Volcano

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Sabancaya volcano erupting, Peru in 2017

A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface.

On Earth, volcanoes are most often found where

Hawaiian hotspot
is an example. Volcanoes are usually not created where two tectonic plates slide past one another.

Large eruptions can affect atmospheric temperature as ash and droplets of sulfuric acid obscure the Sun and cool Earth's troposphere. Historically, large volcanic eruptions have been followed by volcanic winters which have caused catastrophic famines.[1]

Other planets besides Earth have volcanoes. For example, volcanoes are very numerous on Venus.[2] In 2009, a paper was published suggesting a new definition for the word ‘volcano’ that includes processes such as cryovolcanism. It suggested that a volcano be defined as ‘an opening on a planet or moon’s surface from which magma, as defined for that body, and/or magmatic gas is erupted.’[3]

This article mainly covers volcanoes on Earth. See § Volcanoes on other celestial bodies and Cryovolcano for more information.

Etymology

The word volcano is derived from the name of Vulcano, a volcanic island in the Aeolian Islands of Italy whose name in turn comes from Vulcan, the god of fire in Roman mythology.[4] The study of volcanoes is called volcanology, sometimes spelled vulcanology.[5]

Plate tectonics

Map showing the divergent plate boundaries (oceanic spreading ridges) and recent sub-aerial volcanoes (mostly at convergent boundaries)

According to the theory of plate tectonics, Earth's lithosphere, its rigid outer shell, is broken into sixteen larger and several smaller plates. These are in slow motion, due to convection in the underlying ductile mantle, and most volcanic activity on Earth takes place along plate boundaries, where plates are converging (and lithosphere is being destroyed) or are diverging (and new lithosphere is being created).[6]

During the development of geological theory, certain concepts that allowed the grouping of volcanoes in time, place, structure and composition have developed that ultimately have had to be explained in the theory of plate tectonics. For example, some volcanoes are polygenetic with more than one period of activity during their history; other volcanoes that become extinct after erupting exactly once are monogenetic (meaning "one life") and such volcanoes are often grouped together in a geographical region.[7]

Divergent plate boundaries

At the

Black smokers (also known as deep sea vents) are evidence of this kind of volcanic activity. Where the mid-oceanic ridge is above sea level, volcanic islands are formed, such as Iceland.[8]

Convergent plate boundaries

Japanese Archipelago, or the eastern islands of Indonesia.[9]

Hotspots

Hotspots are volcanic areas thought to be formed by mantle plumes, which are hypothesized to be columns of hot material rising from the core-mantle boundary. As with mid-ocean ridges, the rising mantle rock experiences decompression melting which generates large volumes of magma. Because tectonic plates move across mantle plumes, each volcano becomes inactive as it drifts off the plume, and new volcanoes are created where the plate advances over the plume. The Hawaiian Islands are thought to have been formed in such a manner, as has the Snake River Plain, with the Yellowstone Caldera being the part of the North American plate currently above the Yellowstone hotspot.[10] However, the mantle plume hypothesis has been questioned.[11]

Continental rifting

Sustained upwelling of hot mantle rock can develop under the interior of a continent and lead to rifting. Early stages of rifting are characterized by flood basalts and may progress to the point where a tectonic plate is completely split.[12][13] A divergent plate boundary then develops between the two halves of the split plate. However, rifting often fails to completely split the continental lithosphere (such as in an aulacogen), and failed rifts are characterized by volcanoes that erupt unusual alkali lava or carbonatites. Examples include the volcanoes of the East African Rift.[14]

Volcanic features

Video of lava agitating and bubbling in the volcano eruption of Litli-Hrútur, 2023

A volcano needs a reservoir of molten magma (e.g. a magma chamber), a conduit to allow magma to rise through the crust, and a vent to allow the magma to escape above the surface as lava.[15] The erupted volcanic material (lava and tephra) that is deposited around the vent is known as a volcanic edifice, typically a volcanic cone or mountain.[15]

The most common perception of a volcano is of a

Puʻu ʻŌʻō on a flank of Kīlauea in Hawaii. Volcanic craters are not always at the top of a mountain or hill and may be filled with lakes such as with Lake Taupō
in New Zealand. Some volcanoes can be low relief landform features, with the potential to be hard to recognise as such, and be obscured by geological processes.

