The Gros Ventre Slide - Wyoming - Places of Geologic Significance on Waymarking.com

On Sheep Mountain the Tensleep sandstone overlies the Amsden shale which both dip about 20° to the north toward the Gros Ventre River. Deep erosion of the river bed had cut through the sandstone leaving it supported only by friction with the underlying shale. The previous winter had been very wet resulting in saturated bedrock conditions making the shale slippery. A series of earthquake tremors had been occurring, which may have been the final trigger.
On the afternoon of June 23, 1925, the slope of Sheep Mountain failed and within minutes about 50,000,000 cubic yards of material moved down slope and crossed the Gros Ventre River and climbed 300 feet up the opposite valley wall. The landslide resulted in a dam over 200 feet high and 400 yards wide, which within two weeks had backed up the river to form the five mile long Lower Slide Lake.
The spring runoff of 1926 passed with no problems and visiting engineers and geologist felt that the dam was stable and safe. But the winter of 1927 was one of the most severe on recorded and the unusually heavy snowpack melted quickly aided by days of rain. On May 17, water began to spill over low places in the slide formed dam. On May 18, 1927, part of the dam gave way and a wall of water, mud, and rock flowed down the canyon. The small town of Kelley, four miles down stream was destroyed killing six people and flood waters were 6 feet deep for at least 25 miles downstream. Today, Lower Slide Lake is much smaller, only about 3 miles in length and 60 shallower.
At the waymark coordinates there is a parking area, interpretive signs, and a trail.

Waymark is confirmed to be publicly accessible: yes Access fee (In local currency): .00 Requires a high clearance vehicle to visit.: no Requires 4x4 vehicle to visit.: no Public Transport available: no Website reference: [Web Link] Parking Coordinates: Not Listed

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