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Earthflow path down through trees

Slumgullion Earthflow

On September 18, 2023, the Slumgullion Earthflow continues moving downhill from Mesa Seco… a slow, thousand-year-old journey! Produced in tectonic activity, the San Juan Mountains formed tens of millions of years ago in southwest Colorado. As climate altered the volcanic residue in the Mesa Seco, the weaker soils and rock debris collapsed and slid or fell away. The more resistant rock remained in place above its surroundings.

The landslide is called an Earthflow. It is made up of a loose, sometimes muddy combination of volcanic bits and boulders, gravelly and sandy in texture, moved downslope from the Mesa Seco by rains and mountain runoff. As it moves, the material mixes with powdery clay silt that holds and swells with water. This addition adds to the general weakness of the combined material moving downwards. Short-lived rivulets and springs erupt and flow from blocked and covered streams and disappear back into the slow sliding land. Although the rate of landslide movement varies year to year, the fastest movement occurs near the end of spring thaws.  The saturated ground keeps the landslide active as NASA interferometry has detected in the slide’s flow.

Earthflow path down through trees
Slumgullion Earthflow National Landmark
NASA Airborne Inferometry Study of Slumgullion Earthflow


The leading edge or toe of the land-sliding material depresses the ground in front of it. Trees on the north side of the slide all tilt toward the middle. Trees are mostly absent from the south side that also tilts to the middle. As the younger part of the Slumgullion overtops older parts, it bulldozes trees and bush beneath the weight of its mass. Gravity pulls on the mass of landslide to assist the downhill creep at a rate per year of a few centimeters or inches at the top of the slide to six to seven meters (19 to 23 ft) nearer the bottom.

At Slumgullion and other earthflows around the world, international research provides insight to scientists for predicting landslide activity for early-warning purposes.

How does this earthflow earn its name? Slumgullion is a dish cooked up in a skillet, starting with browned meat and thickened up with whatever else is handy – kernel corn, carrots, potatoes, pasta, tomatoes, onions. To prospectors panning for gold, the dregs of their sluice boxes looked like a slumgullion stew. As did this landslide!


B Bondar / Real World Content Advantage