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{{Short description|Rupture in a planet's crust where material escapes}}
{{Redirect|Volcanic||Volcano (disambiguation)|and|Volcanic (disambiguation)}}
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{{Use Oxford spelling|date=November 2024}}
{{Use mdy dates|date=November 2024}}
[[File:Augustine volcano Jan 24 2006 - Cyrus Read.jpg|thumb|upright=1.35|[[Augustine Volcano]] (Alaska) during its eruptive phase on January 24, 2006]]
A '''volcano''' is commonly defined as a vent or fissure in the [[Crust (geology)|crust]] of a [[planetary-mass object]], such as [[Earth]], that allows hot [[lava]], [[volcanic ash]], and [[volcanic gas|gases]] to escape from a [[magma chamber]] below the surface.<ref name=gsa>{{cite book|title=What is a Volcano?|publisher=[[Geological Society of America]]|language=en|year=2010|isbn=978-0813724706|chapter= 1: What is a volcano?|editor-last1=Canon-Tapia|editor-first1=Edgardo|editor-last2=Szakács|editor-first2=Alexandru|page=3}}</ref>

On Earth, volcanoes are most often found where [[list of tectonic plates|tectonic plates]] are [[divergent boundary|diverging]] or [[convergent boundary|converging]], and because most of Earth's plate boundaries are underwater, most volcanoes are found underwater. For example, a [[mid-ocean ridge]], such as the [[Mid-Atlantic Ridge]], has volcanoes caused by divergent tectonic plates whereas the Pacific [[Ring of Fire]] has volcanoes caused by convergent tectonic plates. Volcanoes resulting from divergent tectonic activity are usually non-explosive whereas those resulting from convergent tectonic activity cause violent eruptions.<ref name=dkp>{{cite book|title=The Ultimate Visual Dictionary|year=2012|publisher=[[DK (publisher)|DK Pub.]]|language=en|pages=272–293|isbn=978-0-1434-1954-9|chapter=geology}}</ref><ref name="mor">"Mid-ocean ridge tectonics, volcanism and geomorphology." Geology 26, no. 455 (2001): 458. https://macdonald.faculty.geol.ucsb.edu/papers/Macdonald%20Mid-Ocean%20Ridge%20Tectonics.pdf</ref> Volcanoes can also form where there is stretching and thinning of the crust's plates, such as in the [[East African Rift]], the [[Wells Gray-Clearwater volcanic field]], and the [[Rio Grande rift]] in North America. Volcanism away from plate boundaries most likely arises from upwelling [[diapir]]s from the [[core–mantle boundary]] called [[mantle plume]]s, {{convert|3000|km|mi}} deep within Earth. This results in [[hotspot (geology)|hotspot volcanism]] or [[intraplate volcanism]], in which the plume may cause thinning of the crust and result in a [[volcanic island]] chain due to the continuous movement of the tectonic plate, of which the [[Hawaiian hotspot]] is an example.<ref name=bgs>{{cite web|title=How volcanoes form - British Geological Survey|website=[[British Geological Survey]]|access-date=25 December 2024|url=https://www.bgs.ac.uk/discovering-geology/earth-hazards/volcanoes/how-volcanoes-form-2/#:~:text=Volcanoes%20form%20here%20in%20two,produces%20an%20island%2Darc%20volcano}}</ref> Volcanoes are usually not created at [[transform fault|transform tectonic boundaries]] where two tectonic plates slide past one another.

Volcanoes, based on their frequency of eruption or volcanism, are referred to as either [[active volcano|active]] or extinct.<ref name="www.usgs.gov2">{{Cite web |last=Poland |first=Michael |date=2022-10-10 |title=Active, dormant, and extinct: Clarifying confusing classifications {{!}} U.S. Geological Survey |url=https://www.usgs.gov/observatories/yvo/news/active-dormant-and-extinct-clarifying-confusing-classifications |access-date=2023-11-14 |publisher=United States Geological Survey}}</ref> Active volcanoes have a history of volcanism and are likely to erupt again while extinct ones are not capable of eruption at all as they have no magma source. "Dormant" volcanoes have not erupted in a long time &ndash; generally accepted as since the start of the [[Holocene]], about 12000 years ago &ndash; but may erupt again.<ref name="www.usgs.gov2" /> These categories aren't entirely uniform; they may overlap for certain examples.<ref name=dkp/><ref name=ade/><ref name=ng>{{cite web|title=Volcanoes|website=National Geographic Society|url=https://education.nationalgeographic.org/resource/volcanoes/|access-date=26 December 2024}}</ref>

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 winter]]s which have caused catastrophic famines.<ref>{{cite journal|last1=Rampino|first1=M R|last2=Self|first2=S|last3=Stothers|first3=R B|title=Volcanic Winters|journal=Annual Review of Earth and Planetary Sciences|date=May 1988|volume=16|issue=1|pages=73–99|doi=10.1146/annurev.ea.16.050188.000445|bibcode=1988AREPS..16...73R|issn=0084-6597}}</ref>

Other planets besides Earth have volcanoes. For example, volcanoes are very numerous on Venus.<ref>{{Cite journal|last1=Hahn|first1=Rebecca M.|last2=Byrne|first2=Paul K.|date=April 2023|title=A Morphological and Spatial Analysis of Volcanoes on Venus|url=http://dx.doi.org/10.1029/2023je007753|journal=Journal of Geophysical Research: Planets|volume=128|issue=4|doi=10.1029/2023je007753|bibcode=2023JGRE..12807753H|s2cid=257745255|issn=2169-9097}}</ref> Mars has significant volcanoes.<ref>{{cite web|url=https://www.nasa.gov/solar-system/nasa-confirms-thousands-of-massive-ancient-volcanic-eruptions-on-mars/|title=NASA Confirms Thousands of Massive Ancient Volcanic Eruptions on Mars|access-date=12 November 2024|date=15 September 2021|first=William|last=Steigerwald|publisher=Goddard Space Flight Center, NASA|location=Greenbelt, Md, United States}}</ref> 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.'<ref>{{Cite journal|last1=Lopes|last2=Mitchell|last3=Williams|last4=Mitri|last5=Gregg|first1=R. M.|first2=K. L.|first3=D. A.|first4=G.|first5=T. K.|title=What is a Volcano? How planetary volcanism has changed our definition|url=https://ui.adsabs.harvard.edu/abs/2009AGUFM.V21H..08L/abstract|journal=AGU Fall Meeting Abstracts|date=2009|volume=2009|bibcode=2009AGUFM.V21H..08L}}</ref>

This article mainly covers volcanoes on Earth. See {{section link|nopage=y|Volcano|Volcanoes on other celestial bodies}} and [[cryovolcano]] for more information.

==Etymology and terminology==
The word ''volcano'' ({{IPAc-en|UK|v|ɒ|l|ˈ|k|eɪ|n|ə|ʊ}}; {{IPAc-en|US|v|ɑː|l|ˈ|k|eɪ|n|oʊ}}) originates from the early [[17th century]], derived from the Italian name {{lang|it|[[Vulcano]]}}, a [[volcanic island]] in the [[Aeolian Islands]] of Italy, which in turn comes from the [[Latin]] name {{wikt-lang|la|Volcānus}} or {{wikt-lang|la|Vulcānus}}, referring to [[Vulcan (mythology)|Vulcan]], the god of fire in [[Roman mythology]].<ref name=oed>{{cite OED|volcano |access-date=2024-12-25}}</ref><ref>{{cite book |url=https://press.princeton.edu/chapters/s7694.html |chapter=Volcano |title=Mind over Magma: The Story of Igneous Petrology |first1=Davis A.|last1=Young |publisher=[[Princeton University Press]] |year=2003 |isbn=978-0691187723 |access-date=2016-01-11 |url-status=dead |archive-url=https://web.archive.org/web/20151112071530/http://press.princeton.edu/chapters/s7694.html |archive-date=2015-11-12}}</ref>

The set of processes and phenomena involved in volcanic activity is called [[volcanism]] [early [[19th century]]: from ''volcano'' + ''-ism'']. The study of volcanism and volcanoes is called [[volcanology]] [mid-19th century: from ''volcano'' + ''-logy''], sometimes spelled ''vulcanology''.<ref name=oed/>

==Plate tectonics==
{{Main|Plate tectonics}}

According to the theory of plate tectonics, Earth's [[lithosphere]], its rigid outer shell, is broken into sixteen larger and several smaller plates. These move continuously at a slow pace, due to [[convection]] in the underlying ductile [[Earth's mantle|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).<ref>{{cite book|last1=Schmincke|first1=Hans-Ulrich|title=Volcanism|date=2003|publisher=Springer|location=Berlin|isbn=9783540436508|pages=13–20|url=https://books.google.com/books?id=XHlJrFAhth4C&pg=PA13}}</ref>

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 volcanic field|polygenetic]]'' with more than one period of activity during their history; other volcanoes that become extinct after erupting exactly once are ''[[Monogenetic volcanic field|monogenetic]]'' (meaning "one life") and such volcanoes are often grouped together in a geographical region.<ref>{{cite web|last=Hsu-Buffalo|first=Charlotte|title=Do monogenetic volcanoes threaten the southwestern US?|date=November 4, 2021|work=Futurity|url=https://www.futurity.org/monogenetic-volcano-2652672-2/|access-date=July 21, 2023}}</ref>

===Divergent plate boundaries===
{{Main|Divergent boundary}}
[[File:Spreading ridges volcanoes map-en.svg|thumb|upright=1.8|Map showing the divergent plate boundaries (oceanic spreading ridges) and recent sub-aerial volcanoes (mostly at convergent boundaries)]]

At the [[mid-ocean ridge]]s, two [[list of tectonic plates|tectonic plates]] diverge from one another as hot mantle rock creeps upwards beneath the thinned [[oceanic crust]]. The decrease of pressure in the rising mantle rock leads to [[adiabatic]] expansion and the [[partial melting]] of the rock, causing volcanism and creating new oceanic crust. Most [[divergent plate boundaries]] are at the bottom of the oceans, and so most volcanic activity on Earth is submarine, forming new [[seafloor]]. [[Black smoker]]s (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]].{{sfn|Schmincke|2003|pp=17-18, 276}}<ref name=mor/>

===Convergent plate boundaries===
{{Main|Convergent boundary}}

[[Subduction]] zones are places where two plates, usually an oceanic plate and a continental plate, collide. The oceanic plate subducts (dives beneath the continental plate), forming a deep ocean trench just offshore. In a process called [[flux melting]], water released from the subducting plate lowers the melting temperature of the overlying mantle wedge, thus creating [[magma]]. This magma tends to be extremely [[viscous]] because of its high [[silica]] content, so it often does not reach the surface but [[Igneous intrusion|cools and solidifies at depth]]. When it does reach the surface, however, a volcano is formed. Thus subduction zones are bordered by chains of volcanoes called [[volcanic arc]]s. Typical examples are the volcanoes in the Pacific [[Ring of Fire]], such as the [[Cascade Volcanoes]] or the [[Japanese Archipelago]], or the eastern islands of [[Indonesia]].{{sfn|Schmincke|2003|pp=18,113-126}}<ref name=dkp/>

