Tuesday 16 August 2011

The Volcanic Explosivity Index (VEI)

The volcanic explosive index (VEI) is a non comprehensive scale used for volcanic eruptions. It measures how “big” the eruption is based on the volume of ejected matter.

Intensity = log10(mass eruption rate kg/s) + 3

VEI
Description
Plume height
Volume ejected 
Occurrence
0
Non-explosive
< 100 m
> 1,000 m³
Daily
1
Gentle
100 – 1,000 m
> 10,000 m³
Daily
2
Explosive
1 – 5 km
> 1,000,000 m³
Weekly
3
Severe
3 – 5 km
> 10,000,000 m³
Yearly
4
Cataclysmically
10 – 25 km
> 0.1  km³
≥ 10 yrs
5
Paroxysmal
> 25 km
> 1  km³
≥ 100 yrs
6
Colossal
> 25 km
> 10  km³
≥ 100 yrs
7
Super-colossal
> 25 km
> 100  km³
≥ 1,000 yrs
8
Mega-colossal
> 25 km
> 1,000  km³
≥ 10,000 yrs