The U.S. Geological Survey, in cooperation with the National Park Service, Yellowstone Center for Resources, as part of work for the Yellowstone Volcano Observatory, has compiled a shapefile map of thermal areas and thermal water bodies in Yellowstone National Park. A thermal area is a continuous, or nearly continuous, geologic unit that contains one or more thermal features (e.g., hot springs, mud pots, or fumaroles); hydrothermally altered rocks and/or hydrothermal mineral deposits; heated ground and/or geothermal gas emissions; and is generally barren of vegetation or has stressed / dying vegetation. There are more than 10,000 thermal features in Yellowstone, most of which are clustered together into about 120 distinct thermal areas (e.g., Upper Geyser Basin, Crater Hills Thermal Area, or Roadside Springs). A thermal water body is a body of water, usually a lake, pond, or wetland area, that is thermally emissive because it receives heated water from a nearby thermal area, nearshore thermal springs, or from underwater vents.
The shapefile released here is based on a thermal area polygon shapefile that was initially provided by the Spatial Analysis Center at the Yellowstone Center for Resources in Yellowstone National Park. The thermal area polygons were initially based on field mapping (by R. Hutchinson and others, unpublished data, 1997) and digitizing boundaries over high-spatial-resolution (1 m/pixel) visible color orthophotos from the National Agriculture Imagery Program (NAIP) acquired in 2006. Updates to this map are based on more recent field mapping and remote sensing data analysis, including nighttime thermal infrared data (e.g., ASTER and Landsat 8/9), high-spatial-resolution visible data from commercial satellites (e.g., WorldView-3), and NAIP imagery from 2015, 2017, 2019, and 2022. The downloadable shapefile contains a map of these thermal areas and thermal water bodies with information (if available) about their chemistry and thermal activity. The names of the thermal areas are either derived from the USGS Geographic Names Information System (GNIS) or are locally used names, as indicated in the attribute table.
Thermal area mapping in Yellowstone is a work in progress, partly because there are still remote areas that have not yet been explored in detail, and partly because changes occur frequently. Thermal areas expand and contract, develop and decay, and migrate – over time scales that range from weeks to years. Thus, this map will be periodically assessed and updated.
A note about safety: Thermal areas can be dangerous, with scalding water, mud, or gases that are sometimes hidden beneath unstable ground. Unstable ground sometimes looks solid, but stepping onto unstable ground can result in breaking through a thin crust and being exposed to scalding water, mud, or gases, which can cause severe burns. Since the establishment of the National Park, more than 20 people have died from burns suffered after they entered or fell into a hot spring. For the safety of park visitors and the protection of delicate thermal formations, it is prohibited to enter a thermal area in the back country, and one must stay on the trails or boardwalks when entering front country thermal areas (unless working in a thermal area on an official permit).