Volcano: Difference between revisions
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{{About|the geological feature||Volcano (disambiguation)|and|Volcanic (disambiguation)}} |
{{About|the geological feature||Volcano (disambiguation)|and|Volcanic (disambiguation)}} |
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[[File:Augustine volcano Jan 24 2006 - Cyrus Read.jpg|thumb|upright=1.35|[[Augustine Volcano]] (Alaska) during its eruptive phase on January 24, 2006]] |
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⚫ | 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 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 has been postulated to arise from upwelling [[diapir]]s from the [[core–mantle boundary]], {{convert|3000|km|mi|sp=us}} deep within Earth. This results in [[hotspot (geology)|hotspot volcanism]], of which the [[Hawaiian hotspot]] is an example. Volcanoes are usually not created where two tectonic plates slide past one another. |
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⚫ | 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 can also form where there is stretching and thinning of the crust's plates, such as in the [[East African Rift]] |
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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> |
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> |
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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> 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> |
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> 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> |
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This article mainly covers volcanoes on Earth. See {{section link|nopage=y|Volcano|Volcanoes on other celestial bodies}} and [[cryovolcano]] for more information. |
This article mainly covers volcanoes on Earth. See {{section link|nopage=y|Volcano|Volcanoes on other celestial bodies}} and [[cryovolcano]] for more information. |
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==Etymology== |
==Etymology== |
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The word ''volcano'' is derived from the name of [[Vulcano]], a volcanic island in the [[Aeolian Islands]] of Italy whose name in turn comes from [[Vulcan (mythology)|Vulcan]], the god of fire in [[Roman mythology]].<ref>{{cite web |url=http://press.princeton.edu/chapters/s7694.html |title=Volcano |work=Mind over Magma: The Story of Igneous Petrology |first1=Davis A.|last1=Young |year=2003 |access-date=January 11, 2016 |url-status=dead |archive-url=https://web.archive.org/web/20151112071530/http://press.princeton.edu/chapters/s7694.html |archive-date=November 12, 2015 }}</ref> The study of volcanoes is called [[volcanology]], sometimes spelled ''vulcanology''.<ref>{{cite web |title=Vulcanology |url=https://www.dictionary.com/browse/vulcanology |website=Dictionary.com |access-date= |
The word ''volcano'' is derived from the name of [[Vulcano]], a volcanic island in the [[Aeolian Islands]] of Italy whose name in turn comes from [[Vulcan (mythology)|Vulcan]], the god of fire in [[Roman mythology]].<ref>{{cite web |url=http://press.princeton.edu/chapters/s7694.html |title=Volcano |work=Mind over Magma: The Story of Igneous Petrology |first1=Davis A.|last1=Young |year=2003 |access-date=January 11, 2016 |url-status=dead |archive-url=https://web.archive.org/web/20151112071530/http://press.princeton.edu/chapters/s7694.html |archive-date=November 12, 2015 }}</ref> The study of volcanoes is called [[volcanology]], sometimes spelled ''vulcanology''.<ref>{{cite web |title=Vulcanology |url=https://www.dictionary.com/browse/vulcanology |website=Dictionary.com |access-date=November 27, 2020}}</ref> |
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==Plate tectonics== |
==Plate tectonics== |
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According to the theory of plate tectonics, Earth's [[lithosphere]], its rigid outer shell, is broken into sixteen larger and several smaller plates. These are in slow motion, due to [[convection]] in the underlying ductile [[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> |
According to the theory of plate tectonics, Earth's [[lithosphere]], its rigid outer shell, is broken into sixteen larger and several smaller plates. These are in slow motion, due to [[convection]] in the underlying ductile [[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> |
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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= |
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> |
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===Divergent plate boundaries=== |
===Divergent plate boundaries=== |
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{{Main|Divergent boundary}} |
{{Main|Divergent boundary}} |
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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 [[ |
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}} |
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===Convergent plate boundaries=== |
===Convergent plate boundaries=== |
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{{Main|Hotspot (geology)}} |
{{Main|Hotspot (geology)}} |
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[[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 |
[[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}} 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> |
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===Continental rifting=== |
===Continental rifting=== |
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==Volcanic features== |
==Volcanic features== |
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{{Further|Types of volcanoes}} |
{{Further|Types of volcanoes}} |
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[[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 |
[[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]] |
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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.<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= |
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.<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 | accessdate=November 3, 2023}}</ref> 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="NPS-Anat" /> |
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The most common perception of a volcano is of a [[ |
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 behavior 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 [[Pu'u 'Ō'ō|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 recognise as such and be obscured by geological processes. |
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Other types of volcano include [[cryovolcano]]es (or ice volcanoes), particularly on some moons of [[Jupiter]], [[Saturn]], and [[Neptune]]; and [[mud volcano]]es, which are structures often not associated with known magmatic activity. 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. |
Other types of volcano include [[cryovolcano]]es (or ice volcanoes), particularly on some moons of [[Jupiter]], [[Saturn]], and [[Neptune]]; and [[mud volcano]]es, which are structures often not associated with known magmatic activity. 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. |
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[[File:Skjaldbreidur Herbst 2004.jpg|right|thumbnail|[[Skjaldbreiður]], a shield volcano whose name means "broad shield"]] |
[[File:Skjaldbreidur Herbst 2004.jpg|right|thumbnail|[[Skjaldbreiður]], a shield volcano whose name means "broad shield"]] |
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Shield volcanoes, so named for their broad, shield-like profiles, are formed by the eruption of low-viscosity lava that can flow a great distance from a vent. They generally do not explode catastrophically |
Shield volcanoes, so named for their broad, shield-like profiles, are formed by the eruption of low-viscosity lava that can flow a great distance from a vent. They generally do not explode catastrophically but are characterized by relatively gentle [[effusive eruption]]s. 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. |
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===Lava domes=== |
===Lava domes=== |
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}}{{div col end}}]] |
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{{Main|Stratovolcano}} |
{{Main|Stratovolcano}} |
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Stratovolcanoes (composite volcanoes) are tall conical mountains composed of lava flows and [[tephra]] in alternate layers, the [[ |
Stratovolcanoes (composite volcanoes) 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. Classic examples include [[Mount Fuji]] in Japan, [[Mayon Volcano]] in the Philippines, and [[Mount Vesuvius]] and [[Stromboli]] in Italy. |
