Skip to main content
U.S. flag

An official website of the United States government

Pyroclastic flow from the Aug. 7, 1980 eruption stretches from Moun...

Detailed Description

During the May 18, 1980 eruption, at least 17 separate pyroclastic flows descended the flanks of Mount St. Helens. Pyroclastic flows typically move at speeds of over 60 miles per hour (100 kilometers/hour) and reach temperatures of over 800 Degrees Fahrenheit (400 degrees Celsius).


Public Domain.