Other types of volcano include

igneous
volcanoes except when the mud volcano is actually a vent of an igneous volcano.

Fissure vents

Lakagigar fissure vent in Iceland, the source of the major world climate alteration of 1783–84, has a chain of volcanic cones along its length.

Volcanic fissure vents are flat, linear fractures through which lava emerges.

Shield volcanoes

Skjaldbreiður, a shield volcano whose name means "broad shield"

Shield volcanoes, so named for their broad, shield-like profiles, are formed by the eruption of low-viscosity lava that can flow a great distance from a vent. They generally do not explode catastrophically, but are characterized by relatively gentle effusive eruptions. Since low-viscosity magma is typically low in silica, shield volcanoes are more common in oceanic than continental settings. The Hawaiian volcanic chain is a series of shield cones, and they are common in Iceland, as well.

Lava domes

Lava domes are built by slow eruptions of highly viscous lava. They are sometimes formed within the crater of a previous volcanic eruption, as in the case of Mount St. Helens, but can also form independently, as in the case of Lassen Peak. Like stratovolcanoes, they can produce violent, explosive eruptions, but the lava generally does not flow far from the originating vent.

Cryptodomes

Cryptodomes are formed when viscous lava is forced upward causing the surface to bulge. The 1980 eruption of Mount St. Helens was an example; lava beneath the surface of the mountain created an upward bulge, which later collapsed down the north side of the mountain.

Cinder cones

Izalco volcano, the youngest volcano in El Salvador. Izalco erupted almost continuously from 1770 (when it formed) to 1958, earning it the nickname of "Lighthouse of the Pacific".

Cinder cones result from eruptions of mostly small pieces of

tuff rings.[16] 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. In New Mexico, Caja del Rio is a volcanic field
of over 60 cinder cones.

Based on satellite images, it has been suggested that cinder cones might occur on other terrestrial bodies in the Solar system too; on the surface of Mars and the Moon.[17][18][19][20]

Stratovolcanoes (composite volcanoes)

Cross-section through a stratovolcano (vertical scale is exaggerated):
  1. Large magma chamber
  2. Bedrock
  3. Conduit (pipe)
  4. Base
  5. Sill
  6. Dike
  7. Layers of ash emitted by the volcano
  8. Flank
  9. Layers of lava emitted by the volcano
  10. Throat
  11. Parasitic cone
  12. Lava flow
  13. Vent
  14. Crater
  15. Ash cloud

Stratovolcanoes (composite volcanoes) are tall conical mountains composed of lava flows and

Mayon Volcano in the Philippines, and Mount Vesuvius and Stromboli
in Italy.

Ash produced by the explosive eruption of stratovolcanoes has historically posed the greatest volcanic hazard to civilizations. The lavas of stratovolcanoes are higher in silica, and therefore much more viscous, than lavas from shield volcanoes. High-silica lavas also tend to contain more dissolved gas. The combination is deadly, promoting explosive eruptions that produce great quantities of ash, as well as pyroclastic surges like the one that destroyed the city of Saint-Pierre in Martinique in 1902. They are also steeper than shield volcanoes, with slopes of 30–35° compared to slopes of generally 5–10°, and their loose tephra are material for dangerous lahars.[21] Large pieces of tephra are called volcanic bombs. Big bombs can measure more than 4 feet (1.2 meters) across and weigh several tons.[22]

Supervolcanoes

A supervolcano is a volcano that has experienced one or more eruptions that produced over 1,000 cubic kilometers (240 cu mi) of volcanic deposits in a single explosive event.[23] Such eruptions occur when a very large magma chamber full of gas-rich, silicic magma is emptied in a catastrophic caldera-forming eruption. Ash flow tuffs emplaced by such eruptions are the only volcanic product with volumes rivaling those of flood basalts.[24]

A supervolcano can produce devastation on a continental scale. Such volcanoes are able to severely cool global temperatures for many years after the eruption due to the huge volumes of

Ngorongoro Crater in Tanzania. Fortunately, supervolcano eruptions are very rare events, though because of the enormous area they cover, and subsequent concealment under vegetation and glacial deposits, supervolcanoes can be difficult to identify in the geologic record without careful geologic mapping.[25]

Submarine volcanoes

Hunga Tonga-Hunga Haʻapai

Submarine volcanoes are common features of the ocean floor. Volcanic activity during the

some support peculiar ecosystems based on chemotrophs feeding on dissolved minerals. Over time, the formations created by submarine volcanoes may become so large that they break the ocean surface as new islands or floating pumice rafts
.

