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Volcanic Explosivity Index (VEI)

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Volcanic explosivity index: The spheres in the illustration above represent the volume of erupted tephra for some of the most widely-known explosive volcanic eruptions. Although most people believe that Vesuvius (79 AD — the Pompeii eruption), Mount St. Helens (1980), and Mount Pinatubo (1991) were enormous, they are very small compared to ancient eruptions such as Wah Wah Springs, Toba, Yellowstone, or Long Valley Caldera.Measurement Scales for Natural EventsMeasuring the size or strength of natural events has always been a challenge for natural scientists. They developed the Richter Magnitude scale to estimate the amount of energy released by an earthquake, the Saffir-Simpson scale to estimate a hurricane's potential, and the Fujita scale for rating the intensity of hurricanes. These scales are valuable for comparing different events and for understanding the amount of damage that events of different size can cause.Measuring the strength of a volcanic eruption is more challenging than collecting wind speed data or measuring ground motion with an instrument. Volcanic eruptions produce different types of products, have different durations and develop in different ways. There is also a problem that some eruptions are explosive (rock materials are blasted from the vent), while other eruptions are effusive (molten rock flows from the vent).Measuring Explosive EruptionsChris Newhall of the United States Geological Survey and Stephen Self of the University of Hawaii developed the Volcanic Explosivity Index (VEI) in 1982. It is a relative scale that enables explosive volcanic eruptions to be compared with one another. It is very valuable because it can be used for both recent eruptions that scientists have witnessed and historic eruptions that happened thousands to millions of years ago.The primary eruption characteristic used to determine the volcanic explosivity index is the volume of pyroclastic material ejected by the volcano. For More Details: [url=]Lead Management Video[/url] Examples

Автор: David Hill


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