Volcanic Explosivity Index

Volcanic Explosivity Index chart.

In volcanology, the Volcanic Explosivity Index is the way to measure the strength of a volcanic eruption. In earthquakes, the Richter scale is used to measure the earthquake's strength, and the Volcanic Explosivity Index is used to measure the explosiveness of volcanic eruptions. The index is based on a scale of 1 to 8, 1 being very small, and 8 being huge and very rare. The largest eruption in modern times, the 1980 eruption of Mount St. Helens, was rated as a 5 on the index. The Oruanui eruption of the Taupo volcano in New Zealand was the world’s largest known eruption in the past 70,000 years, with a Volcanic Explosivity Index of 8. Another eruption of the Taupo volcano occurred about 1,800 years ago. It represents the most violent eruption in the world in the last 5,000 years. Mt Tambora was measured a 7 on the Volcanic Explosivity Index

Further reading

• Christopher G. Newhall; Steve Self (1982). "The volcanic explosivity index (VEI): An estimate of explosive magnitude for historical volcanism". Journal of Geophysical Research (87): 1231–1238.
• Ben G. Mason; David M. Pyle, and Clive Oppenheimer (2004). "The size and frequency of the largest explosive eruptions on Earth" (PDF). Bulletin of Volcanology 66 (8): 735–748. doi:10.1007/s00445-004-0355-9.

Other websites

• VEI glossary entry from a USGS website
• How to measure the size of a volcanic eruption, from The Guardian
• The size and frequency of the largest explosive eruptions on Earth, a 2004 article from the Bulletin of Volcanology
• List of Large Holocene Eruptions (VEI > 4) from the Smithsonian Global Volcanism Program