Cleveland Volcano in the Aleutian Islands of Alaska photographed from the International Space Station

A volcano is an opening, or rupture, in a planet's surface or crust, which allows hot, molten rock, ash and gases to escape from below the surface. Volcanic activity involving the extrusion of rock tends to form mountains or features like mountains over a period of time. Image File history File links Download high-resolution version (1000x662, 186 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Volcanic ash Mount Cleveland (Alaska) ... Image File history File links Download high-resolution version (1000x662, 186 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Volcanic ash Mount Cleveland (Alaska) ... Mount Cleveland is an active stratovolcano that forms the western half of Chuginadak Island in the central Aleutian Islands of Alaska. ... Aleutians seen from space The Aleutian Islands (possibly from Chukchi aliat, island) are a chain of more than 300 small volcanic islands forming an island arc in the Northern Pacific Ocean, occupying an area of 6,821 sq mi (17,666 km²) and extending about 1,200 mi (1,900... For other uses, see Alaska (disambiguation). ... ISS redirects here. ... Look up volcano in Wiktionary, the free dictionary. ... Eruption can refer to: Volcanic eruption The eruption of teeth through the gum Eruption (band) Eruption (song), from Van Halens first album. ... Earth cutaway from core to exosphere. ... Extrusive refers to a mode of igneous rock formation, in which hot magma from inside the Earth flows out (extrudes) onto the surface. ...

Volcanoes are generally found where tectonic plates are pulled apart or come together. A mid-oceanic ridge, for example the Mid-Atlantic Ridge, has examples of volcanoes caused by "divergent tectonic plates" pulling apart; the Pacific Ring of Fire has examples of volcanoes caused by "convergent tectonic plates" coming together. By contrast, volcanoes are usually not created where two tectonic plates slide past one another. Volcanoes can also form where there is stretching and thinning of the Earth's crust (called "non-hotspot intraplate volcanism"), such as in the African Rift Valley, the Wells Gray-Clearwater Volcanic Field and the Rio Grande Rift in North America and the European Rhine Graben with its Eifel volcanoes. The tectonic plates of the world were mapped in the second half of the 20th century. ... Courtesy USGS The Mid-Atlantic Ridge is an underwater mountain range of the Atlantic Ocean that runs from Iceland to Antarctica, and is the longest mountain range on Earth. ... Courtesy USGS The ridge was central in the breakup of Pangaea that began some 180 million years ago. ... In plate tectonics, a divergent boundary (divergent fault boundary or divergent plate boundary), (but also known as a constructive boundary or an extensional boundary) is a linear feature that exists between two tectonic plates that are moving away from each other. ... “The Ring of Fire” redirects here. ... In plate tectonics, a convergent boundary (convergent fault boundary, convergent plate boundary, or active margin) is where two tectonic plates slide towards each other and usually collide forming either a subduction zone with its associated island arc or an orogenic belt and associated mountain range. ... Earth cutaway from core to exosphere. ... Northern section of the Great Rift Valley. ... The Wells Gray-Clearwater Volcanic Field is a field of volcanoes located in southeastern British Columbia. ... The Rio Grande Rift is a rift valley extending north from Mexico, near El Paso, Texas through New Mexico into central Colorado. ... For other uses, see Rhine (disambiguation). ... Not to be confused with Eiffel Tower. ...

Volcanoes can be caused by "mantle plumes". These so-called "hotspots" , for example at Hawaii, can occur far from plate boundaries. Hotspot volcanoes are also found elsewhere in the solar system, especially on rocky planets and moons. Mantle plumes are a geological phenomenon originally proposed by W. Jason Morgan in 1971. ... In geology, a hotspot is a location on the Earths surface that has experienced active volcanism for a long period of time. ... This article is about the U.S. State. ... This article is about the Solar System. ...

Plate tectonics and hotspots

Divergent plate boundaries

At the mid-oceanic ridges, two tectonic plates diverge from one another. New oceanic crust is being formed by hot molten rock slowly cooling and solidifying. The crust is very thin at mid-oceanic ridges due to the pull of the tectonic plates. The release of pressure due to the thinning of the crust leads to adiabatic expansion, and the partial melting of the mantle. This melt causes the volcanism and makes the new oceanic crust. Most divergent plate boundaries are at the bottom of the oceans, therefore most volcanic activity is submarine, forming new seafloor. Black smokers or deep sea vents are an example of this kind of volcanic activity. Where the mid-oceanic ridge is above sea-level, volcanic islands are formed, for example, Iceland. An oceanic ridge is an underwater mountain range, usually formed by plate tectonics. ... The tectonic plates of the world were mapped in the second half of the 20th century. ... Age of oceanic crust Oceanic crust is the part of Earths lithosphere that surfaces in the ocean basins. ... In thermodynamics, an adiabatic process or an isocaloric process is a thermodynamic process in which no heat is transferred to or from the working fluid. ... Earth cutaway from core to exosphere. ... In plate tectonics, a divergent boundary (divergent fault boundary or divergent plate boundary), (but also known as a constructive boundary or an extensional boundary) is a linear feature that exists between two tectonic plates that are moving away from each other. ... A black smoker in the Atlantic Ocean Black smokers are a type of hydrothermal vent found on the ocean floor. ...