===Hotspots===
{{Main|Hotspot (geology)}}

[[Hotspot (geology)|Hotspots]] are volcanic areas thought to be formed by [[mantle plume]]s, 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 part of the North American plate currently above the [[Yellowstone hotspot]].{{sfn|Schmincke|2003|pp=18,106-107}}<ref name=bgs/> However, the mantle plume hypothesis has been questioned.<ref name=Foulger>{{cite book|title=Plates vs. Plumes: A Geological Controversy|last1=Foulger|first1=Gillian R.|year=2010|isbn=978-1-4051-6148-0|publisher=Wiley-Blackwell}}</ref>

===Continental rifting===
{{Main|Rift}}

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 basalt]]s and may progress to the point where a tectonic plate is completely split.<ref>{{cite book|last1=Philpotts|first1=Anthony R.|last2=Ague|first2=Jay J.|title=Principles of igneous and metamorphic petrology|date=2009|publisher=Cambridge University Press|location=Cambridge, UK|isbn=9780521880060|pages=380–384, 390|edition=2nd}}</ref>{{sfn|Schmincke|2003|pp=108-110}} 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 [[Alkaline magma series|alkali lava]] or [[carbonatite]]s. Examples include the volcanoes of the [[East African Rift]].{{sfn|Philpotts|Ague|2009|pp=390-394,396-397}}

==Volcanic features==
{{Further|Types of volcanoes}}
[[File:007_Volcano_eruption_of_Litli-Hrútur_in_Iceland_in_2023_Video_by_Giles_Laurent.webm|thumb|Video of lava agitating and bubbling in the volcanic eruption of Litli-Hrútur ([[Fagradalsfjall]]), Iceland, 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. The erupted volcanic material (lava and tephra) that is deposited around the vent is known as a '''{{Visible anchor|volcanic edifice}}''', typically a volcanic cone or mountain.<ref name=dkp/><ref name="NPS-Anat">{{cite web|url=https://www.nps.gov/subjects/volcanoes/anatomy-of-a-volcano.htm|title=Anatomy of a Volcano|publisher=[[National Park Service]]|date=July 5, 2023|access-date=November 3, 2023}}</ref>

The most common perception of a volcano is of a [[conical]] mountain, spewing [[lava]] and poisonous [[volcanic gas|gases]] from a [[volcanic crater|crater]] at its summit; however, this describes just one of the many types of volcano. The features of volcanoes are varied. The structure and behaviour of volcanoes depend on several factors. Some volcanoes have rugged peaks formed by [[lava dome]]s rather than a summit crater while others have [[landscape]] features such as massive [[plateau]]s. Vents that issue volcanic material (including lava and [[volcanic ash|ash]]) and gases (mainly steam and magmatic gases) can develop anywhere on the [[landform]] and may give rise to smaller cones such as [[Puʻu ʻŌʻō|Pu{{okina}}u {{okina}}Ō{{okina}}ō]] on a flank of [[Kīlauea]] in Hawaii. [[Volcanic crater]]s 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 recognize as such and be obscured by geological processes.<ref name=dkp/><ref name=usgs>{{cite web|title=The Pu'u'ō'ō Eruption Lasted 35 Years|date=22 November 2023|website=[[United States Geological Survey]]|url=https://www.usgs.gov/volcanoes/kilauea/science/puuoo-eruption-lasted-35-years|access-date=25 December 2024}}</ref><ref name=taupo>{{cite web|title=Lake Taupo - New Zealand, Map, Volcano, & Facts - Britannica|website=Britannica|access-date=25 December 2024|url=https://www.britannica.com/place/Lake-Taupo}}</ref>

Other types of volcano include [[mud volcano]]es, which are structures often not associated with known magmatic activity; and [[cryovolcano]]es (or ice volcanoes), particularly on some moons of [[Jupiter]], [[Saturn]], and [[Neptune]]. Active mud volcanoes tend to involve temperatures much lower than those of [[igneous]] volcanoes except when the mud volcano is actually a vent of an igneous volcano.

===Fissure vents===
{{Main|Fissure vent}}

[[File:Lakagigar Iceland 2004-07-01.jpg|right|thumbnail|[[Laki|Lakagigar]] fissure vent in [[Iceland]], the source of the [[Laki#Consequences in Iceland|major world climate alteration of 1783–84]], has a chain of volcanic cones along its length.]]
[[Fissure vent|Volcanic fissure vents]] are generally found at [[Divergent boundary|diverging plate boundaries]], they are flat, linear fractures through which [[basaltic lava]] emerges. These kinds of volcanoes are non-explosive and the basaltic lava tends to have a low viscosity and solidifies slowly leading to a gentle sloping basaltic [[Volcanic plateau|lava plateau]]. They often relate or constitute shield volcanoes<ref name=dkp/><ref name=nps/>

===Shield volcanoes===
{{Main|Shield volcano}}

[[File:Skjaldbreidur Herbst 2004.jpg|left|thumbnail|[[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 basaltic or andesitic lava that can flow a great distance from a vent. They generally do not explode catastrophically but are characterized by relatively gentle [[effusive eruption]]s.<ref name=dkp/> 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.<ref name=nps>{{cite web|title=Shield Volcanoes (U.S. National Park Service)|website=[[National Park Service]]|access-date=25 December 2024|url=https://www.nps.gov/articles/000/shield-volcanoes.htm#:~:text=Hawai'i%20Volcanoes%20National%20Park,active%20volcano%20on%20the%20planet.}}</ref> [[Olympus Mons]], an extinct martian shield volcano is the largest known volcano in the [[Solar System]].<ref name=msv>{{cite web|title=Olympus Mons - Description, Height, & Facts - Britannica|website=Britannica|url=https://www.britannica.com/place/Olympus-Mons|access-date=25 December 2024}}</ref>

===Lava domes===
[[File:East Dome Mount St. Helens.jpg|thumb|East dome, a lava dome located on the lower east flank of St. Helens, part of the Sugar Bowl Eruptive Period (1800 YA).]]
{{Main|Lava dome}}
[[Lava dome]]s, also called dome volcanoes, have steep convex sides built by slow eruptions of highly viscous lava, for example, [[rhyolite]].<ref name=dkp/> 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===
{{Main|volcanic cone|Cinder cone}}
[[File:Izalco Volcano.jpg|thumb|[[Izalco (volcano)|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 [[scoria]] and [[Pyroclastic rock|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 {{convert|30 to 400|m|ft|-2}} high. Most cinder cones erupt only once and some may be found in [[monogenetic volcanic field]]s that may include other features that form when magma comes into contact with water such as [[maar]] explosion craters and [[tuff ring]]s.<ref name="Thomas2000">David S.G. Thomas and Andrew Goudie (eds.), ''The Dictionary of Physical Geography'' (Oxford: Blackwell, 2000), 301. {{ISBN|0-631-20473-3}}.</ref> Cinder cones may form as [[parasitic cone|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.<ref>{{cite journal|last1=Wood|first1=C.A.|title=Cindercones on Earth, Moon and Mars|journal=Lunar and Planetary Science|volume=X|year=1979|pages=1370–1372|bibcode=1979LPI....10.1370W}}</ref><ref>{{Cite journal|last1=Meresse|first1=S.|last2=Costard|first2=F.O.|last3=Mangold|first3=N.|last4=Masson|first4=P.|last5=Neukum|first5=G.|title=Formation and evolution of the chaotic terrains by subsidence and magmatism: Hydraotes Chaos, Mars|doi=10.1016/j.icarus.2007.10.023|journal=Icarus|volume=194|issue=2|pages=487|year=2008|bibcode=2008Icar..194..487M}}</ref><ref name="Ulysses">{{Cite journal|doi=10.1016/j.icarus.2011.11.030|title=A unique volcanic field in Tharsis, Mars: Pyroclastic cones as evidence for explosive eruptions|year=2012|last1=Brož|first1=P.|last2=Hauber|first2=E.|journal=Icarus|volume=218|issue=1|pages=88|bibcode=2012Icar..218...88B}}</ref><ref name="mesic">{{Cite journal|last1=Lawrence|first1=S.J.|last2=Stopar|first2=J.D.|last3=Hawke|first3=B.R.|last4=Greenhagen|first4=B.T.|last5=Cahill|first5=J.T.S.|last6=Bandfield|first6=J.L.|last7=Jolliff|first7=B.L.|last8=Denevi|first8=B.W.|last9=Robinson|first9=M.S. | last10 = Glotch | first10 = T.D.|last11=Bussey|first11=D.B.J.|last12=Spudis|first12=P.D.|last13=Giguere|first13=T.A.|last14=Garry|first14=W.B.|title=LRO observations of morphology and surface roughness of volcanic cones and lobate lava flows in the Marius Hills|doi=10.1002/jgre.20060|journal=Journal of Geophysical Research: Planets|volume=118|issue=4|pages=615|year=2013|bibcode=2013JGRE..118..615L|doi-access=free}}</ref>

===Stratovolcanoes (composite volcanoes)===
[[File:Volcano scheme.svg|thumb|upright=1.4|'''Cross-section through a [[stratovolcano]] (vertical scale is exaggerated)''': {{Div col|colwidth=30em}}{{ordered list
    |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
}}{{div col end}}]]
{{Main|Stratovolcano}}
Stratovolcanoes are tall conical mountains composed of lava flows and [[tephra]] in alternate layers, the [[strata]] that gives rise to the name. They are also known as ''composite volcanoes'' because they are created from multiple structures during different kinds of eruptions; the main conduit bringing magma to the surface branches into multiple secondary conduits and occasional [[laccolith]]s or [[Sill (geology)|sill]]s, the branching conduits may form [[parasitic cone]]s on the flanks of the main cone.<ref name=dkp/> Classic examples include [[Mount Fuji]] in Japan, [[Mayon Volcano]] in the Philippines, and [[Mount Vesuvius]] and [[Stromboli]] in Italy.
[[File:Mount Vesuvius Araucaria.jpg|thumb|left|Mt. Vesuvius, a stratovolcano, [[Gulf of Naples]].]]

[[volcanic ash|Ash]] produced by the [[explosive eruption]] of stratovolcanoes has [[recorded history|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 eruption]]s that produce great quantities of ash, as well as [[pyroclastic surge]]s 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 [[lahar]]s.<ref>{{Cite book|url=https://books.google.com/books?id=eJopFDVRgYMC&pg=PA115|title=Volcanoes: Global Perspectives|first1=John P.|last1=Lockwood|first2=Richard W.|last2=Hazlett|year=2010|isbn=978-1-4051-6250-0|page=552|publisher=Wiley}}</ref> Large pieces of tephra are called [[volcanic bomb]]s. Big bombs can measure more than {{convert|4|ft|m|order=flip}} across and weigh several tons.<ref>Berger, Melvin, Gilda Berger, and Higgins Bond. "Volcanoes-why and how ." Why do volcanoes blow their tops?: Questions and answers about volcanoes and earthquakes. New York: Scholastic, 1999. 7. Print.</ref>

===Supervolcanoes===
[[File:Lake Taupo (31071970884).jpg|thumb|Lake Taupō, a volcanogenic lake in the caldera of [[Taupō Volcano|Taupō supervolcano]], New Zealand.]]
{{Main|Supervolcano}}
{{see also|List of largest volcanic eruptions}}
A supervolcano is defined as a volcano that has experienced one or more eruptions that produced over {{convert|1000|km3|cumi}} of volcanic deposits in a single explosive event.<ref>{{cite web|url=https://volcanoes.usgs.gov/volcanoes/yellowstone/yellowstone_sub_page_49.html|title=Questions About Supervolcanoes|publisher=United States Geological Survey|department=Yellowstone Volcano Observatory|date=August 21, 2015|access-date=August 22, 2017|url-status=live|archive-url=https://web.archive.org/web/20170703184836/https://volcanoes.usgs.gov/volcanoes/yellowstone/yellowstone_sub_page_49.html|archive-date=July 3, 2017}}</ref> 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 [[tuff]]s emplaced by such eruptions are the only volcanic product with volumes rivalling those of [[flood basalt]]s.{{sfn|Philpotts|Ague|2009|p=77}}

Supervolcano eruptions, while the most dangerous type, are very rare; [[Supervolcano#Known super eruptions|four are known from the last million years]], and about 60 historical VEI 8 eruptions have been identified in the geologic record over millions of years. A supervolcano can produce devastation on a continental scale, and severely cool global temperatures for many years after the eruption due to the huge volumes of [[sulfur]] and ash released into the atmosphere.

