Volcanic explosivity index

<p>The volcanic explosivity index (VEI) is a scale used to measure the size of explosive volcanic eruptions. It was devised by <a href="/facts/Christopher_G._Newhall/HbPuuz9R">Christopher G. Newhall</a> of the <a href="/facts/United_States_Geological_Survey/nVaGtMjl">United States Geological Survey</a> and <a href="/facts/Stephen_Self/rbILrcU0">Stephen Self</a> in 1982.
</p><p>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 eruptions in history given a magnitude of 8. A value of 0 is given for non-explosive eruptions, defined as less than 10,000 m3 (350,000 cu ft) of <a href="/facts/Tephra/fYHmdLu1">tephra</a> ejected; and 8 representing a <a href="/facts/Supervolcanic_eruption/wTWrBEja">supervolcanic eruption</a> that can eject 1.0×1012 m3 (240 cubic miles) of tephra and have a cloud column height of over 20 km (66,000 ft). The scale is logarithmic, with each interval on the scale representing a tenfold increase in observed ejecta criteria, with the exception of between VEI-0, VEI-1 and VEI-2.
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Volcanic explosivity index open-in-new

Volcanic explosivity index