Volcanic explosivity index

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.

About 40 eruptions of VEI-8 magnitude within the last 132 million years (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, 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.{{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 }} The most recent is Lake Taupō's Oruanui eruption, more than 27,000 years ago, which means that there have not been any Holocene eruptions with a VEI of 8.

{{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=Bulletin of Volcanology

|volume=66 |issue=8 |pages=735–748

|bibcode = 2004BVol...66..735M

|doi=10.1007/s00445-004-0355-9

|s2cid= 129680497

}}

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 Global Volcanism Program of the Smithsonian Institution had cataloged the assignment of a VEI for 7,742 volcanic eruptions that occurred during the 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 lower, and 90% have a VEI of 3 or lower.

{{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

}}

Under the VEI, ash, lava, lava bombs, and ignimbrite are all treated alike. Density and vesicularity (gas bubbling) of the volcanic products in question is not taken into account. In contrast, the DRE (dense-rock equivalent) is sometimes calculated to give the actual amount of 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.{{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|s2cid=53005926 }}

{{Volcanic Eruption Map}}

• Timeline of volcanism on Earth (mostly VEI-6, within 2 kya)
• List of volcanic eruptions 1500–2000
• List of volcanic eruptions in the 21st century
• List of volcanic eruptions by death toll
• List of large Holocene volcanic eruptions (VEI-5–7)
• List of large volcanic eruptions (VEI-5–8, within 450+ Mya)
• List of largest volcanic eruptions (VEI-7–8, mostly within 500 Mya)

• {{annotated link |Supervolcano}}
• {{annotated link |Decade Volcanoes}}
• {{annotated link |Dispersal index}}
• Lists of volcanoes
• List of natural disasters by death toll

{{clear}}

{{reflist}}

• [https://volcanoes.usgs.gov/vsc/glossary/vei.html 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 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 Bulletin of Volcanology
• [http://www.volcano.si.edu/world/largeeruptions.cfm List of Large Holocene Eruptions (VEI > 4) from the Smithsonian Global Volcanism Program] {{Webarchive|url=https://web.archive.org/web/20120117212357/http://volcano.si.edu/world/largeeruptions.cfm |date=2012-01-17 }}

{{List of volcanoes}}

Category:Volcanology

Category:Hazard scales

Category:1982 introductions