More than 10,000 thermal features pepper the landscape of Yellowstone National Park.

Most of the hot springs, geothermal vents, and geysers are clustered around 120 distinct thermal areas. Scientists with the USGS Yellowstone Volcano Observatory use satellite and aerial imagery to map them as they expand and contract.

They recently found an entirely new thermal area.

It emerged quietly over 20 years, miles from the nearest trailhead but close to an existing hot zone.

Landsat 8's thermal infrared sensors captured the change in a nighttime image from April of 2017. Heat signatures are clearest at night, when unheated ground is cool.

Aerial images told more of the story. Forest covered the area in 1994, but the emergent thermal zone had begun to fry trees by 2006. Before long, the hot spot was unmistakable, with felled trees piled like toothpicks in a patch of land roughly the shape of a thumbprint.

Scientists rely on both satellite and high-resolution airborne imagery archived with the Earth Resources Observation and Science (EROS) Center to monitor Yellowstone.