The Volcanic Explosivity Index (VEI) was devised by Chris Newhall of the U.S. Geological Survey and Steve 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). Each interval on the scale represents a tenfold increase in observed eruption criteria.
Note that ash, volcanic bombs, and ignimbrite are all treated alike — this is due to taking into account the vesicularity (gas bubbling) of the volcanic products in question and the DRE (Dense-Rock Equivalent) is calculated to give the actual amount of magma erupted. One weakness of the VEI is that it does not take into account the magnitude of power output of an eruption. This, of course, is extremely difficult to detect with prehistoric or unobserved eruptions.
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Scientists indicate how powerful volcanic eruptions are using the VEI. The VEI stands for Volcanic Explosivity Index. 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 that 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 | Classification | Description | Plume | Ejecta volume | Frequency | Example | Occurrences * |
---|---|---|---|---|---|---|---|
0 | Hawaiian | non-explosive | < 100 m | < 10,000 m³ | daily | Mauna Loa | many |
1 | Hawaiian/Strombolian | gentle | 100-1000 m | > 10,000 m³ | daily | Stromboli | many |
2 | Strombolian/Vulcanian | explosive | 1-5 km | > 1,000,000 m³ | weekly | Galeras (1993) | 3477* |
3 | Vulcanian/Pelean | severe | 3-15 km | > 10,000,000 m³ | yearly | Koryaksky | 868 |
4 | Pelean/Plinian | cataclysmic | 10-25 km | > 0.1 km³ | ≥ 10 yrs | Soufrière Hills (1995) | 278 |
5 | Plinian | paroxysmal | > 25 km | > 1 km³ | ≥ 50 yrs | St. Helens (1980) | 84 |
6 | Plinian/Ultra-Plinian | colossal | > 25 km | > 10 km³ | ≥ 100 yrs | Mount Pinatubo (1991) | 39 |
7 | Plinian/Ultra-Plinian | super-colossal | > 25 km | > 100 km³ | ≥ 1000 yrs | Tambora (1815) | 5 (+2 suspected) |
8 | Ultra-Plinian | mega-colossal | > 25 km | > 1,000 km³ | ≥ 10,000 yrs | Toba (73,000 BP) | 0 |
* Count of eruptions in the last 10,000 years based on 1994 figures maintained by the Global Volcanism Program of the Smithsonian Institution
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.[1]
VEI | Name | Year |
---|---|---|
0 | Mauna Loa | 1984 |
Piton de la Fournaise | 2004 | |
Hoodoo Mountain | 7050 BC? | |
1 | Kilauea | 1983 - present |
Nyiragongo | 2002 | |
Wells Gray-Clearwater volcanic field | 1500? | |
2 | Mount Hood | 1865-1866 |
Kilauea | 1924 | |
Tristan da Cunha | 1961 | |
Whakaari/White Island | 2001 | |
Mount Usu | 2000-2001 | |
3 | Mount Vesuvius | 1913-1944 |
Mount Edziza | 950 AD ± 1000 years | |
Surtsey | 1963-1967 | |
Eldfell | 1973 | |
Nevado del Ruiz | 1985 | |
Mount Etna | 2002-2003 | |
Mount Garibaldi | 9,300 BP | |
Nazko Cone | 7,200 BP | |
4 | Mount Pelée | 1902 |
Parícutin | 1943-1952 | |
Hekla | 1947 | |
Galunggung | 1982 | |
Mount Spurr | 1992 | |
5 | Hekla (Hekla 3 eruption) | 1021 + 130/-100 BC |
Mount Vesuvius (Pompeian eruption) | 79 | |
Mount Tarumae | 1739 | |
Mount Agung | 1963 | |
Mount St. Helens (1980 eruption) | 1980 | |
Mount Meager | ≈400 BC (2350 BP) | |
El Chichón | 1982 | |
Mount Hudson | 1991 | |
Mount Tarawera | 1886 | |
6 | Morne Diablotins | 30,000 BP |
Laacher See | 12,900 BP? | |
Nevado de Toluca | 10,500 BP | |
Mount Okmok | 8300 BP | |
Mount Etna | 8000 BP? | |
Mount Veniaminof | 1750 BC | |
Mount Vesuvius (Avellino eruption) | 1660 BC ± 43 years | |
Thera (Minoan eruption) | 1620s BC | |
Mount Aniakchak | ≈1645 BC | |
Mount Okmok | 2400 BP | |
Mount Churchill (White River Ash) | ≈750 (1200 BP) | |
Ilopango | 450 ± 30 years | |
Laki | 934 | |
Baekdu Mountain (Tianchi eruption) | 969 ± 20 years | |
Kuwae | 1452 or 1453 | |
Huaynaputina | 1600 | |
Laki | 1783 | |
Krakatoa | 1883 | |
Santa María | 1902 | |
Novarupta | 1912 | |
Mount Pinatubo | 1991 | |
7 | Bennett Lake Volcanic Complex | 50 Ma |
Valles (Lower Bandelier eruption) | 1.47 Ma | |
Yellowstone (Mesa Falls eruption) | 1.3 Ma | |
Valles (Upper Bandelier eruption) | 1.15 Ma | |
Long Valley Caldera (Bishop eruption) | 759,000 BP | |
Manijau | 280,000 BP | |
Atitlán (Los Chocoyos eruption) | 84,000 BP | |
Kurile (Golygin eruption) | 41,000 BP | |
Campi Flegrei | 37,000 BP | |
Aira Caldera | 22,000 BP | |
Kurile (Ilinsky eruption) | 6440 BC ± 25 years | |
Crater Lake, Oregon (Mount Mazama eruption) | 5677 BC ± 150 years | |
Kikai (Akahoya eruption) | ≈5300 BC | |
Taupo (Hatepe eruption) | 186 | |
Mount Tambora | 1815 | |
8 | La Garita Caldera | 27 Ma |
Yellowstone (Huckleberry Ridge eruption) | 2.2 Ma | |
Galán | 2.2 Ma | |
Yellowstone (Lava Creek eruption) | 640,000 BP | |
Toba | 73,000 BP | |
Taupo (Oruanui eruption) | 26,500 BP |