The Volcanic Explosivity Index is a scale used to measure the size of explosive eruptions

The Volcanic Explosivity Index (VEI) is a scale used to measure the size of explosive eruptions. Volume of erupted material, size of the ash cloud and qualitative observations are used to determine where an eruption falls on the scale. The scale is logarithmic, meaning a VEI 2 eruption is ten times more powerful than a VEI 1 eruption.

The VEI runs from 0 (non-explosive eruption) to 8 (supervolcanic eruption.)

A volcano that has had an eruption of VEI 8 is known as a supervolcano

A supervolcano is any volcano that is known to have had an eruption of VEI 8 on the eruption scale. Yellowstone caldera and Lake Tobo are both supervolcanoes. Eruptions of supervolcanoes are often associated with mass extinction events .

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