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Eruptions - Windows to the Universe

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This is an image of the eruption of Mt. Pinatubo.
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Image from: U.S. Geological Survey


Volcanic eruptions come in many different forms. Shield volcanoes usually only spew lava and hot gases. These lavas flow slowly down the mountain with speeds of 15 miles per hour or slower. Composite volcanoes can put forth lava accompanied by clouds of ash, bombs, lava fragments, crystallized, glassy material, as well as hot gases. In some eruptions, ash and lava are buoyied by hot vapors and pour down the slopes of a volcano very rapidly, with speeds up to 100 miles per hour. This special type of eruption destroyed the city of St. Pierre in 1902. In other cases hot material from the volcano can melt snow and ice at the volcano summit and the whole mass of mud and lava can sweep rapidly down the mountain, destroying everything in its path. This type of flow is called a lahar.

There have been some spectacular eruptions in Earth history. These include Mt. Pelee, Krakatoa, Crater Lake (formerly Mt. Mazama), Mt. Vesuvius, Mt. St. Helens, Mt. Pinatubo.

Last modified May 22, 2008 by Becca Hatheway.

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Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part by the National Science Foundation and NASA, our Founding Partners (the American Geophysical Union and American Geosciences Institute) as well as through Institutional, Contributing, and Affiliate Partners, individual memberships and generous donors. Thank you for your support! NASA AGU AGI NSF