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[[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|sp=us}} 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> |
[[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|sp=us}} 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> |
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{{Main|Supervolcano}} |
{{Main|Supervolcano}} |
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{{see also|List of largest volcanic eruptions}} |
{{see also|List of largest volcanic eruptions}} |
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A supervolcano is defined as a volcano that has experienced one or more eruptions that produced over {{convert|1000|km3|cumi|sp=us}} 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 |work=Volcanic Hazards Program |publisher=[[USGS]] Yellowstone Volcano Observatory |date= |
A supervolcano is defined as a volcano that has experienced one or more eruptions that produced over {{convert|1000|km3|cumi|sp=us}} 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 |work=Volcanic Hazards Program |publisher=[[USGS]] 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 rivaling those of [[flood basalt]]s.{{sfn|Philpotts|Ague|2009|p=77}} |
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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. |
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. |
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{{Main|Submarine volcano}} |
{{Main|Submarine volcano}} |
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{{See also|Subaqueous volcano}} |
{{See also|Subaqueous volcano}} |
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[[File:Tonga Volcano Eruption 2022-01-15 0320Z to 0610Z Himawari-8 visible.gif|left|thumb|Satellite images of the |
[[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]]]] |
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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 | work=[[Global Volcanism Program]] Volcanoes of the World (version 4.9.1) | publisher=[[Smithsonian Institution]] | editor-last=Venzke | editor-first=E. |year=2013 | access-date= |
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 | work=[[Global Volcanism Program]] Volcanoes of the World (version 4.9.1) | publisher=[[Smithsonian Institution]] | 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? | work=[[Global Volcanism Program]] Volcanoes of the World (version 4.9.1) | publisher=[[Smithsonian Institution]] | 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. |
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In May and June 2018, a multitude of [[ |
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> |
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===Subglacial volcanoes=== |
===Subglacial volcanoes=== |
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{{Main|Subglacial volcano}} |
{{Main|Subglacial volcano}} |
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Subglacial volcanoes develop underneath [[ice cap |
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]] analyzed 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 }}</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]]. |
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===Mud volcanoes=== |
===Mud volcanoes=== |
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{{Main|Mud volcano}} |
{{Main|Mud volcano}} |
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Mud volcanoes (mud domes) are formations created by geo-excreted liquids and gases, although |
Mud volcanoes (mud domes) are formations created by geo-excreted liquids and gases, although several processes may cause such activity.<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> The largest structures are 10 kilometers in diameter and reach 700 meters high.<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> |
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==Erupted material== |
==Erupted material== |
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[[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--> |date= |website= Global Volcanism Program|publisher=Smithsonian Institution |access-date= |
[[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--> |date= |website= Global Volcanism Program|publisher=Smithsonian Institution |access-date=November 8, 2023 |quote=}}</ref>]] |
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[[File:Lava channel overflow.JPG|thumb|Pāhoehoe lava flow on [[Hawaii (island)|Hawaii]]. The picture shows overflows of a main [[lava channel]].]] |
[[File:Lava channel overflow.JPG|thumb|Pāhoehoe lava flow on [[Hawaii (island)|Hawaii]]. The picture shows overflows of a main [[lava channel]].]] |
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[[File:Litli-Hrútur eruption 2023.jpg|thumb|Litli-Hrútur ([[Fagradalsfjall]]) eruption 2023. View from an airplane]] |
[[File:Litli-Hrútur eruption 2023.jpg|thumb|Litli-Hrútur ([[Fagradalsfjall]]) eruption 2023. View from an airplane]] |
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[[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".]] |
[[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".]] |
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The material that is expelled in a [[ |
The material that is expelled in a [[volcanic eruption]] can be classified into three types: |
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#[[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) |
#[[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) |
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===Lava flows=== |
===Lava flows=== |
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{{Main|Lava flow}} |
{{Main|Lava flow}} |
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[[File:Rinjani 1994 cropped.jpg|thumb|[[Mount Rinjani]] eruption in 1994, in [[Lombok]], [[Indonesia]]]]The form and style of eruption of a volcano is largely determined by the composition of the lava it erupts. The viscosity (how fluid the lava is) and the amount of dissolved gas are the most important characteristics of magma, and both are largely determined by the amount of silica in the magma. Magma rich in silica is much more viscous than silica-poor magma, and silica-rich magma also tends to contain more dissolved gases. |
[[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. |
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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> |
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> |
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* 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= |
* 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> |
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: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 |
: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||sp=us}}<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 kilometers before it falls back to ground as a fallout [[tuff]]. Volcanic gases may remain in the [[stratosphere]] for years.{{sfn|Schmincke|2003|p=229}} |
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:Felsic magmas are formed within the crust, usually through melting of crust rock from the heat of underlying mafic magmas. The lighter felsic magma floats on the mafic magma without significant mixing.{{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. |
: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. |
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* If the erupted magma contains 52–63% silica, the lava is of ''[[intermediate composition]]'' or ''[[ |
* 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}} |
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* 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 dry mantle, with limited fractional crystallization and assimilation of crustal material.{{sfn|Philpotts|Ague|2009|p=16}} |
* 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}} |
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: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. |
: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. |
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* 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}} |
* 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}} |
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Mafic lava flows show two varieties of surface texture: {{okina}}A{{okina}}a (pronounced {{IPA |
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}} |
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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}} |
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}} |
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[[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.]] |
[[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.]] |
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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 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 |pages=41–43 |doi=10.1007/BF01822152 |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= |
