YELLOWSTONE NATIONAL PARK — This week’s Caldera Chronicles column, written by student contractor with the U.S. Geological Survey Connor Phillips, describes how high-resolution satellite imagery is used to detect and monitor thermal activity in the backcountry.
The weekly column written by scientists and collaborators of the Yellowstone Volcano Observatory (YVO) explores how scientists have been able to analyze high-resolution satellite data to find small areas of surface thermal activity. While satellites with thermal infrared instruments are great tools for measuring heat output in larger areas, they cannot detect small thermal areas or subtle temperature changes. By examining the high-resolution satellite images, it is possible to see evidence of this thermal activity through vegetation stress, mineral deposits, water discoloration or changing water levels, writes Phillips.
With snowstorms and freezing temperatures typical during the winter in Yellowstone National Park (YNP), satellite images of snowy landscapes have become helpful for finding thermal zones.
“Snowy wintertime images are extremely useful for detecting areas of bare ground and thawed liquid on otherwise icy water bodies that are suggestive of thermal activity,” writes Phillips. “Think of the snow and ice as a layer that helps differentiate warmer ground from the surrounding cooler ground.”
Weather station data is also an important component when mapping snow-free zones. There are seven weather stations across YNP, and data can provide snow depth, average daily temperature, and time since last snowfall. Mapping these zones every season with satellite imagery can help develop understanding of thermal activity and changes over time, and can lead to the discovery of previously unknown thermal areas.
“For instance, when the snow depth is over 1 meter (about 40 inches) and the temperature hasn’t risen above about -7 °C (20 °F) in several days, the conditions are ideal for identifying zones within thermal areas that are producing the most surface heat,” writes Phillips.
Poring through so many satellite images can be time-consuming, so Phillips describes how the process has become automated, through downloading scenes, orienting images geographically, clipping thermal area boundaries, and processing to create color images. According to Phillips, YVO will continue wintertime mapping of the park’s thermal features in order to fill gaps in areas where good satellite data has not yet been acquired.