Convergent plate boundaries

Subduction zones are places where two plates, usually an oceanic plate and a continental plate, collide. In this case, the oceanic plate subducts, or submerges under the continental plate forming a deep ocean trench just offshore. The crust is then melted by the heat from the mantle and becomes magma. This is due to the water content lowering the melting temperature. The magma created here tends to be very viscous due to its high silica content, so often does not reach the surface and cools at depth. When it does reach the surface, a volcano is formed. Typical examples for this kind of volcano are Mount Etna and the volcanoes in the Pacific Ring of Fire. Categories: Geology stubs | Plate tectonics ... Magma is molten rock located beneath the surface of the Earth (or any other terrestrial planet), and which often collects in a magma chamber. ... Viscosity is a measure of the resistance of a fluid to deformation under shear stress. ... The chemical compound silicon dioxide, also known as silica, is the oxide of silicon, chemical formula SiO2. ... Etna redirects here. ... “The Ring of Fire” redirects here. ...

Hotspots

Hotspots are not usually located on the ridges of tectonic plates, but above mantle plumes, where the convection of Earth's mantle creates a column of hot material that rises until it reaches the crust, which tends to be thinner than in other areas of the Earth. The temperature of the plume causes the crust to melt and form pipes, which can vent magma. Because the tectonic plates move whereas the mantle plume remains in the same place, each volcano becomes dormant after a while and a new volcano is then formed as the plate shifts over the hotspot. The Hawaiian Islands are thought to be formed in such a manner, as well as the Snake River Plain, with the Yellowstone Caldera being the part of the North American plate currently above the hotspot. In geology, a hotspot is a location on the Earths surface that has experienced active volcanism for a long period of time. ... A lava lamp illustrates the basic concept of a mantle plume. ... Convection in the most general terms refers to the movement of currents within fluids (i. ... This article is about Earth as a planet. ... Earth cutaway from core to exosphere. ... This article is about Earth as a planet. ... Magma is molten rock located beneath the surface of the Earth (or any other terrestrial planet), and which often collects in a magma chamber. ... Map of the Hawaiian Islands, a chain of islands that stretches 2,400 km in a northwesterly direction from the southern tip of the Island of Hawaii. ... Big Southern Buttes Prominence on Snake River Plain The Snake River Plain is a geological feature of (primarily) the American state of Idaho. ... The Yellowstone Caldera is a volcanic caldera in Yellowstone National Park in the United States. ...

Volcanic features

Look inside of a crater.Aerial view of Puʻu ʻŌʻō taken on 9/10/07

The most common perception of a volcano is of a conical mountain, spewing lava and poisonous gases from a crater at its summit. This describes just one of many types of volcano, and the features of volcanoes are much more complicated. The structure and behavior of volcanoes depends on a number of factors. Some volcanoes have rugged peaks formed by lava domes rather than a summit crater, whereas others present landscape features such as massive plateaus. Vents that issue volcanic material (lava, which is what magma is called once it has escaped to the surface, and ash) and gases (mainly steam and magmatic gases) can be located anywhere on the landform. Many of these vents give rise to smaller cones such as Puʻu ʻŌʻō on a flank of Hawaii's Kīlauea. Image File history File links Size of this preview: 800 × 387 pixelsFull resolution (1536 × 743 pixel, file size: 662 KB, MIME type: image/jpeg) File historyClick on a date/time to view the file as it appeared at that time. ... Image File history File links Size of this preview: 800 × 387 pixelsFull resolution (1536 × 743 pixel, file size: 662 KB, MIME type: image/jpeg) File historyClick on a date/time to view the file as it appeared at that time. ... Puu Ōō (often written as Puu Oo, and is roughly pronounced Poo-oo Ohh-ohh or in the IPA) is a cinder/spatter cone in the eastern rift zone of the KÄ«lauea volcano of the Hawaiian Islands. ... This article is about the geometric object, for other uses see Cone. ... Look up lava, Aa, pahoehoe in Wiktionary, the free dictionary. ... Volcanic gases include a variety of substances given off by active (or, at times, by dormant) volcanos. ... Craters on Mount Cameroon Perhaps the most conspicuous part of a volcano is the crater, a basin of a roughly circular form within which occurs a vent (or vents) from which magma erupts as gases, lava, and ejecta. ... One of the Mono Craters, an example of a rhyolite dome. ... This article does not cite its references or sources. ... For other meanings, see Plateau (disambiguation). ... Ash plume from Mt Cleveland, a stratovolcano Diamond Head, a well-known backdrop to Waikiki in Hawaii, is an ash cone that solidified into tuff Volcanic ash consists of very fine rock and mineral particles less than 2 mm in diameter that are ejected from a volcanic vent. ... Cleveland Volcano in the Aleutian Islands of Alaska photographed from the International Space Station For other uses, see Volcano (disambiguation). ... Puu Ōō (which means Hill of the Ōō Bird in Hawaiian, is often written as Puu Oo, and is roughly pronounced Poo-oo Ohh-ohh or in the IPA) is a cinder/spatter cone in the eastern rift zone of the KÄ«lauea volcano of the Hawaiian Islands. ... This article is about the U.S. State. ... KÄ«lauea (IPA: ) is an active volcano in the Hawaiian Islands, one of five shield volcanoes that together form the Island of Hawaii. ...

Indonesia - Lombok: Mount Rinjani - outbreak in 1994.