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 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 |pages=41–43 |doi=10.1007/BF01822152 |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}}</ref> |
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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}} |
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}} |
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* Hawaiian eruptions 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]]. |
* Hawaiian eruptions 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]]. |
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* Strombolian eruptions are characterized by moderate viscosities and dissolved gas levels. They are characterized by frequent but short-lived eruptions that can produce eruptive columns hundreds of meters high, which can also be seen in [[Gas slug|a gas slug]]. Their primary product is [[scoria]]. They are named after [[Stromboli]]. |
* Strombolian eruptions are characterized by moderate viscosities and dissolved gas levels. They are characterized by frequent but short-lived eruptions that can produce eruptive columns hundreds of meters high, which can also be seen in [[Gas slug|a gas slug]]. Their primary product is [[scoria]]. They are named after [[Stromboli]]. |
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* Vulcanian eruptions are characterized by yet higher viscosities and partial crystallization of magma, which is often intermediate in composition. Eruptions take the form of short-lived explosions |
* Vulcanian eruptions are characterized by yet higher viscosities and partial crystallization of magma, which is often intermediate in composition. Eruptions take the form of short-lived explosions 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]]. |
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* Peléan eruptions are more violent still, being characterized by dome growth and collapse that produces various kinds of pyroclastic flows. They are named after [[Mount Pelée]]. |
* Peléan eruptions are more violent still, being characterized by dome growth and collapse that produces various kinds of pyroclastic flows. They are named after [[Mount Pelée]]. |
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* Plinian eruptions are the most violent of all volcanic eruptions. They are characterized by sustained huge eruption columns whose collapse produces catastrophic pyroclastic flows. They are named after [[Pliny the Younger]], who chronicled the Plinian [[eruption of Mount Vesuvius in 79]] AD. |
* Plinian eruptions are the most violent of all volcanic eruptions. They are characterized by sustained huge eruption columns whose collapse produces catastrophic pyroclastic flows. They are named after [[Pliny the Younger]], who chronicled the Plinian [[eruption of Mount Vesuvius in 79]] AD. |
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[[File:Pompeii - Casa del Centenario - MAN.jpg|thumb|left|upright|[[Fresco]] with [[Mount Vesuvius]] behind [[Bacchus]] and [[Agathodaemon]], as seen in [[Pompeii]]'s [[House of the Centenary]]]] |
[[File:Pompeii - Casa del Centenario - MAN.jpg|thumb|left|upright|[[Fresco]] with [[Mount Vesuvius]] behind [[Bacchus]] and [[Agathodaemon]], as seen in [[Pompeii]]'s [[House of the Centenary]]]] |
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{{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= |
{{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 | accessdate=January 12, 2023 | author=Venzke, E. (compiler) | editor-first1=Edward | editor-last1=Venzke | doi=10.5479/si.GVP.VOTW5-2022.5.0}}</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 | accessdate=January 12, 2023 | author=Venzke, E. (compiler) | editor-first1=Edward | editor-last1=Venzke | doi=10.5479/si.GVP.VOTW5-2022.5.0}}</ref> |
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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= |
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 amongst volcanologists. The level of activity of most volcanoes falls upon a graduated spectrum, with much overlap between categories, and does not always fit neatly into only one of these three separate categories.<ref>{{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> |
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=== Erupting === |
=== Erupting === |
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{{Main|Active volcano}} |
{{Main|Active volcano}} |
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While there is no international consensus among volcanologists on how to define an |
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> |
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===Dormant and reactivated{{anchor|Dormant}}=== |
===Dormant and reactivated{{anchor|Dormant}}=== |
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[[File:Narcondam island.jpg|thumb|[[Narcondam Island]], India, is classified as a dormant volcano by the [[Geological Survey of India]].]] |
[[File:Narcondam island.jpg|thumb|[[Narcondam Island]], India, is classified as a dormant volcano by the [[Geological Survey of India]].]] |
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The USGS defines a dormant volcano as |
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&pred.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.}}</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> |
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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 |
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 |website=Alaska Volcano Observatory |access-date=June 2, 2022}}</ref> however the USGS still widely employs the term. |
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Previously a volcano was often considered to be extinct if there were no written records of its activity. Such a generalisation is inconsistent with observation and deeper study, as has occurred recently with the unexpected eruption of the [[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}}</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 |
Previously a volcano was often considered to be extinct if there were no written records of its activity. Such a generalisation is inconsistent with observation and deeper study, as has occurred recently with the unexpected eruption of the [[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}}</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|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]]. |
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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}} [[ |
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. |
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===Extinct=== |
===Extinct=== |
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[[File:Capulin 1980 tde00005.jpg|thumb|[[Capulin Volcano National Monument]] in New Mexico, US]] |
[[File:Capulin 1980 tde00005.jpg|thumb|[[Capulin Volcano National Monument]] in New Mexico, US]] |
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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]], [[ |
Extinct volcanoes are those that scientists consider unlikely to erupt again because the volcano no longer has a magma supply. Examples of extinct volcanoes are many volcanoes on the [[Hawaiian–Emperor seamount chain]] in the Pacific Ocean (although some volcanoes at the eastern end of the chain are active), [[Hohentwiel]] in [[Germany]], [[Shiprock]] in [[New Mexico]], [[US]], [[Capulin Volcano National Monument|Capulin]] in New Mexico, US, [[Zuidwal volcano]] in the [[Netherlands]], and many volcanoes in [[Italy]] such as [[Monte Vulture]]. [[Edinburgh Castle]] in Scotland is located atop an extinct volcano, which forms [[Castle Rock (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. |
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===Volcanic-alert level=== |
===Volcanic-alert level=== |
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The Decade Volcanoes are 16 volcanoes identified by the [[International Association of Volcanology and Chemistry of the Earth's Interior]] (IAVCEI) as being worthy of particular study in light of their history of large, destructive eruptions and proximity to populated areas. They are named Decade Volcanoes because the project was initiated as part of the United Nations-sponsored [[International Decade for Natural Disaster Reduction]] (the 1990s). The 16 current Decade Volcanoes are: |
The 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: |
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{{div col|colwidth=20em}} |
{{div col|colwidth=20em}} |
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* [[Avachinsky]]-[[Koryaksky]] (grouped together), [[ |
* [[Avachinsky]]-[[Koryaksky]] (grouped together), [[Kamchatka]], Russia |
