A title "volcano" originates from either a title of Vulcan, a god of fire inside Roman mythology. A learn of volcanoes is known as vulcanology (or vulcanology within occasionally spellings).

Volcanoes
Types of volcanoes
Of these way of classifying volcanoes is per nature and severity of lesson erupted, which infects a shape of the volcano. In case the erupting magma contains a high percentage (>65%) of silica the lava is called felsic or "Acidic" & tends to exist as super viscous (not super fluid) & is pushed higher inside the blob that may solidify comparatively quickly. Lassen Peak in California is an example. This nature and severity of volcano has the tendency to explode because it well plugs. Mount Pelée on the island of Martinique is another example.

In case, but then, a magma contains comparatively little numbers (<52%) of silicon dioxide, a lava is known as mafic or "Basic" and is super fluid when it erupts, capable of flow for long-distance call. the good case of the mafic lava flow is the Nifty Þjórsárhraun (Thjórsárhraun) flow by an eruptive fissure about in the geographical center of Icel& about 8,000 years ago; it flowed all the way to the sea, a few feet away of 130 kilometers, and covered an region of 800 square klick. Note that a terms felsic & mafic come occasionally substituted per older chemistry terms "acidic" & "basic", severally. A latter were thought to exist as a bit deceptive, notwithstanding, & come slowly falling into neglect.

Shield volcano: Hawaii and Iceland are examples of places in which volcanoes extrude immense quantities of lavthe that step by step build the wide mountain by owning a shield-rather profile. Their lava flows come usually super hot & super fluid, contributing to yearn flows. A big lava shield on Earth, Mauna Loa, is 9,000 m tall (it sits on the sea floor), 120 kilometre from side to side & forms a portion of the Island of Hawai'i. Olympus Mons is a shield volcano on Mars, and a tallest mountain in the known solar models. Smaller versions of the "lava shield" include a lava dome (tholoid), lava cone, & lava mound. Volcanic cones or cinder cones result from either eruptions that throw out mostly little pieces of rock that build higher as much as a vent. These may be comparatively short-ephemeral eruptions that make the cone-conelike hill peradventure 30 to 300 m high. Stratovolcanoes or composite volcanoes come tall cone-shaped mountains composed of each lava flows & ejected lesson, which form a strata which give rise to the title. Classic examples include Mt. Fuji in Japan and Mount Mayon in the Philippines. Supervolcanoes is the popular term for big volcanoes that commonly have a large caldera & can possibly develop devastatiin on the continental shell and induce major spherical upwind pattern changes. Likely candidates include Yellowstone National Park and Lake Toba, but come protective to identify given that no formal definition of the term. Submarine volcanoes are most commin features on certain zones of the ocean bottom. A bit of move at a present instance &, within shallow a water supply, disclose their presence by blasting steam & rock-debris high above a surface of the sea. Several others lie at such swell depths that a wow weight of a a body of water above the two final result within high, confining pressure & prevents the formation & explosive release of steam & gases. Potentially super big, deepwater eruptions might not disturb a ocean surface.

Mud volcanoes are formations which are then typically non associated by having known magmatic activity. Active mud volcanoes tend to require temperatures great deal moo than people of fiery volcanoes, except whenever the mud volcano is actually the vent of an fiery volcano. This article describes fiery volcanoes.

Volcanoes come commonly placed either at a boundaries between tectonic plates or over hotspots. Volcanoes can be either inactive (getting there are no activity) or even active (nigh constant expulsion & occasional eruptions), & turn erratically.

Volcanoes onto land typically choose a form of flat cones, as a expulsions build higher all over a years, or even concisely-passing cinder cones. Under water, volcanoes often form like steep pillars and in good time break a ocean surface in newly islands.

Behavior of volcanoes
There are several different rather volcanic activity & eruptions: phreatic eruptions (steam) explosive eruption of high-silica lava (e.g., rhyolite) effusive eruption of on line-silica lava (e.g., basalt) pyroclastic flows lahars (debris flow) carbon dioxide emission Completely one activities could pose the hazard to man.

Volcanic activity is typically accompanied by earthquakes, hot springs, fumaroles, mud pots and geysers. On line-magnitude earthquakes typically precede eruptions.

Active, Dormant, or Extinct?

