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
See also
References and external links
Last updated: 05-07-2005 10:40:57
Last updated: 05-13-2005 07:56:04