Other types of volcano include cryovolcanoes (or ice volcanoes), particularly on some moons of Jupiter, Saturn and Neptune; and mud volcanoes, which are formations often not associated with known magmatic activity. Active mud volcanoes tend to involve temperatures much lower than those of igneous volcanoes, except when a mud volcano is actually a vent of an igneous volcano. Image File history File linksMetadata Rinjani_1994. ... Image File history File linksMetadata Rinjani_1994. ... Gunung Rinjani from Gili Trawangan Lombok (1990 pop. ... Mount Rinjani is an active volcano in Indonesia on the island of Lombok. ... Ganesa Macula, a dark feature on Saturns moon Titan, might be a cryovolcanic dome. ... For other uses, see Jupiter (disambiguation). ... This article is about the planet. ... For other uses, see Neptune (disambiguation). ... A gaseous mud volcano The term mud volcano or mud dome is used to refer to formations created by geologically excreted liquids and gases, although there are several different processes which may cause such activity. ... Igneous rocks are formed when molten rock (magma) cools and solidifies, with or without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks. ...

Shield volcanoes

Toes of a pāhoehoe advance across a road in Kalapana on the east rift zone of Kīlauea Volcano in Hawaii.

Main article: Shield volcano

Hawaii and Iceland are examples of places where volcanoes extrude huge quantities of basaltic lava in effusive eruptions that gradually build a wide mountain with a shield-like profile. Their lava flows are generally very hot and very fluid, contributing to long flows. The largest lava shield on Earth, Mauna Loa, rises over 9,000 m from the ocean floor, is 120 km in diameter and forms part of the Big Island of Hawaii, along with other shield volcanoes such as Mauna Kea and Kīlauea. Olympus Mons on Mars is the largest shield volcano and also tallest known mountain in the solar system. Smaller versions of shield volcanoes include lava cones, and lava mounds. Image File history File links Download high resolution version (500x800, 85 KB) Pahoehoe - Hawaiian smooth lava. ... Image File history File links Download high resolution version (500x800, 85 KB) Pahoehoe - Hawaiian smooth lava. ... Look up lava, Aa, pahoehoe in Wiktionary, the free dictionary. ... One of the over 100 houses destroyed by the lava flow in 1990 Kalapana is a town on the Island of Hawai‘i in the Hawaiian Islands that was completely destroyed and partly buried by the eruptive flow of lava from Kīlauea volcano in 1990. ... KÄ«lauea is an active volcano in the Hawaiian Islands, one of five shield volcanoes that together form the Island of Hawaii. ... This article is about the U.S. State. ... Shield volcano A shield volcano is a large volcano with shallow-sloping side. ... This article is about the U.S. State. ... Look up lava, Aa, pahoehoe in Wiktionary, the free dictionary. ... Effusive eruptions are a volcanic phenomenom; in some ways the opposite of explosive eruptions. ... Mauna Loa map Mauna Loa is an active shield volcano in the Hawaiian Islands, one of five volcanoes that form the Island of Hawaii. ... The Island of Hawaii (called the Big Island or Hawaii Island) is a volcanic island in the Pacific Ocean and one of the eight main islands that comprise the U.S. state of Hawaii. ... Mauna Kea is a dormant volcano in the Hawaiian Islands, one of five volcanoes which together form the island of Hawaii. ... KÄ«lauea (IPA: ) is an active volcano in the Hawaiian Islands, one of five shield volcanoes that together form the Island of Hawaii. ... This article is about the volcano on Mars and Solar Systems tallest mountain in Latin, For other uses, see Olympus (disambiguation). ... Adjectives: Martian Atmosphere Surface pressure: 0. ... This article is about the Solar System. ...

Cinder cones

Main article: Volcanic cone

Volcanic cones or cinder cones result from eruptions that erupt mostly small pieces of scoria and pyroclastics (both resemble cinders, hence the name of this volcano type) that build up around the vent. These can be relatively short-lived eruptions that produce a cone-shaped hill perhaps 30 to 400 meters high. Most cinder cones erupt only once. Cinder cones may form as flank vents on larger volcanoes, or occur on their own. Parícutin in Mexico and Sunset Crater in Arizona are examples of cinder cones. Puu Ōō, a cinder-and-spatter cone on KÄ«lauea, Hawaii Volcanic cones are among the simplest volcano formations in the world. ... Puu Ōō, a cinder-and-spatter cone on KÄ«lauea, Hawaii Volcanic cones are among the simplest volcano formations in the world. ... For peaks named Cinder Cone, see list of peaks named Cinder Cone. ... Scoria Scoria is a textural term for macrovesicular volcanic rock ejecta. ... It has been suggested that this article or section be merged with Pyroclastic rock. ... Parícutin (or Volcán de Parícutin, commonly also accented Paricutín or spelled unaccented as Paricutin) is a volcano in the Mexican state of Michoacán, close to a lava-covered village of the same name. ... Sunset Crater is a cinder cone located north of Flagstaff, Arizona in the United States. ... Official language(s) English Spoken language(s) English 74. ...

Stratovolcanoes

In contrast to pāhoehoe, ʻAʻā (pronounced Ah-ah), is a rough, jagged, lava flow.

Main article: Strato volcano

Stratovolcanoes are tall conical mountains composed of lava flows and other ejecta in alternate layers, the strata that give rise to the name. Stratovolcanoes are also known as composite volcanoes. Strato/composite volcanoes are made of cinders, ash and lava. The volcanoes are made by another volcano. Cinders and ash pile on top of each other, then lava flows on top and dries and then the process begins again. Classic examples include Mt. Fuji in Japan, Mount Mayon in the Philippines, and Mount Vesuvius and Stromboli in Italy. Image File history File links Aa_large. ... Image File history File links Aa_large. ... View of Mount Rainier, a stratovolcano. ... A cutaway diagram of a stratovolcano Mount St. ... For other uses, see strata (novel) and strata title. ... Mount Fuji (富士山 Fuji-san, IPA: [ɸuʝisaɴ]) is the highest mountain on the island of Honshu and indeed in all of Japan. ... Mayon Volcano is a volcano in the Philippines. ... This article is about the mountain in Italy. ... Sciara del fuoco For other uses see Stromboli (disambiguation) Stromboli is a small island in the Tyrrhenian Sea, off the north coast of Sicily, containing one of the three active volcanoes in Italy. ...