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 [[geological map]]ping.<ref>{{cite journal|jstor=24968920|title=Giant Volcanic Calderas|last1=Francis|first1=Peter|journal=Scientific American|year=1983|volume=248|issue=6|pages=60–73|doi=10.1038/scientificamerican0683-60|bibcode=1983SciAm.248f..60F}}</ref> Known examples include [[Yellowstone Caldera]] in [[Yellowstone National Park]] and [[Valles Caldera]] in [[New Mexico]] (both western United States); [[Lake Taupō]] in New Zealand; [[Lake Toba]] in [[Sumatra]], Indonesia; and [[Ngorongoro Crater]] in Tanzania.

====Caldera volcanoes====
[[File:Crater Lake winter pano2.jpg|thumb|Crater lake, a volcanic lake in [[Oregon]].]]
Volcanoes that, though large, are not large enough to be called supervolcanoes, may also form calderas (collapsed crater) in the same way. There may be active or dormant cones inside of the caldera or even a lake, such lakes are called [[Volcanogenic lake]]s, or simply, volcanic lakes.<ref>{{cite journal|last1=Druitt|first1=T. H.|last2=Costa|first2=F.|last3=Deloule|first3=E.|last4=Dungan|first4=M.|last5=Scaillet|first5=B.|title=Decadal to monthly timescales of magma transfer and reservoir growth at a caldera volcano|journal=Nature|volume=482|issue=7383|date=2012|issn=0028-0836|doi=10.1038/nature10706|pages=77–80|pmid=22297973|bibcode=2012Natur.482...77D|hdl=10220/7536|hdl-access=free}}</ref><ref name=dkp/>

===Submarine volcanoes===
{{Main|Submarine volcano}}
{{See also|Subaqueous volcano}}
[[File:Tonga Volcano Eruption 2022-01-15 0320Z to 0610Z Himawari-8 visible.gif|left|thumb|Satellite images of the January 15, 2022, eruption of [[Hunga Tonga-Hunga Haʻapai]]]]
Submarine volcanoes are common features of the ocean floor. Volcanic activity during the [[Holocene]] Epoch has been documented at only 119 submarine volcanoes, but there may be more than one million geologically young submarine volcanoes on the ocean floor.<ref name="GVPDatabase2020">{{cite web|url=https://volcano.si.edu/list_volcano_holocene.cfm|title=Holocene Volcano List|publisher=[[Global Volcanism Program]] Volcanoes of the World (version 4.9.1)|editor-last=Venzke|editor-first=E.|year=2013|access-date=November 18, 2020}}</ref><ref name="GVP-FAQ">{{cite web|url=https://volcano.si.edu/faq/index.cfm?question=activevolcanoes|title=How many active volcanoes are there?|publisher=[[Global Volcanism Program]] Volcanoes of the World (version 4.9.1)|editor-last=Venzke|editor-first=E.|year=2013|access-date=November 18, 2020}}</ref> In shallow water, active volcanoes disclose their presence by blasting steam and rocky debris high above the ocean's surface. In the deep ocean basins, the tremendous weight of the water prevents the explosive release of steam and gases; however, submarine eruptions can be detected by [[hydrophone]]s and by the discoloration of water because of [[volcanic gas]]es. [[Pillow lava]] is a common eruptive product of submarine volcanoes and is characterized by thick sequences of discontinuous pillow-shaped masses which form underwater. Even large submarine eruptions may not disturb the ocean surface, due to the rapid cooling effect and increased buoyancy in water (as compared to air), which often causes volcanic vents to form steep pillars on the ocean floor. [[Hydrothermal vent]]s are common near these volcanoes, and [[Black smoker|some support peculiar ecosystems]] based on [[chemotroph]]s 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 raft]]s.

In May and June 2018, a multitude of [[seismic]] signals were detected by [[earthquake]] monitoring agencies all over the world. They took the form of unusual humming sounds, and some of the signals detected in November of that year had a duration of up to 20 minutes. An [[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]].<ref>{{cite web|language=en|title=Origin of mystery humming noises heard around the world, uncovered|author=Ashley Strickland|publisher=CNN|date=January 10, 2020|url=https://www.msn.com/en-us/news/technology/origin-of-mystery-humming-noises-heard-around-the-world-uncovered/ar-BBYN2oY?ocid=spartanntp}}</ref>

===Subglacial volcanoes===
{{Main|Subglacial volcano}}
Subglacial volcanoes develop underneath [[ice cap]]s. They are made up of lava plateaus capping extensive pillow lavas and [[palagonite]]. These volcanoes are also called table mountains, [[tuya]]s,{{sfn|Philpotts|Ague|2009|p=66}} or (in Iceland) mobergs.<ref>{{cite book|editor1-last=Allaby|editor1-first=Michael|title=A dictionary of geology and earth sciences|location=Oxford|publisher=Oxford University Press|isbn=9780199653065|edition=Fourth|chapter=Tuya|date=July 4, 2013}}</ref> Very good examples of this type of volcano can be seen in Iceland and 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]] analysed and so its name has entered the geological literature for this kind of volcanic formation.<ref>{{cite journal|doi=10.2475/ajs.245.9.560|last=Mathews|first=W. H.|title=Tuyas, flat-topped volcanoes in northern British Columbia|journal=[[American Journal of Science]]|volume=245|issue=9|pages=560–570|date=September 1, 1947|url=http://www.ajsonline.org/cgi/content/abstract/245/9/560|bibcode=1947AmJS..245..560M|access-date=November 27, 2020|archive-date=September 29, 2011|archive-url=https://web.archive.org/web/20110929220601/http://www.ajsonline.org/cgi/content/abstract/245/9/560|url-status=dead|url-access=subscription}}</ref> 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]].

===Hydrothermal features===
Hydrothermal features, for example [[geyser]]s, [[fumarole]]s, [[Mudpot|mud pools]], [[mud volcano]]es, [[hot spring]]s and acidic hot springs involve water as well as geothermal or magmatic activity. Such features are common around volcanoes and are often indicative of volcanism.<ref name=dkp/><ref name=sd>{{cite book|title=Treatise on Geomorphology|edition=2nd|year=2022|publisher=[[Elsevier Inc.]]|isbn=978-0-12-818235-2}}</ref>

====Mud volcanoes====
[[File:Gobustan mud volcano.jpg|thumb|Mud volcano at [[Gobustan State Historical and Cultural Reserve|Gobustan]]]]
{{Main|Mud volcano}}
[[Mud volcano]]es or mud domes are conical structures created by eruption of liquids and gases, particularly mud (slurries), water and gases, although several activities may contribute. The largest mud volcanoes are {{convert|10|km|mi}} in diameter and reach {{convert|700|m|ft}} high.<ref>{{cite journal|last1=Mazzini|first1=Adriano|last2=Etiope|first2=Giuseppe|title=Mud volcanism: An updated review|journal=Earth-Science Reviews|date=May 2017|volume=168|pages=81–112|doi=10.1016/j.earscirev.2017.03.001|bibcode=2017ESRv..168...81M|hdl=10852/61234|hdl-access=free}}</ref><ref>{{cite journal|last1=Kioka|first1=Arata|last2=Ashi|first2=Juichiro|title=Episodic massive mud eruptions from submarine mud volcanoes examined through topographical signatures|journal=Geophysical Research Letters|date=October 28, 2015|volume=42|issue=20|pages=8406–8414|doi=10.1002/2015GL065713|bibcode=2015GeoRL..42.8406K|doi-access=free}}</ref> Mud volcanoes can be seen off the shore of [[Indonesia]], on the island of [[Baratang Island|Baratang]], in [[Balochistan, Pakistan|Balochistan]] and in central Asia.

====Fumarole====
{{main|Fumarole}}

[[Fumarole]]s are vents on the surface from which hot steam and volcanic gases erupt due to the presence of superheated groundwater, these may indicate volcanic activity. Fumaroles erupting sulfurous gases are also often called solfataras.<ref name=old>{{cite web|title=fumarole noun - Definition, pictures, pronunciation and usage notes - Oxford Advanced Learner's Dictionary at OxfordLearnersDictionaries.com|url=https://www.oxfordlearnersdictionaries.com/definition/english/fumarole|website=Oxford Learner's Dictionary|access-date=25 December 2024}}</ref><ref name=dkp/>

====Geysers====
{{main|Geyser}}

[[File:Yellowstone Castle Geysir Edit.jpg|thumb|Castle geyser eruption, [[Yellowstone National Park]].]]
Geysers are springs which will occasionally erupt and discharge hot water and steam. Geysers may indicate ongoing magmatism, water underground is heated by hot rocks and [[steam]] [[Vapor pressure|pressure]] builds up before being released along with a jet of hot water. Almost half of all active geysers are present in Yellowstone National Park, US.<ref name=dkp/><ref name=nps2>{{cite web|title=Yellowstone National Park (U.S. National Park Service)|website=[[National Park Service]]|url=https://www.nps.gov/yell/index.htm|access-date=26 December 2024}}</ref>

==Erupted material==
[[File:Volcan San Miguel Chaparrastique en El Salvador.webm|thumb|Timelapse of [[San Miguel (volcano)]] degassing in 2022. [[El Salvador]] is home to 20 Holocene volcanoes, 3 of which have erupted in last 100yrs<ref>{{cite web|url=https://volcano.si.edu/volcanolist_countries.cfm?country=El%20Salvador|title=El Salvador Volcanoes|author=<!--Not stated-->|publisher=Global Volcanism Program|access-date=November 8, 2023}}</ref>]]
[[File:Lava channel overflow.JPG|thumb|Pāhoehoe lava flow on [[Hawaii (island)|Hawaii]]. The picture shows overflows of a main [[lava channel]].]]
[[File:Litli-Hrútur eruption 2023.jpg|thumb|Litli-Hrútur ([[Fagradalsfjall]]) eruption 2023. View from an aeroplane]]
[[File:Aerial image of Stromboli (view from the northeast).jpg|thumb|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:

#[[Volcanic gas]]es, a mixture made mostly of [[steam]], [[carbon dioxide]], and a sulfur compound (either [[sulfur dioxide]], SO<sub>2</sub>, or [[hydrogen sulfide]], H<sub>2</sub>S, depending on the temperature)
#[[Lava]], the name of magma when it emerges and flows over the surface
#[[Tephra]], particles of solid material of all shapes and sizes ejected and thrown through the air<ref name=EB1911/><ref name="schmidt-1981"/>

=== Volcanic gases ===
{{Main|Volcanic gas}}
The concentrations of different [[volcanic gas]]es can vary considerably from one volcano to the next. [[Water vapour]] is typically the most abundant volcanic gas, followed by [[carbon dioxide]]<ref>{{cite journal|last1=Pedone|first1=M.|last2=Aiuppa|first2=A.|last3=Giudice|first3=G.|last4=Grassa|first4=F.|last5=Francofonte|first5=V.|last6=Bergsson|first6=B.|last7=Ilyinskaya|first7=E.|title=Tunable diode laser measurements of hydrothermal/volcanic CO2 and implications for the global CO2 budget|journal=Solid Earth|year=2014|volume=5|issue=2|pages=1209–1221|doi=10.5194/se-5-1209-2014|bibcode=2014SolE....5.1209P|doi-access=free}}</ref> 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]], [[halocarbon]]s, organic compounds, and [[Volatile (astrogeology)|volatile]] metal chlorides.

