View source for Earth:Volcanic Explosivity Index

{{Short description|Qualitative scale for explosiveness of volcanic eruptions}}
[[File:VEIfigure en.svg|thumb|270px|VEI and ejecta volume correlation]]

The '''Volcanic Explosivity Index''' ('''VEI''') is a relative measure of the explosiveness of [[Earth:Types of volcanic eruptions|volcanic eruptions]]. It was devised by Chris Newhall of the United States Geological Survey and Stephen Self at the [[Organization:University of Hawaii at Manoa|University of Hawaii]] in 1982.

Volume of products, eruption cloud height, and qualitative observations (using terms ranging from "gentle" to "mega-colossal") are used to determine the explosivity value. The scale is open-ended with the largest eruptions in history given a magnitude of 8. A value of 0 is given for non-explosive eruptions, defined as less than {{convert|10000|m3|cuft|abbr=on}} of tephra ejected; and 8 representing a mega-colossal explosive eruption that can eject {{val|1.0|e=12|u=m3}} (240 cubic miles) of tephra and have a cloud column height of over {{convert|20|km|ft|abbr=on}}. The scale is logarithmic, with each interval on the scale representing a tenfold increase in observed ejecta criteria, with the exception of between VEI-0, VEI-1 and VEI-2.<ref>
{{cite journal
 |first1=Christopher G. |last1=Newhall
 |first2=Stephen |last2=Self
 |year=1982
 |title=The Volcanic Explosivity Index (VEI): An Estimate of Explosive Magnitude for Historical Volcanism
 |url=http://www.agu.org/books/hg/v002/HG002p0143/HG002p0143.pdf
 |journal=[[Earth:Journal of Geophysical Research|Journal of Geophysical Research]]
 |volume=87 |issue=C2 |pages=1231–1238
 |bibcode=1982JGR....87.1231N
 |doi=10.1029/JC087iC02p01231
 |archive-url=https://web.archive.org/web/20131213194307/http://www.agu.org/books/hg/v002/HG002p0143/HG002p0143.pdf
 |archive-date=December 13, 2013
}}</ref>

==Classification==
With indices running from 0 to 8, the VEI associated with an eruption is dependent on how much volcanic material is thrown out, to what height, and how long the eruption lasts. The scale is logarithmic from VEI-2 and up; an increase of 1 index indicates an eruption that is 10 times as powerful. As such, there is a discontinuity in the definition of the VEI between indices 1 and 2. The lower border of the volume of ejecta jumps by a factor of one hundred, from {{convert|10000|to|1000000|m3|cuft|abbr=on}}, while the factor is ten between all higher indices. In the following table, the frequency of each VEI indicates the approximate frequency of new eruptions of that VEI or higher.<!-- Please do not list new eruptions here until a VEI is confirmed by Smithsonian Institution Global Volcanism Program or a local agency.--> 