Amazingly, no consensus among volcanologists in training define an "active" volcano. a life-time of the volcano may alter from either months to many million years, making such a distinction for instance nonmeaningful once in comparison the life-time of human being or civilizations. E.g., several of Globe's volcanoes use erupted twelve of days it used to be that pack thou years however are non presently showing signs of activity. Given a yearn life-time of such volcanoes, it is super active. By my life-time, notwithstanding, it is does'nt. Complicating a definition come volcanoes that get restless however don't actually erupt. Come these volcanoes active?

Man of science ordinarily assume the volcano active whenever these are presently erupting or even even showing signs of unrest, like unusual earthquake activity or important recently flatulency emissions. Several man of science as well assume the volcano active within case it has erupted in historic period. These are significant to note that a span of recorded history differs from either vicinity to vicinity; in the Mediterranean, recorded history reaches back more than 3,000 years however inside the Pacific Northwest of the United States, it reaches back less than 300 years, & in Hawaii, little more than 200 years.

Inactive volcanoes come victims that are non presently active (equally defined above), however can turn into restless or even erupt once more.

Out volcanoes come people that man of science assume unbelievable to erupt once again. Whether the volcano is truly out is typically hard to determine. Since calderas have lifetime periodically measured inside hundreds to hundreds to thousands of years, the caldera that has non produced an eruption around tens of thousands of years is in all probability to exist as considered inactive instead of out.

For instance, a Yellowstone Caldera (considered a Supervolcano) in Yellowstone National Park is at least 2 million years old & hasn't erupted violently for roughly 640,000 years — although there hwhen been a bit of minor activity when comparatively recent as 70,000 years ago. For this cause, man of science don't assume a Yellowstone Caldera as extinct. In point of fact, because the caldera has frequent earthquakes, a super active geothermic formulas (we.e., a integrality of the geothermic activity observed inside Yellowstone National Park), and rapid rates of ground uplift, several man of science assume it to exist as the super active volcano.

Volcanoes on Earth
Mount Baker (Washington, USA) Cold Bay Volcano (Alaska, USA) El Chichon/El Chichonal, (Chiapas, Mexico) Citlaltépetl/Pico de Orizaba, (Veracruz/Puebla, Mexico) Cotopaxi (Ecuador) Mount Fuji (Honshu, Japan) Mount Hood (Oregon, USA) Mount Erebus (Ross Island, Antarctica) Etna (Sicily, Italy) Krafla (Iceland) Hekla (Iceland) Kick-'em-Jenny, (Grenada) Kilauea (Hawaii, USA) Kluchevskaya (Kamchatka, Russia) Krakatoa (Rakata, Indonesia) Mauna Kea (Hawaii, USA) Mauna Loa (Hawaii, USA) El Misti (Arequipa, Peru) Novarupta (Alaska, USA) Paricutín (Michoacán, Mexico) Mount Pinatubo (Luzon Island, Philippines) Popocatépetl (Mexico-Puebla state line, Mexico) Santorini (Santorini islands, Greece) Soufriere Hills volcano, (Montserrat) Mount Rainier (Washington, USA) Mount Shasta (California, USA) Mount St. Helens (Washington, USA) Surtsey (Iceland) Tambora (Sumbawa, Indonesia) Teide (Tenerife, Canary Islands, Spain) White Island (Bay of Plenty, New Zealand) Mount Vesuvius (Bay of Naples, Italy)

Volcanoes elsewhere in the solar system

Olympus Mons (Latin, "Mount Olympus") is the tallest known mountain in our solar system, located on the Mars.]]

A Globe's Moon has no big volcanoes, however does use numerous volcanic features like rilles and domes.

A planet Venus is believed to be fall active, & its surface is 90% basalt, indicating that volcanism plays a major role within shaping its surface. Lava flows come far flung & numerous of its skin-deep features come attributed to exotic forms of volcanism non present olympian games. More Venusian phenomena, like changes in the planet's atmosphere & observations of lightning, use at times been attributed to on-going volcanic eruptions.

There are many out volcanoes in Mars, four of which are then brobdingnagian shield volcanoes far large than any olympian games:

Arsia Mons Ascraeus Mons Hecates Tholus Olympus Mons Pavonis Mons

These volcanoes own been out for numerous hundreds to thousands of years, however a European Mars Express spacecraft has found grounds to believe that volcanic activity could use occurred in Mars in the recent past also.

