KINEMATIC ANALYSIS OF ROCK GLACIERS ON MT. MESTAS, SOUTHERN CO

Rock glaciers are lobate masses of rock debris found in alpine environments consisting of rock debris connected by interstitial ice in pore spaces. This study examines short-term variability in the kinematics of talus-derived rock glaciers along the flanks of Mt. Mestas, a tertiary age plutonic laccolith in the eastern Sangre de Cristo Range of southern Colorado. Our fundamental hypothesis is that seasonal variations relate to changing hydrological conditions involving a mixture of meteoric precipitation and the melting of relict, interstitial ice. Kinematic observations are made using both static Global Positioning System (GPS) measurements, ground-based radar interferometry (GBIR), and satellite-based interferometric synthetic aperture radar (InSAR). Satellite InSAR uses c-band data from the Sentinel-1 mission from mid-2015 through 2018. Ground-based surveys (GPS & GBIR) are acquired multiple times from 2014 through 2018. These measurements are more precise and higher in spatial resolution than satellite measurements. Velocities can get up to 15 mm/month during the spring and early summer months. As a first step in assessing time-dependent variability of hydrologic forcings, we compare the stable isotope compositions of basal spring water and seasonal precipitation. Specifically, spring and meteoric sourced water samples were analyzed using ¹⁸O/¹⁶O - ²H/¹H isotope ratios to begin developing a geochemical fingerprint of spring water flowing beneath the rock glaciers. While these data are mostly preliminary, there is a clear distinction between the meteoric water (rain & snow) and the spring water suggesting spring discharge is primarily the result of from melting of perennial, interstitial ice. Although meteoric water isotopic ratios are relatively constant, seasonal isotopic changes of the spring water may suggest changing hydrological conditions that modulate rock glacier flow. A next step in this study will be monitoring of hydraulic head variations by logging spring discharge. The results help elucidate the relationship between rock glacier kinematics and water/ice mass within. Thus, remotely measured kinematics may be key to identifying rock-glacier sources of water, on earth, as well as Mars, where similar landforms have been identified.