Volcanic Explosivity Index

VEI and ejecta volume correlation

The Volcanic Explosivity Index (VEI) was devised by Chris Newhall of the U.S. Geological Survey and Steve Self at the University of Hawaiʻi in 1982 to provide a relative measure of the explosiveness of volcanic eruptions.

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 volcanoes in history given magnitude 8. A value of 0 is given for non-explosive eruptions (less than 104 cubic metres of tephra ejected) with 8 representing a mega-colossal explosive eruption that can eject 1012 cubic metres of tephra and have a cloud column height of over 25 km. Each interval on the scale represents a tenfold increase in observed eruption criteria.

Note that ash, volcanic bombs, and ignimbrite are all treated alike — this is due to taking into account the vesicularity (gas bubbling) of the volcanic products in question and the DRE (Dense-Rock Equivalent) is calculated to give the actual amount of magma erupted. One weakness of the VEI is that it does not take into account the magnitude of power output of an eruption. This, of course, is extremely difficult to detect with prehistoric or unobserved eruptions.

1 Classification
2 List of eruptions
3 See also
4 Footnotes
5 References
6 External links

Classification

Scientists measure how powerful volcanic eruptions are using the VEI. The VEI stands for Volcanic Explosivity Index. It records how much volcanic matierial is thrown out, how high the eruption goes, and how long it lasts. The scale goes from 0 to 8. A score of 1 is 10 times more powerful than a score of 0.

VEI Classification Description Plume Ejecta volume Frequency Example Occurrences * 0 Hawaiʻiannon-explosive < 100 m < 10,000 m³ daily Mauna Loamany 1 Hawaiʻian/Stromboliangentle 100-1000 m > 10,000 m³ daily Strombolimany 2 Strombolian/Vulcanian explosive 1-5 km > 1,000,000 m³ weekly Galeras(1993) 3477* 3 Vulcanian/Pelean severe 3-15 km > 10,000,000 m³ yearly Koryaksky868 4 Pelean/Plinian cataclysmic 10-25 km > 0.1 km³ ≥ 10 yrs Soufrière Hills(1995) 278 5 Plinianparoxysmal > 25 km > 1 km³ ≥ 50 yrs St. Helens(1980) 84 6 Plinian/Ultra-Plinian colossal > 25 km > 10 km³ ≥ 100 yrs Mount Pinatubo(1991) 39 7 Plinian/Ultra-Plinian super-colossal > 25 km > 100 km³ ≥ 1000 yrs Tambora(1815) 5 (+2 suspected) 8 Ultra-Plinian mega-colossal > 25 km > 1,000 km³ ≥ 10,000 yrs Toba(73,000 BP) 1

* Count of eruptions in the last 10,000 years based on 1994 figures maintained by the Global Volcanism Program of the Smithsonian Institution

Note that 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 100 from 10,000 to 1,000,000 m³ while the factor is 10 between all higher indices.

List of eruptions

This list is incomplete; you can help by expanding it. VEI Name Year 0 Mauna Loa 1984 Piton de la Fournaise 2004 Hoodoo Mountain7050 BC? 1 Kilauea 1983- present Nyiragongo 2002 Wells Gray-Clearwater Volcanic Field 1500? 2 Mount Hood 1865-1866 Kilauea 1924 Tristan da Cunha 1961 Whakaari/White Island 2001 Mount Usu 2000-20013 Mount Vesuvius 1913-1944 Mount Edziza950 AD ± 1000 years Surtsey 1963-1967 Eldfell 1973 Nevado del Ruiz 1985 Mount Etna 2002-2003 Mount Garibaldi9,300 BP Nazko Cone7,200 BP4 Mount Pelée1902 Parícutin 1943-1952 Hekla 1947 Galunggung 1982 Mount Spurr 19925 Hekla(Hekla 3 eruption) 1159 BC Mount Vesuvius(Pompeiieruption) 79 Mount Tarumae 1739 Mount Agung 1963 Mount St. Helens(1980 eruption) 1980 Mount Meager2350 BP El Chichón 1982 Mount Hudson 1991 Mount Tarawera 18866 Mount Etna8000 BP? Mount Veniaminof 1750 BC Mount Vesuvius(Avellino eruption) 1660 BC± 43 years Thera(Minoan eruption) 1620s BCor 1520s BC Mount Churchill(White River Ash) 1200 BP Ilopango 450± 30 years Laki 934 Baekdu Mountain(Tianchi eruption) ≈1200 Kuwae 1452or 1453 Huaynaputina 1600 Laki 1783 Krakatoa 1883 Santa María 1902 Novarupta 1912 Mount Pinatubo 19917 Bennett Lake Volcanic Complex50 Ma Yellowstone(Mesa Falls eruption) 1.3 Ma Long Valley Caldera760,000 BP Aira Caldera22,000 BP Kurile 6440 BC± 25 years Crater Lake, Oregon(Mount Mazama eruption) ≈4860 BC Kikai(Akahoya eruption) ≈4350 BC Taupo(Hatepe eruption) ≈180 Mount Tambora 18158 La Garita Caldera27 Ma Yellowstone(Huckleberry Ridge eruption) 2.2 Ma Galán2.2 Ma Yellowstone(Lava Creek eruption) 640,000 BP Toba73,000 BP Taupo(Oruanui eruption) 26,500 BP

Note that there have not been any Holocene (within the last 10,000 years) eruptions with a VEI of 8. Lake Taupo's Oruanui eruption is probably the most recent, occurring 26,500 years ago.

Footnotes

References

Newhall, Christopher G.; Self, Steve (1982). "The volcanic explosivity index (VEI): An estimate of explosive magnitude for historical volcanism". Journal of Geophysical Research 87 (C2): 1231–1238.
Mason, Ben G.; Pyle, David M.; Oppenheimer, Clive (2004). "The size and frequency of the largest explosive eruptions on Earth". Bulletin of Volcanology 66 (8): 735–748. doi:10.1007/s00445-004-0355-9.