not bound to one eruptive style, and frequently display many different types, both passive and explosive, even in the span of

2610-422: The plume away from the volcano . These highly explosive eruptions are usually associated with volatile-rich dacitic to rhyolitic lavas, and occur most typically at stratovolcanoes . Eruptions can last anywhere from hours to days, with longer eruptions being associated with more felsic volcanoes. Although they are usually associated with felsic magma, Plinian eruptions can occur at basaltic volcanoes, if

2668-693: The properties that may be perceived to be important. It is used by the Smithsonian Institution 's Global Volcanism Program in assessing the impact of historic and prehistoric lava flows. It operates in a way similar to the Richter scale for earthquakes , in that each interval in value represents a tenfold increasing in magnitude (it is logarithmic ). The vast majority of volcanic eruptions are of VEIs between 0 and 2. Magmatic eruptions produce juvenile clasts during explosive decompression from gas release. They range in intensity from

2726-500: The relatively small lava fountains on Hawaii to catastrophic Ultra-Plinian eruption columns more than 30 km (19 mi) high, bigger than the eruption of Mount Vesuvius in 79 AD that buried Pompeii . Hawaiian eruptions are a type of volcanic eruption named after the Hawaiian volcanoes , such as Mauna Loa , with this eruptive type is hallmark. Hawaiian eruptions are the calmest types of volcanic events, characterized by

2784-524: The remote location of the volcano. Subsequent lava dome growth has since filled the 1956 caldera with a new cone. Mount Pelée is a volcano located on Martinique , in the Caribbean . It underwent a lateral eruption on May 8, 1902 , killing 28,000 people in the deadliest volcanic event of the 20th century. San Francisco Peaks in Arizona are the remnants of a single taller volcano that may have had

2842-572: The rising plate, lowering its melting point . Each process generates different rock; mid-ocean ridge volcanics are primarily basaltic , whereas subduction flows are mostly calc-alkaline , and more explosive and viscous . Spreading rates along mid-ocean ridges vary widely, from 2 cm (0.8 in) per year at the Mid-Atlantic Ridge , to up to 16 cm (6 in) along the East Pacific Rise . Higher spreading rates are

2900-732: The strongest eruptions are called Ultra-Plinian . Subglacial and phreatic eruptions are defined by their eruptive mechanism, and vary in strength. An important measure of eruptive strength is the Volcanic Explosivity Index an order-of-magnitude scale, ranging from 0 to 8, that often correlates to eruptive types. Volcanic eruptions arise through three main mechanisms: In terms of activity, there are explosive eruptions and effusive eruptions . The former are characterized by gas-driven explosions that propel magma and tephra. The latter pour out lava without significant explosion. Volcanic eruptions vary widely in strength. On

2958-471: The summit and from fissure vents radiating out of the center. Hawaiian eruptions often begin as a line of vent eruptions along a fissure vent , a so-called "curtain of fire." These die down as the lava begins to concentrate at a few of the vents. Central-vent eruptions, meanwhile, often take the form of large lava fountains (both continuous and sporadic), which can reach heights of hundreds of meters or more. The particles from lava fountains usually cool in

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3016-400: The surface and form volcanic islands. Submarine volcanism is driven by various processes. Volcanoes near plate boundaries and mid-ocean ridges are built by the decompression melting of mantle rock that rises on an upwelling portion of a convection cell to the crustal surface. Eruptions associated with subducting zones , meanwhile, are driven by subducting plates that add volatiles to

3074-424: The two causes violent water-lava interactions that make up the eruption. The products of phreatomagmatic eruptions are believed to be more regular in shape and finer grained than the products of magmatic eruptions because of the differences in eruptive mechanisms. There is debate about the exact nature of phreatomagmatic eruptions, and some scientists believe that fuel-coolant reactions may be more critical to

3132-429: The volcano can cause them. The products of Surtseyan eruptions are generally oxidized palagonite basalts (though andesitic eruptions do occur, albeit rarely), and like Strombolian eruptions Surtseyan eruptions are generally continuous or otherwise rhythmic. A defining feature of a Surtseyan eruption is the formation of a pyroclastic surge (or base surge ), a ground hugging radial cloud that develops along with

3190-467: The volcano's slope. Deposits near the source vent consist of large volcanic blocks and bombs , with so-called " bread-crust bombs " being especially common. These deeply cracked volcanic chunks form when the exterior of ejected lava cools quickly into a glassy or fine-grained shell, but the inside continues to cool and vesiculate . The center of the fragment expands, cracking the exterior. The bulk of Vulcanian deposits are fine grained ash . The ash

3248-463: The volcanoes away from their eruptive source, eruption rates start to die down, and water erosion grinds the volcano down. The final stages of eruption cap the seamount in alkalic flows. There are about 100,000 deepwater volcanoes in the world, although most are beyond the active stage of their life. Some exemplary seamounts are Kamaʻehuakanaloa (formerly Loihi), Bowie Seamount , Davidson Seamount , and Axial Seamount . Subglacial eruptions are

3306-603: The world, and is an active system. The magma, geothermal activity, and hydrothermal system can lead to caldera motion, ash clouds, and earthquakes , so the Yellowstone Caldera is labeled as a geohazard . A large amount of the Yellowstone Plateau volcanic field is in the Yellowstone National Park . 44°28′16″N 110°30′07″W  /  44.471031°N 110.501862°W  / 44.471031; -110.501862 This article about

3364-605: Was flung out by the explosive eruption and followed a ballistic path to the ground. Accumulations of wet, spherical ash known as accretionary lapilli are another common surge indicator. Over time Surtseyan eruptions tend to form maars , broad low- relief volcanic craters dug into the ground, and tuff rings , circular structures built of rapidly quenched lava. These structures are associated with single vent eruptions. If eruptions arise along fracture zones , rift zones may be dug out. Such eruptions tend to be more violent than those which form tuff rings or maars, an example being

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