===Lava flows===
{{Main|Lava flow}}
[[File:Rinjani 1994 cropped.jpg|thumb|[[Mount Rinjani]] eruption in 1994, in [[Lombok]], [[Indonesia]]]]The form and style of an 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:<ref>{{cite book|last1=Casq|first1=R.A.F.|url=https://archive.org/details/volcanicsuccessi0000casr/page/528/mode/2up|title=Volcanic Successions|last2=Wright|first2=J.V.|date=1987|publisher=Unwin Hyman Inc|isbn=978-0-04-552022-0|page=528|url-access=registration}}</ref>

<!-- Please do not remove the bulleted paragraph hack used in the following bulleted list. Doing so will spoil the formatting. -->
* If the erupted [[magma]] contains a high percentage (>63%) of [[silica]], the lava is described as ''[[felsic]]''. Felsic lavas ([[dacite]]s or [[rhyolite]]s) are highly [[viscous]] and are erupted as domes or short, stubby flows.{{sfn|Philpotts|Ague|2009|p=70–72}} [[Lassen Peak]] in California is an example of a volcano formed from felsic lava and is actually a large lava dome.<ref>{{cite web|title=Volcanoes|url=https://www.nps.gov/lavo/learn/nature/volcanoes.htm|website=Lassen Volcanic National Park California|publisher=National Park Service|access-date=November 27, 2020}}</ref>

:Because felsic magmas are so viscous, they tend to trap volatiles (gases) that are present, which leads to explosive volcanism. [[Pyroclastic flow]]s ([[ignimbrite]]s) are highly hazardous products of such volcanoes since they hug the volcano's slopes and travel far from their vents during large eruptions. Temperatures as high as {{convert|850|C|}}<ref>{{cite book|last1=Fisher|first1=Richard V.|last2=Schmincke|first2=H.-U.|title=Pyroclastic rocks|date=1984|publisher=Springer-Verlag|location=Berlin|isbn=3540127569|pages=210–211}}</ref> 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 many meters thick.{{sfn|Philpotts|Ague|2009|p=73–77}} [[Alaska]]'s [[Valley of Ten Thousand Smokes]], formed by the eruption of [[Novarupta]] near [[Mount Katmai|Katmai]] in 1912, is an example of a thick pyroclastic flow or ignimbrite deposit.<ref>{{cite web|title=Exploring the Valley of Ten Thousand Smokes|url=https://www.nps.gov/katm/planyourvisit/exploring-the-valley-of-ten-thousand-smokes.htm|website=Katmai National Park and Preserve, Alaska|publisher=National Park Service|access-date=November 27, 2020}}</ref> Volcanic ash that is light enough to erupt high into the [[Earth's atmosphere]] as an [[eruption column]] may travel hundreds of kilometres before it falls back to ground as a fallout [[tuff]]. Volcanic gases may remain in the [[stratosphere]] for years.{{sfn|Schmincke|2003|p=229}}

:Felsic magmas are formed within the crust, usually through the melting of crust rock from the heat of underlying mafic magmas. The lighter felsic magma floats on the mafic magma without significant mixing.{{sfn|Philpotts|Ague|2009|pp=15-16}} Less commonly, felsic magmas are produced by extreme [[fractional crystallization (geology)|fractional crystallization]] of more mafic magmas.{{sfn|Philpotts|Ague|2009|p=378}} 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 ''[[intermediate composition]]'' or ''[[andesitic]]''. Intermediate magmas are characteristic of stratovolcanoes.{{sfn|Schmincke|2003|p=143}} They are most commonly formed at [[convergent boundaries]] between [[tectonic plate]]s, by several processes. One process is the hydration melting of mantle peridotite followed by fractional crystallization. Water from a subducting [[Slab (geology)|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 the melting of sediments carried downwards by the subducted slab.<ref>{{cite journal|last1=Castro|first1=Antonio|title=The off-crust origin of granite batholiths|journal=Geoscience Frontiers|date=January 2014|volume=5|issue=1|pages=63–75|doi=10.1016/j.gsf.2013.06.006|bibcode=2014GeoFr...5...63C|doi-access=free}}</ref> Another process is magma mixing between felsic rhyolitic and mafic basaltic magmas in an intermediate reservoir before emplacement or lava flow.{{sfn|Philpotts|Ague|2009|p=377}}
* 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 [[basalt]]ic. These lavas are usually hotter and much less viscous than felsic lavas. Mafic magmas are formed by partial melting of the dry mantle, with limited fractional crystallization and assimilation of crustal material.{{sfn|Philpotts|Ague|2009|p=16}}

:Mafic lavas occur in a wide range of settings. These include [[mid-ocean ridge]]s; [[Shield volcanoes]] (such the [[Hawaiian Islands]], including [[Mauna Loa]] and [[Kilauea]]), on both [[oceanic crust|oceanic]] and [[continental crust]]; and as continental [[flood basalt]]s.

* Some erupted magmas contain ≤45% silica and produce ''[[ultramafic]]'' lava. Ultramafic flows, also known as [[komatiite]]s, are very rare; indeed, very few have been erupted at Earth's surface since the [[Proterozoic]], when the planet's heat flow was higher. They are (or were) the hottest lavas, and were probably more fluid than common mafic lavas, with a viscosity less than a tenth that of hot basalt magma.{{sfn|Philpotts|Ague|2009|p=24}}
Mafic lava flows show two varieties of surface texture: {{okina}}A{{okina}}a (pronounced {{IPA|haw|ˈʔaʔa|}}) and [[pāhoehoe]] ({{IPA|haw|paːˈho.eˈho.e|}}), both [[Hawaiian language|Hawaiian]] words. {{okina}}A{{okina}}a 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 {{okina}}a{{okina}}a flows as they move away from the vent, but never the reverse.{{sfn|Schmincke|2003|pp=131-132}}

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]].{{sfn|Schmincke|2003|pp=132}}

===Tephra===
{{main|Tephra}}

[[File:Tuff shards.jpg|thumb|right|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 [[Extrusion|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&nbsp;mm in diameter ([[sand|sand-sized]] or smaller) are called volcanic ash.<ref name="EB1911">{{EB1911|wstitle=Tuff|inline=1}}</ref><ref name="schmidt-1981">{{cite journal|last1=Schmidt|first1=R.|title=Descriptive nomenclature and classification of pyroclastic deposits and fragments: recommendations of the IUGS Subcommission on the Systematics of Igneous Rocks|journal=Geology|volume=9|year=1981|issue=2|pages=41–43|doi=10.1007/BF01822152|bibcode=1981GeoRu..70..794S|s2cid=128375559|url=https://scholar.google.com/scholar_url?url=https://idp.springer.com/authorize/casa%3Fredirect_uri%3Dhttps://link.springer.com/content/pdf/10.1007/BF01822152.pdf%26casa_token%3DEeQQK-27EzMAAAAA:NxHAz8w30oOg24-BcWvJPAgMBjRc419lq-7Jz-6VV0-ma9Mv2wxmt4JqRZoPtxQvU501TeyvkUDq1fmmJw&hl=en&sa=T&oi=gsb-gga&ct=res&cd=0&d=227239637425471251&ei=PBhxX4PbJrXCywTH6bfYBg&scisig=AAGBfm2m9NmvueO9pSpn98cYOcYAhzm0nw|access-date=September 27, 2020|url-access=subscription}}</ref>

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.{{sfn|Fisher|Schmincke|1984|p=89}}

===Dissection===
Through natural processes, mainly [[erosion]], so much of the solidified erupted material that makes up the mantle of a volcano may be stripped away that its inner anatomy becomes apparent. Using the metaphor of [[Anatomy|biological anatomy]], such a process is called "dissection".<ref>{{cite book|title=Volcanoes: What They Are and What They Teach|author=John W. Judd|author-link=John Wesley Judd|pages=114–115|publisher=Appleton|year=1881|url=https://archive.org/details/volcanoeswhatthe00juddrich/page/114/mode/2up}}</ref> When the volcano is extinct, a plug forms on its vent, over time due to erosion, the volcanic cone slowly erodes away leaving the resistant lava plug intact.<ref name=dkp/> [[Cinder Hill]], a feature of [[Mount Bird]] on [[Ross Island]], [[Antarctica]], is a prominent example of a dissected volcano. Volcanoes that were, on a geological timescale, recently active, such as for example [[Mount Kaimon]] in southern [[Kyūshū]], [[Japan]], tend to be undissected. [[Devils Tower]] in Wyoming is a famous example of exposed volcanic plug.

==Volcanic eruptions==
{{Main|Volcanic eruption}}

{{As of|2022|12}}, the [[Smithsonian Institution]]'s [[Global Volcanism Program]] database of volcanic eruptions in the [[Holocene]] [[Epoch (geology)|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.<ref name="GVP501">{{cite journal|url=https://volcano.si.edu/search_eruption.cfm|title=Database Search|journal=Volcanoes of the World (Version 5.0.1)|publisher=[[Smithsonian Institution]] [[Global Volcanism Program]]|date=December 19, 2022|access-date=January 12, 2023|author=Venzke, E. (compiler)|editor-first1=Edward|editor-last1=Venzke|doi=10.5479/si.GVP.VOTW5-2022.5.0|url-access=subscription}}</ref><ref name="Volc_Count">{{cite journal|url=https://volcano.si.edu/faq/index.cfm?question=activevolcanoes|title=How many active volcanoes are there?|journal=Volcanoes of the World (Version 5.0.1)|publisher=[[Smithsonian Institution]] [[Global Volcanism Program]]|date=December 19, 2022|access-date=January 12, 2023|author=Venzke, E. (compiler)|editor-first1=Edward|editor-last1=Venzke|doi=10.5479/si.GVP.VOTW5-2022.5.0|url-access=subscription}}</ref>

