VOLCANIC EXPLOSIVITY INDEX 🌋 The Volcanic Explosivity Index, or VEI, is a scale that measures the size and intensity of volcanic eruptions. It was developed by Chris Newhall and Stephen Self in 1982 as a way to compare eruptions based on the volume of material ejected, the height of the eruption column, and other observable features. The scale ranges from 0 to 8. Each level represents a tenfold increase in eruption size. For example, a VEI 5 eruption is ten times more explosive than a VEI 4. He