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Frequency of Volcanic Eruptions |John Seach
The volcanic explosivity index is a scale from 1 to 8 to measure the magnitude (erupted volume) and intensity
(eruption column height) of an eruption.
The VEI is not used to describe eruptions of lava which are non explosive.
Ancient eruptions are determined by the volume of deposits.
Modern eruptions are determined by the observed column height.
About 50-60 volcanoes erupt every year.
20-30 are effusive (lava flows), 20-30 are explosive.
360 volcanoes erupted in the 20th century.
Volcanic Explosivity |
Column |
Tephra m3 |
Examples |
Eruption Frequency |
non explosive |
<0.1 |
104 |
20-30 such eruptions per year |
|
1 |
0.1-1.0 |
106 |
VEI 1 eruptions |
|
2 |
1-5 |
107 |
VEI 2 eruptions |
|
3 |
3-15 |
108 |
Lopevi 2001 |
3 per year |
4 |
10-25 |
109 |
Galunggung 1982 |
1 per year |
5 |
>25 |
1010 |
Chaitén 2008 |
1 every 10 years |
6 |
- |
1011 |
1 every 100 years |
|
7 |
- |
1012 |
1 every 1000 yr |
|
8 |
- |
1013 |
1 every 10 million yr |
Another measure of an eruption is the Destructiveness Index.
This is the logarithm of the area covered by pyroclastic flows or covered in tephra.