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* [[ |
* [[Nevado de Colima]], [[Jalisco]] and [[Colima]], Mexico |
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* [[Mount Etna]], Sicily, Italy |
* [[Mount Etna]], Sicily, Italy |
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* [[Galeras]], [[Nariño]], Colombia |
* [[Galeras]], [[Nariño]], Colombia |
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===Hazards=== |
===Hazards=== |
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{{Main|Volcanic hazard}} |
{{Main|Volcanic hazard}} |
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There are many different [[types of volcanic eruptions]] and associated activity: [[phreatic eruptions]] (steam-generated eruptions), explosive |
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. |
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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 |
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 |
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[[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.]] |
[[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.]] |
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A [[volcanic winter]] is thought to have taken place around 70,000 years ago after the [[ |
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> |
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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> |
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> |
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===Benefits=== |
===Benefits=== |
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{{See also|Volcanogenic massive sulfide ore deposit|Geothermal power}} |
{{See also|Volcanogenic massive sulfide ore deposit|Geothermal power}} |
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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= |
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 }}</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> |
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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= |
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" /> |
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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> |
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> |
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=== Safety considerations === |
=== Safety considerations === |
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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 |
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. |
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Scientists are known to perceive risk, with its social elements, differently |
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}} |
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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 |
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/> |
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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. |
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> |
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==Volcanoes on other celestial bodies== |
==Volcanoes on other celestial bodies== |
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[[File:Tvashtarvideo.gif|left|thumb|The [[Tvashtar Paterae|Tvashtar]] volcano erupts a plume 330 km (205 mi) above the surface of [[Jupiter]]'s moon [[Io (moon)|Io]].]] |
[[File:Tvashtarvideo.gif|left|thumb|The [[Tvashtar Paterae|Tvashtar]] volcano erupts a plume 330 km (205 mi) above the surface of [[Jupiter]]'s moon [[Io (moon)|Io]].]] |
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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= |
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 |quote=}}</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 |quote=}}</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}}</ref> |
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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. [[ |
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> |
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[[File:Olympus Mons. |
[[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]].]] |
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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"/> |
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"/> |
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[[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 °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=2015 |
[[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 °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}}</ref> |
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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]] [[ |
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]]. |
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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 neighboring 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> |
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 neighboring 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> |
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{{Main|Volcanology#History}} |
{{Main|Volcanology#History}} |
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Volcanoes are not distributed evenly over Earth's surface but active ones with significant impact were encountered early in human history, evidenced by footprints of [[hominina]] found in East |
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> |
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Many ancient accounts ascribe volcanic eruptions to [[supernatural]] causes, such as the actions of [[ |
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/> |
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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 CE, [[Seneca the Younger]] proposed combustion as the cause,<ref name=Sigurdsson2000/> an idea also adopted by the [[ |
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 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 = |
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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 |
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 |
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| 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 synthesised 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= |
| 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 synthesised 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 |page=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> |
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==See also== |
==See also== |
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* {{annotated link|List of extraterrestrial volcanoes}} |
* {{annotated link|List of extraterrestrial volcanoes}} |
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* [[List of volcanic eruptions by death toll]] |
* [[List of volcanic eruptions by death toll]] |
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* [[ |
* [[List of volcanic landforms]] |
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* {{annotated link|Maritime impacts of volcanic eruptions}} |
* {{annotated link|Maritime impacts of volcanic eruptions}} |
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* {{annotated link|Prediction of volcanic activity}} |
* {{annotated link|Prediction of volcanic activity}} |
Revision as of 06:45, 5 September 2024
A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. The process that forms volcanoes is called volcanism.
On Earth, volcanoes are most often found where tectonic plates are diverging or 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 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 has been postulated to arise from upwelling diapirs from the core–mantle boundary, 3,000 kilometers (1,900 mi) deep within Earth. This results in hotspot volcanism, of which the Hawaiian hotspot is an example. Volcanoes are usually not created where two tectonic plates slide past one another.
Large eruptions can affect atmospheric temperature as ash and droplets of sulfuric acid obscure the Sun and cool Earth's troposphere. Historically, large volcanic eruptions have been followed by volcanic winters which have caused catastrophic famines.[1]
Other planets besides Earth have volcanoes. For example, volcanoes are very numerous on Venus.[2] In 2009, a paper was published suggesting a new definition for the word 'volcano' that includes processes such as cryovolcanism. It suggested that a volcano be defined as 'an opening on a planet or moon's surface from which magma, as defined for that body, and/or magmatic gas is erupted.'[3]
This article mainly covers volcanoes on Earth. See § Volcanoes on other celestial bodies and cryovolcano for more information.
