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Volcanic Explosivity Index

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. Values higher than 8 can be determined if needed.

One weakness of the VEI is that it does not take into account of the density of erupted material; ash, volcanic bombs, and ignimbrite are all treated alike. In addition, the VEI does not take into account the magnitude of power output of an eruption.

VEI	Classification	Description	Plume height	Volume ejected	How often	Example	Total historic eruptions as of 1994
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, 1992	3477
3	Vulcanian (Sub-Plinian)	severe	3-15 km	> 10,000,000 m³	yearly	Nevado del Ruiz, 1985	868
4	Vulcanian (Sub-Plinian)/ Plinian	cataclysmic	10-25 km	> 0.1 km³	≥ 10 yrs	Galunggung, 1982	278
5	Plinian	paroxysmal	> 25 km	> 1 km³	≥ 100 yrs	St. Helens, 1980	84
6	Plinian/ Ultra-Plinian (Krakatoan)	colossal	> 25 km	> 10 km³	≥ 100 yrs	Krakatau, 1883	39
7	Ultra-Plinian (Krakatoan )	super-colossal	> 25 km	> 100 km³	≥ 1000 yrs	Tambora, 1815	4
8	Ultra-Plinian (Krakatoan)	mega-colossal	> 25 km	> 1000 km³	≥ 10,000 yrs	Toba, 71,000 BP	1

Count of historic eruptions based on 1994 figures maintained by the Global Volcanism Program of the Smithsonian Institution

References and external links

Christopher G. Newhall and Steve Self (Journal of Geophysical Research , v. 87, p. 1231–1238, 1982)
VEI glossary entry from a USGS website
How to measure the size of a volcanic eruption, from The Guardian
The size and frequency of the largest explosive eruptions on Earth, a 2004 article from the Bulletin of Volcanology

Categories: Volcanology | Scales

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01-04-2007 01:21:04

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Volcanic Explosivity Index

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References and external links