[[File:Volcanic injection.svg|thumb|Schematic of volcano injection of aerosols and gases]]
Eruption styles are broadly divided into magmatic, phreatomagmatic (hydrovolcanic), and phreatic eruptions.<ref name="vol cash">{{cite book|title=Volcanic Ash|publisher=[[University of California Press]]|page=246|last1=Heiken|first1=G.|last2=Wohletz|first2=K.|name-list-style=amp <!--|access-date=3 August 2010 -->}}</ref> The intensity of explosive volcanism is expressed using the [[volcanic explosivity index]] (VEI), which ranges from 0 for Hawaiian-type eruptions to 8 for supervolcanic eruptions:<ref>{{cite journal|last1=Newhall|first1=Christopher G.|last2=Self|first2=Stephen|year=1982|title=The Volcanic Explosivity Index (VEI): An Estimate of Explosive Magnitude for Historical Volcanism|url=http://www.agu.org/books/hg/v002/HG002p0143/HG002p0143.pdf|journal=[[Journal of Geophysical Research]]|volume=87|issue=C2|pages=1231–1238|bibcode=1982JGR....87.1231N|doi=10.1029/JC087iC02p01231|archive-url=https://web.archive.org/web/20131213194307/http://www.agu.org/books/hg/v002/HG002p0143/HG002p0143.pdf|archive-date=December 13, 2013}}</ref><ref name=nps3>{{cite web|title=Eruption Classifications - Volcanoes, Craters & Lava Flows (U.S. National Park Service)|website=[[National Park Service]]|url=https://www.nps.gov/subjects/volcanoes/eruption-classifications.htm|access-date=26 December 2024}}</ref>

* Magmatic eruptions are driven primarily by gas release due to decompression.<ref name="vol cash"/> 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 eruption]]s. The range of observed eruption styles is expressed from historical examples.
* [[Hawaiian eruption]]s are typical of volcanoes that erupt mafic lava with a relatively low gas content. These are almost entirely effusive, producing local [[lava fountain]]s and highly fluid lava flows but relatively little tephra. They are named after the [[Hawaii hotspot|Hawaiian volcanoes]]. The eruption column from these eruptions does not exceed {{convert|2|km|mi}} in height.
* [[Strombolian eruption]]s 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 eruption]]s 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 for 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]]. Eruption columns from these eruptions do not exceed {{convert|20|km|mi}} in height.
* [[Peléan eruption]]s 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 eruption]]s are characterized by sustained huge eruption columns whose collapse produces catastrophic pyroclastic flows. They are named after [[Pliny the Younger]], who chronicled the Plinian [[eruption of Mount Vesuvius in 79]] AD.
* Ultra-Plinian eruptions are the largest of all volcanic eruptions are more intense, have a higher eruption rate than Plinian ones, form higher eruption columns and may form large calderas. These eruptions produce rhyolitic lava, tephra, [[pumice]] and thick pyroclastic flows that cover vast areas and may produce widespread [[Volcanic ash|ash-fall]] deposits. Examples are [[Mount Mazama|Mt. Mazama]] and Yellowstone.
* [[Phreatomagmatic eruption]]s (hydrovolcanic) are characterized by interaction of rising magma with [[groundwater]]. They are driven by the resulting rapid buildup of pressure in the [[Superheating|superheated]] groundwater.
* [[Phreatic eruption]]s 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 (geology)|country rock]]; no magma is erupted.

==Volcanic activity== <!-- [[Dormant volcano]] redirects here -->
[[File:Pompeii - Casa del Centenario - MAN.jpg|thumb|upright|[[Fresco]] with [[Mount Vesuvius]] behind [[Bacchus]] and [[Agathodaemon]], as seen in [[Pompeii]]'s [[House of the Centenary]]]]

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.<ref>{{cite book|last1=Martí Molist|first1=Joan|title=Oxford Handbook Topics in Physical Sciences|chapter=Assessing Volcanic Hazard|date=September 6, 2017|volume=1|doi=10.1093/oxfordhb/9780190699420.013.32|isbn=978-0-19-069942-0}}</ref> Volcanoes are informally described as '''erupting''', '''active''', '''dormant''', or '''extinct''', but the definitions of these terms are not entirely uniform among 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.<ref name=ade>{{cite web|last1=Pariona|first1=Amber|title=Difference Between an Active, Dormant, and Extinct Volcano|date=September 19, 2019|url=https://www.worldatlas.com/articles/when-is-a-volcano-considered-active-dormant-or-extinct.html|publisher=WorldAtlas.com|access-date=November 27, 2020}}</ref>

=== 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===
{{Main|Active volcano}}

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 swarm]]s, ground inflation, or unusually high levels of carbon dioxide or sulfur dioxide are present.<ref>[https://www.usgs.gov/volcanoes/kilauea/recent-eruption Kilauea eruption confined to crater] {{Webarchive|url=https://web.archive.org/web/20220717144650/https://www.usgs.gov/volcanoes/kilauea/recent-eruption |date=July 17, 2022 }} usgs.gov. Updated July 24, 2022. Downloaded July 24, 2022.</ref><ref name="activity_levels">[https://www.wired.com/2015/08/tell-volcano-active-dormant-extinct/ How We Tell if a Volcano Is Active, Dormant, or Extinct] {{Webarchive|url=https://web.archive.org/web/20220725042124/https://www.wired.com/2015/08/tell-volcano-active-dormant-extinct/ |date=July 25, 2022 }} Wired. August 15, 2015. By Erik Klimetti. Downloaded July 24, 2022.</ref>

===Dormant and reactivated{{anchor|Dormant}}===
<!-- [[Dormant volcano]] redirects here -->
[[File:Narcondam island.jpg|thumb|[[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.<ref name="activity_levels" /> 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.<ref name="Nelson2016">{{cite web|url=http://www.tulane.edu/~sanelson/Natural_Disasters/volhaz%26pred.htm|title=Volcanic Hazards & Prediction of Volcanic Eruptions|publisher=Tulane University|date=October 4, 2016|access-date=September 5, 2018|last=Nelson|first=Stephen A.|archive-date=March 19, 2023|archive-url=https://web.archive.org/web/20230319081358/http://www2.tulane.edu/~sanelson/Natural_Disasters/volhaz%26pred.htm|url-status=dead}}</ref><ref name="VolcWorldDormant">{{cite web|url=http://volcano.oregonstate.edu/how-volcano-defined-being-active-dormant-or-extinct|title=How is a volcano defined as being active, dormant, or extinct?|work=Volcano World|publisher=Oregon State University|access-date=September 5, 2018|archive-date=January 12, 2013|archive-url=https://web.archive.org/web/20130112014631/http://volcano.oregonstate.edu/how-volcano-defined-being-active-dormant-or-extinct|url-status=dead}}</ref>

In an article justifying the re-classification of Alaska's [[Mount Edgecumbe (Alaska)|Mount Edgecumbe]] volcano from "dormant" to "active", volcanologists at the [[Alaska Volcano Observatory]] pointed out that the term "dormant" in reference to volcanoes has been deprecated over the past few decades and that "[t]he term "dormant volcano" is so little used and undefined in modern volcanology that the Encyclopedia of Volcanoes (2000) does not contain it in the glossaries or index",<ref>{{cite web|url=https://www.avo.alaska.edu/news.php?id=1576|title=Mount Edgecumbe volcanic field changes from 'dormant' to 'active' -- what does that mean?|author=<!--Not stated-->|date=May 9, 2022|publisher=Alaska Volcano Observatory|access-date=June 2, 2022}}{{Dead link|date=August 2025 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> 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 generalization is inconsistent with observation and deeper study, as has occurred recently with the unexpected eruption of the [[Chaitén (volcano)|Chaitén volcano]] in 2008.<ref name=Castro2009>{{cite journal|last1=Castro|first1=J.|last2=Dingwell|first2=D.|title=Rapid ascent of rhyolitic magma at Chaitén volcano, Chile|journal=Nature|volume=461|pages=780–783|year=2009|issue=7265|doi=10.1038/nature08458|pmid=19812671|bibcode=2009Natur.461..780C|s2cid=4339493|url=https://insu.hal.science/insu-00423346 }}</ref> Modern volcanic activity monitoring techniques, and improvements in the modelling of the factors that produce eruptions, have helped the understanding of why volcanoes may remain dormant for a long time, and then become unexpectedly active again. The potential for eruptions, and their style, depend mainly upon the state of the magma storage system under the volcano, the eruption trigger mechanism and its timescale.<ref name="Cserép2023">{{cite journal|last1=Cserép|first1=B.|last2=Szemerédi|first2=M.|last3=Harangi|first3=S.|last4=Erdmann|first4=S.|last5=Bachmann|first5=O.|last6=Dunkl|first6=I.|last7=Seghedi|first7=I.|last8=Mészáros|first8=K.|last9=Kovács|first9=Z.|last10 =Virág| first10=A|last11=Ntaflos|first11=T.|title=Constraints on the pre-eruptive magma storage conditions and magma evolution of the 56–30 ka explosive volcanism of Ciomadul (East Carpathians, Romania)|journal=Contribribtions to Mineralogy and Petrology|volume=178|issue=96|year=2023|article-number=96 |doi=10.1007/s00410-023-02075-z|bibcode=2023CoMP..178...96C|doi-access=free|hdl=20.500.11850/646219|hdl-access=free}}</ref>{{rp|95}} For example, the [[Yellowstone Caldera|Yellowstone]] volcano has a repose/recharge period of around 700,000 years, and [[Toba Lake|Toba]] of around 380,000 years.<ref name="chesner1991">{{cite journal|doi=10.1130/0091-7613(1991)019<0200:EHOESL>2.3.CO;2|url=http://www.geo.mtu.edu/~raman/papers/ChesnerGeology.pdf|last1=Chesner|first1=C.A.|last2=Rose|first2=J.A.|last3=Deino|first3=W.I.|last4=Drake|first4=R.|last5=Westgate|first5=A.|title=Eruptive History of Earth's Largest Quaternary caldera (Toba, Indonesia) Clarified|volume=19|pages=200–203|journal=Geology|date=March 1991|access-date=January 20, 2010|issue=3|bibcode=1991Geo....19..200C}}</ref> [[Vesuvius]] was described by Roman writers as having been covered with gardens and vineyards before its unexpected [[Eruption of Mount Vesuvius in 79|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.<ref name="Cserép2023"/>{{rp|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 that 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, Montserrat|Plymouth]] into a [[ghost town]]) and [[Fourpeaked Mountain]] in Alaska, which, before its September 2006 eruption, had not erupted since before 8000 BCE.

===Extinct===
<!-- [[Extinct volcano]] redirects here -->
[[File:Capulin 1980 tde00005.jpg|thumb|[[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]], [[United States|U.S.]], [[Capulin Volcano National Monument|Capulin]] in New Mexico, U.S., [[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 (Edinburgh)|Castle Rock]]. Whether a volcano is truly extinct is often difficult to determine. Since "supervolcano" [[caldera]]s 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.<ref>{{cite web|url=http://www.volcanolive.com/alerts.html|title=Volcanic Alert Levels of Various Countries|publisher=Volcanolive.com|access-date=August 22, 2011}}</ref> Some alert systems use different numbers or colours to designate the different stages. Other systems use colours and words. Some systems use a combination of both.