{| class="wikitable" 
! rowspan="2" | VEI
! rowspan="2" | Ejecta<br> volume<br>(bulk)
! Classification
! Description
! Plume
! Frequency
! Tropospheric<br>injection
! Stratospheric<br>injection<ref>
{{cite web
 |title=Volcanic Explosivity Index (VEI)
 |url=http://www.volcano.si.edu/world/eruptioncriteria.cfm#VEI
 |work=Global Volcanism Program
 |publisher=Smithsonian National Museum of Natural History
 |access-date=August 21, 2014
 |archive-url=https://web.archive.org/web/20111110173623/http://www.volcano.si.edu/world/eruptioncriteria.cfm
 |archive-date=November 10, 2011
}}</ref>
|-
! colspan="7" style="font-size:90%; color:#888;" | Examples
|-
! rowspan="2" style="background-color: white;" | 0
| rowspan="2" | <&nbsp;10<sup>4</sup> m<sup>3</sup> || [[Earth:Hawaiian eruption|Hawaiian]] || Effusive || < 100 m || continuous || negligible || none
|-
| colspan="7" style="font-size:90%; color:#888; max-width:1px; background:white;" | [[Earth:Hoodoo Mountain|Hoodoo Mountain]] (c. 7050 BC),<ref>{{cite gvp|name=Hoodoo Mountain: Eruptive History|vtab=Eruptions|vn=320080|access-date=2021-07-15}}</ref> [[Earth:Mount Erebus|Erebus]] (1963), [[Earth:Kīlauea|Kīlauea]] (1977), [[Earth:Mauna Loa|Mauna Loa]] (1984), [[Earth:Socorro Island|Socorro Island]] (1993), [[Earth:Mawson Peak|Mawson Peak]] (2006), [[Earth:Dallol (volcano)|Dallol]] (2011), [[Earth:Axial Seamount|Axial Seamount]] (1998, 2011, 2015), Holuhraun (2014-2015), [[Earth:Piton de la Fournaise|Piton de la Fournaise]] (2017)    
|-
| rowspan="2" | >&nbsp;10<sup>4</sup> m<sup>3</sup> || Hawaiian / [[Earth:Strombolian eruption|Strombolian]] || Gentle || {{nowrap|100 m – 1 km}} || daily || minor || none
|-
| colspan="7" style="font-size:90%; color:#888; background:white;" | [[Earth:Stromboli|Stromboli]] (since [[History:Ancient Rome|Roman]] times), [[Earth:Mount Etna|Mount Etna]] (since Roman times), [[Earth:Kick 'em Jenny|Kick 'em Jenny]] (1939), [[Earth:Ritter Island|Ritter Island]] (1972, 1974, 2007), [[Earth:Iliwerung|Iliwerung]] (1983), [[Earth:Mount Unzen|Unzen]] (1991), [[Earth:Mount Nyiragongo|Nyiragongo]] (2002), [[Earth:Raoul Island|Raoul Island]] (2006), [[Earth:Havre Seamount|Havre Seamount]] (2012)
|-
| rowspan="2" | >&nbsp;10<sup>6</sup> m<sup>3</sup> || Strombolian / [[Earth:Vulcanian eruption|Vulcanian]] || Explosive || 1–5 km || every two weeks || moderate || none
|-
| colspan="7" style="font-size:90%; color:#888; max-width:1px; background:white;" |  [[Earth:Mount Unzen|Unzen]] (1792), Mount Hood (1865), Ruang (1871), [[Earth:Mount Baker|Mount Baker]] (1880), [[Earth:Ritter Island|Ritter Island]] ([[Earth:1888 Ritter Island eruption and tsunami|1888]]), [[Earth:Teide|Teide]] (1909), Tristan da Cunha (1961), Didicas (1969), [[Earth:Cumbre Vieja|Cumbre Vieja]] (1949, 1971), [[Earth:Galeras|Galeras]] (1993), Mayon (1993), Mount Bromo (2004), [[Earth:Koryaksky|Koryaksky]] (2009), Sinabung (2010), El Hierro (2011-2012), Mount Stromboli (2019), Whakaari (2019)
|-
| rowspan="2" | >&nbsp;10<sup>7</sup> m<sup>3</sup> || Strombolian / Vulcanian / [[Earth:Peléan eruption|Peléan]] / Sub-Plinian || Paroxysmic || 3–15 km || 3 months || substantial || possible
|-
| colspan="7" style="font-size:90%; color:#888; max-width:1px; background:white;" | [[Earth:Mount Etna|Mount Etna]] (1669), Mount Papandayan (1772), Dubbi (1861), [[Earth:Tori-shima (Izu Islands)|Tori-shima]] (1902), [[Earth:Taal Volcano|Taal]] (1911), [[Earth:Lassen Peak|Lassen Peak]] (1915), Paluweh (1928), Mount Merapi (1931), [[Earth:Mount Vesuvius|Mount Vesuvius]] (1944), Hibok-Hibok (1948-1953), [[Earth:Surtsey|Surtsey]] (1963-1967), [[Earth:Arenal Volcano|Volcán Arenal]] (1968), [[Earth:Eldfell|Eldfell]] (1973), [[Earth:Nevado del Ruiz|Nevado del Ruiz]] (1985), [[Earth:Mount Redoubt|Mount Redoubt]] (1989), [[Earth:Karymsky (volcano)|Karymsky]] (1996), [[Earth:Soufrière Hills|Soufrière Hills]] (1997), Jabal al-Tair (2007), [[Earth:Mount Ontake|Ontake]] (2014), [[Earth:Kīlauea|Kīlauea]] (2018), [[Earth:Volcán de Fuego|Volcán de Fuego]] (2018), Anak Krakatoa (2018), [[Earth:Cumbre Vieja|Cumbre Vieja]] ([[Earth:2021 Cumbre Vieja volcanic eruption|2021]]), Mount Semeru (2021)
|-
| rowspan="2" | >&nbsp;0.1&nbsp;km<sup>3</sup> || Peléan / [[Earth:Plinian eruption|Plinian]]/Sub-Plinian|| Catastrophic || > 10 km (Plinian or sub-Plinian) || 18 months || substantial || definite
|-
| colspan="7" style="font-size:90%; color:#888; max-width:1px; background:white;" | [[Earth:Mount Rainier|Mount Rainier]] (c. 250 BC), [[Earth:Kolumbo|Kolumbo]] (1650), Oshima–Ōshima (1741), [[Earth:Laki|Laki]] (1783), [[Earth:Kīlauea|Kīlauea]] ([[Earth:Keanakakoi eruption|1790]]), Mayon (1814), Makian (1861), [[Earth:Cotopaxi|Cotopaxi]] (1877), Mount Bandai ([[Earth:1888 eruption of Mount Bandai|1888]]), [[Earth:Mount Pelée|Pelée]] ([[Earth:1902 eruption of Mount Pelée|1902]]), [[Earth:Volcán de Colima|Colima]] (1889, 1913), [[Earth:Sakurajima|Sakurajima]] (1914), [[Earth:Kelud|Kelud]] (1919), Rabaul (1937), [[Earth:Mount Lamington|Mount Lamington]] ([[Earth:1951 eruption of Mount Lamington|1951]]), Galunggung (1982), Chaitén (2008), [[Earth:Eyjafjallajökull|Eyjafjallajökull]] ([[Earth:2010 eruptions of Eyjafjallajökull|2010]]), Mount Merapi (2010), [[Earth:Nabro Volcano|Nabro]] ([[Earth:2011 Nabro eruption|2011]]), Mount Sinabung (2013-2018), [[Earth:Calbuco (volcano)|Calbuco]] (1893, 2015), [[Earth:Ulawun|Ulawun]] (2000, 2019), [[Earth:Taal Volcano|Taal]] ([[Earth:2020–2021 Taal Volcano eruptions|2020]]), [[Earth:La Soufrière (volcano)|La Soufrière]] ([[Earth:2021 eruption of La Soufrière|2021]])
