|Location||Hinsdale County, Colorado, United States|
|Nearest city||Lake City, Colorado|
The Slumgullion Earthflow in the San Juan Mountains in Hinsdale County, Colorado has been a National Natural Landmark since 1983. It is also a Colorado Natural Area and an Area of Critical Environmental Concern.
The earthflow, a slow moving landslide, crawled down the valley about 700 years ago creating the 4 miles (6.4 km) long and 2,000 feet (610 m) wide mass. The earthflow lies a few miles south east of Lake City. The landmark site covers 1,291 acres (522 ha) and is owned by the US Forest Service and the Bureau of Land Management. It is "a striking example of mass wasting (the movement of large masses of earth material)." Lake San Cristobal was dammed by the earthflow. A second earthflow has been moving continuously for about 300 years over older stable rock. It moves at a rate of about 7 meters (23 feet) per year.
- "Slumgullion Earthflow". Colorado Parks and Wildlife. Archived from the original on August 27, 2012. Retrieved July 5, 2013.
- "Slumgullion Earthflow". U.S. Department of the Interior - Bureau of Land Management. Retrieved July 5, 2013.
- D.J. Varnes and W.Z. Savage, ed. (March 23, 2012). "Bulletin 2130 -The Slumgullion Earth flow: A Large-Scale Natural Laboratory". US Department of Interior - US Geological Survey. Retrieved July 5, 2013.
- Hagenauer, Beth (October 8, 2012). "NASA Conducts Airborne Study of Colorado Landslide". NASA Dryden Flight Research Center. Retrieved May 9, 2014.