File:North Fork Toutle River valley in November 1983.jpg

Summary

This downstream view of the North Fork Toutle River valley, north and west of St. Helens, shows part of the nearly 2/3 cubic miles (2.3 cubic kilometers) of debris avalanche that slid from the volcano on May 18. This is enough material to cover Washington, D.C. to a depth of 14 feet (4 meters). The avalanche traveled approximately 15 miles (24 kilometers) downstream at a velocity exceeding 150 miles per hour (240 kilometers/hour). It left behind a hummocky deposit with an average thickness of 150 feet (45 meters) and a maximum thickness of 600 feet (180 meters). (November 30, 1983, by Lyn Topinka, USGS/CVO) USGS image

Summary

Licensing

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• 1980 eruption of Mount St. Helens