DYNAMIC RESPONSE OF A SURGE-TYPE GLACIER TO ROCK AVALANCHE LOADING

McGinnis Glacier is a small valley glacier located immediately north of the Denali fault in the central Alaska Range. Both lobes of the glacier were completely covered by deposits of rock avalanches triggered by the 2002 Denali earthquake (magnitude 7.9). The earthquake also triggered large rock avalanches onto nearby Black Rapids, Gakona and West Fork glaciers. The southeast lobe of McGinnis Glacier surged during the winter of 2005-2006. We use synthetic aperture radar (SAR) intensity tracking to characterize ice flow dynamics following the rock avalanche and through surge onset. Our analysis suggests that flow velocities, prior to the surge, were relatively high and increasing on the southeast lobe of the glacier and relatively low and decreasing on the lobe that did not surge. We also compare SAR interferometry-derived glacier velocities prior to and after the landslides in an attempt to determine whether there is a causal connection between rock avalanche loading and surge onset.