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Volcanoes and Their Products
Published in Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough, Earth Materials, 2019
Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough
In 1982, Chris Newhall of the United States Geological Survey and Stephen Self at the University of Hawaii developed a quantitative measure to compare volcano explosiveness: the volcanic explosivity index (VEI). This index is based primarily on the volume of pyroclastic material ejected by the volcano, with some consideration of eruption column height and duration of eruption. The VEI scale is a logarithmic scale. A volcano with a VEI of 6, then, is 10 times more powerful than one with a VEI of 5, and 100 times more powerful than a volcano with a VEI of 4. As shown in Figure 7.33, the VEI scale correlates well with eruption types. Volcanoes with low VEI (Hawaiian or Strombolian type) are commonplace today, but those with high index (ultra-Plinian) occur rarely. Only four eruptions with VEI of 7, and none with VEI of 8, have occurred during the past 10,000 years. Supervolcanoes are exceptionally rare. Toba, 74,000 years ago, was the last one.
Air pollution and climate change
Published in Abhishek Tiwary, Ian Williams, Air Pollution, 2018
Two main measures of volcanic impact have been used. The volcanic explosivity index (VEI) ranks volcanoes according to the rate of energy release, giving a range for recent volcanoes of up to 7 for Tambora, Indonesia in 1815, and 6 for Krakatoa and Pinatubo. The dust veil index (DVI) is compounded from various observations of the severity of an eruption, and of the extent and effects of the resulting dust cloud. These might include historical reports of the eruption itself, optical phenomena such as obscuration of the sun or moon, radiation measurements, temperature measurements, or estimates of the volume of ejected material. The DVI takes on values of 3000, 1000 and 1000 for the same three volcanoes, respectively. The two measures are well correlated in general, although individual eruptions may not fit. For example, Mt St Helen’s in 1980 was a powerful eruption with VEI = 5, but because it mainly came out sideways the stratospheric injection was low. Large eruptions (greater than 5 on the VEI) overcome the temperature inversion at the stratopause and project material into the stratosphere, where it has a long residence time. Smaller volcanic emissions are much more common, but material remains in the troposphere and has shorter lifetime.
Greenhouse gases and climate change
Published in Abhishek Tiwary, Jeremy Colls, Air Pollution, 2017
Two main measures of volcanic impact have been used. The volcanic explosivity index (VEI) ranks volcanoes according to the rate of energy release, giving a range for recent volcanoes of up to 7 for Tambora, Indonesia in 1815, and 6 for Krakatoa and Pinatubo. The dust veil index (DVI) is compounded from various observations of the severity of an eruption, and of the extent and effects of the resulting dust cloud. These might include historical reports of the eruption itself, optical phenomena such as obscuration of the Sun or Moon, radiation measurements, temperature measurements, or estimates of the volume of ejected material. The DVI takes on values of 3000, 1000 and 1000 for the same three volcanoes, respectively. The two measures are well correlated in general, although individual eruptions may not fit. For example, Mt St Helen’s in 1980 was a powerful eruption with VEI = 5, but because it mainly came out sideways the stratospheric injection was low. Large eruptions (greater than 5 on the VEI) overcome the temperature inversion at the stratopause and project material into the stratosphere, where it has a long residence time. Smaller volcanic emissions are much more common, but material remains in the troposphere and has shorter lifetime.
Middle–Upper Pleistocene tephras in the Papua New Guinea highlands
Published in Australian Journal of Earth Sciences, 2023
The VEI (Newhall & Self, 1982) is a general indicator of the explosive character of an eruption. It is based on several criteria, including eruptive column height and duration, but the most important is the volume of ejecta. The index ranges from 0 to 8 on a log scale (Table 5).