Jupiter's moon Io is the most volcanic object in the solar models, due to tidal interaction with Jupiter. These are covered sustaining volcanoes that erupt sulfur, sulfur dioxide and silicate rock, with a effect that a moon is constantly existence resurfaced. Its lavas come a hottest known anywhere in the solar patterns, by having temperatures exceeding 1800 K (1500 °C). Around February 2001, the big recorded volcanic eruptions in the solar rules occurred in Io [http://www2.keck.hawaii.edu/news/archive/eruption/]. Watch a list of geological features on Io for a listings of known as volcanoes on the moon.

A Cassini-Huygens mission has found grounds to believe of the methane-spewing cryovolcano on the Saturnian moon Titan. This volcanism is believed to exist as the important source of the methane noticed inside its atmosphere. [http://www.newscientist.com/article.ns?id=dn7489]

Several 'ice volcanoes' have been uncovered in Triton, a moon of Neptune; they are believed to eject liquid nitrogen, dust, or methane compounds.

A Kuiper Belt Object Quaoar is also suspected of with ice volcanoes.

Volcanology
Volcano formation
Diagram of a destructive margin causing earthquakes and a volcanic eruption Prefer virtually all of a interior of the globe, the movements & moral force of magma come badly understood. But, these are known that an eruption commonly follows movement of magma upwards into a firm layer (a globe's crust) below the volcano & occupying the magma chamber. Finally, magma in a chamber is forced upwards & flows out through the planet surface when lava, or even a rising magma potty heat a water supply in a circumferent landform & stimulator explosive discharges of steam; either this or escaping gases from either the magma might develop emphatic ejections of rocks, cinders, volcanic glass, and/or volcanic ash. When universally displaying right forces, eruptions potty alter from either effusive to super explosive.

Virtually all volcanoes on the land come formed at destructive plate margins: where pelagic crust is forced beneath a continental crust because pelagic crust is denser than continental crust. Friction between these moving plates might are causal agents for a pelagic crust to melt, & decreased density might click a fresh formed magma to rise. When a magma rises across frail arewhen in the continental crust it could sooner or even later erupt as 1 or further volcanoes. E.g., Mount St. Helens is found inland from the margin between the oceanic Juan de Fuca Plate and the continental North American Plate.

Shiprock, New Mexico a volcanic neck in the distance, with radiating dike on its south side. Photo credit: USGS Digital Data Series

The volcano usually presents itself to the imagination as a mountain sending forth river from either its summit smashing clouds of smoke by having brobdingnagian sheets of fire. the truth is that a volcano rarely emits either smoke or flame, although various combinations of hydrogen, carbon, oxygen, and sulfur do sometimes ignite. What is mistaken for smoke consists of huge volumes of ticket dust, mingled using steam & more vapors, mainly sulphurous. Virtually all of what appears to become fire is a glare from either a erupting materials, glowing because of their heat; this glare reflects off the clouds of dust & steam, resembling fire.

Perchance the virtually all blatant a portion of a volcano is the crater, the basin of the about round form inside which occurs a vent (or even vents) from either which magma erupts when gases, lava, & ejecta. The crater may be of big dimensions, & every now and again of huge depth. Super big features of this sort come termed calderas. Occasionally volcanoes consist of the crater alone, by owning scarcely any mountain at all; however in a majority of instances the crater is placed in top of a mountain (the volcano), which might tower to an tremendous height. Volcanoes that terminate inside the main crater come commonly of the conical form.

Volcanic cones come usually little features composed of free ash & clinker, using occasional people of stone which st& been discarded violently into a air per eruptive forces (and are so known as ejecta). In the crater of a volcano there can be many cones from either which vapours come hard-hitting issuing, by having occasional volleys of ashes & stones. Inside a bit of volcanoes these cones form lower down the mountain, along rift zones or even fractures. Once a cone is eroded these rifts or even lava filled fractures remain when radial tire touching vertical dikes of volcanic rock. For instance a radiating dikes at Shiprock in NW New Mexico.

Tectonic environments of volcanoes

Volcanoes might inside the main exist as observed in iii tectonic environments.

Constructive plate margins

Which are actually out and away a usual volcanoes on the Globe. It is as well a least oftentimes seen, because virtually all of their activity will require place below a surface of the oceans. Along a whole of the oceanic ridge system are irregularly separated superficial eruptions, & extra frequent sub-skin-deep intrusions forgoing surface expression. A big majority one come simply known astir at surface because of earthquakes when a share of the eruptions/ intrusions, or even even at times whenever pass transport happens to notice remarkably high a lake temperatures or chemical precipitates in the saltwater. Within two or three site oceanic ridge activity has lead to a volcanoes coming up to the surface - Saint Helena and Tristan da Cunha in the Atlantic Ocean; the Galapagos Islands in the Pacific Ocean, allowing the two to exist as exposed around a bit of detail. However virtually all activity will require place inside considerable fluids depths. Iceland is likewise in the ridge, however has different characteristics than the elementary volcano.