In May and June 2018, a multitude of

oceanographic research campaign in May 2019 showed that the previously mysterious humming noises were caused by the formation of a submarine volcano off the coast of Mayotte.[28]

Subglacial volcanoes

Subglacial volcanoes develop underneath

Yukon Territory
.

Mud volcanoes

Mud volcanoes (mud domes) are formations created by geo-excreted liquids and gases, although there are several processes which may cause such activity.[32] The largest structures are 10 kilometers in diameter and reach 700 meters high.[33]

Erupted material

Timelapse of San Miguel (volcano) degassing in 2022. El Salvador is home to 20 Holocene volcanoes, 3 of which have erupted in last 100yrs[34]
Pāhoehoe lava flow on Hawaii. The picture shows overflows of a main lava channel.
Litli-Hrútur (Fagradalsfjall) eruption 2023. View from an airplane
The Stromboli stratovolcano off the coast of Sicily has erupted continuously for thousands of years, giving rise to its nickname "Lighthouse of the Mediterranean".

The material that is expelled in a volcanic eruption can be classified into three types:

  1. Volcanic gases, a mixture made mostly of steam, carbon dioxide, and a sulfur compound (either sulfur dioxide, SO2, or hydrogen sulfide, H2S, depending on the temperature)
  2. Lava, the name of magma when it emerges and flows over the surface
  3. Tephra, particles of solid material of all shapes and sizes ejected and thrown through the air[35][36]

Volcanic gases

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[37] 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.

Lava flows

Mount Rinjani eruption in 1994, in Lombok, Indonesia

The form and style of eruption of a volcano is largely determined by the composition of the lava it erupts. The viscosity (how fluid the lava is) and the amount of dissolved gas are the most important characteristics of magma, and both are largely determined by the amount of silica in the magma. Magma rich in silica is much more viscous than silica-poor magma, and silica-rich magma also tends to contain more dissolved gases.

Lava can be broadly classified into four different compositions:[38]

  • If the erupted
    viscous and are erupted as domes or short, stubby flows.[39] Lassen Peak in California is an example of a volcano formed from felsic lava and is actually a large lava dome.[40]
Because felsic magmas are so viscous, they tend to trap volatiles (gases) that are present, which leads to explosive volcanism.
Earth's atmosphere as an eruption column may travel hundreds of kilometers before it falls back to ground as a fallout tuff. Volcanic gases may remain in the stratosphere for years.[44]
Felsic magmas are formed within the crust, usually through melting of crust rock from the heat of underlying mafic magmas. The lighter felsic magma floats on the mafic magma without significant mixing.[45] Less commonly, felsic magmas are produced by extreme fractional crystallization of more mafic magmas.[46] This is a process in which mafic minerals crystallize out of the slowly cooling magma, which enriches the remaining liquid in silica.
  • If the erupted magma contains 52–63% silica, the lava is of
    tectonic plates, by several processes. One process is hydration melting of mantle peridotite followed by fractional crystallization. Water from a subducting slab rises into the overlying mantle, lowering its melting point, particularly for the more silica-rich minerals. Fractional crystallization further enriches the magma in silica. It has also been suggested that intermediate magmas are produced by melting of sediments carried downwards by the subducted slab.[48] Another process is magma mixing between felsic rhyolitic and mafic basaltic magmas in an intermediate reservoir prior to emplacement or lava flow.[49]
  • 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 hotter and much less viscous than felsic lavas. Mafic magmas are formed by partial melting of dry mantle, with limited fractional crystallization and assimilation of crustal material.[50]
Mafic lavas occur in a wide range of settings. These include
Kilauea), on both oceanic and continental crust; and as continental flood basalts
.

