Volcanic Explosivity Index
Volume of products, eruption cloud height, and qualitative observations (using terms ranging from "gentle" to "mega-colossal") are used to determine the explosivity value. The scale is
open-ended with the largest
volcanoes in history given magnitude 8. TheVolcanic Explosivity Index (
VEI) was devised byChris Newhall of theUS Geological Survey and Stephen Self at theUniversity of Hawaii in 1982 to provide a relative measure of the explosiveness ofvolcanic eruptions.