Volcanic Explosivity Index

From Academic Kids

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

List of eruptions and their VEI

See also

References and external links

it:VEI

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