Mafic lava flows show two varieties of surface texture: ʻAʻa (pronounced

pāhoehoe ([paːˈho.eˈho.e]), both Hawaiian words. ʻAʻa is characterized by a rough, clinkery surface and is the typical texture of cooler basalt lava flows. Pāhoehoe is characterized by its smooth and often ropey or wrinkly surface and is generally formed from more fluid lava flows. Pāhoehoe flows are sometimes observed to transition to ʻaʻa flows as they move away from the vent, but never the reverse.[52]

More silicic lava flows take the form of block lava, where the flow is covered with angular, vesicle-poor blocks.

Rhyolitic flows typically consist largely of obsidian.[53]

Tephra

Light-microscope image of tuff as seen in thin section (long dimension is several mm): the curved shapes of altered glass shards (ash fragments) are well preserved, although the glass is partly altered. The shapes were formed around bubbles of expanding, water-rich gas.

Tephra is made when magma inside the volcano is blown apart by the rapid expansion of hot volcanic gases. Magma commonly explodes as the gas dissolved in it comes out of solution as the pressure decreases when it flows to the surface. These violent explosions produce particles of material that can then fly from the volcano. Solid particles smaller than 2 mm in diameter (sand-sized or smaller) are called volcanic ash.[35][36]

Tephra and other volcaniclastics (shattered volcanic material) make up more of the volume of many volcanoes than do lava flows. Volcaniclastics may have contributed as much as a third of all sedimentation in the geologic record. The production of large volumes of tephra is characteristic of explosive volcanism.[54]

Types of volcanic eruptions

Schematic of volcano injection of aerosols and gases

Eruption styles are broadly divided into magmatic, phreatomagmatic, and phreatic eruptions.

Volcanic Explosivity Index (VEI), which ranges from 0 for Hawaiian-type eruptions to 8 for supervolcanic eruptions.[56]

  • Magmatic eruptions are driven primarily by gas release due to decompression.[55] Low-viscosity magma with little dissolved gas produces relatively gentle effusive eruptions. High-viscosity magma with a high content of dissolved gas produces violent explosive eruptions. The range of observed eruption styles is expressed from historical examples.
  • Hawaiian eruptions are typical of volcanoes that erupt mafic lava with a relatively low gas content. These are almost entirely effusive, producing local fire fountains and highly fluid lava flows but relatively little tephra. They are named after the Hawaiian volcanoes.
  • Strombolian eruptions are characterized by moderate viscosities and dissolved gas levels. They are characterized by frequent but short-lived eruptions that can produce eruptive columns hundreds of meters high, which can also be seen in a gas slug. Their primary product is scoria. They are named after Stromboli.
  • Vulcanian eruptions are characterized by yet higher viscosities and partial crystallization of magma, which is often intermediate in composition. Eruptions take the form of short-lived explosions over the course of several hours, which destroy a central dome and eject large lava blocks and bombs. This is followed by an effusive phase that rebuilds the central dome. Vulcanian eruptions are named after Vulcano.
  • Peléan eruptions are more violent still, being characterized by dome growth and collapse that produces various kinds of pyroclastic flows. They are named after Mount Pelée.
  • Plinian eruptions are the most violent of all volcanic eruptions. They are characterized by sustained huge eruption columns whose collapse produces catastrophic pyroclastic flows. They are named after
    eruption of Mount Vesuvius in 79
    AD.
  • Phreatomagmatic eruptions are characterized by interaction of rising magma with groundwater. They are driven by the resulting rapid buildup of pressure in the superheated groundwater.
  • Phreatic eruptions are characterized by superheating of groundwater that comes in contact with hot rock or magma. They are distinguished from phreatomagmatic eruptions because the erupted material is all country rock; no magma is erupted.

