The flow of fireweed rock glacier, Alaska, U.S.A

Abstract

Fireweed rock glacier is a large rock glacier in south central Alaska, U.S.A. It flows relatively fast, with velocities up to 3.5 m a -1, and exhibits both seasonal and annual velocity variations, some of which are related to periodic terminus calving and increased rainfall. Our analysis reveals that motion is likely concentrated in a pseudo-rectangular channel within the larger parabolic channel with a "shear plane" at ∼27 m depth. There is likely motion along the shear plane as well as internal deformation above it. We estimate that the ice-rock mixture is up to seven times softer than clean glacier ice with a temperature of-2°C. Calving at the terminus is an important component of the mass balance of this rock glacier.