The Slumgullion Earthflow is a remnant of a

landslide Landslides, also known as landslips, rockslips or rockslides, are several forms of mass wasting that may include a wide range of ground movements, such as rockfalls, mudflows, shallow or deep-seated slope failures and debris flows. Landslides ...

in the

San Juan Mountains The San Juan Mountains is a high and rugged mountain range in the Rocky Mountains in southwestern Colorado and northwestern New Mexico. The area is highly mineralized (the Colorado Mineral Belt) and figured in the gold and silver mining industry ...

in Hinsdale County,

Colorado Colorado is a U.S. state, state in the Western United States. It is one of the Mountain states, sharing the Four Corners region with Arizona, New Mexico, and Utah. It is also bordered by Wyoming to the north, Nebraska to the northeast, Kansas ...

. It was designated a

National Natural Landmark The National Natural Landmarks (NNL) Program recognizes and encourages the conservation of outstanding examples of the natural history of the United States. It is the only national natural areas program that identifies and recognizes the best e ...

in 1983. It is also a Colorado Natural Area and an

Area of Critical Environmental Concern Areas of Critical Environmental Concern (ACEC) is a conservation ecology program in the Western United States, managed by the Bureau of Land Management (BLM). The ACEC program was conceived in the 1976 Federal Lands Policy and Management Act ( ...

. The

earthflow An earthflow (earth flow) is a downslope viscous flow of fine-grained materials that have been saturated with water and moves under the pull of gravity. It is an intermediate type of mass wasting that is between downhill creep and mudflow. The ...

, a slow-moving landslide, crawled down the valley about 700 years ago creating the and wide mass. The earthflow lies a few miles southeast of Lake City. The landmark site covers and is owned and managed by the

US Forest Service The United States Forest Service (USFS) is an agency within the U.S. Department of Agriculture. It administers the nation's 154 national forests and 20 national grasslands covering of land. The major divisions of the agency are the Chief's ...

and the

Bureau of Land Management The Bureau of Land Management (BLM) is an agency within the United States Department of the Interior responsible for administering federal lands, U.S. federal lands. Headquartered in Washington, D.C., the BLM oversees more than of land, or one ...

. It is "a striking example of

mass wasting Mass wasting, also known as mass movement, is a general term for the movement of rock (geology), rock or soil down slopes under the force of gravity. It differs from other processes of erosion in that the debris transported by mass wasting is no ...

(the movement of large masses of earth material)." The Lake Fork of the

Gunnison River The Gunnison River is located in western Colorado, United States and is one of the largest tributaries of the Colorado River. Description The river flows east to west and has a drainage area of according to the USGS. The drainage basin of the ...

was dammed by the earthflow, creating Lake San Cristobal. A second earthflow has been moving continuously for about 300 years over older, stable rock. It moves at a rate of about per year. The area is a habitat for elk and deer. It is crossed by Colorado Highway 149, the principal highway of the area connecting Lake City with Creede.

References

{{authority control Landforms of Hinsdale County, Colorado San Juan Mountains (Colorado) National Natural Landmarks in Colorado Protected areas of Hinsdale County, Colorado Geology of Colorado