Volcanic Explosivity Index (VEI)
The Volcanic Explosivity Index (VEI) is a scale from 0 to 8 that rates the size of an explosive volcanic eruption. Scientists set a VEI number from the volume of ash and rock the eruption throws out, the height of its eruption column, and how long the blast lasts. Each step up the scale marks a far larger eruption than the step below it.
Preppers meet the term in news reports and volcano observatory updates. A low VEI points to a local event. A high VEI points to ash that can travel far beyond the volcano, onto roofs, roads, and water supplies in towns that never saw the mountain erupt. Lava flows, gas, and mudflows near the volcano are separate hazards with their own warnings.
Read the VEI number as a measure of reach, then check your local alerts to see what it means for your family's next step.