|-
| rowspan="2" | >&nbsp;1&nbsp;km<sup>3</sup> || Peléan / Plinian || Cataclysmic || > 10 km (Plinian) || 12 years || substantial || significant
|-
| colspan="7" style="font-size:90%; color:#888; max-width:1px; background:white;" | [[Earth:Avachinsky|Avachinsky]] (c. 1500 BC), [[Earth:Mount Etna|Mount Etna]] (122 BC), [[Earth:Mount Vesuvius|Mount Vesuvius]] ([[Earth:Eruption of Mount Vesuvius in 79 AD|79]]), [[Earth:Mount Haruna|Mount Haruna]] (550), [[Earth:Lake Towada|Towada]] (915), [[Earth:Hekla|Hekla]] (1104), [[Earth:Mount Asama|Mount Asama]] (1108), [[Earth:Água de Pau Massif|Agua de Pau]] (1563), [[Earth:Mount Fuji|Mount Fuji]] ([[Earth:Hōei eruption|1707]]), [[Earth:Mount Tarumae|Mount Tarumae]] (1667, 1739), [[Earth:Katla (volcano)|Katla]] (1625, 1721, 1755), Galunggung (1822), [[Earth:Cosigüina|Cosigüina]] (1835), [[Earth:Askja|Askja]] (1875), [[Earth:Mount Tarawera|Mount Tarawera]] ([[Earth:1886 eruption of Mount Tarawera|1886]]), [[Earth:Cerro Azul (Chile volcano)|Cerro Azul]] (1932), Agung (1963), [[Earth:Mount St. Helens|Mount St. Helens]] ([[Earth:1980 eruption of Mount St. Helens|1980]]), [[Earth:El Chichón|El Chichón]] (1982), [[Earth:Mount Hudson|Hudson]] (1991), [[Earth:Puyehue-Cordón Caulle|Puyehue]] (2011-2012), [[Earth:Hunga Tonga–Hunga Ha'apai|Hunga Tonga–Hunga Ha'apai]] ([[Earth:2022 Hunga Tonga–Hunga Ha'apai eruption and tsunami|2022]])
|-
| rowspan="2" | >&nbsp;10&nbsp;km<sup>3</sup> || Plinian / Ultra-Plinian|| Colossal || > 20 km || 50–100 yrs || substantial || substantial
|-
| colspan="7" style="font-size:90%; color:#888; max-width:1px; background:white;" | [[Earth:Laacher See#The eruption|Laacher See]] (c. 10,950 BC), [[Earth:Nevado de Toluca|Nevado de Toluca]] (8,550 BC), Fisher Caldera (c. 7420 BC), [[Earth:Menengai|Menengai]] (c. 6050 BC), Veniaminof (c. 1750 BC), [[Earth:Ambrym|Ambrym]] (50), [[Earth:Lake Ilopango|Lake Ilopango]] ([[Earth:Tierra Blanca Joven eruption|450]]), Ceboruco (930), [[Earth:Quilotoa|Quilotoa]] (1280),   [[Earth:Bárðarbunga|Bárðarbunga]] (1477), Billy Mitchell (1580), Huaynaputina (1600), [[Earth:Long Island (Papua New Guinea)|Long Island (Papua New Guinea)]] (1660), Krakatoa ([[Earth:1883 eruption of Krakatoa|1883]]), Santa Maria (1902), [[Earth:Novarupta|Novarupta]] (1912), [[Earth:Mount Pinatubo|Mount Pinatubo]] ([[Earth:1991 eruption of Mount Pinatubo|1991]])
|-
| rowspan="2" | >&nbsp;100&nbsp;km<sup>3</sup> || Ultra-Plinian || Super-colossal || > 20 km || 500–1,000 yrs || substantial || substantial
|-
| colspan="7" style="font-size:90%; color:#888; max-width:1px; background:white;" | [[Earth:Mesa Falls Tuff|Mesa Falls Tuff]] (1,300,000 BC), [[Earth:Valles Caldera|Valles Caldera]] (1,264,000 BC),  [[Earth:Phlegraean Fields|Phlegraean Fields]] ([[Earth:Campanian Ignimbrite eruption|37,000 BC]]), [[Earth:Aira Caldera|Aira Caldera]] (22,000 BC), [[Earth:Kurile Lake|Kurile Lake]] (c. 6460 BC) [[Earth:Mount Mazama|Mount Mazama]] (c. 5,700 BC), [[Earth:Kikai Caldera|Kikai Caldera]] ([[Earth:Akahoya eruption|4,300 BC]]), [[Earth:Cerro Blanco (volcano)|Cerro Blanco]] (c. 2300 BC), [[Biography:Santorini|Santorini]] ([[Earth:Minoan eruption|c. 1620 BC]]), [[Earth:Taupō Volcano|Taupō]] ([[Earth:Hatepe eruption|180]]), [[Earth:Paektu Mountain|Paektu]] ([[Earth:946 eruption of Paektu Mountain|946]]), [[Earth:Lake Segara Anak|Samalas]] ([[Earth:1257 Samalas eruption|1257]]), Mount Tambora ([[Earth:1815 eruption of Mount Tambora|1815]])
|-
| rowspan="2" | >&nbsp;1,000&nbsp;km<sup>3</sup> || Ultra-Plinian || Mega-colossal || > 20 km || > 50,000 yrs<ref name="Dosseto">{{cite book | title=Timescales of Magmatic Processes: From Core to Atmosphere | publisher=Wiley-Blackwell | date=2011 |last1= Dosseto |first1= A. |editor-last1= Turner |editor-first1= S. P. |editor-last2= Van-Orman |editor-first2= J. A. |isbn= 978-1-4443-3260-5}}</ref><ref name="Rothery2010">{{citation | title=Volcanoes, Earthquakes and Tsunamis | publisher=Teach Yourself | date=2010 | last= Rothery |first= David A.}}</ref> || vast || vast
|-
| colspan="7" style="font-size:90%; color:#888; max-width:1px; background:white;" | Wah Wah Springs  (30,000,000 BC), [[Earth:La Garita Caldera|La Garita]] ([[Earth:Fish Canyon Tuff|26,300,000 BC]]), Ōdai Caldera (13,700,000 BC), [[Earth:Galán|Cerro Galán]] (2,200,000 BC), [[Earth:Huckleberry Ridge Tuff|Huckleberry Ridge Tuff]] (2,100,000 BC), [[Earth:Yellowstone Caldera|Yellowstone]] ([[Earth:Lava Creek Tuff|630,000 BC]]), Whakamaru (in [[Earth:Taupō Volcanic Zone#Volcanoes, lakes and geothermal fields|TVZ]]) (254,000 BC),<ref name="Nelson">{{cite journal |last=Froggatt |first=P. C. |author2=Nelson, C. S. |author3=Carter, L. |author4=Griggs, G. |author5=Black, K. P.  |title=An exceptionally large late Quaternary eruption from New Zealand |journal=Nature |volume=319 |pages=578–582 |date=13 February 1986 |doi=10.1038/319578a0 |issue=6054|bibcode = 1986Natur.319..578F |s2cid=4332421 }}</ref> [[Earth:Lake Toba|Toba]] ([[Earth:Toba catastrophe theory|74,000 BC]]), [[Earth:Taupō Volcano|Taupō]] ([[Earth:Oruanui eruption|26,500 BC]])
|}

