The Slumgullion Earthflow is a National Natural Landmark located just south of Lake City on Hwy 149. It’s one of the rarest examples of mass wasting; the geomorphic process by which soil and rock move downslope.
It began roughly 850 years back when a chunk of the Mesa Seco broke away and started slowly sliding down the mountain. A chunk of rock, dirt and forest oozed 4 miles and over 3,000 feet in elevation, forming Lake San Cristobal.
Parts of the Earthflow are still active, as evidenced by leaning trees. Another younger flow began 300 years ago and is actually sliding over the previous earthflow.
It was designated a National Natural Landmark in December 1983 and contains 1718 acres. Slumgullion is a mining term used to describe the muddy clay left in the bottom of a sluice box.
Take Highway 149 south from Lake City for approx. 7 miles. There is a parking and interpretative displays on the side of Silver Thread Byway.
Address: Hwy 149, Lake City
Season: Year round