Volcanic activity

Bacchus and Agathodaemon, as seen in Pompeii's House of the Centenary

As of December 2022[update], the

Epoch (the last 11,700 years) lists 9,901 confirmed eruptions from 859 volcanoes. The database also lists 1,113 uncertain eruptions and 168 discredited eruptions for the same time interval.[57][58]

Volcanoes vary greatly in their level of activity, with individual volcanic systems having an eruption recurrence ranging from several times a year to once in tens of thousands of years.[59] Volcanoes are informally described as erupting, active, dormant, or extinct, but the definitions of these terms are not entirely uniform amongst volcanologists. The level of activity of most volcanoes falls upon a graduated spectrum, with much overlap between categories, and does not always fit neatly into only one of these three separate categories.[60]

Erupting

The USGS defines a volcano as "erupting" whenever the ejection of magma from any point on the volcano is visible, including visible magma still contained within the walls of the summit crater.

Active

While there is no international consensus among volcanologists on how to define an "active" volcano, the USGS defines a volcano as "active" whenever subterranean indicators, such as earthquake swarms, ground inflation, or unusually high levels of carbon dioxide and/or sulfur dioxide are present.[61][62]

Dormant and reactivated

Narcondam Island, India, is classified as a dormant volcano by the Geological Survey of India.

The USGS defines a dormant volcano as any volcano that is not showing any signs of unrest such as earthquake swarms, ground swelling, or excessive noxious gas emissions, but which shows signs that it could yet become active again.[62] Many dormant volcanoes have not erupted for thousands of years, but have still shown signs that they may be likely to erupt again in the future.[63][64]

In an article justifying the re-classification of Alaska's

Encyclopedia of Volcanoes (2000) does not contain it in the glossaries or index",[65]
however the USGS still widely employs the term.

Previously a volcano was often considered to be extinct if there were no written records of its activity. Such a generalisation is inconsistent with observation and deeper study, as has occurred recently with the unexpected eruption of the

eruption of 79 CE, which destroyed the towns of Herculaneum and Pompeii
.

Accordingly, it can sometimes be difficult to distinguish between an extinct volcano and a dormant (inactive) one. Long volcano dormancy is known to decrease awareness.[67]: 96  Pinatubo was an inconspicuous volcano, unknown to most people in the surrounding areas, and initially not seismically monitored before its unanticipated and catastrophic eruption of 1991. Two other examples of volcanoes which were once thought to be extinct, before springing back into eruptive activity were the long-dormant Soufrière Hills volcano on the island of Montserrat, thought to be extinct until activity resumed in 1995 (turning its capital Plymouth into a ghost town) and Fourpeaked Mountain in Alaska, which, before its September 2006 eruption, had not erupted since before 8000 BCE.

Extinct

Capulin Volcano National Monument in New Mexico, US

Extinct volcanoes are those that scientists consider unlikely to erupt again because the volcano no longer has a magma supply. Examples of extinct volcanoes are many volcanoes on the Hawaiian–Emperor seamount chain in the Pacific Ocean (although some volcanoes at the eastern end of the chain are active), Hohentwiel in Germany, Shiprock in New Mexico, US, Capulin in New Mexico, US, Zuidwal volcano in the Netherlands, and many volcanoes in Italy such as Monte Vulture. Edinburgh Castle in Scotland is located atop an extinct volcano, which forms Castle Rock. 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 may be considered dormant instead of extinct. An individual volcano in a monogenetic volcanic field can be extinct but that does not mean a completely new volcano might not erupt close by with little or no warning as its field may have an active magma supply.

Volcanic-alert level

The three common popular classifications of volcanoes can be subjective and some volcanoes thought to have been extinct have erupted again. To help prevent people from falsely believing they are not at risk when living on or near a volcano, countries have adopted new classifications to describe the various levels and stages of volcanic activity.[69] Some alert systems use different numbers or colors to designate the different stages. Other systems use colors and words. Some systems use a combination of both.