About 40 eruptions of VEI-8 magnitude within the last 132 million years ([[Megaannum|Mya]]) have been identified, of which 30 occurred in the past 36 million years. Considering the estimated frequency is on the order of once in 50,000 years,<ref name="Dosseto"/> there are likely many such eruptions in the last 132 Mya that are not yet known. Based on incomplete statistics, other authors assume that at least 60 VEI-8 eruptions have been identified.<ref>{{Cite journal|title = The size and frequency of the largest explosive eruptions on Earth|last = BG|first = Mason|date = 2004|journal = Bull Volcanol|volume = 66|issue = 8|pages = 735–748|doi = 10.1007/s00445-004-0355-9|bibcode = 2004BVol...66..735M|s2cid = 129680497}}</ref><ref>{{Cite journal|url= https://eprints.qut.edu.au/40259/1/c40259.pdf|title=The largest volcanic eruptions on Earth |last=Bryan |first=S.E. |date=2010 |journal=Earth-Science Reviews |volume=102 |issue=3–4 |pages=207–229 |doi=10.1016/j.earscirev.2010.07.001 |bibcode=2010ESRv..102..207B }}</ref> The most recent is [[Earth:Lake Taupō|Lake Taupō]]'s [[Earth:Oruanui eruption|Oruanui eruption]], more than 27,000 years ago, which means that there have not been any [[Earth:Holocene|Holocene]] eruptions with a VEI of 8.<ref name="Mason2004">
{{cite journal
 |last1= Mason |first1= Ben G.
 |last2= Pyle |first2= David M.
 |last3= Oppenheimer |first3= Clive
 |year=2004
 |title=The size and frequency of the largest explosive eruptions on Earth
 |journal=[[Earth:Bulletin of Volcanology|Bulletin of Volcanology]]
 |volume=66 |issue=8 |pages=735–748
 |bibcode = 2004BVol...66..735M
 |doi=10.1007/s00445-004-0355-9
|s2cid= 129680497
 }}</ref>

