The Geography of Rock Glaciers in the American West

Abstract:

Rock glaciers are flowing geomorphic landforms composed of an ice/debris mixture. Although they form in many mountainous regions around the world, they are a generally unrecognized water resource, which may become more important in the future as alpine glaciers disappear. A uniform rock glacier classification scheme was created for the western continental US, based on internationally recognized criteria, to merge the various regional published inventories. A total of 2249 rock glaciers (1564 active, 685 inactive) and 7852 features of interest were identified in 10 states (WA, OR, CA, ID, NV, UT, ID, MT, WY, CO, NM). Sulfur Creek rock glacier in Wyoming is the largest active rock glacier (2.39 km²). The mean area and elevation for active and inactive rock glaciers are 0.18 km², 3384 m; and 0.20 km², 3072 m, respectively. Mean elevation increases from the northwest in Washington State, ~1670 m to the southeast, in Colorado ~4100 m. Rock glaciers are found in climates that are slightly warmer, +1^oC, and drier ~ 50% compared to alpine glaciers. Few rock glaciers occur in locations where precipitation exceeds 1300 mm. The total volume of ice in rock glaciers in the western US is about 6.99 ± 0.278 km³, which is about half of that contained in the glaciers, 12.37 km³. The water volume in rock glaciers, 6.29 ± 0.25 km³, is a little less than half the volume of Yellowstone Lake in Wyoming (14.9 km³).