Editing Volcanic explosivity index (section)

{{Short description|Predictive qualitative scale for explosiveness of volcanic eruptions}}
{{Redirect|VEI|the company|Visual Entertainment Inc.}}
[[File:VEIfigure en.svg|thumb|270px|VEI and ejecta volume correlation]]

The '''volcanic explosivity index''' ('''VEI''') is a scale used to measure the size of explosive volcanic eruptions. It was devised by [[Christopher G. Newhall]] of the [[United States Geological Survey]] and [[Stephen Self]] in 1982.

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 {{convert|10000|m3|cuft|abbr=on}} of [[tephra]] ejected; and 8 representing a [[supervolcanic eruption]] that can eject {{val|1.0|e=12|u=m3}} (240 cubic miles) of tephra and have a cloud column height of over {{convert|20|km|ft|abbr=on}}. 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.<ref>
{{cite journal
 |first1=Christopher G. |last1=Newhall
 |first2=Stephen |last2=Self
 |year=1982
 |title=The Volcanic Explosivity Index (VEI): An Estimate of Explosive Magnitude for Historical Volcanism
 |url=http://www.agu.org/books/hg/v002/HG002p0143/HG002p0143.pdf
 |journal=[[Journal of Geophysical Research]]
 |volume=87 |issue=C2 |pages=1231–1238
 |bibcode=1982JGR....87.1231N
 |doi=10.1029/JC087iC02p01231
 |archive-url=https://web.archive.org/web/20131213194307/http://www.agu.org/books/hg/v002/HG002p0143/HG002p0143.pdf
 |archive-date=December 13, 2013
}}</ref>