Slumgullion Earthflow — Active Landslide Geologic Feature

Pull off on CO-149 between Lake City and Slumgullion Pass and you’re looking at one of North America’s most documented active earthflows. The Slumgullion Earthflow is roughly 4 miles long and has been moving continuously for centuries — the older, stabilized lobe dammed the Lake Fork of the Gunnison to create Lake San Cristobal, and the younger active lobe is still on the move. The yellow-orange color comes from sulfur and iron minerals leaching from volcanic debris. It’s geologic chaos frozen in slow motion, and it genuinely looks like the hillside is melting.

There’s a small pull-off with an interpretive sign on the east side of CO-149 at approximately the 8-mile mark north of Lake City. No facilities, but the roadside view is clear and dramatic. Worth stopping even if geology isn’t your thing — it looks like something from another planet. A short informal trail leads up into the earthflow from the highway shoulder.

A mountainside that's been sliding for 700 years.