Slumgullion Earthflow

Location: Hinsdale County
Size: 1291 acres
Designated: 1983
Landowner: Bureau of Land Management and the US Forest Service

Two major earthflows included in this natural area illustrate a striking example of mass wasting (the movement of large masses of earth material).  Slumgullion earthflow is over four miles long and 2000 feet wide. A huge mass of volcanic rock slumped down the valley about 700 years ago, damming Lake San Cristobal. This flow is gradually being covered by a younger flow which began 300 years ago. Trees on the earthflow are being pushed over by the forward advance of the younger flow.