Skip to main content
U.S. flag

An official website of the United States government

Generation of pyroclastic flows and surges by hot-rock avalanches from the dome of Mount St. Helens volcano, USA

January 1, 1988

Several hot-rock avalanches have occurred during the growth of the composite dome of Mount St. Helens, Washington between 1980 and 1987. One of these occurred on 9 May 1986 and produced a fan-shaped avalanche deposit of juvenile dacite debris together with a more extensive pyroclastic-flow deposit. Laterally thinning deposits and abrasion and baking of wooden and plastic objects show that a hot ash-cloud surge swept beyond the limits of the pyroclastic flow. Plumes that rose 2-3 km above the dome and vitric ash that fell downwind of the volcano were also effects of this event, but no explosion occurred. All the facies observed originated from a single avalanche. Erosion and melting of craterfloor snow by the hot debris caused debris flows in the crater, and a small flood that carried juvenile and other clasts north of the crater. A second, broadly similar event occurred in October 1986. Larger events of this nature could present a significant volcanic hazard. ?? 1988 Springer-Verlag.

Publication Year 1988
Title Generation of pyroclastic flows and surges by hot-rock avalanches from the dome of Mount St. Helens volcano, USA
DOI 10.1007/BF01047505
Authors R.A. Mellors, R. B. Waitt, D. A. Swanson
Publication Type Article
Publication Subtype Journal Article
Series Title Bulletin of Volcanology
Index ID 70013644
Record Source USGS Publications Warehouse
Was this page helpful?