Decade volcanoes

Koryaksky volcano towering over Petropavlovsk-Kamchatsky on Kamchatka Peninsula, Far Eastern Russia

The Decade Volcanoes are 16 volcanoes identified by the International Association of Volcanology and Chemistry of the Earth's Interior (IAVCEI) as being worthy of particular study in light of their history of large, destructive eruptions and proximity to populated areas. They are named Decade Volcanoes because the project was initiated as part of the United Nations-sponsored International Decade for Natural Disaster Reduction (the 1990s). The 16 current Decade Volcanoes are:

The

Multi-Component Gas Analyzer System instruments to measure CO2/SO2 ratios in real-time and in high-resolution to allow detection of the pre-eruptive degassing of rising magmas, improving prediction of volcanic activity.[70]

Volcanoes and humans

Solar radiation graph 1958–2008, showing how the radiation is reduced after major volcanic eruptions
Galapagos Islands
, during an eruption in October 2005

Volcanic eruptions pose a significant threat to human civilization. However, volcanic activity has also provided humans with important resources.

Hazards

There are many different

mud pots and geysers
often accompany volcanic activity.

Volcanic gases can reach the stratosphere, where they form sulfuric acid aerosols that can reflect solar radiation and lower surface temperatures significantly.[71] Sulfur dioxide from the eruption of Huaynaputina may have caused the Russian famine of 1601–1603.[72] Chemical reactions of sulfate aerosols in the stratosphere can also damage the ozone layer, and acids such as hydrogen chloride (HCl) and hydrogen fluoride (HF) can fall to the ground as acid rain. Excessive fluoride salts from eruptions have poisoned livestock in Iceland on multiple occasions.[73]: 39–58  Explosive volcanic eruptions release the greenhouse gas carbon dioxide and thus provide a deep source of carbon for biogeochemical cycles.[74]

Ash thrown into the air by eruptions can present a hazard to aircraft, especially jet aircraft where the particles can be melted by the high operating temperature; the melted particles then adhere to the turbine blades and alter their shape, disrupting the operation of the turbine. This can cause major disruptions to air travel.

VEI 7 and 8
) with major historical volcanic eruptions in the 19th and 20th century (VEI 5, 6 and 7). From left to right: Yellowstone 2.1 Ma, Yellowstone 1.3 Ma, Long Valley 6.26 Ma, Yellowstone 0.64 Ma . 19th century eruptions: Tambora 1815, Krakatoa 1883. 20th century eruptions: Novarupta 1912, St. Helens 1980, Pinatubo 1991.

A

mass extinctions.[77]

The 1815 eruption of Mount Tambora created global climate anomalies that became known as the "Year Without a Summer" because of the effect on North American and European weather.[78] The freezing winter of 1740–41, which led to widespread famine in northern Europe, may also owe its origins to a volcanic eruption.[79]

Benefits

Although volcanic eruptions pose considerable hazards to humans, past volcanic activity has created important economic resources. Tuff formed from volcanic ash is a relatively soft rock, and it has been used for construction since ancient times.

Rapa Nui people used tuff to make most of the moai statues in Easter Island.[83]

Volcanic ash and weathered basalt produce some of the most fertile soil in the world, rich in nutrients such as iron, magnesium, potassium, calcium, and phosphorus.[84] Volcanic activity is responsible for emplacing valuable mineral resources, such as metal ores.[84] It is accompanied by high rates of heat flow from Earth's interior. These can be tapped as geothermal power.[84]

Tourism associated with volcanoes is also a worldwide industry.[85]

Safety considerations

Many volcanoes near human settlements are heavily monitored with the aim of providing adequate advance warnings of imminent eruptions to nearby populations. Also, a better modern-day understanding of volcanology has led to some better informed governmental and public responses to unanticipated volcanic activities. While the science of volcanology may not yet be capable of predicting the exact times and dates of eruptions far into the future, on suitably monitored volcanoes the monitoring of ongoing volcanic indicators is often capable of predicting imminent eruptions with advance warnings minimally of hours, and usually of days prior to any eruptions.[86] The diversity of volcanoes and their complexities mean that eruption forecasts for the foreseeable future will be based on probability, and the application of risk management. Even then, some eruptions will have no useful warning. An example of this occurred in March 2017, when a tourist group was witnessing an apparently predictable Mount Etna eruption and the flowing lava came in contact with a snow accumulation causing a situational phreatic explosion causing injury to ten persons.[85] But other types of significant eruptions are known to give useful warnings of only hours at the most by seismic monitoring.[66] The recent demonstration of a magma chamber with repose times of tens of thousands of years, with potental for rapid recharge so potentially decreasing warning times, under the youngest volcano in central Europe,[67] does not tell us if more careful monitoring will be useful.