Etymology
The word volcano is derived from the name of Vulcano, a volcanic island in the Aeolian Islands of Italy whose name in turn comes from Vulcan, the god of fire in Roman mythology.[4] The study of volcanoes is called volcanology, sometimes spelled vulcanology.[5]
Plate tectonics
According to the theory of plate tectonics, Earth's lithosphere, its rigid outer shell, is broken into sixteen larger and several smaller plates. These are in slow motion, due to convection in the underlying ductile mantle, and most volcanic activity on Earth takes place along plate boundaries, where plates are converging (and lithosphere is being destroyed) or are diverging (and new lithosphere is being created).[6]
During the development of geological theory, certain concepts that allowed the grouping of volcanoes in time, place, structure and composition have developed that ultimately have had to be explained in the theory of plate tectonics. For example, some volcanoes are polygenetic with more than one period of activity during their history; other volcanoes that become extinct after erupting exactly once are monogenetic (meaning "one life") and such volcanoes are often grouped together in a geographical region.[7]
Divergent plate boundaries
At the mid-ocean ridges, two 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 smokers (also known as deep sea vents) are evidence of this kind of volcanic activity. Where the mid-oceanic ridge is above sea level, volcanic islands are formed, such as Iceland.[8]
Convergent plate boundaries
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 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 arcs. 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.[9]
Hotspots
Hotspots are volcanic areas thought to be formed by mantle plumes, which are hypothesized to be columns of hot material rising from the core-mantle boundary. As with mid-ocean ridges, the rising mantle rock experiences decompression melting which generates large volumes of magma. Because tectonic plates move across mantle plumes, each volcano becomes inactive as it drifts off the plume, and new volcanoes are created where the plate advances over the plume. The Hawaiian Islands are thought to have been formed in such a manner, as has the Snake River Plain, with the Yellowstone Caldera being part of the North American plate currently above the Yellowstone hotspot.[10] However, the mantle plume hypothesis has been questioned.[11]
Continental rifting
Sustained upwelling of hot mantle rock can develop under the interior of a continent and lead to rifting. Early stages of rifting are characterized by flood basalts and may progress to the point where a tectonic plate is completely split.[12][13] A divergent plate boundary then develops between the two halves of the split plate. However, rifting often fails to completely split the continental lithosphere (such as in an aulacogen), and failed rifts are characterized by volcanoes that erupt unusual alkali lava or carbonatites. Examples include the volcanoes of the East African Rift.[14]
Volcanic features
A volcano needs a reservoir of molten magma (e.g. a magma chamber), a conduit to allow magma to rise through the crust, and a vent to allow the magma to escape above the surface as lava.[15] The erupted volcanic material (lava and tephra) that is deposited around the vent is known as a volcanic edifice, typically a volcanic cone or mountain.[15]
The most common perception of a volcano is of a conical mountain, spewing lava and poisonous gases from a crater at its summit; however, this describes just one of the many types of volcano. The features of volcanoes are varied. The structure and behavior of volcanoes depend on several factors. Some volcanoes have rugged peaks formed by lava domes rather than a summit crater while others have landscape features such as massive plateaus. Vents that issue volcanic material (including lava and 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 on a flank of Kīlauea in Hawaii. Volcanic craters are not always at the top of a mountain or hill and may be filled with lakes such as with Lake Taupō in New Zealand. Some volcanoes can be low-relief landform features, with the potential to be hard to recognise as such and be obscured by geological processes.
Other types of volcano include cryovolcanoes (or ice volcanoes), particularly on some moons of Jupiter, Saturn, and Neptune; and mud volcanoes, which are structures often not associated with known magmatic activity. 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
Volcanic fissure vents are flat, linear fractures through which lava emerges.
Shield volcanoes
Shield volcanoes, so named for their broad, shield-like profiles, are formed by the eruption of low-viscosity lava that can flow a great distance from a vent. They generally do not explode catastrophically but are characterized by relatively gentle effusive eruptions. Since low-viscosity magma is typically low in silica, shield volcanoes are more common in oceanic than continental settings. The Hawaiian volcanic chain is a series of shield cones, and they are common in Iceland, as well.
Lava domes
Lava domes are built by slow eruptions of highly viscous lava. They are sometimes formed within the crater of a previous volcanic eruption, as in the case of Mount St. Helens, but can also form independently, as in the case of Lassen Peak. Like stratovolcanoes, they can produce violent, explosive eruptions, but the lava generally does not flow far from the originating vent.
Cryptodomes
Cryptodomes are formed when viscous lava is forced upward causing the surface to bulge. The 1980 eruption of Mount St. Helens was an example; lava beneath the surface of the mountain created an upward bulge, which later collapsed down the north side of the mountain.
Cinder cones
Cinder cones result from eruptions of mostly small pieces of scoria and pyroclastics (both resemble cinders, hence the name of this volcano type) that build up around the vent. These can be relatively short-lived eruptions that produce a cone-shaped hill perhaps 30 to 400 meters (100 to 1,300 ft) high. Most cinder cones erupt only once and some may be found in monogenetic volcanic fields that may include other features that form when magma comes into contact with water such as maar explosion craters and tuff rings.[16] Cinder cones may form as flank vents on larger volcanoes, or occur on their own. Parícutin in Mexico and Sunset Crater in Arizona are examples of cinder cones. In New Mexico, Caja del Rio is a volcanic field of over 60 cinder cones.
Based on satellite images, it has been suggested that cinder cones might occur on other terrestrial bodies in the Solar system too; on the surface of Mars and the Moon.[17][18][19][20]
Stratovolcanoes (composite volcanoes)
Stratovolcanoes (composite volcanoes) 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. Classic examples include Mount Fuji in Japan, Mayon Volcano in the Philippines, and Mount Vesuvius and Stromboli in Italy.