Super volcanoes

Main article: Supervolcano

Supervolcano is the popular term for a large volcano that usually has a large caldera and can potentially produce devastation on an enormous, sometimes continental, scale. Such eruptions would be able to cause severe cooling of global temperatures for many years afterwards because of the huge volumes of sulfur and ash erupted. They are the most dangerous type of volcano. Examples include Yellowstone Caldera in Yellowstone National Park of western USA, Lake Taupo in New Zealand and Lake Toba in Sumatra, Indonesia. Supervolcanoes are hard to identify centuries later, given the enormous areas they cover. Large igneous provinces are also considered supervolcanoes because of the vast amount of basalt lava erupted. A supervolcano is a volcano that produces the largest and most voluminous kinds of eruption on Earth. ... Satellite image of Santorini. ... This article is about the chemical element. ... The Yellowstone Caldera is a volcanic caldera in Yellowstone National Park in the United States. ... Yellowstone redirects here. ... Lake Taupo is a lake situated in the North Island of New Zealand. ... Lake Toba (Indonesian: Danau Toba) is a lake, 100 km long and 30 km wide, and 505 m. ... Sumatra (also spelled Sumatera) is the sixth largest island in the world (approximately 470,000 km²) and is the largest island entirely in Indonesia (two larger islands, Borneo and New Guinea, are partially in Indonesia). ... Large Igneous provinces (LIPS) were originally defined by Coffin and Eldholm (1992) as areas of Earths surface that contain very large volumes of magmatic rocks (typically basalt but including rhyolites) erupted over extremely short geological time intervals of a few million years or less. ... For the cities, see Basalt, Colorado and Basalt, Idaho. ...

Submarine volcanoes

Main article: Submarine volcano

Pillow lava (NOAA)

Submarine volcanoes are common features on the ocean floor. Some are active and, in shallow water, disclose their presence by blasting steam and rocky debris high above the surface of the sea. Many others lie at such great depths that the tremendous weight of the water above them prevents the explosive release of steam and gases, although they can be detected by hydrophones and discoloration of water because of volcanic gases. Even large submarine eruptions may not disturb the ocean surface. Because of the rapid cooling effect of water as compared to air, and increased buoyancy, submarine volcanoes often form rather steep pillars over their volcanic vents as compared to above-surface volcanoes. They may become so large that they break the ocean surface as new islands. Pillow lava is a common eruptive product of submarine volcanoes. Submarine volcanoes and volcanic vents are common features on certain zones of the ocean floor. ... Image ID: nur05018, National Undersearch Research Program (NURP) Collection Location: Hawaii Photo Date: 1988 July Credit: OAR/National Undersea Research Program (NURP) This NOAA image was previously uploaded as Image:Pillow lava small. ... Image ID: nur05018, National Undersearch Research Program (NURP) Collection Location: Hawaii Photo Date: 1988 July Credit: OAR/National Undersea Research Program (NURP) This NOAA image was previously uploaded as Image:Pillow lava small. ... The National Oceanic and Atmospheric Administration (NOAA) is a scientific agency of the United States Department of Commerce focused on the conditions of the oceans and the atmosphere. ... Submarine volcanoes and volcanic vents are common features on certain zones of the ocean floor. ... A hydrophone is a sound-to-electricity transducer for use in water or other liquids, analogous to a microphone for air. ... Volcanic gases include a variety of substances given off by active (or, at times, by dormant) volcanos. ... Look up lava, Aa, pahoehoe in Wiktionary, the free dictionary. ...

