Slumgullion Earthflow in the San Juan Mountains of southwestern Colorado preserves the remnant of a massive landslide that moved down the valley about 700 years ago, spreading into a flow about 4 miles long and 2,000 feet wide. That movement dammed the Lake Fork of the Gunnison River and created Lake San Cristobal, directly shaping the modern valley landscape. Especially notable is a second earthflow that has continued creeping over older, stable rock for about 300 years at roughly 7 meters per year. Formally protected, the area also provides habitat for elk and deer and offers a rare view of mountain terrain still actively changing.