It can be argued that a volcanoes of the Great Rift Valley system of East Africa are modified constructive margin volcanoes. Nevertheless a modifications from either either a presence of heavy continental crust may be real, & a magmas produced may be different from a generally super homogeneous MORB (Mid-Ocean Ridge Basalt) that is a brobdingnagian majority of constructive margin volcanoes.

Destructive plate margins

Which are actually a virtually all seeable & easily-known types of volcanoes olympian games, forming above a subduction zones where (oceanic) plates dive into a Globe to their destruction. Their magmas come usually "calc-alkaline" following of their origins in the upper area of altered ocean shell materials, mixed using deposit, & made across variable thicknesses of other-or even-less continental crust. Unsurprisingly, their compositions come lot extra varied than at constructive margins.

Hotspot situations

Hotspots were originally a catch-everthing for volcanoes that didn't healthy into one of the above 2 categories, however these times this refers to a other specific circumstance - in which an isolated plume of hot mantle material intersects a undersurface of crust (oceanic or continental), leading to the volcanic center that is non apparently attached sustaining a shell margin. A classic lesson is a Hawaiian chain of volcanoes & seamounts; Yellowstone is cited when a second classic pack, in that case a intersection is by using the bottom of continental crust. Iceland is another time cited til now the third definitive case, however complicated per coincidence of the hotspot intersecting an oceanic ridge constructive margin.

There are debates all about a elementary "hotspot" construct, since idealogue just can not agree in whether a "hot mantle plumes" originate in the upper mantle or even in the lower mantle. Meanwhile, field geologists & petrologists understand considerable variation in the elaborated chemistry of a single hotspot's magmas versus another hotspot's magmas. On the third hand, high-guide seismology of different hotspots is yielding different pictures of the deep sub-structure of Hawaii versus Iceland. No elaborate consensus just about training interpret these varied resolutions, & it seems plausible that sooner or later many different sub-types of hotspots is identified.

Predicting eruptions
Science has non eventually been suspire to predict using absolute certainty whenever the volcanic eruption may hap, however important progress around judgment after a single is likely has been processed inside recent instance. Mount St. Helens erupted explosively on May 18, 1980 at 8:32 a.m. PDT Volcanologists apply a as punishment to forecast eruptions.

Seismicity
Seismal activity (little earthquakes & tremors) universally is recognized through it's volcanoes wake up & develop to erupt. A bit of volcanoes usually develop continuing online-subordinate seismal activity, however an increase could signify an eruption. A types of earthquakes that occur & in which it run & prevent come too key signs. Volcanic seismicity has terzetto major forms: short-time period of time earthquakes, long-period earthquakes, & harmonic tremor.

Short-time earthquakes come prefer gravity fault-related earthquakes. It is related to a fracturing of brittle rock when the magma forces its way upward. These short-time period earthquakes signify a incubation of a magma person touching the surface.

Long-period of time earthquakes come believed to suggest increased barking spiders pressure inside the volcano's "plumbing system." It is similar to the clanging for instance heard for your front yard's plumbing. These cycles come a same of acoustical vibrations inside a chamber, in the context of magma chambers inside the volcanic dome.

Harmonic tremor occurs once there exists sustained movement of magma beneath a surface.

System of seismicity come complex & typically hard to interpret. But, increasing activity is very unreassuring, especially whenever long-time period cases be dominant & episodes of harmonic tremor pop up.

Within December 2000, man of science at a National Center for Prevention of Disasters in Mexico City predicted an eruption within 2 years from either Popocatépetl, on the outskirts of Mexico City. Their prediction utilized the food and drug administration done by Dr. Bernard Chouet, a Swiss vulacanologist working at the United States Geological Survey, into increasing long-period cycles as an indicator of an impendent eruption. The food and drug administration evacuated tens of hundreds to thousands of humans. Forty eight hours late, bang prompt, a volcano erupted stunningly. It was Popocatépetl's big eruption for the thous& years and however there are no a single was injured.

