INTEGRATING LIDAR AND AIRBORNE THERMAL INFRARED IMAGERY FOR GEOLOGIC MAPPING OF HOT SPRING BASIN, YELLOWSTONE NATIONAL PARK

High-resolution LiDAR of Hot Spring Basin (HSB) in Yellowstone National Park allows new, detailed mapping of faults and fractures that permit flow of hydrothermal fluids. While previous geologic mapping identified the major faults (Prostka and others, 1975), the LiDAR digital elevation model (DEM) allows detailed mapping in this remote area with active ground deformation. The linear trends on the LiDAR DEM are similar to field observations of fractured Lava Creek tuff (NNW, NW) and overlying compacted lacustrine deposits (N-S, and E-W).

Integration of LiDAR with airborne, night-time thermal-infrared (TIR) imagery from 2007 and 2008 allows new insights into this dynamic hydrothermal system. Overlaying the 2007 and 2008 TIR imagery on LiDAR, easily shows the relationship of NW, nearly E-W, and approximately N-S trends to these two main basins (eastern and western), a nearby hydrothermal explosion crater and other active thermal areas. Both the LiDAR and TIR imagery show similar compartmentalization of the hydrothermal system. Comparison of the 2007 and 2008 TIR imagery reveals little change in the total area of the low-temperature (10-40^oC) hydrothermal system whereas, the high-temperature system (~40-80^oC in 2007 and ~40-60^oC in 2008) shows a distinct decrease in area at the eastern Basin. In the western Basin, field reconnaissance and TIR imagery show a small increase in the area of the low-temperature, hydrothermally-altered ground along NW and nearly E-W trending linear features. Thus, high-temperature and low-temperature changes in the western and eastern basins occurred along NW trending linear features and one E-W trending linear feature.

The LiDAR also allows new, detailed mapping of the glacial geology. Even though previous geologists (Pierce, 1974; Richmond and Waldrop, 1972) mapped the complex of glacial and late glacial deposits, LiDAR makes it easy to construct a detailed map of recessional moraine ridges, kame terraces, faulted kame deposits, meltwater streams, levels of ice stagnation on hillsides, and streamlined topography. Because the surficial expression of the HSB hydrothermal system develops through an overlying veneer of sediments, detailed mapping of bedrock faults and fractures as well as surficial deposits assists analysis of this remote and dynamic hydrothermal system.