PARKWIDE 2020 LIDAR FOR YELLOWSTONE ENABLES REFINEMENT OF SURFICIAL FEATURES INCLUDING FAULTS, MORAINES, LANDSLIDES AND OTHER PREVIOUSLY OBSCURED TEXTURES

Yellowstone’s surficial geology was mapped in the early 1970s by Pierce, Richmond and Waldrop using aerial photography and field observation. Their efforts established the current catalog of quaternary faults, glacial extents and other landscape elements that define our understanding of the topographic evolution of one of the most dynamic landscapes in the United States. Though a 2020 parkwide LiDAR dataset reveals the ground surface in breathtaking detail, the USGS team’s major observations and interpretations are not only validated but substantiated 50 years later.

Though the major findings are largely unchallenged, new data offers opportunity for refinement. Hundreds of previously unmapped fault scarps are now recognized. These occur in areas of previously mapped faults (adding detail to known structures) and in areas without previously mapped scarps. Some scarps previously mapped with latest Quaternary movement have little evidence for post-glacial surface displacement such as the Upper Yellowstone Valley faults and strands of the Buffalo Fork and East Mount Sheridan Faults. Along and especially at the tips, many fault scarps in Yellowstone have abundant pit craters. Formed by either expulsion of water or steam or near-surface collapse into subterranean voids, these pits are not previously noted along faults within the park.

Terminal glacial deposits are far more abundant than previously mapped near the margin of former ice sheet and are sparse toward the center of the plateau. Sculped topography is pervasive and consistent with previously mapped flow directions. Unmapped subglacial deposits such as eskers and complex, discontinuous fluvial sculpting such as tunnel valleys are also common, especially in the eastern half of the park.

Landslides are especially abundant outside the caldera and LiDAR reveals hundreds more than previously mapped. The interaction between mass movements, glacial deposits and fault rupture provide opportunity for relative dating of events. In particular, a handful of dense patches of sackung, reveale deep-seated gravitational slope deformation, often associated with nearby fault scarps or historic seismic swarms. Distinguishing morphologically between sackung scarps (a form of mass movement) and fault scarps will be a challenge ahead.