Subglacial volcanoes

Main article: Subglacial volcano

Herðubreið, one of the tuyas in Iceland

Subglacial volcanoes develop underneath icecaps. They are made up of flat lava flows atop extensive pillow lavas and palagonite. When the icecap melts, the lavas on the top collapse leaving a flat-topped mountain. Then, the pillow lavas also collapse, giving an angle of 37.5 degrees. These volcanoes are also called table mountains, tuyas or (uncommonly) mobergs. Very good examples of this type of volcano can be seen in Iceland, however, there are also tuyas in British Columbia. The origin of the term comes from Tuya Butte, which is one of the several tuyas in the area of the Tuya River and Tuya Range in northern British Columbia. Tuya Butte was the first such landform analyzed and so its name has entered the geological literature for this kind of volcanic formation. The Tuya Mountains Provincial Park was recently established to protect this unusual landscape, which lies north of Tuya Lake and south of the Jennings River near the boundary with the Yukon Territory. A subglacial volcano is a volcanic form produced by eruptions beneath a glacier or beneath the surface of a lake within a glacier. ... Image File history File links Metadata Size of this preview: 800 × 533 pixelsFull resolution (1800 × 1200 pixel, file size: 650 KB, MIME type: image/jpeg) File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Image File history File links Metadata Size of this preview: 800 × 533 pixelsFull resolution (1800 × 1200 pixel, file size: 650 KB, MIME type: image/jpeg) File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Herðubreið Herðubreið (1682 m) is a volcano and table mountain (moberg mountain) in the north-east of Iceland at . It is situated in the Highlands of Iceland in the midst of the desert Óðáðahraun and not far from Askja, another famous volcano. ... Herðubreið, Iceland The Table, British Columbia, Canada A tuya is a type of distinctive, flat-topped, steep-sided volcano formed when lava erupts through a thick glacier or ice sheet. ... A subglacial volcano is a volcanic form produced by eruptions beneath a glacier or beneath the surface of a lake within a glacier. ... An ice cap is a dome-shaped water ice mass that covers less than 50,000 km² of land area (usually covering a highland area). ... Look up lava, Aa, pahoehoe in Wiktionary, the free dictionary. ... Palagonite is a form of volcanic glass similar to obsidian but with a chemical composition more closely related to basalt. ... Besides being a famous mountain in Cape Town, South Africa, a number of other mountains have been called Table Mountain: Table Mountain (Washington) is a minor peak with sheer cliff face on the Columbia River Gorge in the Pacific Northwest of the United States. ... Herðubreið, Iceland The Table, British Columbia, Canada A tuya is a type of distinctive, flat-topped, steep-sided volcano formed when lava erupts through a thick glacier or ice sheet. ... Motto: Splendor sine occasu (Latin: Splendour without diminishment) Capital Victoria Largest city Vancouver Official languages English (de facto) Government Lieutenant-Governor Steven Point Premier Gordon Campbell (BC Liberal) Federal representation in Canadian Parliament House seats 36 Senate seats 6 Confederation July 20, 1871 (6th province) Area  Ranked 5th Total 944... Tuya Butte is a Tuya in northcentral British Columbia. ... The Tuya Range is a range of tuyas, located in the Stikine Ranges of the Cassiar Mountains in the Canadian province of British Columbia, near its border with the Yukon territory. ... A landform comprises a geomorphological unit, and is largely defined by its surface form and location in the landscape, as part of the terrain, and as such, is typically an element of topography. ... Tuya Mountains Provincial Park is a provincial park in British Columbia, Canada. ... Motto: none Other Canadian provinces and territories Capital Whitehorse Largest city Whitehorse Commissioner Jack Cable Premier Dennis Fentie (Yukon Party) Area 482,443 km² (9th)  - Land 474,391 km²  - Water 8,052 km² (1. ...

Erupted material

Lava composition

Pāhoehoe Lava flow at Hawaii (island). The picture shows few overflows of a main lava channel.

Another way of classifying volcanoes is by the composition of material erupted (lava), since this affects the shape of the volcano. Lava can be broadly classified into 4 different compositions (Cas & Wright, 1987): Image File history File links Metadata Size of this preview: 800 × 533 pixelsFull resolution (3888 × 2592 pixel, file size: 6. ... Image File history File links Metadata Size of this preview: 800 × 533 pixelsFull resolution (3888 × 2592 pixel, file size: 6. ... Look up lava, Aa, pahoehoe in Wiktionary, the free dictionary. ... The Island of Hawaii (called the Big Island or Hawaii Island) is a volcanic island in the Pacific Ocean and one of the eight main islands that comprise the U.S. state of Hawaii. ... Look up lava, Aa, pahoehoe in Wiktionary, the free dictionary. ... Look up lava, Aa, pahoehoe in Wiktionary, the free dictionary. ...

• If the erupted magma contains a high percentage (>63%) of silica, the lava is called felsic.
  • Felsic lavas (or rhyolites) tend to be highly viscous (not very fluid) and are erupted as domes or short, stubby flows. Viscous lavas tend to form stratovolcanoes or lava domes. Lassen Peak in California is an example of a volcano formed from felsic lava and is actually a large lava dome.
  • Because siliceous magmas are so viscous, they tend to trap volatiles (gases) that are present, which cause the magma to erupt catastrophically, eventually forming stratovolcanoes. Pyroclastic flows (ignimbrites) are highly hazardous products of such volcanoes, since they are composed of molten volcanic ash too heavy to go up into the atmosphere, so they hug the volcano's slopes and travel far from their vents during large eruptions. Temperatures as high as 1,200 °C are known to occur in pyroclastic flows, which will incinerate everything flammable in their path and thick layers of hot pyroclastic flow deposits can be laid down, often up to many meters thick. Alaska's Valley of Ten Thousand Smokes, formed by the eruption of Novarupta near Katmai in 1912, is an example of a thick pyroclastic flow or ignimbrite deposit. Volcanic ash that is light enough to be erupted high into the Earth's atmosphere may travel many kilometres before it falls back to ground as a tuff.
• If the erupted magma contains 52–63% silica, the lava is of intermediate composition.
  • These "andesitic" volcanoes generally only occur above subduction zones (e.g. Mount Merapi in Indonesia).
• If the erupted magma contains <52% and >45% silica, the lava is called mafic (because it contains higher percentages of magnesium (Mg) and iron (Fe)) or basaltic. These lavas are usually much less viscous than rhyolitic lavas, depending on their eruption temperature; they also tend to be hotter than felsic lavas. Mafic lavas occur in a wide range of settings:
  • At mid-ocean ridges, where two oceanic plates are pulling apart, basaltic lava erupts as pillows to fill the gap;
  • Shield volcanoes (e.g. the Hawaiian Islands, including Mauna Loa and Kilauea), on both oceanic and continental crust;
  • As continental flood basalts.
• Some erupted magmas contain <=45% silica and produce ultramafic lava. Ultramafic flows, also known as komatiites, are very rare; indeed, very few have been erupted at the Earth's surface since the Proterozoic, when the planet's heat flow was higher. They are (or were) the hottest lavas, and probably more fluid than common mafic lavas.

