"The May 18th eruption, viewed from the east in late morning. The eruptive cloud rose to an altitude of more than 12 miles in 10 minutes. The swirling ash particles in the eruptive cloud generated lightning which in turn started forest fires. Other fires were ignited by the initial blasts and later pyroclastic flows. Ash can be seen falling out of the cloud. Nearly 550 million tons of ash fell over a 22,000 square mile area on May 18th." (U.S. Dept. of Commerce, 1980, p. 4)

Image of an eruptive cloud over Mount St. Helens which rose to an altitude of more than 12 miles in 10 minutes.
May 18th eruption, 1980
Photo: Courtesy of NGDC/NOAA.

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