Volcanic Explosivity Index

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The Volcanic Explosivity Index (VEI) was devised by Chris Newhall of the U.S. Geological Survey and Steve Self at the University of Hawaii 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 and ranges from 0, for non-explosive eruptions (less than 10⁴ cubic metres of tephra ejected) to 8, for mega-colossal explosive eruptions 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 ten-fold increase in observed eruption criteria.

Note that ash, volcanic bombs, and ignimbrite are all treated alike - this is due to taking into account of 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. But one weakness is that the VEI does not take into account the magnitude of power output of an eruption. However, this 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

[edit] Classification

VEI	Classification	Description	Plume	Ejecta volume	Frequency	Example	Occurrences †
0	Hawaiian	non-explosive	< 100 m	> 1000 m³	daily	Kilauea	-
1	Hawaiian/Strombolian	gentle	100-1000 m	> 10,000 m³	daily	Stromboli	-
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	Nevado del Ruiz (1985)	868
4	Pelean/Plinian	cataclysmic	10-25 km	> 0.1 km³	≥ 10 yrs	Galunggung (1982)	278
5	Plinian	paroxysmal	> 25 km	> 1 km³	≥ 50 yrs	St. Helens (1980)	84
6	Plinian/Ultra-Plinian	colossal	> 25 km	> 10 km³	≥ 100 yrs	Krakatoa (1883)	39
7	Plinian/Ultra-Plinian	super-colossal	> 25 km	> 100 km³	≥ 1000 yrs	Tambora (1815)	4
8	Plinian/Ultra-Plinian	mega-colossal	> 25 km	> 1000 km³	≥ 10,000 yrs	Toba (73,000 BP)	-

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

[edit] List of eruptions

VEI	Name	Year
0	Mauna Loa	1984
0	Piton de la Fournaise	2004
1	Kilauea	1983 - present
1	Nyiragongo	2002
2	Mount Hood	1865-1866
	Kilauea	1924
	Tristan da Cunha	1961
	Whakaari/White Island	2001
	Mount Usu	2000-2001
3	Vesuvius	1913-1944
	Surtsey	1963-1967
	Eldfell	1973
	Nevado del Ruiz	1985
	Mount Etna	2002-2003
4	Mount Pelée	1902
	Parícutin	1943-1952
	Hekla	1947
	Galunggung	1982
	Mount Spurr	1992
5	Vesuvius	79
	Mount Agung	1963
	Mount St. Helens	1980
	El Chichón	1982
	Mount Hudson	1991
6	Ilopango	450 ± 30 years
	Kuwae	1452 or 1453
	Laki	1783
	Krakatoa	1883
	Novarupta (Katmai)	1912
	Mount Pinatubo	1991
	Santorini (Thera)	1627 BC ± 11 years
7	Long Valley Caldera	760,000 BP
	Mount Mazama	4860 BC
	Taupo	181
	Mount Tambora	1815
8	La Garita Caldera	27 million years BP
	Yellowstone	2,200,000 BP
	Yellowstone	640,000 BP
	Toba	73,000 BP
	Taupo (Oruanui)	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. There is a new theory that the Santorini eruption may have been twice as large as originally thought, placing it behind Taupo's 181 eruption and Mount Tambora as the third largest eruption in recorded history.<ref>McCoy, F. W. and Dunn, S., 2002, Modelling the Climatic Effects fo the LBA Eruption of Thera: New Calculations of Tephra Volumes May Suggest a Significantly Larger Eruption than Previously Reported [abst.]; Proceedings of the Chapman Conference on Volcanism and the Earth’s Atmosphere, Am. Geophysical Union, Santorini, Greece: 21-22.</ref>

[edit] See also

[edit] Footnotes

[edit] References

Christopher G. Newhall and Steve Self (Journal of Geophysical Research, v. 87, p. 1231–1238, 1982)
Ben G. Mason, David M. Pyle, and Clive Oppenheimer (2004). "The size and frequency of the largest explosive eruptions on Earth" (PDF). Bulletin of Volcanology 66 (8): 735-748. DOI:10.1007/s00445-004-0355-9. Retrieved on 2006-07-14.