Ash produced by the explosive eruption of stratovolcanoes has historically posed the greatest volcanic hazard to civilizations. The lavas of stratovolcanoes are higher in silica, and therefore much more viscous, than lavas from shield volcanoes. High-silica lavas also tend to contain more dissolved gas. The combination is deadly, promoting explosive eruptions that produce great quantities of ash, as well as pyroclastic surges like the one that destroyed the city of Saint-Pierre in Martinique in 1902. They are also steeper than shield volcanoes, with slopes of 30–35° compared to slopes of generally 5–10°, and their loose tephra are material for dangerous lahars.[21] Large pieces of tephra are called volcanic bombs. Big bombs can measure more than 1.2 meters (4 ft) across and weigh several tons.[22]
Supervolcanoes
A supervolcano is defined as a volcano that has experienced one or more eruptions that produced over 1,000 cubic kilometers (240 cu mi) of volcanic deposits in a single explosive event.[23] Such eruptions occur when a very large magma chamber full of gas-rich, silicic magma is emptied in a catastrophic caldera-forming eruption. Ash flow tuffs emplaced by such eruptions are the only volcanic product with volumes rivaling those of flood basalts.[24]
Supervolcano eruptions, while the most dangerous type, are very rare; 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 geologic mapping.[25] 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
Volcanoes that, though large, are not large enough to be called supervolcanoes, may also form calderas in the same way; they are often described as "caldera volcanoes".[26]
Submarine volcanoes
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.[27][28] 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 hydrophones and by the discoloration of water because of volcanic gases. 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 vents are common near these volcanoes, and some support peculiar ecosystems based on chemotrophs feeding on dissolved minerals. Over time, the formations created by submarine volcanoes may become so large that they break the ocean surface as new islands or floating pumice rafts.
In May and June 2018, a multitude of 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.[29]
Subglacial volcanoes
Subglacial volcanoes develop underneath ice caps. They are made up of lava plateaus capping extensive pillow lavas and palagonite. These volcanoes are also called table mountains, tuyas,[30] or (in Iceland) mobergs.[31] 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 analyzed and so its name has entered the geological literature for this kind of volcanic formation.[32] 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.
Mud volcanoes
Mud volcanoes (mud domes) are formations created by geo-excreted liquids and gases, although several processes may cause such activity.[33] The largest structures are 10 kilometers in diameter and reach 700 meters high.[34]
Erupted material
The material that is expelled in a volcanic eruption can be classified into three types:
- Volcanic gases, a mixture made mostly of steam, carbon dioxide, and a sulfur compound (either sulfur dioxide, SO2, or hydrogen sulfide, H2S, depending on the temperature)
- 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[36][37]
Volcanic gases
The concentrations of different volcanic gases can vary considerably from one volcano to the next. Water vapor is typically the most abundant volcanic gas, followed by carbon dioxide[38] and sulfur dioxide. Other principal volcanic gases include hydrogen sulfide, hydrogen chloride, and hydrogen fluoride. A large number of minor and trace gases are also found in volcanic emissions, for example hydrogen, carbon monoxide, halocarbons, organic compounds, and volatile metal chlorides.
Lava flows
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:[39]
- If the erupted magma contains a high percentage (>63%) of silica, the lava is described as felsic. Felsic lavas (dacites or rhyolites) are highly viscous and are erupted as domes or short, stubby flows.[40] Lassen Peak in California is an example of a volcano formed from felsic lava and is actually a large lava dome.[41]
- Because felsic magmas are so viscous, they tend to trap volatiles (gases) that are present, which leads to explosive volcanism. Pyroclastic flows (ignimbrites) 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 850 °C (1,560 °F)[42] 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.[43] Alaska's Valley of Ten Thousand Smokes, formed by the eruption of Novarupta near Katmai in 1912, is an example of a thick pyroclastic flow or ignimbrite deposit.[44] Volcanic ash that is light enough to erupt high into the Earth's atmosphere as an eruption column may travel hundreds of kilometers before it falls back to ground as a fallout tuff. Volcanic gases may remain in the stratosphere for years.[45]
- 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.[46] Less commonly, felsic magmas are produced by extreme fractional crystallization of more mafic magmas.[47] 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.[48] They are most commonly formed at convergent boundaries between tectonic plates, by several processes. One process is the hydration melting of mantle peridotite followed by fractional crystallization. Water from a subducting slab rises into the overlying mantle, lowering its melting point, particularly for the more silica-rich minerals. Fractional crystallization further enriches the magma in silica. It has also been suggested that intermediate magmas are produced by the melting of sediments carried downwards by the subducted slab.[49] Another process is magma mixing between felsic rhyolitic and mafic basaltic magmas in an intermediate reservoir before emplacement or lava flow.[50]
- If the erupted magma contains <52% and >45% silica, the lava is called mafic (because it contains higher percentages of magnesium (Mg) and iron (Fe)) or basaltic. These lavas are usually hotter and much less viscous than felsic lavas. Mafic magmas are formed by partial melting of the dry mantle, with limited fractional crystallization and assimilation of crustal material.[51]
- Mafic lavas occur in a wide range of settings. These include mid-ocean ridges; Shield volcanoes (such the Hawaiian Islands, including Mauna Loa and Kilauea), on both oceanic and continental crust; and as continental flood basalts.
- Some erupted magmas contain ≤45% silica and produce ultramafic lava. Ultramafic flows, also known as komatiites, are very rare; indeed, very few have been erupted at 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.[52]
Mafic lava flows show two varieties of surface texture: ʻAʻa (pronounced [ˈʔaʔa]) and pāhoehoe ([paːˈho.eˈho.e]), both Hawaiian words. ʻAʻa is characterized by a rough, clinkery surface and is the typical texture of cooler basalt lava flows. Pāhoehoe is characterized by its smooth and often ropey or wrinkly surface and is generally formed from more fluid lava flows. Pāhoehoe flows are sometimes observed to transition to ʻaʻa flows as they move away from the vent, but never the reverse.[53]
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.[54]
Tephra
Tephra is made when magma inside the volcano is blown apart by the rapid expansion of hot volcanic gases. Magma commonly explodes as the gas dissolved in it comes out of solution as the pressure decreases when it flows to the surface. These violent explosions produce particles of material that can then fly from the volcano. Solid particles smaller than 2 mm in diameter (sand-sized or smaller) are called volcanic ash.[36][37]
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.[55]
Types of volcanic eruptions
Eruption styles are broadly divided into magmatic, phreatomagmatic, and phreatic eruptions.[56] 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.[57]
- Magmatic eruptions are driven primarily by gas release due to decompression.[56] Low-viscosity magma with little dissolved gas produces relatively gentle effusive eruptions. High-viscosity magma with a high content of dissolved gas produces violent explosive eruptions. The range of observed eruption styles is expressed from historical examples.
