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Lake San Cristobal and the Slumgullion Earthflow

Geologic Feature

Lake San Cristobal, Colorado’s second largest natural lake located in Hinsdale County near the town of Lake City, was formed about 700 years ago when the first Slumgullion Earthflow created a dam across the Lake Fork of the Gunnison River.

Visible and actually crossing Colorado Highway 149 just below 11,361-foot Slumgullion Pass, the earthflow was spurred when weak volcanic tuff and breccia were lubricated by heavy rains, causing the southern flank of the Mesa Seco to “slump” several miles down the steep mountain side. Because natural landslide dams have been known to fail, the United States Geological Survey investigated this possibility in relation to the Lake San Cristobal blockage. Based on the dam’s non-porous nature and the fact that part of its “natural spillway” actually cuts into bedrock, the dam was deemed stable. However, approximately 350 years ago, a second flow started from the top of the mountain and is still moving. Sediments washing down via the Lake Fork and Slumgullion Creek are slowly filling in the lake, but are not expected to affect the dam's stability. Some estimates show that if sedimentation continues at its past rate, the lake will be completely filled with sediment in approximately 2,500 years.

Recreational Opportunities

The area surrounding Lake San Cristobal offers hiking, biking, camping, mountain climbing, four wheeling, and much more . Enjoy a canoe ride or motorboat ride on the lake or fishing (any time of year).


Seasons Accessible

year round

Nearby Places