Former University of Michigan graduate student Katy Keller with a hand on eroded and melting permafrost near Toolik Lake, Alaska. The gully erosion seen here is a type of thermokarst failure, formed when ice-rich, permanently frozen soils are warmed and thawed. Photo by George Kling.

University of Michigan ecologist George Kling at a landslide thermokarst on a glacial headwall near Toolik Lake, Alaska. As permafrost ice melts, the soil collapses and either creates an erosional hole in the tundra or a landslide such as this one. These features are called thermokarst failures. Photo courtesy of George Kling.