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Volcanoes and the Theory of Plate Tectonics

 Volcanoes are not randomly distributed over the Earth's surface. Most are concentrated on the edges of continents, along island chains, or beneath the sea forming long mountain ranges. More than half of the world's active volcanoes above sea level encircle the Pacific Ocean to form the circum-Pacific "Ring of Fire." In the past 25 years, scientists have developed a theory--called plate tectonics--that explains the locations of volcanoes and their relationship to other large-scale geologic features.

Major tectonic plates of the Earth. Only a few of the Earth's active volcanoes are shown. (Sketch by Ellen Lougae.)

 World tectonic plates

<http://pubs.usgs.gov/gip/volcus/page06.html>
Maintained by John Watson
Updated 06.24.97

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