Volcanic explosivity index

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VEI and ejecta volume correlation

The Volcanic Explosivity Index (VEI) was devised by Chris Newhall of the U.S. Geological Survey and Stephen Self at the University of Hawaiʻi 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 (less than 10⁴ cubic metres of tephra ejected) with 8 representing a mega-colossal explosive eruption that can eject 10¹² cubic metres of tephra and have a cloud column height of over 25 km (16 mi). The scale is logarithmic, with each interval on the scale representing a tenfold increase in observed eruption criteria (exception: between VEI 0 and VEI 1).

Note that ash, volcanic 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

Scientists indicate how powerful volcanic eruptions are using the VEI. It records how much volcanic material is thrown out, how high the eruption goes, and how long it lasts. The scale goes from 0 to 8. An increase of 1 indicates a 10 times more powerful eruption.

Note: 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 while the factor is 10 between all higher indices.

VEI	Ejecta volume	Classification	Description	Plume	Frequency	Example	Occurrences in last 10,000 years*
0	< 10,000 m³	Hawaiian	non-explosive	< 100 m	constant	Mauna Loa	many
1	> 10,000 m³	Hawaiian/Strombolian	gentle	100–1000 m	daily	Stromboli	many
2	> 1,000,000 m³	Strombolian/Vulcanian	explosive	1–5 km	weekly	Galeras (1993)	3477*
3	> 10,000,000 m³	Vulcanian/Peléan	severe	3–15 km	yearly	Cordón Caulle (1921)	868
4	> 0.1 km³	Peléan/Plinian	cataclysmic	10–25 km	≥ 10 yrs	Eyjafjallajökull (2010)	421
5	> 1 km³	Plinian	paroxysmal	> 25 km	≥ 50 yrs	Mount St. Helens (1980)	166
6	> 10 km³	Plinian/Ultra-Plinian	colossal	> 25 km	≥ 100 yrs	Krakatoa (1883)	51
7	> 100 km³	Plinian/Ultra-Plinian	super-colossal	> 25 km	≥ 1000 yrs	Tambora (1815)	5 (+2 suspected)
8	> 1,000 km³	Ultra-Plinian	mega-colossal	> 25 km	≥ 10,000 yrs	Taupo (26,500 BP)	0

*Count of VEI 2 and VEI 3 eruptions in the last 10,000 years are based on 1994 figures maintained by the Global Volcanism Program of the Smithsonian Institution. Count of eruptions greater than VEI 3 in the last 10,000 years are based on its 2010 figures. There are also 58 plinian eruptions, and 13 caldera-forming eruptions, of large, but unknown magnitudes.

A total of 47 eruptions of VEI–8 magnitude or above, ranging in age from Ordovician to Pleistocene, are identified, of which 42 eruptions are known from the past 36 million years. The most recent one is Lake Taupo's Oruanui eruption, occurring 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.

Examples of eruptions by VEI

See also: World's largest eruptions

VEI	Volcano (eruption)	Year
0	Hoodoo Mountain	7050 BC?
0	Mauna Loa	1984
0	Lake Nyos	1986
0	Piton de la Fournaise	2004
1	Wells Gray-Clearwater volcanic field	1500?
1	Kilauea	1983–present
1	Nyiragongo	2002
2	Mount Hood	1865–1866
2	Kilauea	1924
2	Tristan da Cunha	1961
2	Mount Usu	2000–2001
2	Whakaari/White Island	2001
3	Mount Garibaldi	9,300 BP
3	Nazko Cone	7,200 BP
3	Mount Edziza	950 AD ± 1000 years
3	Mount Vesuvius	1913–1944
3	Surtsey	1963–1967
3	Eldfell	1973
3	Nevado del Ruiz	1985
3	Mount Etna	2002–2003
4	Mount Pelée	1902
4	Parícutin	1943–1952
4	Hekla	1947
4	Galunggung	1982
4	Mount Spurr	1992
4	Mount Okmok	2008
4	Eyjafjallajökull	2010
4	Mount Merapi	2010
5	Hekla (Hekla 3 eruption)	1021 + 130/-100 BC
5	Mount Meager	≈400 BC (2350 BP)
5	Mount Vesuvius (Pompeian eruption)	79
5	Mount Edgecumbe/Pūtauaki	c. 300
5	Mount Tarumae	1739
5	Mount Mayon	1814
5	Mount Tarawera	1886
5	Katla	1918
5	Mount Agung	1963
5	Mount St. Helens	1980
5	El Chichón	1982
5	Mount Hudson	1991
5	Chaiten	2008
6	Morne Diablotins	30,000 BP
6	Laacher See	12,900 BP?
6	Nevado de Toluca	10,500 BP
6	Mount Okmok	8300 BP
6	Mount Etna	8000 BP?
6	Mount Veniaminof	1750 BC
6	Mount Vesuvius (Avellino eruption)	1660 BC ± 43 years
6	Grímsvötn	8230 BC ± 50 years
6	Mount Aniakchak	≈1645 BC
6	Mount Okmok	c. 400 BC
6	Ambrym	c. AD 100
6	Ilopango	450 ± 30 years
6	Mount Churchill (White River Ash)	≈750 (1200 BP)
6	Katla (Eldgjá)	934
6	Baekdu Mountain (Tianchi eruption)	969 ± 20 years
6	Kuwae	1452 or 1453
6	Bárðarbunga	1477
6	Huaynaputina	1600
6	Laki	1783
6	Krakatoa	1883
6	Santa María	1902
6	Novarupta	1912
6	Mount Pinatubo	1991
7	Sesia Valley caldera	280 Ma
7	Bennett Lake Volcanic Complex	50 Ma
7	Valles (Lower Bandelier eruption)	1.47 Ma
7	Yellowstone (Mesa Falls eruption)	1.3 Ma
7	Valles (Upper Bandelier eruption)	1.15 Ma
7	Long Valley Caldera (Bishop eruption)	759,000 BP
7	Maninjau	280,000 BP
7	Atitlán (Los Chocoyos eruption)	84,000 BP
7	Kurile (Golygin eruption)	41,500 BP
7	Campi Flegrei	37,000 BP
7	Aira Caldera	22,000 BP
7	Kurile (Ilinsky eruption)	≈6400 BC
7	Crater Lake (Mount Mazama eruption)	≈5700 BC
7	Kikai (Akahoya eruption)	≈5300 BC
7	Thera (Minoan eruption)	1620s BC
7	Taupo (Hatepe eruption)	186
7	Mount Tambora (1815 eruption)	1815
8	Scafells	Ordovician
8	Glen Coe	420 Ma
8	La Garita Caldera	27 Ma
8	Yellowstone (Huckleberry Ridge eruption)	2.2 Ma
8	Galán	2.2 Ma
8	Yellowstone (Lava Creek eruption)	640,000 BP
8	Whakamaru (Whakamaru Ignimbrite/Mount Curl Tephra)	254,000 BP
8	Toba	69,000–77,000 BP
8	Taupo (Oruanui eruption)	26,500 BP

See also

• Supervolcano
• List of volcanoes
• List of deadliest natural disasters

References

• Newhall, Christopher G. (1982). "The volcanic explosivity index (VEI): An estimate of explosive magnitude for historical volcanism". Journal of Geophysical Research. 87 (C2): 1231–1238. doi:10.1029/JC087iC02p01231. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)

External links

• 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
• VEI (Volcanic Explosivity Index) from the Global Volcanism Program of the Smithsonian National Museum of Natural History