USING AIRBORNE THERMAL INFRARED REMOTE SENSING FOR HYDROTHERMAL MONITORING OF NORRIS GEYSER BASIN

Norris Geyser Basin is one of the most dynamic and hot hydrothermal systems in Yellowstone National Park. The basin contains both acid sulfate and neutral chloride hydrothermal features. The fractured 640 ka Lava Creek Tuff forms permeable pathways for hydrothermal fluid flow.

Airborne thermal infrared imagery (TIR) has been acquired over Norris Geyser Basin by different groups since the early 1960’s. This time sequence of imagery provides an opportunity for documenting change and monitoring the Norris hydrothermal system. Recent (2006-2013) fixed-wing TIR image acquisitions (8 to 12 micron senor) were flown at night, generally in late Fall, to minimize solar heating.

Quantifiable changes were detected in Norris Geyser Basin using a simple difference technique that subtracts one temperature image from another temperature image. Significant changes were calculated using images acquired for Porcelain Terrace (2010 to 2012) and the Back Basin (2009 to 2012). Helicopter-oblique daytime TIR, and ground observations confirm significant changes in these two areas. However, hydrothermally stable areas of moderate temperature, such as the Reservoir, remain consistent between acquisitions.

Norris Geyser Basin was subdivided into subareas using the fracture system and associated surface hydrothermal fluid flow. These subareas were then used to compute total radiative heat output (solar plus hydrothermal heat) for the years 2008 through 20013. Using a vegetated area as an estimate of background solar heat a hydrothermal heat estimate for each subarea is calculated.