- Hawaiian eruptions are typical of volcanoes that erupt mafic lava with a relatively low gas content. These are almost entirely effusive, producing local lava fountains and highly fluid lava flows but relatively little tephra. They are named after the Hawaiian volcanoes.
- Strombolian eruptions are characterized by moderate viscosities and dissolved gas levels. They are characterized by frequent but short-lived eruptions that can produce eruptive columns hundreds of meters high, which can also be seen in a gas slug. Their primary product is scoria. They are named after Stromboli.
- Vulcanian eruptions are characterized by yet higher viscosities and partial crystallization of magma, which is often intermediate in composition. Eruptions take the form of short-lived explosions 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.
- Peléan eruptions are more violent still, being characterized by dome growth and collapse that produces various kinds of pyroclastic flows. They are named after Mount Pelée.
- Plinian eruptions are the most violent of all volcanic eruptions. They are characterized by sustained huge eruption columns whose collapse produces catastrophic pyroclastic flows. They are named after Pliny the Younger, who chronicled the Plinian eruption of Mount Vesuvius in 79 AD.
- Phreatomagmatic eruptions are characterized by interaction of rising magma with groundwater. They are driven by the resulting rapid buildup of pressure in the superheated groundwater.
- Phreatic eruptions are characterized by superheating of groundwater that comes in contact with hot rock or magma. They are distinguished from phreatomagmatic eruptions because the erupted material is all country rock; no magma is erupted.
Volcanic activity
As of December 2022[update], the Smithsonian Institution's Global Volcanism Program database of volcanic eruptions in the Holocene 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.[58][59]
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.[60] Volcanoes are informally described as erupting, active, dormant, or extinct, but the definitions of these terms are not entirely uniform amongst volcanologists. The level of activity of most volcanoes falls upon a graduated spectrum, with much overlap between categories, and does not always fit neatly into only one of these three separate categories.[61]
Erupting
The USGS defines a volcano as "erupting" whenever the ejection of magma from any point on the volcano is visible, including visible magma still contained within the walls of the summit crater.
Active
While there is no international consensus among volcanologists on how to define an active volcano, the USGS defines a volcano as active whenever subterranean indicators, such as earthquake swarms, ground inflation, or unusually high levels of carbon dioxide or sulfur dioxide are present.[62][63]
Dormant and reactivated
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.[63] 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.[64][65]
In an article justifying the re-classification of Alaska's 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",[66] however the USGS still widely employs the term.
Previously a volcano was often considered to be extinct if there were no written records of its activity. Such a generalisation is inconsistent with observation and deeper study, as has occurred recently with the unexpected eruption of the Chaitén volcano in 2008.[67] 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.[68]: 95 For example, the Yellowstone volcano has a repose/recharge period of around 700,000 years, and Toba of around 380,000 years.[69] Vesuvius was described by Roman writers as having been covered with gardens and vineyards before its unexpected 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.[68]: 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 into a ghost town) and Fourpeaked Mountain in Alaska, which, before its September 2006 eruption, had not erupted since before 8000 BCE.
Extinct
Extinct volcanoes are those that scientists consider unlikely to erupt again because the volcano no longer has a magma supply. Examples of extinct volcanoes are many volcanoes on the Hawaiian–Emperor seamount chain in the Pacific Ocean (although some volcanoes at the eastern end of the chain are active), Hohentwiel in Germany, Shiprock in New Mexico, US, Capulin in New Mexico, US, Zuidwal volcano in the Netherlands, and many volcanoes in Italy such as Monte Vulture. Edinburgh Castle in Scotland is located atop an extinct volcano, which forms Castle Rock. Whether a volcano is truly extinct is often difficult to determine. Since "supervolcano" calderas can have eruptive lifespans sometimes measured in millions of years, a caldera that has not produced an eruption in tens of thousands of years may be considered dormant instead of extinct. An individual volcano in a monogenetic volcanic field can be extinct but that does not mean a completely new volcano might not erupt close by with little or no warning as its field may have an active magma supply.
Volcanic-alert level
The three common popular classifications of volcanoes can be subjective and some volcanoes thought to have been extinct have erupted again. To help prevent people from falsely believing they are not at risk when living on or near a volcano, countries have adopted new classifications to describe the various levels and stages of volcanic activity.[70] Some alert systems use different numbers or colors to designate the different stages. Other systems use colors and words. Some systems use a combination of both.
Decade volcanoes
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:
- 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, US
- Sakurajima, Kagoshima Prefecture, Japan
- 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, Naples, Italy
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 CO2/SO2 ratios in real-time and in high-resolution to allow detection of the pre-eruptive degassing of rising magmas, improving prediction of volcanic activity.[71]
Volcanoes and humans
Volcanic eruptions pose a significant threat to human civilization. However, volcanic activity has also provided humans with important resources.
Hazards
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 collapses, pyroclastic flows, lahars (debris flows) and volcanic gas emissions. These can pose a hazard to humans. Earthquakes, hot springs, fumaroles, mud pots and geysers often accompany volcanic activity.
Volcanic gases can reach the stratosphere, where they form sulfuric acid aerosols that can reflect solar radiation and lower surface temperatures significantly.[72] Sulfur dioxide from the eruption of Huaynaputina may have caused the Russian famine of 1601–1603.[73] 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.[74]: 39–58 Explosive volcanic eruptions release the greenhouse gas carbon dioxide and thus provide a deep source of carbon for biogeochemical cycles.[75]
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.
