Volcanic Explosivity Index

Invented in 1982 by Chris Newhall and Stephen Self, the Volcanic Explosivity Index (VEI) is a bit like a Richter scale for volcanoes.

The VEI measures the “explosiveness” of a volcanic eruption, and takes into account the amount of material ejected, the height to which the material is ejected, and how long the eruption lasts. The scale runs from 0 (“effusive”) to 8 (“apocalyptic”), and is logarithmic from VEI-2 onwards (so VEI-3 is ten times more explosive than VEI-2, etc.).

VEI Classification Material ejected /km3 Plume height /km
0 Effusive < 0.000 01 < 0.1
1 Gentle > 0.000 01 0.1-1
2 Explosive > 0.001 1-5
3 Catastrophic > 0.01 3-15
4 Cataclysmic > 0.1 10-25
5 Paroxysmic > 1 20-35
6 Colossal > 10 > 30
7 Mega-colossal > 100 > 40
8 Apocalyptic > 1000 > 50

Newhall and Self’s original paper contains a list of eruptions by VEI running back to 1500 (note their footnote about reporting at the bottom of the table).

vei-list

The paper only lists one VEI-7 event, the “Mega-colossal” eruption of Mount Tambora in Indonesia in 1815 that caused The Year Without a Summer. They state that VEI-8 eruptions should occur with a frequency of ? 10 000 years, with the most recent being the eruption of New Zealand’s Taupo Volcano around 26 500 years ago.

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