OREGON STATE UNIVERSITY

How Big are Eruptions?

How BIG are Volcanic Eruptions?

Every year about 60 volcanoes erupt, but most of the activity is pretty weak. How do volcanologists measure how big an eruption is? There is not any single feature that determines the "bigness", but the following eruption magnitude scale - called the Volcanic Explosivity Index or VEI - is based on a number of things that can be observed during an eruption. According to this scale, really huge eruptions don't happen very often, luckily!

 

VEI Description Plume Height Volume Classification How often Example
0 non-explosive < 100 m 1000s m3 Hawaiian daily Kilauea
1 gentle 100-1000 m 10,000s m3 Haw/Strombolian daily Stromboli
2 explosive 1-5 km 1,000,000s m3 Strom/Vulcanian weekly Galeras, 1992
3 severe 3-15 km 10,000,000s m3 Vulcanian yearly Ruiz, 1985
4 cataclysmic 10-25 km 100,000,000s m3 Vulc/Plinian 10's of years Galunggung, 1982
5 paroxysmal >25 km 1 km3 Plinian 100's of years St. Helens, 1980
6 colossal >25 km 10s km3 Plin/Ultra-Plinian 100's of years Krakatau, 1883
7 super-colossal >25 km 100s km3 Ultra-Plinian 1000's of years Tambora, 1815
8 mega-colossal >25 km 1,000s km3 Ultra-Plinian 10,000's of years Yellowstone, 2 Ma