Introduction
Supervolcanoes are volcanic centers that have experienced the eruptions ranked at level 8 on the Volcanic Explosivity Index (VEI). The VEI is a scale that describes the size of volcanic eruptions based on magnitude and intensity. It is a numerical scale (from 0 to 8) on a logarithmic basis that is generally analogous to earthquake magnitude scales.
VEI 8 eruptions:
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Have ejected volumes of lava (as pyroclastic fragments and volcanic ash) that are greater than 200 cubic miles (1,000 cubic km).
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Produce eruption columns that reach more than 16 miles (25 km) or approximately 85,000 ft into the stratosphere. Winds can carry ash from these eruptions across the planet. Ash-fall deposits from Lava Creek eruption from Yellowstone 640,000 years ago can be found as far away as the Mississippi River in Louisiana.
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Are classified as Ultra-Plinian in the traditional classification description (eruption style) based on characteristics of classic eruptions of well-known volcanoes. These eruptions are larger than the eruption of Vesuvius in 79 CE that was witnessed by Pliny the Elder.
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Are described qualitatively as Apocalyptic. Each value on the VEI has a qualitative description ranging from Effusive (VEI 0) to Apocalyptic (VEI 8).
The volcanic centers (known as resurgent calderas) that have produced VEI 8 eruptions are truly massive in scale, although they do not build imposing volcanic edifices like shield volcanos. For example, the Yellowstone Caldera is approximately 53 by 28 mi (85 by 45 km) in diameter but its walls only rise approximately 1,600 ft (500 m).
Source: U.S. Department of the Interior, National Park Service