Magma is molten rock located beneath the surface of the Earth (or any other terrestrial planet), and which often collects in a magma chamber. ... The chemical compound silicon dioxide, also known as silica, is the oxide of silicon, chemical formula SiO2. ... Felsic is a term used in geology to refer to silicate minerals, magmas, and rocks which are enriched in the lighter elements such as silica, oxygen, aluminium, sodium, and potassium. ... This page is about a volcanic rock. ... Viscosity is a measure of the resistance of a fluid to deformation under shear stress. ... A cutaway diagram of a stratovolcano Mount St. ... One of the Mono Craters, an example of a rhyolite dome. ... Lassen Peak[1] (also known as Mount Lassen) is the southernmost active volcano in the Cascade Range. ... This article is about the U.S. state. ... Volatiles are that group of compounds with low boiling points (see volatile) that are associated with a planets or moons crust and/or atmosphere. ... A cutaway diagram of a stratovolcano Mount St. ... Pyroclastic flows sweep down the flanks of Mayon Volcano, Philippines, in 1984 A pyroclastic flow (also known as a pyroclastic density current) is a common and devastating result of some volcanic eruptions. ... Ignimbrite is a volcanic pyroclastic rock, often of dacitic or rhyolitic composition. ... Pyroclastic flows sweep down the flanks of Mayon Volcano, Philippines, in 1984 A pyroclastic flow (also known as a pyroclastic density current) is a common and devastating result of some volcanic eruptions. ... For other uses, see Alaska (disambiguation). ... The Valley of Ten Thousand Smokes is a valley within Katmai National Park and Preserve in Alaska which is filled with ash flow from the eruption of Novarupta on June 6-June 8, 1912. ... Novarupta, meaning new eruption, is a volcano located on the Alaska Peninsula in the Katmai area, about 290 miles southwest of Anchorage. ... Katmai can mean: Katmai National Park and Preserve - a park in Alaska Mount Katmai - a volcano in the Katmai Park in Alaska; the site of a colossal 1912 eruption Katmai - Pentium III computer microprocessor core USS Mount Katmai (AE-16) - an ammunition ship in the US Navy from 1945-1973... Pyroclastic flows sweep down the flanks of Mayon Volcano, Philippines, in 1984 A pyroclastic flow (also known as a pyroclastic density current) is a common and devastating result of some volcanic eruptions. ... Ignimbrite is a volcanic pyroclastic rock, often of dacitic or rhyolitic composition. ... Air redirects here. ... Welded tuff at Golden Gate in Yellowstone National Park Tuff (from the Italian tufo) is a type of rock consisting of consolidated volcanic ash ejected from vents during a volcanic eruption. ... A sample of andesite (dark groundmass) with amygdaloidal vesicules filled with zeolite. ... Categories: Geology stubs | Plate tectonics ... Mount Merapi, Gunung Merapi in Indonesian language, is a conical volcano in Central Java, Indonesia. ... In geology, mafic minerals and rocks are silicate minerals, magmas, and volcanic and intrusive igneous rocks that have relatively high concentrations of the heavier elements. ... General Name, symbol, number magnesium, Mg, 12 Chemical series alkaline earth metals Group, period, block 2, 3, s Appearance silvery white solid at room temp Standard atomic weight 24. ... For other uses, see Iron (disambiguation). ... For the cities, see Basalt, Colorado and Basalt, Idaho. ... For other uses, see Temperature (disambiguation). ... Oceanic Ridge Oceanic crust is formed at an oceanic ridge, while the lithosphere is subducted back into the asthenosphere at trenches. ... The tectonic plates of the world were mapped in the second half of the 20th century. ... Look up lava, Aa, pahoehoe in Wiktionary, the free dictionary. ... Mauna Kea, a shield volcano, on the Island of Hawai&#8216;i with a light dusting of snow. ... Map of the Hawaiian Islands, a chain of islands that stretches 2,400 km in a northwesterly direction from the southern tip of the Island of Hawaii. ... Mauna Loa map Mauna Loa is an active shield volcano in the Hawaiian Islands, one of five volcanoes that form the Island of Hawaii. ... KÄ«lauea is an active volcano in the Hawaiian Islands, one of five shield volcanoes that together form the Island of Hawaii. ... Age of oceanic crust Oceanic crust is the part of Earths lithosphere that surfaces in the ocean basins. ... The thickness of the Earths crust (km). ... Moses Coulee showing multiple flood basalt flows of the Columbia River Basalt Group. ... Ultramafic (or ultrabasic) rocks are igneous rocks with very low silica content (less than 45%), generally >18% MgO, high FeO, low potassium and are composed of usually greater than 90% mafic minerals (dark colored, high magnesium and iron content). ... Komatiites are ultramafic mantle-derived volcanic rocks. ... The Proterozoic (IPA: ) is a geological eon representing a period before the first abundant complex life on Earth. ...

Lava texture

Two types of lava are named according to the surface texture: ʻAʻa (pronounced [ʔaʔa]) and pāhoehoe (pronounced IPA: paːhoehoe), both words having Hawaiian origins. ʻAʻa is characterized by a rough, clinkery surface and is what most viscous and hot lava flows look like. However, even basaltic or mafic flows can be erupted as ʻaʻa flows, particularly if the eruption rate is high and the slope is steep. Pāhoehoe is characterized by its smooth and often ropey or wrinkly surface and is generally formed from more fluid lava flows. Usually, only mafic flows will erupt as pāhoehoe, since they often erupt at higher temperatures or have the proper chemical make-up to allow them to flow at a higher fluidity. An open surface with X-, Y-, and Z-contours shown. ... Look up lava, Aa, pahoehoe in Wiktionary, the free dictionary. ... The Hawaiian language is an Austronesian language that takes its name from HawaiÊ»i, the largest island in the tropical North Pacific archipelago where it developed. ...

