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Potential hazards from future eruptions of Mount St. Helens Volcano, Washington

Bulletin 1383-C
By:  and 
https://doi.org/10.3133/b1383C

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Abstract

Mount St. Helens has been more active and more explosive during the last 4,500 years than any other volcano in the conterminous United States. Eruptions of that period repeatedly formed domes, large volumes of pumice, hot pyroclastic flows, and, during the last 2,500 years, lava flows. Some of this activity resulted in mudflows that extended tens of kilometers down the floors of valleys that head at the volcano. This report describes the nature of the phenomena and their threat to people and property; the accompanying maps show areas likely to be affected by future eruptions of Mount St. Helens. Explosive eruptions that produce large volumes of pumice affect large areas because winds can carry the lightweight material hundreds of kilometers from the volcano. Because of prevailing winds, the 180-degree sector east of the volcano will be affected most often and most severely by future eruptions of this kind. However, the pumice from any one eruption will fall in only a small part of that sector. Pyroclastic flows and mudflows also can affect areas far from the volcano, but the areas they affect are smaller because they follow valleys. Mudflows and possibly pyroclastic flows moving rapidly down Swift and Pine Creeks could displace water in Swift Reservoir, which could cause disastrous floods farther downvalley.
Publication type Report
Publication Subtype USGS Numbered Series
Title Potential hazards from future eruptions of Mount St. Helens Volcano, Washington
Series title Bulletin
Series number 1383
Chapter C
DOI 10.3133/b1383C
Edition -
Year Published 1978
Language ENGLISH
Publisher U.S. Govt. Print. Off.,
Description 26 p
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