BEDROCK LANDSLIDES AND THEIR CONTRIBUTION TO DENUDATION OF A GLACIATED BASIN IN SOUTHERN ALASKA
The volume of material in the three landslides was calculated by combining field measurements of surface profiles, area and thickness. The sediment flux rate (volume/time) for the basin is 8005 m3 a-1 and the basin-scale erosion rate (volume/time/area) is 0.4 mm a-1. Previous studies have quantified the sediment contribution from basin walls to be 25-40% of the overall denudation. This would imply an overall basin-scale denudation rate of 1 to 1.6 mm a-1. Reported denudation rates for Alaskan glaciers range from 7-100 mm a-1. Rockwall retreat rate is 4.4 mm a-1. This rate greatly exceeds reported values for present day retreat rates, which range from 0.05 to 3.0 mm a-1.
Large-scale bedrock landslides such as these contribute a significant amount to the overall denudation of alpine basins and represent failure of the length of the valley wall, which is a key mechanism of peak and basin relief and lowering.