Volcanic activity

A volcanic fissure and lava channel.

Mount St. Helens in May 1980, shortly after the eruption of May 18

A popular way of classifying magmatic volcanoes is by their frequency of eruption, with those that erupt regularly called active, those that have erupted in historical times but are now quiet called dormant, and those that have not erupted in historical times called extinct. However, these popular classifications—extinct in particular—are practically meaningless to scientists. They use classifications which refer to a particular volcano's formative and eruptive processes and resulting shapes, which was explained above. Wikipedia does not have an article with this exact name. ... Wikipedia does not have an article with this exact name. ... A fissure vent is a linear volcanic vent through which lava erupts, usually without any explosive activity. ... Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... For the mountain in California, see Mount Saint Helena. ... The 1980 eruption of Mount St. ... Towering over the city of Naples, Vesuvius is dormant but certainly not extinct A dormant volcano is a volcano which is not currently erupting, but is believed to still be capable of erupting in the future. ...

There is no real consensus among volcanologists on how to define an "active" volcano. The lifespan of a volcano can vary from months to several million years, making such a distinction sometimes meaningless when compared to the lifespans of humans or even civilizations. For example, many of Earth's volcanoes have erupted dozens of times in the past few thousand years but are not currently showing signs of eruption. Given the long lifespan of such volcanoes, they are very active. By human lifespans, however, they are not.

Scientists usually consider a volcano to be active if it is currently erupting or showing signs of unrest, such as unusual earthquake activity or significant new gas emissions. Many scientists also consider a volcano active if it has erupted in historic time. It is important to note that the span of recorded history differs from region to region; in the Mediterranean, recorded history reaches back more than 3,000 years but in the Pacific Northwest of the United States, it reaches back less than 300 years, and in Hawaii, little more than 200 years. The Smithsonian Global Volcanism Program's definition of 'active' is having erupted within the last 10,000 years. The Mediterranean Sea is an intercontinental sea positioned between Europe to the north, Africa to the south and Asia to the east, covering an approximate area of 2. ... This article is about the U.S. State. ...

Dormant volcanoes are those that are not currently active (as defined above), but could become restless or erupt again. Confusion however, can arise because many volcanoes which scientists consider to be active are referred to as dormant by laypersons or in the media.

Extinct volcanoes are those that scientists consider unlikely to erupt again. Whether a volcano is truly extinct is often difficult to determine. Since "supervolcano" calderas can have eruptive lifespans sometimes measured in millions of years, a caldera that has not produced an eruption in tens of thousands of years is likely to be considered dormant instead of extinct. For example, the Yellowstone Caldera in Yellowstone National Park is at least 2 million years old and hasn't erupted violently for approximately 640,000 years, although there has been some minor activity relatively recently, with hydrothermal eruptions less than 10,000 years ago and lava flows about 70,000 years ago. For this reason, scientists do not consider the Yellowstone Caldera extinct. In fact, because the caldera has frequent earthquakes, a very active geothermal system (i.e. the entirety of the geothermal activity found in Yellowstone National Park), and rapid rates of ground uplift, many scientists consider it to be an active volcano. Satellite image of Santorini. ... The Yellowstone Caldera is a volcanic caldera in Yellowstone National Park in the United States. ... Yellowstone redirects here. ...

Notable volcanoes

Main article: List of volcanoes

The 16 current Decade Volcanoes are: This is a list of lists of active and extinct volcanoes sorted by country. ... A map showing locations of the 16 Decade Volcanoes The Decade Volcanoes are 16 volcanoes identified by the International Association of Volcanology and Chemistry of the Earths Interior (IAVCEI) as being worthy of particular study in light of their history of large, destructive eruptions and proximity to populated areas. ...

Avachinsky-Koryaksky, Kamchatka, Russia Colima, Mexico Mount Etna, Sicily, Italy Galeras, Colombia Mauna Loa, Hawaii, USA Merapi, Indonesia Nyiragongo, Democratic Republic of the Congo Mount Rainier, Washington, USA

Sakurajima, Japan Santamaria/Santiaguito, Guatemala Santorini, Greece Taal Volcano, Philippines Teide, Canary Islands, Spain Ulawun, Papua New Guinea Mount Unzen, Japan Vesuvius, Italy

