Eruption-Triggered Avalanche, Flood, and Lahar at Mount St. Helens—Effects of Winter Snowpack

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Science  30 Sep 1983:
Vol. 221, Issue 4618, pp. 1394-1397
DOI: 10.1126/science.221.4618.1394


An explosive eruption of Mount St. Helens on 19 March 1982 had substantial impact beyond the vent because hot eruption products interacted with a thick snowpack. A blast of hot pumice, dome rocks, and gas dislodged crater-wall snow that avalanched through the crater and down the north flank. Snow in the crater swiftly melted to form a transient lake, from which a destructive flood and lahar swept down the north flank and the North Fork Toutle River.