The Volcanic Explosivity Index reference article from the English Wikipedia on 24-Apr-2004 (provided by Fixed Reference: snapshots of Wikipedia from wikipedia.org)

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 (from Gentle to Cataclysmic) 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 cataclysmic explosive eruptions that can eject (10¹² cubic metres of tephra and a cloud column height of over 25 km). Values higher than 8 can be determined if needed.

VEI Index

VEI	Plume Height	Volume Ejected	How Often	Example
0	<100 m	>1000 m3	daily	Kilauea
1	100–1000 m	>10,000 m3	daily	Stromboli
2	1–5 km	>1,000,000 m3	weekly	Galeras, 1992
3	3–15 km	>10,000,000 m3	yearly	Ruiz, 1985
4	10–25 km	>0.1 km3	>10 yrs	Galunggung, 1982
5	>25 km	>1 km3	>100 yrs	St. Helens, 1981
6	>25 km	>10 km3	>100 yrs	Krakatau, 1883
7	>25 km	>100 km3	>1000 yrs	Tambora, 1815
8	>25 km	>1000 km3	>10,000 yrs	Toba, 71 ka

VEI	0	1	2	3	4	5	6	7	8
Total Historic Eruptions	487	623	3176	733	119	19	5	2	1

See also:

• Nevado del Ruiz, 1985 (VEI = 3)
• Mount St. Helens, 1980 (VEI = 5)
• Krakatoa, 1883 (VEI = 6)
• Novarupta, 1912 (VEI = 6)
• Mount Tambora, 1815 (VEI = 7)
• Long Valley Caldera (VEI = 7)
• Yellowstone (VEI = 8)

References: Newhall and Self (J. Geophys. Research, v. 87, p. 1231–1238, 1982)

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