COMPARING 1981 AND 2022 ROCK GLACIER EXTENTS IN THE MOUNT WHITNEY, CA QUADRANGLE

We measured changes in rock glacier extent in the Mt. Whitney, CA quadrangle, by comparing previously mapped outlines of rock glaciers from 1981 (Moore) with 2022 satellite imagery from the National Agricultural Imagery Program. Preliminary results suggest an increase in the extent of 17 of the 26 rock glaciers we mapped. For example, our analysis of Gregory’s Monument rock glacier, the largest rock glacier within the boundaries of the Mt. Whitney quadrangle, has shown a 2% increase in area from 0.46 km² in 1981 to 0.53 km² in 2022. Ericsson Crags rock glacier, 2 km west of Gregory’s Monument rock glacier with roughly half its area, has shown an 21% increase in area from 0.18 km² in 1981 to 0.22 km² in 2022. Rock glaciers are an amalgamation of rocky debris and interstitial ice, and research has shown creep rates up to 80 cm/year. It is possible that our initial findings reflect rock glacier creep; however, our preliminary results may also be a function of inconsistencies or errors in our rock glacier boundary interpretations. We are in the process of revisiting these results to confirm or revise our initial interpretations of changes in rock glacier boundaries in the Mount Whitney, CA quadrangle. Our work will inform ongoing efforts to understand how Sierra Nevada rock glaciers may evolve in the future.