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Information about VEI |
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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 with the largest volcanoes in history given magnitude 8. A value of 0 is given for non-explosive eruptions (less than 104 cubic metres of tephra ejected) with 8 representing a mega-colossal explosive eruption 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 tenfold increase in observed eruption criteria.
VEI and ejecta volume correlation © USGS
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Note that ash, volcanic bombs, and ignimbrite are all treated alike - this is due to taking into account the vesicularity (gas bubbling) of the volcanic products in question and the DRE (Dense-Rock Equivalent) is calculated to give the actual amount of magma erupted. One weakness of the VEI is that it does not take into account the magnitude of power output of an eruption. This, of course, is extremely difficult to detect with prehistoric or unobserved eruptions.
Classification
| VEI |
Classification |
Description |
Plume |
Ejecta volume |
Frequency |
Occurrences * |
| 0 |
Hawaiian Eruption |
non-explosive |
< 100 m |
< 10,000 m³ |
daily |
many |
| 1 |
Strombolian Eruption |
gentle |
100-1000 m |
> 10,000 m³ |
daily |
many |
| 2 |
Vulcanian Eruption |
explosive |
1-5 km |
> 1,000,000 m³ |
weekly |
3477 |
| 3 |
Pelean Eruption |
severe |
3-15 km |
> 10,000,000 m³ |
yearly |
868 |
| 4 |
Plinian |
cataclysmic |
10-25 km |
> 0.1 km³ |
≥ 10 yrs |
278 |
| 5 |
Plinian Eruption |
paroxysmal |
> 25 km |
> 1 km³ |
≥ 50 yrs |
84 |
| 6 |
Ultra-Plinian |
colossal |
> 25 km |
> 10 km³ |
≥ 100 yrs |
39 |
| 7 |
Ultra-Plinian |
super-colossal |
> 25 km |
> 100 km³ |
≥ 1000 yrs |
4 |
| 8 |
Ultra-Plinian |
mega-colossal |
> 25 km |
> 1,000 km³ |
≥ 10,000 yrs |
none |
*) Count of eruptions in the last 10,000 years based on 1994 figures maintained by the Global Volcanism Program of the Smithsonian Institution.
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| VOLCANOES IN INDONESIA PICTURES |
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| EXCHANGE RATES |
@ 20 Jul 2008 20:29 CET
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@ 20 Jul 2008 19:28 CET
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@ 20 Jul 2008 19:18 CET
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@ 20 Jul 2008 18:55 CET
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@ 20 Jul 2008 18:05 CET
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