Gas emissions
When magma nears a surface & its pressure lessens, gases escape. This run is tremendously prefer what happens when you open the bottle of soda & carbon dioxide escapes. Sulfur dioxide is one of a independent components of volcanic gases, & increasing numbers of it herald a arrival of further & further magma touching a surface. E.g., in May 13, 1991, 500 t of sulfur dioxide were freed from either Mount Pinatubo in the Philippines. In Might 28, good fortnight late, sulfur dioxide emissions got increased to 5,000 mt, 10 days a earliest total. Mount Pinatubo erupted in June 12, 1991. In many occasions, like before a Mount Pinatubo eruption, sulfur dioxide emissions keep close at hand dropped to online levels prior to eruptions. Virtually all man of science guess that this come by flatulency levels is from either a waterproofing of flatulence passages by hardened magma. Such an event leads to increased pressure in the volcano's plumbing & an increased risk of an explosive eruption.

Ground deformation
Swelling of a volcano signals that magma has accumulated touching the surface. Man of science monitoring an active volcano may typically measure a tilt of the slope & track changes in the rate of swelling. An increased rate of swelling, especially within case attended by an increase in sulfur dioxide emissions & harmonic tremors, occurs as high probability sign of an close at hand event.

Effects of volcanoes

A concentrations of different volcanic gases potty alter substantially from either of these volcano to the next. Water vapor is typically a virtually all abundant volcanic flatulence, followed by carbon dioxide and sulfur dioxide. More principal volcanic gases include hydrogen sulfide, hydrogen chloride, and hydrogen fluoride. The big total of shaver & trace gases come likewise incurred inside volcanic emissions, e.g.: hydrogen, carbon monoxide, and volatile metallic chlorides.

Big, explosive volcanic eruptions inject fluids vapor (H_TwoO), carbon dioxide (CO_Ii), sulfur dioxide (Thus_Deuce), hydrogen chloride (HCl), hydrogen fluoride (HF) & ash (pulverised rock & pumice stone) into a stratosphere to heights of 10-20 miles above a Globe's surface. A virtually all important impacts from either either these injections came from a conversion of sulfur dioxide to sulfuric acid (H_DeuceAnd so_Iv), which condenses apace in the stratosphere to form fine sulphate aerosols. A aerosols increase a reflection of radiation from either a Sun back into space & so cool a Globe's moo atmosphere or even troposphere; all a same, it too sop higher heat radiated up from either a Globe, thereby warming the stratosphere. Many eruptions in a period of the preceding century keep close at hand stimulated a decline in the typical temperature at the Globe's surface of as much as half the degree (Fahrenheit shell) for periods of of these to 3 years. A sulphate aerosols besides promote complex reactiin on their shells that vary cl & n chemical coinage in the stratosphere. This symptom, together by owning increased stratospheric atomic number 17 levels from either cfc pollution, generates cl monoxide (ClO), which destroys ozone (O₃). When a aerosols develop & coagulate, it settle down into a upper troposphere in which it help when nuclei for cirrus clouds & farther modify a Globe's radiation balance. Virtually all of the hydrogen chloride (HCl) & hydrogen fluoride (HF) come dissolved within a lake droplets in the eruption cloud & quickly fall to the ground when acid precipitation. A injected ash besides lessens speedily from either a stratosphere; virtually all of these are flushed in many times to two or three weeks. Eventually, explosive volcanic eruptions release the greenhouse emission carbon dioxide & so provide a deep source of carbon for biogeochemical cycles.

Flatulency emissions from either volcanoes come the natural contributor to acid rain.

Volcanic activity okay, releases astir 130 to 230 teragrams (145 million to 255 million short tons) of carbon dioxide each year.

Volcanic eruptions will inject an aerosol of particles and chemical substance in the Earth's atmosphere. Big injections could develop ocular results & affect spherical climate across climate forcing.

Past beliefs

Prior to it was understood that virtually all of the Globe's interior is molten, various explanations existed for volcano behavior. For decades fallowing awareness that compression & radioactive materials can be heat sources, their contributions were specifically discounted. Volcanic action was typically attributed to reaction & a thinly layer of liquefied rock touching the surface.

Jesuit Athanasius Kircher (1602-1680), witnessed eruptions of Aetna and Stromboli, then visited a crater of Vesuvius and published his view of an Globe by using a central fire attached to many others from either the burning of sulfur, bitumen and coal.