Volcanic explosive index
The volcanic explosivity index abbreviated VEI (from English Volcanic Explosivity Index ) is an indication of the strength of an explosive volcanic eruption in values from 0 to 8 on a logarithmic stepped scale. Measured variables are primarily the amount of volcanic loose material ( tephra ) expelled , as well as the height of the eruption column and qualitative descriptions. It was introduced in 1982 by the US geologists Christopher G. Newhall and Stephen Self .
The scale begins with level 0 and is logarithmic from level 2, so that the class limits of the next higher levels, measured by the volume of ejected pyroclastic material, correspond to a volcanic eruption ten times larger. Starting with a harmless volcanic event, it extends to a gigantic eruption with global effects of level 8. The scale is open at the top. Scientists point out that it is very difficult to accurately measure the strength of volcanic eruptions.
Volcanic explosive index
VEI | 0 | 1 | 2 | 3 | 4th | 5 | 6th | 7th | 8th |
---|---|---|---|---|---|---|---|---|---|
classification | not explosive | small | moderate | moderate to large | big | very large | |||
Ejected tephra volume 1 | ≤ 10 4 | 10 4 -10 6 | 10 6 -10 7 | 10 7 -10 8 | 10 8 -10 9 | 1-10 | 10-100 | 100-1000 | ≥ 1000 |
m³ | km³ | ||||||||
Height of the eruption column [km] | ≤ 0.1 | 0.1-1 | 1-5 | 3-15 | 10-25 | ≥ 25 | |||
Number of events since the last glacial period 11,700 years ago | 3,631 | 924 | 307 | 106 | 46 | 5 | 0 | ||
Well-known example (year of outbreak) |
Kīlauea (1977) |
Poas (1991) |
Ruapehu (1971) |
Nevado del Ruiz (1985) |
Eyjafjallajökull (2010) |
Mount St. Helens (1980) |
Krakatau (1883) |
Tambora (1815) |
Taupo (about 26,500 years ago) |
Examples from the history of the earth
Strength 8
The Toba eruption in Sumatra 74,000 years ago was the largest in the last two million years. It was also larger than the last major eruption of the Yellowstone volcano around 630,000 years ago. According to the controversially discussed Toba catastrophe theory , mankind at that time was decimated to a few thousand individuals and had to pass a so-called " genetic bottleneck ".
- Wah Wah Springs Eruption in Utah and Nevada about 30 million years ago, 5500 km³
- La Garita Caldera Eruption in Colorado, about 28 to 26 million years ago, 5000 km³
- Huckleberry Ridge eruption, Yellowstone (volcano) 2.1 million years ago, with 2500 km³ tephra
- Yellowstone (volcano) 630,000 years ago, with 1000 km³ of tephra
- Toba almost 74,000 years ago, with 2800 km³ of tephra
- Taupo ( New Zealand ), Oruanui eruption 26,500 years ago, with 1170 km³ tephra
Strength 7
The eruption of the Phlegraean Fields 39,000 years ago with 250 km³ of tephra is an example of this level. The Minoan eruption of the volcano of Santorin about 3,600 years ago was smaller, but probably reached strength 7. More recent eruptions with a tephra ejection of 100 km³ or more occurred at Taupo in the 2nd or 3rd century, at Paektusan 969, at Samalas 1257 and at Tambora in 1815. The eruption of the Ilopango (around 430?), which did not quite reach magnitude 7, also had serious global consequences .
There have been no magnitude 8 eruptions in the past 10,000 years, but there have been at least seven magnitude 7 eruptions:
- Kurilensee volcano around 6450 BC BC, with 155 km³ tephra
- Mount Mazama around 5700 BC BC, with 150 km³ tephra
- Kikai around 4350 BC BC, with 200 km³ tephra
- Cerro Blanco around 2,300 BC At about 110 km³ tephra
- Santorini around 1600 BC At about 120 km³ tephra
- Samalas 1257, with 100 km³ of tephra
- Tambora 1815, with 160 km³ of tephra
In addition, other eruptions are known from the last 2,000 years that were approximately 7:
- Taupo (Hatepe eruption, around 130 to 230), around 100 km³ tephra
- Ilopango (eruption dated to the 2nd to 6th century), about 84 km³ tephra
- Paektusan around 946, with 96 (± 19) km³ tephra
Strength 6
A major eruption in Central Europe took place around 13,000 years ago at the Laacher volcano . The Laacher See represents the sagging caldera of the volcano. During the eruption, an area of 1300 km² was covered by a layer of lava up to 10 meters thick. The ash column rose up to 40 kilometers.
- Laacher Vulkan , 10,920 BC BC, with 20 km³ tephra
- Ambrym around 50, with 70 km³ tephra
- Kuwae , 1453, with 32–39 km³ tephra
- Huaynaputina , 1600, with 30 km³ of tephra
- Krakatau , 1883, with 20 km³ of tephra
- Santa María , 1902, with 20 km³ of tephra
- Novarupta , 1912, with 13–15 km³ tephra
- Pinatubo , 1991, with 10 km³ tephra
Strength 5
- Etna , 122 BC Chr.