There have been at least 10 eruptions of VEI-7 in the last 11,700 years. There are also 58 Plinian eruptions, and 13 caldera-forming eruptions, of large, but unknown magnitudes. By 2010, the [[Earth:Global Volcanism Program|Global Volcanism Program]] of the Smithsonian Institution had cataloged the assignment of a VEI for 7,742 volcanic eruptions that occurred during the [[Earth:Holocene|Holocene]] (the last 11,700 years) which account for about 75% of the total known eruptions during the Holocene. Of these 7,742 eruptions, about 49% have a VEI of 2 or less, and 90% have a VEI of 3 or less.<ref>
{{cite book
 |last1=Siebert |first1=L.
 |last2=Simkin |first2=T.
 |last3=Kimberly |first3=P.
 |date=2010
 |title=Volcanoes of the World
 |edition=3rd |pages=28–38
 |publisher=University of California Press
 |isbn=978-0-520-26877-7
}}</ref>

==Limitations==
Under the VEI, [[Earth:Volcanic ash|ash]], [[Earth:Lava|lava]], [[Earth:Volcanic bomb|lava bombs]], and [[Earth:Ignimbrite|ignimbrite]] are all treated alike. [[Physics:Density|Density]] and [[Earth:Vesicular texture|vesicularity]] (gas bubbling) of the volcanic products in question is not taken into account. In contrast, the DRE ([[Earth:Dense-rock equivalent|dense-rock equivalent]]) is sometimes calculated to give the actual amount of [[Biology:Magma|magma]] erupted. Another weakness of the VEI is that it does not take into account the power output of an eruption, which makes the VEI extremely difficult to determine with prehistoric or unobserved eruptions.

