Cordilleran Section - 115th Annual Meeting - 2019

Paper No. 27-1
Presentation Time: 9:00 AM-6:00 PM


TRCKA, Allison, Department of Geology, Portland State Universtiy, Portland, OR 97207-0751 and FOUNTAIN, Andrew G., Department of Geology, Portland State University, Portland, OR 97207-0751

Rock glaciers are found in many mountainous regions around the world and are an underappreciated source of meltwater. To better understand their contribution and potential hazards, rock glacier inventories in the western United States are re-examined to create consistent standards to identify rock glaciers remotely. Although regional inventories have been completed in the western U.S. including the activity, shape, and size; the identification criteria are not consistent. Also, they do not cover the entire western U.S. A preliminary inventory of rock glaciers in the contiguous United States was recently developed based on three categories of certainty. We used the intersection of the preliminary inventory with the regional inventories to test classification criteria of each towards developing uniform criteria for the western U.S.

Preliminary results from the Lemhi Range, Idaho, show 401 features in the preliminary inventory compared to 53 in the regional inventory. All but one rock glacier feature from the regional inventory were included in the preliminary inventory; however, almost half were identified with certainty as rock glaciers by the preliminary inventory. The other half, as well as most of the preliminary inventory, were identified either as relict rock glaciers or as features of interest, such as protalus ramparts. In the preliminary inventory, only 22 features were identified as rock glaciers. Other inventories are currently being compared with the preliminary inventory. In the future, a new vetted and comprehensive rock glacier inventory will be made available.