==Decade volcanoes==
[[File:Koryaksky volcano Petropavlovsk-Kamchatsky oct-2005.jpg|thumb|[[Koryaksky]] volcano towering over [[Petropavlovsk-Kamchatsky]] on [[Kamchatka Peninsula]], Far Eastern [[Russia]]]]
{{Main|Lists of volcanoes|Decade Volcanoes}}
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:
{{div col|colwidth=20em}}
* [[Avachinsky]]-[[Koryaksky]] (grouped together), [[Kamchatka]], Russia
* [[Nevado de Colima]], [[Jalisco]] and [[Colima]], Mexico
* [[Mount Etna]], Sicily, Italy
* [[Galeras]], [[Nariño]], Colombia
* [[Mauna Loa]], Hawaii, US
* [[Mount Merapi]], [[Central Java]], Indonesia
* [[Mount Nyiragongo]], Democratic Republic of the Congo
* [[Mount Rainier]], [[Washington (state)|Washington]], US
* [[Sakurajima]], [[Kagoshima Prefecture]], Japan
* [[Santa María (volcano)|Santa Maria/Santiaguito]], Guatemala
* [[Santorini]], [[Cyclades]], Greece
* [[Taal Volcano]], [[Luzon]], Philippines
* [[Teide]], Canary Islands, Spain
* [[Ulawun]], [[New Britain]], Papua New Guinea
* [[Mount Unzen]], [[Nagasaki Prefecture]], Japan
* [[Vesuvius]], [[Province of Naples|Naples]], Italy
{{div col end}}

The [[Deep Earth Carbon Degassing Project]], an initiative of the [[Deep Carbon Observatory]], monitors nine volcanoes, two of which are Decade volcanoes. The focus of the Deep Earth Carbon Degassing Project is to use [[Multi-Component Gas Analyzer System]] instruments to measure CO<sub>2</sub>/SO<sub>2</sub> ratios in real-time and in high-resolution to allow detection of the pre-eruptive degassing of rising magmas, improving [[prediction of volcanic activity]].<ref>{{cite journal|last1=Aiuppa|first1=Alessandro|last2=Moretti|first2=Roberto|last3=Federico|first3=Cinzia|last4=Giudice|first4=Gaetano|last5=Gurrieri|first5=Sergio|last6=Liuzzo|first6=Marco|last7=Papale|first7=Paolo|last8=Shinohara|first8=Hiroshi|last9=Valenza|first9=Mariano|title=Forecasting Etna eruptions by real-time observation of volcanic gas composition|journal=Geology|year=2007|volume=35|issue=12|pages=1115–1118|doi=10.1130/G24149A.1|bibcode=2007Geo....35.1115A}}</ref>

==Volcanoes and humans==
[[File:Mauna Loa atmospheric transmission.png|thumb|Solar radiation graph 1958–2008, showing how the radiation is reduced after major volcanic eruptions]]
[[File:SO2 Galapagos 20051101.jpg|thumb|right|[[Sulfur dioxide]] concentration over the [[Sierra Negra (Galápagos)|Sierra Negra Volcano]], [[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===
{{Main|Volcanic hazard}}
There are many different [[types of volcanic eruptions]] and associated activity: [[phreatic eruptions]] (steam-generated eruptions), explosive eruptions of high-[[silica]] lava (e.g., [[rhyolite]]), effusive eruptions of low-silica lava (e.g., [[basalt]]), [[sector collapse]]s, [[pyroclastic flow]]s, [[lahar]]s (debris flows) and [[Volcanic gas|volcanic gas emissions]]. These can pose a hazard to humans. Earthquakes, [[hot spring]]s, [[fumarole]]s, [[mud pot]]s and [[geyser]]s 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.<ref>{{cite journal|last1=Miles|first1=M.G.|last2=Grainger|first2=R.G.|last3=Highwood|first3=E.J.|title=The significance of volcanic eruption strength and frequency for climate|journal=Quarterly Journal of the Royal Meteorological Society|year=2004|volume=130|issue=602|pages=2361–2376|doi=10.1256/qj.03.60|url=http://eodg.atm.ox.ac.uk/eodg/papers/2004Miles1.pdf|bibcode=2004QJRMS.130.2361M|s2cid=53005926}}

</ref> Sulfur dioxide from the eruption of [[Huaynaputina]] may have caused the [[Russian famine of 1601–1603]].<ref>{{cite web|author=University of California – Davis|title=Volcanic Eruption Of 1600 Caused Global Disruption|date=April 25, 2008|work=ScienceDaily|url=https://www.sciencedaily.com/releases/2008/04/080423135236.htm}}</ref> 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.<ref>{{cite book|last=Thorarinsson|first=Sigurdur|author-link=Sigurdur Thorarinsson|others=trans. Jóhann Hannesson, Pétur Karlsson|title=Hekla, A Notorious Volcano|year=1970|publisher=Almenna bókafélagið|location=Reykjavík}}</ref>{{rp|pp=39–58}} [[Explosive eruption|Explosive volcanic eruptions]] release the greenhouse gas [[carbon dioxide]] and thus provide a deep source of [[carbon]] for [[biogeochemical cycle]]s.<ref>{{citation-attribution|1={{cite web|url=https://pubs.usgs.gov/of/1997/of97-262/of97-262.html|title=Impacts of Volcanic Gases on Climate, the Environment, and People|first1=Kenneth A.|last1=McGee|first2=Michael P.|last2=Doukas|first3=Richard|last3=Kessler|first4=Terrence M.|last4=Gerlach|date=May 1997|publisher=United States Geological Survey|access-date=August 9, 2014}} }}</ref>

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.

[[File:Large eruptions.jpg|thumb|upright=1.3|Comparison of major United States prehistoric eruptions ([[VEI|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 [[volcanic winter]] is thought to have taken place around 70,000 years ago after the [[supereruption]] of [[Lake Toba]] on Sumatra island in Indonesia.<ref>{{cite web|title=Supervolcano eruption – in Sumatra – deforested India 73,000 years ago|url=https://www.sciencedaily.com/releases/2009/11/091123142739.htm|website=ScienceDaily|date=November 24, 2009}}</ref> This may have created a [[Toba catastrophe theory|population bottleneck]] that affected the genetic inheritance of all humans today.<ref>{{cite news|url=http://news.bbc.co.uk/2/hi/science/nature/2975862.stm|title=When humans faced extinction|publisher=BBC|date=June 9, 2003|access-date=January 5, 2007}}</ref> Volcanic eruptions may have contributed to major extinction events, such as the [[Ordovician-Silurian extinction events|End-Ordovician]], [[Permian-Triassic]], and [[Late Devonian extinction|Late Devonian]] [[mass extinction]]s.<ref>{{cite web|last1=O'Hanlon|first1=Larry|title=Yellowstone's Super Sister|url=http://www.discovery.com/convergence/supervolcano/others/others_07.html|website=Discovery Channel|archive-url=https://web.archive.org/web/20050314025022/http://dsc.discovery.com/convergence/supervolcano/others/others_07.html|archive-date=March 14, 2005|date=March 14, 2005}}</ref>

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.<ref>''[https://books.google.com/books?id=ipNcKc0Mv5IC&pg=PA155 Volcanoes in human history: the far-reaching effects of major eruptions]''. Jelle Zeilinga de Boer, Donald Theodore Sanders (2002). [[Princeton University Press]]. p. 155. {{ISBN|0-691-05081-3}}</ref> The freezing winter of 1740–41, which led to widespread [[Irish Famine (1740–1741)|famine]] in northern Europe, may also owe its origins to a volcanic eruption.<ref>{{cite web|last1=Ó Gráda|first1=Cormac|title=Famine: A Short History|url=http://press.princeton.edu/chapters/s8857.html|publisher=Princeton University Press|archive-url=https://web.archive.org/web/20160112061115/http://press.princeton.edu/chapters/s8857.html|archive-date=January 12, 2016|date=February 6, 2009}}</ref>

===Benefits===
{{See also|Volcanogenic massive sulfide ore deposit|Geothermal power}}
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.<ref name="marcari-etal-2007">Marcari, G., G. Fabbrocino, and G. Manfredi. "Shear seismic capacity of tuff masonry panels in heritage constructions." Structural Studies, Repairs and Maintenance of Heritage Architecture X 95 (2007): 73.</ref><ref name="dolan-etal-2019">{{cite journal|last1=Dolan|first1=S.G.|last2=Cates|first2=K.M.|last3=Conrad|first3=C.N.|last4=Copeland|first4=S.R.|title=Home Away from Home: Ancestral Pueblo Fieldhouses in the Northern Rio Grande|journal=Lanl-Ur|date=March 14, 2019|volume=19-21132|pages=96|url=https://permalink.lanl.gov/object/tr?what=info:lanl-repo/lareport/LA-UR-19-21132|access-date=September 29, 2020}}</ref> The Romans often used tuff, which is abundant in Italy, for construction.<ref name="jackson-etal-2005">{{cite journal|last1=Jackson|first1=M. D.|last2=Marra|first2=F.|last3=Hay|first3=R. L.|last4=Cawood|first4=C.|last5=Winkler|first5=E. M.|title=The Judicious Selection and Preservation of Tuff and Travertine Building Stone in Ancient Rome*|journal=Archaeometry|year=2005|volume=47|issue=3|pages=485–510|doi=10.1111/j.1475-4754.2005.00215.x|doi-access=free|bibcode=2005Archa..47..485J }}</ref> The [[Rapa Nui]] people used tuff to make most of the ''[[moai]]'' statues in [[Easter Island]].<ref name="collins-2016-150-151">Richards, Colin. 2016. [https://books.google.com/books?id=FPQhDAAAQBAJ&dq=moai+construction&pg=PA149 "Making Moai: Reconsidering Concepts of Risk in the Construction of Megalithic Architecture in Rapa Nui (Easter Island)"] {{Webarchive|url=https://web.archive.org/web/20221114150457/https://books.google.com/books?hl=en&lr=&id=FPQhDAAAQBAJ&oi=fnd&pg=PA149&dq=moai+construction&ots=j1xHNuEeze&sig=G8ncDnByQt0qat7itwXSXpSPY4M#v=onepage&q=moai%20construction&f=false |date=November 14, 2022 }}. ''Rapa Nui–Easter Island: Cultural and Historical Perspectives'', pp.150-151</ref>

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.<ref name="kiprop-2019">{{cite web|last1=Kiprop|first1=Joseph|date=January 18, 2019|title=Why Is Volcanic Soil Fertile?|url=https://www.worldatlas.com/articles/why-is-volcanic-soil-fertile.html|access-date=November 27, 2020|website=WorldAtlas.com}}</ref> Volcanic activity is responsible for emplacing valuable mineral resources, such as metal ores.<ref name="kiprop-2019" /> It is accompanied by high rates of heat flow from Earth's interior. These can be tapped as [[geothermal power]].<ref name="kiprop-2019" />

Tourism associated with volcanoes is also a worldwide industry.<ref name=Thomaidis2021>{{cite journal|last1=Thomaidis|first1=K|last2=Troll|first2=VR|last3=Deegan|first3=FM|last4=Freda|first4=C|last5=Corsaro|first5=RA|last6=Behncke|first6=B|last7=Rafailidis|first7=S|title=A message from the 'underground forge of the gods': History and current eruptions at Mt Etna|journal=Geology Today|year=2021|volume=37|issue=4|pages=141–9|doi=10.1111/gto.12362|bibcode=2021GeolT..37..141T|s2cid=238802288|url=https://www.earth-prints.org/bitstream/2122/15268/3/Geology_Today_Mt.Etna.pdf}}</ref>

=== 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.<ref>[https://www.nationalgeographic.com/environment/article/volcano-safety-tips Volcano Safety Tips] {{Webarchive|url=https://web.archive.org/web/20220725072141/https://www.nationalgeographic.com/environment/article/volcano-safety-tips |date=July 25, 2022 }} National Geographic. By Maya Wei-Haas. 2015. Downloaded June 24, 2022.</ref> The diversity of volcanoes and their complexities mean that eruption forecasts for the foreseeable future will be based on [[Probability theory|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 a presumed to be 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.<ref name=Thomaidis2021/> Other types of significant eruptions are known to give useful warnings of only hours at the most by seismic monitoring.<ref name=Castro2009/> The recent demonstration of a magma chamber with repose times of tens of thousands of years, with potential for rapid recharge so potentially decreasing warning times, under the youngest volcano in central Europe,<ref name="Cserép2023"/> does not tell us if more careful monitoring will be useful.

