On the Volcanic Explosivity Index, what is the highest magnitude category? The highest category is VEI 8.
The Volcanic Explosivity Index, or VEI, ranks explosive eruptions from 0 to 8 using factors such as the volume of erupted material, eruption-column height, and duration. VEI 8 is called “mega-colossal” and represents an eruption ejecting more than 1,000 cubic kilometres of material, with an eruption column rising above 50 kilometres in the index’s typical description.
The scale is logarithmic from VEI 2 upward: each increase generally represents about ten times more erupted material. VEI 8 events are exceptionally rare and are associated with giant caldera-forming eruptions. Examples include Toba about 74,000 years ago, Yellowstone’s major eruptions, and the Wah Wah Springs eruption about 30 million years ago.
VEI is not the same as earthquake magnitude, and it does not perfectly measure every aspect of an eruption’s danger. A lower-ranked eruption near a populated area can be more destructive locally than a larger prehistoric event in an uninhabited region. VEI 0 describes non-explosive eruptions, while VEI 8 is the scale’s upper limit.