MULTI-TEMPORAL ASSESSMENT OF ROCK GLACIER MASS TRANSPORT IN THE SPANISH PEAKS REGION, COLORADO

In semi-arid, alpine regions, rock glaciers serve a central role in downslope mass transport. Although not fully understood, rock glacier dynamics are generally regarded to be sensitive to climate variations. This study under takes a multitemporal assessment of rock glacier movement in the Spanish Peaks of southern Colorado using remote sensing and field-based methods. Specifically, the rates of movement of talus-derived rock glaicers along the flanks of Mt. Mestas are investigated. Methods involve lichenometry (century to millennial time scales), aerial photographs (decadal time scale), satellite radar interferometry (a.k.a. InSAR) (spanning several years), and GPS and ground based radar interferometry (annual and seasonal time scales). InSAR and aerial photos permit assessing velocities of all rock glaciers on the mountain, and velocities appear to vary with maximum rates of up to 10s of cm/yr. Field investigations focused on two rock glaciers. On one of the rock glaciers, preliminary results of lichenology suggest average flow rates of 8 cm/yr over the past ~2000 years. In contrast, GPS measurements and ground-based radar interferometry spanning one year show that this rock glacier presently moves much slower. A second rock glacier in our study demonstrates much higher rates of movement of up to 1cm/month during the summer; based on ground based radar interferometry and GPS measurements. The preliminary results suggest temporal variability of velocity over a short (seasonal) span of time as well as a declining velocity during the Holocene.