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Water fact sheet, history of landslides and debris flows at Mount Rainier

January 1, 1993

Many landslides and debris flows have originated from Mount Rainier since the retreat of glaciers from Puget Sound about 10,000 years ago. The recurrent instability is due to several factors--height of the steep-sided volcanic cone, frequent volcanic activity, continuous weakening of rock by steam and hot, chemical-laden water, and exposure of unstable areas as the mountains glaciers have receded. The landslide scars and deposits tell a fascinating story of the changing shape of the volcano. Landslides occur when part of the volcano "collapses" or fails and slides away from the rest of the volcano. The failed mass rapidly breaks up into a jumble of disaggregated pieces that flow at high velocity like a fluid. Clay and water in the debris cause further change to a liquid slurry known as a debris flow or mudflow. Volcanic debris flows are also widely known by the Indonesian term "lahar." Although the largest debris flows at Rainier form from landslides, many smaller flows are caused by volcanic eruptions, intense rainfall, and glacial-outburst floods.

Publication Year 1993
Title Water fact sheet, history of landslides and debris flows at Mount Rainier
DOI 10.3133/ofr93111
Authors K. M. Scott, J. W. Vallance
Publication Type Report
Publication Subtype USGS Numbered Series
Series Title Open-File Report
Series Number 93-111
Index ID ofr93111
Record Source USGS Publications Warehouse
USGS Organization Volcano Science Center