83 Deep-Seated Gravitational Slope Deformation in the Sawatch Range of Colorado

Faculty Mentor: JEffrey Moore: (Geology and Geophysics, University of Utah)

 Deep-seated gravitational slope deformations (DSGSDs) are large-scale, creeping mass movements often involving entire mountain slopes. These enormous landslides may be on the order of kilometers in height and length but only move a few millimeters to centimeters a year. Secondary hazards are produced from frontal landslide failures, rock fall, and debris flows. While there have been many studies on DSGSD from the European Alps, few similar studies have been conducted in the United States. This research aims to identify DSGSD in a 2200 km2 area in the Sawatch range of Colorado, followed by mapping, geomorphic analysis, and comparison with satellite Interferometric Synthetic Aperture Radar (InSAR) displacement data. We used satellite imagery and Light Detection and Ranging (LiDAR) data to identify DSGSD features across the range, followed by a week-long field visit to collect ground data and imagery. Results show that DSGSD are relatively common across the Sawatch range, and many of these features are actively moving. We identified 28 sites that exhibit physical characteristics of DSGSD, of which eight appeared to be moving with a downward velocity of one to two centimeters per year. About half of the identified DSGSDs were west-facing. Almost all DSGSD occurred in granitic bedrock, with a few in metamorphic rock. The largest DSGSD was over 8 km2, but most fell between .5-1 km2. This research provides insights into their distribution and geomorphology of DSGSDs in the Sawatch range, while contributing to their broader understanding.