Internal Structure and Composition of Rock Glaciers in the Eastern Cascades, Washington

Authors: Adam Riffle*, Central Washington University, Karl Lillquist, Central Washington University
Topics: Mountain Environments, Geomorphology
Keywords: Rock Glacier, Ground Penetrating Radar, GPR, Permafrost,
Session Type: Poster
Day: 4/12/2018
Start / End Time: 1:20 PM / 3:00 PM
Room: Napoleon Foyer/Common St. Corridor, Sheraton, 3rd Floor
Presentation File: No File Uploaded


Glacial meltwater, which contributes significantly to base flow in summer dry periods, will eventually diminish with global warming in mid-latitude mountains. However, rock glaciers, because their internal ice is insulated by overlying debris, react slowly to climate change. Therefore, they act as sinks for ice and liquid water in mountain environments. Washington State’s Eastern Cascades include over 125 rock glaciers; however, we know little about internal structure in rock glaciers there. The purpose of this study was to investigate the hydrological significance of rock glaciers in the Eastern Cascades. Specifically, we determined ice contents of 11 active and inactive rock glaciers through ground penetrating radar (GPR). Preliminary results indicate the presence of permafrost in two of the five inactive and all six active rock glaciers, and clearly show the delineation of the active layer in each. Ten of the rock glaciers contain a heterogeneous mix of permafrost and debris indicating non-glacial origins. One rock glacier with a solid ice core indicates a glacial origin. Liquid water is present within all the rock glaciers indicating a meltwater presence. This research contributes to our understanding of the internal structure and ice content of Eastern Cascade rock glaciers. Future analyses will use ice contents to quantify potential water equivalency for the entire population of rock glaciers. This will provide insight for water management for a region experiencing shifting water resources due to a warming climate.

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