Fireweed Rock Glacier: Geophysical Survey and Flow Modeling

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Rock glaciers are the largest and most pronounced mountain permafrost landforms. Recently, scientific interest in rock glaciers has dramatically increased due to the geotechnical problems and natural hazards they pose, their potential for archiving past and present geologic conditions in alpine environments, their significance in the hydrologic cycle, and their role as a debris transport mechanism. Knowledge of rock glaciers' internal composition and rheology is important for addressing these topics. Our understanding of internal structures of rock glaciers is often speculative because rock glaciers are difficult to inspect internally. This is a unique opportunity to document the internal composition and structure in a complete transverse cross-section through the Fireweed Rock Glacier, Wrangell Mountains, Alaska because the entire snout was recently catastrophically calved. This rock glacier consists of a debris-covered m(lange. The ice matrix, which accounts for about one-half of the ice-rock, displays prominent flow signatures. The Fireweed Rock Glacier is also unique in that it has a high flow rate. The Principal Investigator will take advantage of this unique opportunity to investigate the structure and flow mechanics of the Fireweed Rock Glacier. The first objective will be to perform a complete geophysical survey of the glacier. Geophysical techniques will be calibrated using known geometry and structure at the exposed terminus section, and then extend up glacier to provide a detailed picture of the internal structure and geometry. The second objective will be to develop a numerical model of rock glacier flow by analyzing velocity measurements and the geometry determined by the geophysical survey. The results should significantly improve the application of geophysical survey techniques to rock glaciers and mountain permafrost and lead to a better understanding of the rheological laws for the ice-rock mixtures that compose rock glaciers and frozen ground.