Volcanic Explosivity Index (VEI)

The VEI ranks eruptions from 0 to 8 by the volume of material ejected and the height of the plume. As with magnitude, the scale is logarithmic. Each step means about ten times more material.

A VEI 0 or 1 eruption is effusive, as often in Hawaii. Pinatubo in 1991 was VEI 6, and Tambora in 1815, the most powerful eruption in recent history, was VEI 7. The timelines on volcano pages show the VEI of each known eruption.