Author(s):
Leland R. Dexter - Northern Arizona University
Donald A. Friend - Minnesota State University
Richard S. Trujillo - Consulting Geologist
Donald F. Earnest - Resource Evaluation, Inc.
Abstract:
We present results of short-term energy balance measurements and flow rate estimates for several rock glaciers in the San Juan Mountains of Colorado [108ºW, 38ºN]. Two active rock glaciers (Engineer Pass and Gilpin Peak) are instrumented with a full array of energy balance sensors along with shallow-depth thermistors and a soil heat flux plate. The instrument array is sampled every minute and averaged or totalized every ten minutes for 96 hours. The Engineer Pass Rock Glacier was sampled in September, 2003 and the Gilpin Peak Rock Glacier was sampled in June, 2004. Results show a remarkably steep near-surface temperature gradient of 2.40ºC cm-1 during the warmest part of the day. Summed ground heat flux was slightly negative for the Engineer Pass Rock Glacier and slightly positive for the Gilpin Peak Rock Glacier. More extensive work is planned using a fixed array of instruments on the Trico Peak Rock Glacier. Finally, results of a reconnaissance trip to two very unique rock glaciers are presented. The Mears Peak rock glacier terminates at relatively low elevations, ~3,121m (10,300ft), and is advancing rapidly enough to be over-running a mature spruce-fir forest. In 1972, a line was painted across the Imogene Rock Glacier. Based on deformation of this line, the surface of the Imogene Rock Glacier appears to be moving at 0.3 to 0.45m yr-1 (1 to1.5 ft yr-1).