Although VEI is quite suitable for classifying the explosive magnitude of eruptions, the index is not as significant as sulfur dioxide emissions in quantifying their atmospheric and climatic impact.<ref name=JRMS>{{cite journal  |last1=Miles |first1=M. G. |last2=Grainger |first2=R. G. |last3=Highwood |first3=E. J. |year=2004 |title=Volcanic Aerosols: The significance of volcanic eruption strength and frequency for climate | url=http://eodg.atm.ox.ac.uk/eodg/papers/2004Miles1.pdf |journal=Quarterly Journal of the Royal Meteorological Society |volume=130 |issue=602 |pages=2361–2376 |doi=10.1256/qj.03.60 |bibcode=2004QJRMS.130.2361M}}</ref>

==Lists of large eruptions==
* [[Earth:Timeline of volcanism on Earth|Timeline of volcanism on Earth]] (mostly VEI-6, within 2 kya)
* List of large volcanic eruptions of the 19th century (≥ VEI-4)
* List of large volcanic eruptions of the 20th century (≥ VEI-4)
* List of large volcanic eruptions in the 21st century (≥ VEI-4)
* List of large historical volcanic eruptions (VEI-5-7 within recorded history)
* List of large volcanic eruptions (mostly VEI-6–8, within 50 Mya)
* List of largest volcanic eruptions (VEI-7–8, mostly within 500 Mya)

==See also==
* {{annotated link|Earth:Supervolcano}} 
* {{annotated link|Earth:Dispersal index}}
* [[Earth:Lists of volcanoes|Lists of volcanoes]]
* List of natural disasters by death toll
* List of volcanic eruptions by death toll
{{clear}}

==References==
{{reflist}}

==External links==
* [http://volcanoes.usgs.gov/images/pglossary/vei.php VEI glossary entry] from a USGS website
* [https://web.archive.org/web/20070312094637/http://talk.workunlimited.co.uk/life/feature/story/0,13026,1294868,00.html How to measure the size of a volcanic eruption], from ''{{wipe|The Guardian}}''
* [https://doi.org/10.1007%2Fs00445-004-0355-9 The size and frequency of the largest explosive eruptions on Earth], a 2004 article from the ''[[Earth:Bulletin of Volcanology|Bulletin of Volcanology]]''
* [http://www.volcano.si.edu/world/largeeruptions.cfm List of Large Holocene Eruptions (VEI > 4) from the Smithsonian Global Volcanism Program]

{{List of volcanoes}}

[[Category:Volcanology]]

{{Sourceattribution|Volcanic Explosivity Index|1}}