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: 10-20-2005 03:30:18
