InSAR-based characterization of rock glacier kinematics in the La Sal Mountains, Utah, USA

Abstract

<p>Rock glaciers are perennially frozen bodies of ice and poorly sorted rock debris that flow downslope due to basal shear and deformation of interstitial ice. As common features in high mountain environments, rock glaciers constitute an important component of alpine hydrology and landscape evolution through release of seasonal meltwater and transport of debris downslope. Here, we use satellite-based interferometric synthetic aperture radar (InSAR) from 2015 to 2021 to identify and characterize rock glaciers in the La Sal Mountains of Utah, USA. Following the IPA Action Group guidelines, we created an inventory of 45 active and transitional rock glaciers in the La Sal Mountains based on mean InSAR velocity maps. La Sal Mountain rock glaciers have an average area of 0.09 km<sup>2</sup> and are found at a mean elevation of 3187 m, where mean annual air temperature and precipitation are estimated to be 2.44 °C and 1012 mm, respectively. The mean downslope velocity for the inventory is 3.58 ± 1.13 cm yr <sup>-1</sup> with individual rock glacier velocities ranging from 1.98 cm yr <sup>-1</sup> to 7.54 cm yr <sup>-1</sup>. Time-dependent deformation of 19 representative rock glaciers shows that rock glacier motion varies seasonally, with rates of up to 38.2 cm yr<sup>-1</sup> during the late summer. Average annual rock glacier velocities are also strongly correlated to the overall amount of precipitation received each year (R<sup>2</sup> = 0.97). Our results offer insight into environmental factors that may govern rock glacier kinematics, suggesting that rock glacier kinematics are controlled by the availability of liquid water.</p>