9 July 2017
The Willow Creek landslide: a large valley-blocking slide in Wyoming
The Jackson Hole News and Guide is carrying a report about the Willow Creek landslide, a new, large, valley-blocking slide in the Wyoming Range in the USA. The slide, located in Lincoln County, appears to be substantial:
The report gives some details about the landslide, and its discovery:
To [Dustin Child’s] eye the landslide was as high as 200 feet in places, covered 1/4 mile of the Willow Creek canyon and formed a 15- to 20-acre lake that’s probably 30 or 40 feet deep. As for the hazard, he didn’t think there was one.
“It could possibly could do something next spring, but there’s so much debris,” Child said. “It’s an unreal amount of debris. It dammed it up as far as it’s going to go, and now the river’s cut a stream between the debris pile and the far west side.”
It’s unclear when the yet-to-be named landslide was triggered, or if it all came down at once or slowly over the course of the spring. The remote geological phenomenon was discovered this past week, when a Bridger-Teton National Forest firefighter saw that a mountainside had given way from above.
“They were doing a flight, looking for a fire,” Bridger-Teton spokeswoman Mary Cernicek said. “They didn’t find the fire, but they found the landslide.”
Buckrail has some additional images of the landslide, taken by Tracy Shull:-
The slide appears to be a mobile earth / mud flow, which has entrained a significant amount of debris from within the channel. Note the deep erosion and sidewall cutting in the upper reaches of the landslide (before the major bend in the landslide track), and then the apparent deposition, starting a short distance downslope from this point.
This is of course not an unusual event for Wyoming. Previous examples include the spectacular Bighorn Mountains landslide in 2015 and the Snake River landslide in 2011 (including the brilliant video).