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. 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
- Nevado del Ruiz, 1985 (VEI 3)
- Mount St. Helens, 1980 eruption (VEI 5)
- El Chichon, 1982 (VEI 5)
- Laki, 1783 (VEI 6)
- Krakatoa, 1883 (VEI 6)
- Novarupta (Katmai), 1912 (VEI 6)
- Mount Pinatubo, 1991 (VEI 6)
- Santorini (Thera), 1640 BC (VEI 6-7)
- Taupo, 181 (VEI 6-7)
- Mount Tambora, 1815 (VEI 6-7)
- Long Valley Caldera, 760,000 BP (VEI 7)
- Yellowstone, 640,000 BP (VEI 8)
- Toba 73,000 BP (VEI 8)
See also
References and external links
- Christopher G. Newhall and Steve Self (Journal of Geophysical Research, v. 87, p. 1231–1238, 1982)
- VEI glossary entry (http://volcanoes.usgs.gov/Products/Pglossary/vei.html) from a USGS website
- How to measure the size of a volcanic eruption (http://talk.workunlimited.co.uk/life/feature/story/0,13026,1294868,00.html), from The Guardian
- The size and frequency of the largest explosive eruptions on Earth (http://springerlink.metapress.com/openurl.asp?genre=article&id=doi:10.1007/s00445-004-0355-9), a 2004 article from the Bulletin of Volcanologyde:Volcanic Explosivity Index