Scientists are known to perceive risk, with its social elements, differently to local populations and those that undertake social risk assessments on their behalf, so that both disruptive false alarms and retrospective blame when disasters occur will continue to happen.[87]: 1–3 

Thus in many cases, while volcanic eruptions may still cause major property destruction, the periodic large-scale loss of human life that was once associated with many volcanic eruptions, has recently been significantly reduced in areas where volcanoes are adequately monitored. This life-saving ability is derived via such volcanic-activity monitoring programs, through the greater abilities of local officials to facilitate timely evacuations based upon the greater modern-day knowledge of volcanism that is now available, and upon improved communications technologies such as cell phones. Such operations tend to provide enough time for humans to escape at least with their lives prior to a pending eruption. One example of such a recent successful volcanic evacuation was the Mount Pinatubo evacuation of 1991. This evacuation is believed to have saved 20,000 lives.[88] In the case of Mount Etna, a 2021 review found 77 deaths due to eruptions since 1536 but none since 1987.[85]

Citizens who may be concerned about their own exposure to risk from nearby volcanic activity should familiarize themselves with the types of, and quality of, volcano monitoring and public notification procedures being employed by governmental authorities in their areas.[89]

Volcanoes on other celestial bodies

The Tvashtar volcano erupts a plume 330 km (205 mi) above the surface of Jupiter's moon Io.

Earth's Moon has no large volcanoes and no current volcanic activity, although recent evidence suggests it may still possess a partially molten core.[90] However, the Moon does have many volcanic features such as maria[91] (the darker patches seen on the Moon), rilles[92] and domes.[93]

The planet

ash flows near the summit and on the northern flank.[95] However, the interpretation of the flows as ash flows has been questioned.[96]

Olympus Mons (Latin, "Mount Olympus"), located on the planet Mars, is the tallest known mountain in the Solar System.

There are several extinct volcanoes on Mars, four of which are vast shield volcanoes far bigger than any on Earth. They include Arsia Mons, Ascraeus Mons, Hecates Tholus, Olympus Mons, and Pavonis Mons. These volcanoes have been extinct for many millions of years,[97] but the European Mars Express spacecraft has found evidence that volcanic activity may have occurred on Mars in the recent past as well.[97]

cryovolcanism, and is apparently most common on the moons of the outer planets of the Solar System.[99]

In 1989, the

.

A 2010 study of the

transit in 2009, suggested that tidal heating from the host star very close to the planet and neighboring planets could generate intense volcanic activity similar to that found on Io.[103]

History of volcano understanding

Volcanoes are not distributed evenly over Earth's surface but active ones with significant impact were encountered early in human history, evidenced by footprints of

hominina found in East Africian volcanic ash dated at 3.66 million years old.[104]: 104  The association of volcanoes with fire and disaster is found in many oral traditions and had religious and thus social significance before the first written record of concepts related to volcanoes. Examples are: (1) the stories in the Athabascan subcultures about humans living inside mountains and a woman who uses fire to escape from a mountain,[105]: 135  (2) Pele's migration through the Hawarian island chain, ability to destroy forests and manifestations of the god's temper,[106] and (3) the association in Javanese folklore of a king resident in Mount Merapi volcano and a queen resident at a beach 50 km (31 mi) away on what is now known to be an earthquake fault that interacts with that volcano.[107]

Many ancient accounts ascribe volcanic eruptions to

Hephaistos and the concepts of the underworld are aligned to volcanoes in that Greek culture.[85]

However, others proposed more natural (but still incorrect) causes of volcanic activity. In the fifth century BC,

hydrothermal eruptions from dry explosive eruption, of, as it turned out, a basalt dyke.[112]: 16–18 [113]: 4  Alfred Lacroix built upon his other knowledge with his studies on the 1902 eruption of Mount Pelée,[109] and by 1928 Arthur Holmes work had brought together the concepts of radioactive generation of heat, Earth's mantle structure, partial decompression melting of magma, and magma convection.[109] This eventually led to the acceptance of plate tectonics.[114]

See also

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Further reading

External links