- Vesuvius , 79, with 3.3 km³ of tephra
- Eldgjá , 934 or 939, with 1.4 km³ of tephra
- Fujisan , 1707, with 2.1 km³ of tephra
- Mount St. Helens , 1980, with 1.2 km³ of tephra
- Cerro Hudson , 1991, with 7.6 km³ of tephra
Strength 4
- Parker , 1641, with less than 1 km³ of tephra
- Laki crater , 1783, with 0.91 km³ of tephra
- Mont Pelée , 1902, with 0.2 km³ tephra
- Eyjafjallajökull , 2010, with 0.14 km³ tephra
Magnitude
In the volcanological literature and the relevant databases, in addition to the VEI, the term magnitude (M), defined as:
- .
Using the ejected mass as a reference variable, differences in density of the various magma types and a different bubble content of the deposited material are balanced out, so that the eruptions are more comparable. The result now has one decimal place, but is predominantly in the order of magnitude of the previously assigned VEI. For example, results for 200,000 t ejected material a magnitude of .
Further classification methods of volcanic eruptions
- Tsuya classes : Similar to the VEI, they are divided into classes I to IX.
- Turbidity index : The turbidity index has a value of 1000 for the Krakatau eruption of 1883 and is used as a parameter to describe the volcanic disturbances in atmospheric layers, which can then influence the climate.
- Volcano Population Index (CPI): The index indicates how many people live in a dangerous area within a certain radius of the eruption site during a volcanic eruption. VPI5 and VPI10 are often used, which stand for VPIs with a radius of 5 km and 10 km, respectively, the relevant areas for outbreaks with VEI 2 to 4.
See also
Remarks
- ↑ See e.g. B. http://www.geology.sdsu.edu/how_volcanoes_work/index.html NASA: Eruption Variability , How Volcanoes Work; Retrieved September 23, 2012.
- ↑ Number of known outbreaks of each strength in the Holocene , based on data from the Smithsonian Institute .
- ↑ Diagram of the USGS for the definition of the VEI The table in the article is essentially based on this diagram. Note the discontinuity in powers of ten of upper limits for the ejection quantity between VEI 0 and VEI 1, which unfortunately was not explained in the original source.
- ↑ Geological Society of America, October 27, 2017: Yellowstone Experienced Double Eruption , at [1] , accessed March 13, 2018.
- ↑ Brooks Mitchell: What Was the Biggest Volcanic Eruption in History? , at [2] , accessed June 10, 2018.
- ↑ Marc Szeglat: Super volcanoes and flood basalts , on [3] , accessed on March 13, 2018.
- ↑ See Sara Pratt: AAG: Eruption of El Salvador's Ilopango explains AD 536 cooling. from www.earthmagazine.org, February 2012, accessed June 11, 2018.
- ↑ C. Newhall, S. Self, A. Robock: Anticipating future Volcanic Explosivity Index (VEI) 7 eruptions and their chilling impacts. In: Geosphere. February 2018. Volume 14, No. 2, doi: 10.1130 / GES01513.1 , pp. 572–603.
- ^ W. Báez, E. Bustos, A. Chiodi, F. Reckziegel, M. Arnosio, S. Silva, G. Giordano, J. Viramonte, M. Sampietro-Vattuone, J. Peña-Monné: Eruptive style and flow dynamics of the pyroclastic density currents related to the Holocene Cerro Blanco eruption (Southern Puna plateau, Argentina). In: Journal of South American Earth Sciences. Volume 98, March 1, 2020, doi: 10.1016 / j.jsames.2019.102482 .
- ↑ Felix Riede: The eruption of the Laacher See volcano 12,920 years ago and prehistoric cultural change at the end of the Alleröd. A new hypothesis on the origin of the Bromme culture and Perstunia , on [4] , accessed June 11, 2018.
- ^ DM Pyle: "Sizes of volcanic eruptions." In Encyclopedia of Volcanoes. Academic Press, London 2000, ISBN 0-12-643140-X
literature
- Christopher Newhall, Stephen Self: The volcanic explosivity index (VEI). An estimate of explosive magnitude for historical volcanism. In: Journal of Geophysical Research 87, 1982, pp. 1231-1238, doi: 10.1029 / JC087iC02p01231 .
Web links
- Volcanic Explosivity Index as a VEI table with criteria
- How big is an eruption? in the US Geological Survey web archive
- What were the largest eruptions in the world? on the website of the Earth Observatory of Singapore
- Climate changes caused by volcanoes (MPI for Meteorology) with a table of explosivity and turbidity indices
- John W. Ewert and Christopher J. Harpel: In Harm's Way: Population and Volcanic Risk - Geotimes, April 2004