Volcanic Explosivity Index

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VEI and ejecta volume correlation

The Volcanic Explosivity Index (VEI) was devised by Chris Newhall of the US Geological Survey and Stephen Self at the University of Hawaii in 1982 to provide a relative measure of the explosiveness of volcanic eruptions.

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 volcanoes in history given magnitude 8. A value of 0 is given for non-explosive eruptions, defined as less than 10,000 m3 (350,000 cu ft) of tephra ejected; and 8 representing a mega-colossal explosive eruption that can eject 1.0×1012 m3 (3.5×1013 cu ft) of tephra and have a cloud column height of over 50 km (31 mi). 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.[1]

Ash, lava, lava bombs and ignimbrite are all treated alike. Density and vesicularity (gas bubbling) of the volcanic products in question is not taken into account. In contrast, the DRE (Dense-Rock Equivalent) is sometimes calculated to give the actual amount of magma erupted. Another weakness of the VEI is that it does not take into account the power output of an eruption, which makes it extremely difficult to determine with prehistoric or unobserved eruptions.

Classification

With indices running from 0 to 8, the VEI associated with an eruption is dependent on how much volcanic material is thrown out, to what height, and how long the eruption lasts. The scale is logarithmic from VEI 2 and up; an increase of 1 index indicates an eruption that is 10 times as powerful. As such there is a discontinuity in the definition of the VEI between indices 1 and 2. The lower border of the volume of ejecta jumps by a factor of 100 from 10,000 to 1,000,000 m3 (350,000 to 35,310,000 cu ft) while the factor is 10 between all higher indices.

VEI Ejecta volume Classification Description Plume Frequency Tropospheric
injection		 Stratospheric
injection[2]		 Examples
0 < 10,000 m³ Hawaiian Effusive < 100 m constant negligible none Kīlauea, Piton de la Fournaise, Erebus
1 > 10,000 m³ Hawaiian / Strombolian Gentle 100–1000 m daily minor none Nyiragongo (2002), Raoul Island (2006)
2 > 1,000,000 m³ Strombolian / Vulcanian Explosive 1–5 km weekly moderate none Unzen (1792), Cumbre Vieja (1949), Galeras (1993), Sinabung (2010)
3 > 10,000,000 m³ Vulcanian / Peléan Catastrophic 3–15 km few months substantial possible Nevado del Ruiz (1985), Soufrière Hills (1995), Nabro (2011)
4 > 0.1 km³ Peléan / Plinian Cataclysmic 10–25 km ≥ 1 yr substantial definite Mayon (1814), Pelée (1902), Eyjafjallajökull (2010)
5 > 1 km³ Plinian Paroxysmic 20–35 km ≥ 10 yrs substantial significant Vesuvius (79), Fuji (1707), St. Helens (1980)
6 > 10 km³ Plinian / Ultra-Plinian Colossal > 30 km ≥ 100 yrs substantial substantial Veniaminof (c. 1750 BC), Huaynaputina (1600), Krakatoa (1883), Pinatubo (1991)
7 > 100 km³ Ultra-Plinian Mega-colossal > 40 km ≥ 1,000 yrs substantial substantial Mazama (c. 5600 BC), Thera (c. 1620 BC), Samalas (1257), Tambora (1815)
8 > 1,000 km³ Supervolcanic Apocalyptic > 50 km ≥ 10,000 yrs substantial substantial Yellowstone (640,000 BC), Toba (74,000 BC), Taupo (24,500 BC)

A total of 47 eruptions of VEI 8 magnitude or above, ranging in age from Ordovician to Pleistocene, have been identified, of which 42 occurred in the past 36 million years. The most recent is Lake Taupo's Oruanui eruption, 26,500 years ago, which means that there have not been any Holocene (within the last 10,000 years) eruptions with a VEI of 8.[3] There have been at least five identified Holocene eruptions with a VEI of 7. There are also 58 plinian eruptions, and 13 caldera-forming eruptions, of large, but unknown magnitudes. There are likely many other eruptions that are not identified.

List of eruptions

2011 Puyehue-Cordón Caulle eruption 1980 eruption of Mount St. Helens 1280 eruption of Quilotoa 2010 eruptions of Eyjafjallajökull 1650 eruption of Kolumbo Toba catastrophe theory Kuril Islands Kikai Caldera Long Island (Papua New Guinea) 1883 eruption of Krakatoa 2010 eruptions of Mount Merapi Billy Mitchell (volcano) Taupo Volcano Taupo Volcano Taupo Volcano
Clickable imagemap of notable volcanic eruptions. The apparent volume of each bubble is linearly proportional to the volume of tephra ejected, colour-coded by time of eruption as in the legend. Pink lines denote convergent boundaries, blue lines denote divergent boundaries and yellow spots denote hotspots.

See also

References

  1. ↑ Newhall, Christopher G.; Self, Stephen (1982). "The Volcanic Explosivity Index (VEI): An Estimate of Explosive Magnitude for Historical Volcanism" (PDF). Journal of Geophysical Research 87 (C2): 1231–1238. Bibcode:1982JGR....87.1231N. doi:10.1029/JC087iC02p01231. 
  2. ↑ VEI (Volcanic Explosivity Index), Global Volcanism Program, Smithsonian National Museum of Natural History Accessed 21 September 2013
  3. ↑ Mason, Ben G.; Pyle, David M.; Oppenheimer, Clive (2004). "The size and frequency of the largest explosive eruptions on Earth". Bulletin of Volcanology 66 (8): 735–748. Bibcode:2004BVol...66..735M. doi:10.1007/s00445-004-0355-9. 

External links

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