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.[76] This may have created a population bottleneck that affected the genetic inheritance of all humans today.[77] Volcanic eruptions may have contributed to major extinction events, such as the End-Ordovician, Permian-Triassic, and Late Devonian mass extinctions.[78]
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.[79] The freezing winter of 1740–41, which led to widespread famine in northern Europe, may also owe its origins to a volcanic eruption.[80]
Benefits
Although volcanic eruptions pose considerable hazards to humans, past volcanic activity has created important economic resources. Tuff formed from volcanic ash is a relatively soft rock, and it has been used for construction since ancient times.[81][82] The Romans often used tuff, which is abundant in Italy, for construction.[83] The Rapa Nui people used tuff to make most of the moai statues in Easter Island.[84]
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.[85] Volcanic activity is responsible for emplacing valuable mineral resources, such as metal ores.[85] It is accompanied by high rates of heat flow from Earth's interior. These can be tapped as geothermal power.[85]
Tourism associated with volcanoes is also a worldwide industry.[86]
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.[87] The diversity of volcanoes and their complexities mean that eruption forecasts for the foreseeable future will be based on probability, and the application of risk management. Even then, some eruptions will have no useful warning. An example of this occurred in March 2017, when a tourist group was witnessing 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.[86] Other types of significant eruptions are known to give useful warnings of only hours at the most by seismic monitoring.[67] 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,[68] 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.[88]: 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.[89] In the case of Mount Etna, a 2021 review found 77 deaths due to eruptions since 1536 but none since 1987.[86]
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.[90]
Volcanoes on other celestial bodies
Earth's Moon has no large volcanoes and no current volcanic activity, although recent evidence suggests it may still possess a partially molten core.[91] However, the Moon does have many volcanic features such as maria[92] (the darker patches seen on the Moon), rilles[93] and domes.[94]
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,[95] 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 flows near the summit and on the northern flank.[96] However, the interpretation of the flows as ash flows has been questioned.[97]
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,[98] but the European Mars Express spacecraft has found evidence that volcanic activity may have occurred on Mars in the recent past as well.[98]
Jupiter's moon Io is the most volcanically active object in the Solar System because of tidal interaction with Jupiter. It is covered with volcanoes that erupt sulfur, sulfur dioxide and silicate rock, and as a result, Io is constantly being resurfaced. Its lavas are the hottest known anywhere in the Solar System, with temperatures exceeding 1,800 K (1,500 °C). In February 2001, the largest recorded volcanic eruptions in the Solar System occurred on Io.[99] Europa, the smallest of Jupiter's Galilean moons, 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.[100]
In 1989, the Voyager 2 spacecraft observed cryovolcanoes (ice volcanoes) on Triton, a moon of Neptune, and in 2005 the Cassini–Huygens probe photographed fountains of frozen particles erupting from Enceladus, a moon of Saturn.[101][102] 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 Saturnian moon Titan, which is believed to be a significant source of the methane found in its atmosphere.[103] 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 in 2009, suggested that tidal heating from the host star very close to the planet and neighboring planets could generate intense volcanic activity similar to that found on Io.[104]
History of volcano understanding
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.[105]: 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,[106]: 135 (2) Pele's migration through the Hawarian island chain, ability to destroy forests and manifestations of the god's temper,[107] and (3) the association in Javanese folklore of a king resident in Mount Merapi volcano and a queen resident at a beach 50 km (31 mi) away on what is now known to be an earthquake fault that interacts with that volcano.[108]
Many ancient accounts ascribe volcanic eruptions to supernatural causes, such as the actions of gods or demigods. The earliest known such example is a neolithic goddess at Çatalhöyük.[109]: 203 The Ancient Greek god Hephaistos and the concepts of the underworld are aligned to volcanoes in that Greek culture.[86]
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.[110] By 65 CE, Seneca the Younger proposed combustion as the cause,[110] 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.[111] Edward Jorden, in his work on mineral waters, challenged this view; in 1632 he proposed sulfur "fermentation" as a heat source within Earth,[110] Astronomer Johannes Kepler (1571–1630) believed volcanoes were ducts for Earth's tears.[112][better source needed] In 1650, René Descartes proposed the core of Earth was incandescent and, by 1785, the works of Decartes and others were synthesised into geology by James Hutton in his writings about igneous intrusions of magma.[110] 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 dyke.[113]: 16–18 [114]: 4 Alfred Lacroix built upon his other knowledge with his studies on the 1902 eruption of Mount Pelée,[110] and by 1928 Arthur Holmes work had brought together the concepts of radioactive generation of heat, Earth's mantle structure, partial decompression melting of magma, and magma convection.[110] This eventually led to the acceptance of plate tectonics.[115]
See also
- List of extraterrestrial volcanoes
- List of volcanic eruptions by death toll
- List of volcanic landforms
- Maritime impacts of volcanic eruptions
- Prediction of volcanic activity – Research to predict volcanic activity
- Timeline of volcanism on Earth
- Volcano Number – System for uniquely identifying volcanic features on Earth
- Volcano observatory – Institution that monitors volcano activity
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Further reading
- Macdonald, Gordon; Abbott, Agatin (1970). Volcanoes in the Sea: The Geology of Hawaii. University of Hawaii Press. ISBN 978-0-870-22495-9.
- Marti, Joan & Ernst, Gerald. (2005). Volcanoes and the Environment. Cambridge University Press. ISBN 978-0-521-59254-3.
- Ollier, Cliff (1969). Volcanoes. Australian National University Press. ISBN 978-0-7081-0532-0.
- Sigurðsson, Haraldur, ed. (2015). The Encyclopedia of Volcanoes (2 ed.). Academic Press. ISBN 978-0-12-385938-9. This is a reference aimed at geologists, but many articles are accessible to non-professionals.