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. 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.
| 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 | severe | 3-15 km | > 10,000,000 m³ | yearly | Nevado del Ruiz, 1985 | 868 |
| 4 | Vulcanian/ 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
- Nevado del Ruiz, 1985 (VEI = 3)
- Mount St. Helens, 1980 eruption (VEI = 5)
- Krakatoa, 1883 (VEI = 6)
- Novarupta, 1912 (VEI = 6)
- Mount Tambora, 1815 (VEI = 7)
- Long Valley Caldera (VEI = 7)
- Yellowstone (VEI = 8)
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