Scientists are known to perceive risk, with its social elements, differently from 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.<ref>{{cite journal|last1=Donovan|first1=A|last2=Eiser|first2=JR|last3=Sparks|first3=RS|title=Scientists' views about lay perceptions of volcanic hazard and risk|journal=Journal of Applied Volcanology|year=2014|volume=3|issue=1|pages=1–14|doi=10.1186/s13617-014-0015-5|bibcode=2014JApV....3...15D|doi-access=free}}</ref>{{rp|pp=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 before 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.<ref>[https://www.livescience.com/14603-pinatubo-eruption-20-anniversary.html Pinatubo: Why the Biggest Volcanic Eruption Wasn't the Deadliest] {{Webarchive|url=https://web.archive.org/web/20220719034051/https://www.livescience.com/14603-pinatubo-eruption-20-anniversary.html |date=July 19, 2022 }} LiveScience. By Stephanie Pappas. June 15, 2011.  Downloaded July 25, 2022.</ref> In the case of [[Mount Etna]], a 2021 review found 77 deaths due to eruptions since 1536 but none since 1987.<ref name=Thomaidis2021/>

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.<ref>[https://www.courthousenews.com/about-to-blow-are-we-ready-for-the-next-volcanic-catastrophe/ About to blow: Are we ready for the next volcanic catastrophe?] {{Webarchive|url=https://web.archive.org/web/20220817224316/https://www.courthousenews.com/about-to-blow-are-we-ready-for-the-next-volcanic-catastrophe/ |date=August 17, 2022 }} Courthouse News Service. By Candace Cheung.  August 17, 2022. Downloaded August 17, 2022.</ref>

==Volcanoes on other celestial bodies==
{{see also|List of extraterrestrial volcanoes|Volcanism on the Moon|Volcanism on Mars|Volcanism on Io|Volcanism on Venus}}
[[File:Tvashtarvideo.gif|left|thumb|The [[Tvashtar Paterae|Tvashtar]] volcano erupts a plume 330&nbsp;km (205&nbsp;mi) above the surface of [[Jupiter]]'s moon [[Io (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.<ref>{{cite journal|last1=Wieczorek|first1=Mark A.|last2=Jolliff|first2=Bradley L.|last3=Khan|first3=Amir|last4=Pritchard|first4=Matthew E.|last5=Weiss|first5=Benjamin P.|last6=Williams|first6=James G.|last7=Hood|first7=Lon L.|last8=Righter|first8=Kevin|last9=Neal|first9=Clive R.|last10=Shearer|first10=Charles K.|last11=McCallum|first11=I. Stewart|last12=Tompkins|first12=Stephanie|last13=Hawke|first13=B. Ray|last14=Peterson|first14=Chris|last15=Gillis|first15=Jeffrey J.|last16=Bussey|first16=Ben|title=The constitution and structure of the lunar interior|journal=[[Reviews in Mineralogy and Geochemistry]]|date=January 1, 2006|volume=60|issue=1|pages=221–364|doi=10.2138/rmg.2006.60.3|bibcode=2006RvMG...60..221W|s2cid=130734866}}</ref> However, the Moon does have many volcanic features such as [[lunar mare|maria]]<ref>{{cite web|url=https://volcano.oregonstate.edu/mare|title=Mare|author=<!--Not stated-->|date=January 4, 2012|website=Volcano World|publisher=Oregon State University|access-date=November 12, 2023}}</ref> (the darker patches seen on the Moon), [[rille]]s<ref>{{cite web|url=https://volcano.oregonstate.edu/sinuous-rilles|title=Sinuous Rilles|author=<!--Not stated-->|date=January 4, 2012|website=Volcano World|publisher=Oregon State University|access-date=November 17, 2023}}</ref> and [[lunar dome|domes]].<ref>{{Cite web|title=A Lunar Mystery: The Gruithuisen Domes|url=https://moon.nasa.gov/resources/482/a-lunar-mystery-the-gruithuisen-domes|access-date=January 6, 2024|website=Moon: NASA Science|date=April 20, 2022 }}</ref>

The planet [[Venus]] has a surface that is 90% [[basalt]], indicating that volcanism played a major role in shaping its surface. The planet may have had a major global resurfacing event about 500 million years ago,<ref>{{cite journal|last1=Bindschadler|first1=D.L.|title=Magellan: A new view of Venus' geology and geophysics|journal=Reviews of Geophysics|year=1995|volume=33|issue=S1|pages=459–467|doi=10.1029/95RG00281|bibcode=1995RvGeo..33S.459B}}</ref> from what scientists can tell from the density of impact craters on the surface. [[Lava flows]] are widespread and forms of volcanism not present on Earth occur as well. Changes in the planet's atmosphere and observations of lightning have been attributed to ongoing volcanic eruptions, although there is no confirmation of whether or not Venus is still volcanically active. However, radar sounding by the Magellan probe revealed evidence for comparatively recent volcanic activity at Venus's highest volcano [[Maat Mons]], in the form of [[ash flow]]s near the summit and on the northern flank.<ref>{{cite journal|last1=Robinson|first1=Cordula A.|last2=Thornhill|first2=Gill D.|last3=Parfitt|first3=Elisabeth A.|title=Large-scale volcanic activity at Maat Mons: Can this explain fluctuations in atmospheric chemistry observed by Pioneer Venus?|journal=Journal of Geophysical Research|year=1995|volume=100|issue=E6|pages=11755|doi=10.1029/95JE00147|bibcode=1995JGR...10011755R}}</ref> However, the interpretation of the flows as ash flows has been questioned.<ref>{{cite journal|last1=Mouginis-Mark|first1=Peter J.|title=Geomorphology and volcanology of Maat Mons, Venus|journal=Icarus|date=October 2016|volume=277|pages=433–441|doi=10.1016/j.icarus.2016.05.022|bibcode=2016Icar..277..433M}}</ref>

[[File:Olympus Mons alt.jpg|thumb|upright|[[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,<ref name="ESAmarsvolcanoes">{{cite web|url=https://www.esa.int/Science_Exploration/Space_Science/Mars_Express/Glacial_volcanic_and_fluvial_activity_on_Mars_latest_images|title=Glacial, volcanic and fluvial activity on Mars: latest images|publisher=[[European Space Agency]]|access-date=July 21, 2024|date=February 25, 2005}}</ref> but the European ''[[Mars Express]]'' spacecraft has found evidence that volcanic activity may have occurred on Mars in the recent past as well.<ref name="ESAmarsvolcanoes"/>

[[Jupiter]]'s [[Natural satellite|moon]] [[Io (moon)|Io]] is the most volcanically active object in the Solar System because of [[tides|tidal]] interaction with Jupiter. It is covered with volcanoes that erupt [[sulfur]], [[sulfur dioxide]] and [[silicate]] rock, and as a result, [[Io (moon)|Io]] is constantly being resurfaced. Its lavas are the hottest known anywhere in the Solar System, with temperatures exceeding 1,800 K (1,500&nbsp;°C). In February 2001, the largest recorded volcanic eruptions in the Solar System occurred on Io.<ref>{{cite web|title=Exceptionally bright eruption on Io rivals largest in solar system|url=http://keckobservatory.org/recent/entry/exceptionally_bright_eruption_on_io_rivals_largest_in_solar_syatem/|website=W.M. Keck Observatory|date=November 13, 2002|access-date=May 2, 2018|archive-date=August 6, 2017|archive-url=https://web.archive.org/web/20170806235121/http://www.keckobservatory.org/recent/entry/exceptionally_bright_eruption_on_io_rivals_largest_in_solar_syatem|url-status=dead}}</ref> [[Europa (moon)|Europa]], the smallest of Jupiter's [[Galilean moon]]s, also appears to have an active volcanic system, except that its volcanic activity is entirely in the form of water, which freezes into [[ice]] on the frigid surface. This process is known as [[cryovolcanism]], and is apparently most common on the moons of the outer planets of the [[Solar System]].<ref>{{Citation|last=Geissler|first=Paul|title=Chapter 44 – Cryovolcanism in the Outer Solar System|date=January 1, 2015|url=https://www.sciencedirect.com/science/article/pii/B9780123859389000444|encyclopedia=The Encyclopedia of Volcanoes (Second Edition)|pages=763–776|editor-last=Sigurdsson|editor-first=Haraldur|access-date=January 6, 2024|place=Amsterdam|publisher=Academic Press|doi=10.1016/b978-0-12-385938-9.00044-4|isbn=978-0-12-385938-9|url-access=subscription}}</ref>

In 1989, the ''[[Voyager 2]]'' spacecraft observed [[cryovolcano]]es (ice volcanoes) on [[Triton (moon)|Triton]], a [[Natural satellite|moon]] of [[Neptune]], and in 2005 the ''[[Cassini–Huygens]]'' probe photographed [[Enceladus (moon)#Cryovolcanism|fountains of frozen particles erupting from Enceladus]], a moon of [[Saturn]].<ref>{{cite web|url=http://www.pparc.ac.uk/Nw/enceladus.asp|title=Cassini Finds an Atmosphere on Saturn's Moon Enceladus|date=March 16, 2005|work=[[PPARC]]|access-date=July 4, 2014|archive-url=https://web.archive.org/web/20070310211512/http://www.pparc.ac.uk/Nw/enceladus.asp|archive-date=March 10, 2007}}</ref><!-- replaced it above<ref>{{cite web|url=http://www.pparc.ac.uk/Nw/enceladus.asp|title=Cassini Finds an Atmosphere on Saturn's Moon Enceladus'|publisher=Pparc.ac.uk|access-date=October 24, 2010}}</ref> --><ref>{{cite web|url=http://www.nasa.gov/multimedia/imagegallery/image_feature_2198.html|title=Enceladus, Saturn's Moon|last=Smith|first=Yvette|date=March 15, 2012|work=Image of the Day Gallery|publisher=[[NASA]]|access-date=July 4, 2014}}</ref> The ejecta may be composed of water, [[liquid nitrogen]], [[ammonia]], dust, or [[methane]] compounds. ''Cassini–Huygens'' also found evidence of a methane-spewing cryovolcano on the [[Saturn]]ian moon [[Titan (moon)|Titan]], which is believed to be a significant source of the methane found in its atmosphere.<ref>{{cite web|url=https://www.newscientist.com/article.ns?id=dn7489|title=Hydrocarbon volcano discovered on Titan|date=June 8, 2005|work=New Scientist|access-date=October 24, 2010|archive-date=September 19, 2007|archive-url=https://web.archive.org/web/20070919022956/http://www.newscientist.com/article.ns?id=dn7489|url-status=dead}}</ref> It is theorized that cryovolcanism may also be present on the [[Kuiper Belt Object]] [[Quaoar]].

