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Slumgullion Earthflow

Slumgullion Earthflow
Slumgullion Earthflow. Photo by S. Hutchison.

Slumgullion Earthflow is an excellent illustration of the geologic process of mass wasting. Seven hundred years ago, a huge mass of volcanic rock slumped from the mountainside and flowed into the main valley where it spread laterally to form Lake San Cristobal. The older flow is presently being overridden by a new flow moving up to 20 feet per year.

Location: Hinsdale County, CO

Year designated: 1965

Acres: 800

Ownership: Federal, Private

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Please remember, National Natural Landmarks (NNLs) are not national parks. NNL status does not indicate public ownership, and many sites are not open for visitation.

Last Updated: June 28, 2012