Avachinsky is a volcano on the Kamchatka Peninsula in the far east of Russia. ... Koryaksky is a volcano on the Kamchatka Peninsula in the far east of Russia. ... “Kamchatka” redirects here. ... Colimas Volcano is the most active volcano in Mexico, and has erupted more than 40 times since 1576. ... Etna redirects here. ... Sicily ( in Italian and Sicilian) is an autonomous region of Italy and the largest island in the Mediterranean Sea, with an area of 25,708 km² (9,926 sq. ... Galeras is a volcano in Colombia, near the city of Pasto. ... Mauna Loa map Mauna Loa is an active shield volcano in the Hawaiian Islands, one of five volcanoes that form the Island of Hawaii. ... This article is about the U.S. State. ... Mount Merapi, Gunung Merapi in Indonesian language, is a conical volcano in Central Java, Indonesia. ... Mount Nyiragongo is a dormant volcano in the Virunga Mountains associated with the Great Rift Valley or East African Rift. ... For other uses, see Mount Rainier (disambiguation). ... For the capital city of the United States, see Washington, D.C.. For other uses, see Washington (disambiguation). ... Sakurajima (桜島火山) is an active volcano and a former island (now connected to the mainland) of the same name in Kagoshima Prefecture in KyÅ«shÅ«, Japan. ... Volcán Santamaria is a large active volcano in the Western Highlands of Guatemala, close to the city of Quetzaltenango. ... Santorini (Greek Σαντορίνη, IPA: ) is a small, circular archipelago of volcanic islands located in southern Aegean Sea, about 200 km south-east from Greeces mainland. ... Taal Volcano is an active volcano on the island of Luzon in the Philippines. ... Teide (Mount Teide or Pico del Teide) is a volcano and mountain on Tenerife, Canary Islands (28. ... Anthem: Arrorró Capital Las Palmas de Gran Canaria and Santa Cruz de Tenerife Official language(s) Spanish Area  â€“ Total  â€“ % of Spain Ranked 13th  7,447 km²  1. ... Ulawun is a volcano situated on the island of New Britain, Papua New Guinea, about 130 km southwest of Rabaul. ... Mount Unzen (雲仙岳) is an active volcano near the city of Shimabara in Nagasaki Prefecture on the island of Kyushu in Japan. ... Mount Vesuvius (Italian: Monte Vesuvio) is a volcano east of Naples, Italy, located at 40°49&#8242;N 14°26&#8242; E. It is the only active volcano on the European mainland, although it is not currently erupting. ...

Effects of volcanoes

Volcanic "injection"

Solar radiation reduction from volcanic eruptions

Sulfur dioxide emissions by volcanoes.

Average concentration of sulfur dioxide over the Sierra Negra Volcano (Galapagos Islands) from October 23–November 1, 2005

There are many different kinds of volcanic activity and eruptions: phreatic eruptions (steam-generated eruptions), explosive eruption of high-silica lava (e.g., rhyolite), effusive eruption of low-silica lava (e.g., basalt), pyroclastic flows, lahars (debris flow) and carbon dioxide emission. All of these activities can pose a hazard to humans. Earthquakes, hot springs, fumaroles, mud pots and geysers often accompany volcanic activity. Image File history File links Volcanic_injection. ... Image File history File links Volcanic_injection. ... Mauna Loa Observatory atmospheric transmission. ... Mauna Loa Observatory atmospheric transmission. ... Download high resolution version (839x500, 165 KB)TOMS chart of sulfur dioxide emissions from volcanoes. ... Download high resolution version (839x500, 165 KB)TOMS chart of sulfur dioxide emissions from volcanoes. ... Image File history File links SO2_Galapagos_20051101. ... Image File history File links SO2_Galapagos_20051101. ... NASA Satellite photo of the Galápagos archipelago. ... Categories: Geology stubs | Volcanoes ... The chemical compound silicon dioxide, also known as silica, is the oxide of silicon, chemical formula SiO2. ... Look up lava, Aa, pahoehoe in Wiktionary, the free dictionary. ... This page is about a volcanic rock. ... For the cities, see Basalt, Colorado and Basalt, Idaho. ... Pyroclastic flows sweep down the flanks of Mayon Volcano, Philippines, in 1984 A pyroclastic flow (also known as a pyroclastic density current) is a common and devastating result of some volcanic eruptions. ... Lahar from a March 1982 eruption of Mount St. ... Carbon dioxide is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. ... This article is about the natural seismic phenomenon. ... Green Dragon Spring at Norris Geyser A hot spring is a place where warm or hot groundwater issues from the ground on a regular basis for at least a predictable part of the year, and is significantly above the ambient ground temperature (which is usually around 55~57 F or... “Solfatara” redirects here. ... Fountain Paint Pots, Yellowstone National Park A mud pot (technically known as solfatare) is a hot spring or fumarole formed in high-temperature geothermal areas where water is in short supply. ... Strokkur geyser, Iceland A geyser is a type of hot spring that erupts periodically, ejecting a column of hot water and steam into the air. ...

The concentrations of different volcanic gases can vary considerably from one volcano to the next. Water vapor is typically the most abundant volcanic gas, followed by carbon dioxide and sulfur dioxide. Other principal volcanic gases include hydrogen sulfide, hydrogen chloride, and hydrogen fluoride. A large number of minor and trace gases are also found in volcanic emissions, for example hydrogen, carbon monoxide, halocarbons, organic compounds, and volatile metal chlorides. Volcanic gases include a variety of substances given off by active (or, at times, by dormant) volcanos. ... Water vapor or water vapour (see spelling differences), also aqueous vapor, is the gas phase of water. ... Carbon dioxide is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. ... Sulfur dioxide (or Sulphur dioxide) has the chemical formula SO2. ... Hydrogen sulfide (hydrogen sulphide in British English) is the chemical compound with the formula H2S. This colorless, toxic and flammable gas is responsible for the foul odor of rotten eggs and flatulence. ... R-phrases , S-phrases , , , , Flash point non-flammable Supplementary data page Structure and properties n, εr, etc. ... Hydrogen fluoride is a chemical compound with the formula HF. Together with hydrofluoric acid, it is the principal industrial source of fluorine and hence the precursor to many important compounds including pharmaceuticals and polymers (e. ... This article is about the chemistry of hydrogen. ... Carbon monoxide, with the chemical formula CO, is a colorless, odorless, and tasteless gas. ...