A 2010 study of the [[exoplanet]] [[COROT-7b]], which was detected by [[transit method|transit]] in 2009, suggested that [[tidal heating]] from the host star very close to the planet and neighbouring planets could generate intense volcanic activity similar to that found on Io.<ref>{{cite web|last=Jaggard|first=Victoria|title="Super Earth" May Really Be New Planet Type: Super-Io|work=National Geographic web site daily news|publisher=[[National Geographic Society]]|date=February 5, 2010|url=http://news.nationalgeographic.com/news/2010/02/100205-new-type-planet-corot-7b-io/|archive-url=https://web.archive.org/web/20100209014528/http://news.nationalgeographic.com/news/2010/02/100205-new-type-planet-corot-7b-io/|url-status=dead|archive-date=February 9, 2010|access-date=March 11, 2010}}</ref>

==History of volcano understanding==
{{Main|Volcanology#History}}

Volcanoes are not distributed evenly over the Earth's surface but active ones with significant impact were encountered early in human history, evidenced by footprints of [[hominina]] found in East African volcanic ash dated at 3.66 million years old.<ref>{{cite journal|last1=Zaitsev|first1=AN|last2=Chakhmouradian|first2=AR|last3=Musiba|first3=C|title=Laetoli: The Oldest Known Hominin Footprints in Volcanic Ash|journal=Elements|year=2023|volume=19|issue=2|pages=104–10|doi=10.2138/gselements.19.2.104|bibcode=2023Eleme..19..104Z|s2cid=259423377}}</ref>{{rp|p=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,<ref>,{{cite journal|last1=Fast|first1=PA|title=The volcano in Athabascan oral narratives|journal=Alaska Journal of Anthropology|year=2008|volume=6|issue=1–2|pages=131–40|url=https://www.alaskaanthropology.org/wp-content/uploads/2017/08/akanth-articles_261_v6_n12_Fast.pdf|access-date=November 11, 2023}}</ref>{{rp|p=135}} (2) [[Pele (deity)|Pele]]'s migration through the Hawarian island chain, ability to destroy forests and manifestations of the god's temper,<ref>{{cite journal|last1=Swanson|first1=DA|title=Hawaiian oral tradition describes 400 years of volcanic activity at Kīlauea|journal=Journal of Volcanology and Geothermal Research|year=2008|volume=176|issue=3|pages=427–31|doi=10.1016/j.jvolgeores.2008.01.033|bibcode=2008JVGR..176..427S}}</ref> and (3) the association in Javanese folklore of a king resident in [[Mount Merapi]] volcano and a queen resident at a beach {{convert|50|km|abbr=on}} away on what is now known to be an earthquake fault that interacts with that volcano.<ref>{{cite journal|last1=Troll|first1=VR|last2=Deegan|first2=FM|last3=Jolis|first3=EM|last4=Budd|first4=DA|last5=Dahren|first5=B|last6=Schwarzkopf|first6=LM|title=Ancient oral tradition describes volcano–earthquake interaction at Merapi volcano, Indonesia|journal=Geografiska Annaler: Series A, Physical Geography|year=2015|volume=97|issue=1|pages=137–66|doi=10.1111/geoa.12099|bibcode=2015GeAnA..97..137T|s2cid=129186824}}</ref>

Many ancient accounts ascribe volcanic eruptions to [[supernatural]] causes, such as the actions of [[gods]] or [[demigod]]s. The earliest known such example is a neolithic goddess at [[Çatalhöyük]].<ref name=Chester2007>{{cite book|last1=Chester|first1=DK|last2=Duncan|first2=AM|chapter=Geomythology, theodicy, and the continuing relevance of religious worldviews on responses to volcanic eruptions|title=Living under the shadow: The cultural impacts of volcanic eruptions|year=2007|pages=203–24|chapter-url=https://assets.pubpub.org/dzhycvw5/41608048843389.pdf|editor-last1=Grattan|editor-first1=J|editor-last2=Torrence|editor-first2=R|publisher=Walnut Creek: Left Coast|isbn=9781315425177}}</ref>{{rp|p=203}} The Ancient Greek god [[Hephaistos]] and the concepts of the underworld are aligned to volcanoes in that Greek culture.<ref name=Thomaidis2021/>

However, others proposed more natural (but still incorrect) causes of volcanic activity. In the fifth century BC, [[Anaxagoras]] proposed eruptions were caused by a great wind.<ref name=Sigurdsson2000>{{cite book|last1=Sigurdsson|first1=H|last2=Houghton|first2=B|last3=Rymer|first3=H|last4=Stix|first4=J|last5=McNutt|first5=S|chapter=The history of volcanology|title=Encyclopedia of volcanoes|year=2000|pages=15–37|publisher=Academic Press|isbn=9780123859396}}</ref> By 65&nbsp;CE, [[Seneca the Younger]] proposed combustion as the cause,<ref name=Sigurdsson2000/> an idea also adopted by the [[Jesuit]] [[Athanasius Kircher]] (1602–1680), who witnessed eruptions of [[Mount Etna]] and [[Stromboli]], then visited the crater of [[Vesuvius]] and published his view of an Earth in ''[[Mundus Subterraneus]]'' with a central fire connected to numerous others depicting volcanoes as a type of safety valve.<ref>{{cite journal|last1=Major|first1=RH|title=Athanasius Kircher|journal=Annals of Medical History|year=1939|volume=1|issue=2|pages=105–120|pmid=33943407|pmc=7939598}}</ref> Edward Jorden, in his work on mineral waters, challenged this view; in 1632 he proposed [[sulfur]] "fermentation" as a heat source within Earth,<ref name=Sigurdsson2000/> Astronomer [[Johannes Kepler]] (1571–1630) believed volcanoes were ducts for Earth's tears.<ref>{{cite magazine|first=Micheal|last=Williams|date=November 2007|title=Hearts of fire|magazine=Morning Calm|publisher=[[Korean Air Lines]]|issue=11–2007|page=6}}</ref>{{Better source needed|reason=cited source reference – an article in "Morning Calm", a Korean airline's in-flight magazine for passengers – is probably not a reliable source of science history|date=November 2023}} In 1650, [[René Descartes]] proposed the core of Earth was incandescent and, by 1785, the works of Decartes and others were synthesized into geology by [[James Hutton]] in his writings about [[igneous intrusion]]s of magma.<ref name=Sigurdsson2000/> [[Lazzaro Spallanzani]] had demonstrated by 1794 that steam explosions could cause explosive eruptions and many geologists held this as the universal cause of explosive eruptions up to the [[1886 eruption of Mount Tarawera]] which allowed in one event differentiation of the concurrent [[phreatomagmatic]] and [[hydrothermal]] eruptions from dry explosive eruption, of, as it turned out, a basalt [[Dike (geology)|dyke]].<ref>{{cite book|first1=F.W.|last1=Hutton|title=Report on the Tarawera volcanic district|publisher=Government Printer|location=Wellington, New Zealand|url=https://nzetc.victoria.ac.nz/tm/scholarly/tei-Stout67-t17.html|year=1887|access-date=August 30, 2023|archive-date=August 29, 2023|archive-url=https://web.archive.org/web/20230829102014/https://nzetc.victoria.ac.nz/tm/scholarly/tei-Stout67-t17.html|url-status=live}}</ref>{{rp|16–18}}<ref>{{cite journal|last1=Berryman|first1=Kelvin|last2=Villamor|first2=Pilar|last3=Nairn|first3=Ian.A.|last4=Begg|first4=John|last5=Alloway|first5=Brent V.|last6=Rowland|first6=Julie|last7=Lee|first7=Julie|last8=Capote|first8=Ramon|volume=427|date=July 1, 2022|title=Volcano-tectonic interactions at the southern margin of the Okataina Volcanic Centre, Taupō Volcanic Zone, New Zealand|doi=10.1016/j.jvolgeores.2022.107552|journal=Journal of Volcanology and Geothermal Research|article-number=107552|bibcode=2022JVGR..42707552B|s2cid=248111450|doi-access=free|hdl=2292/59681|hdl-access=free}}</ref>{{rp|4}} [[Alfred Lacroix]] built upon his other knowledge with his studies on the [[1902 eruption of Mount Pelée]],<ref name=Sigurdsson2000/> and by 1928 [[Arthur Holmes]] work had brought together the concepts of radioactive generation of heat, Earth's [[mantle (geology)|mantle]] structure, partial decompression melting of magma, and magma convection.<ref name=Sigurdsson2000/> This eventually led to the acceptance of plate tectonics.<ref>{{cite web|title=Arthur Holmes: Harnessing the Mechanics of Mantle Convection to the Theory of Continental Drift|url=https://www.amnh.org/education/resources/rfl/web/essaybooks/earth/p_holmes.html|access-date=November 12, 2023}}</ref>

==See also==
{{Portal|Volcanoes}}
{{div col|colwidth=30em}}
* {{annotated link|List of extraterrestrial volcanoes}}
* [[List of volcanoes]]
* [[List of volcanic eruptions by death toll]]
* [[List of volcanic landforms]]
* {{annotated link|Maritime impacts of volcanic eruptions}}
* {{annotated link|Prediction of volcanic activity}}
* {{annotated link|Timeline of volcanism on Earth}}
* {{annotated link|Volcano Number}}
* {{annotated link|Volcano observatory}}
{{div col end}}

==References==
{{reflist}}

==Further reading==
{{refbegin|30em}}
* {{cite book|last1=Macdonald|first1=Gordon|last2=Abbott|first2=Agatin|title=Volcanoes in the Sea: The Geology of Hawaii|publisher=University of Hawaii Press|year=1970|isbn=978-0-870-22495-9|url-access=registration|url=https://archive.org/details/volcanoesinseage00macd}}
* {{cite book|last1=Marti|first1=Joan|last2=Ernst|first2=Gerald.|name-list-style=amp|title=Volcanoes and the Environment|publisher=Cambridge University Press|year=2005|isbn=978-0-521-59254-3}}
* {{cite book|last=Ollier|first=Cliff|title=Volcanoes|publisher=Australian National University Press|year=1969|isbn=978-0-7081-0532-0}}
* {{cite book|editor-last=Sigurðsson|editor-first=Haraldur|title=The Encyclopedia of Volcanoes|publisher=Academic Press|year=2015|edition=2|isbn=978-0-12-385938-9}} This is a reference aimed at geologists, but many articles are accessible to non-professionals.
{{refend}}

==External links==
{{Commons category|Volcanoes}}
{{Wikivoyage|Volcanoes}}
{{Library resources box}}
* [https://www.disasterassistance.gov/information/disaster-types/volcano U.S. Federal Emergency Management Agency Volcano advice] {{Webarchive|url=https://web.archive.org/web/20210827114921/https://www.disasterassistance.gov/information/disaster-types/volcano |date=August 27, 2021 }}
* [https://volcano.oregonstate.edu/ Volcano World]
* {{cite GVP}}

{{Earth's landforms}}
{{List of volcanoes}}
{{Volcanoes}}

{{Authority control}}

[[Category:Volcanoes| ]]
[[Category:Geological hazards]]
[[Category:Volcanism]]
[[Category:Plate tectonics]]
[[Category:Volcanic landforms]]
[[Category:Volcanoes by status|*]]
[[Category:Volcanic rocks|*]]
[[Category:Volcanology]]
[[Category:Articles containing video clips]]