When a giant crack in the ground appeared seemingly overnight in the foothills of Wyoming’s bighorn mountains there were lots of guesses as to what it was. Could it be a sinkhole, a result of fracking or an earthquake?
The answer is none of the above. Hunting guides in the area with SNS Outfitter and Guides posted images of the fissure, which locals are calling the “gash” to Facebook, prompting hundreds of comments and speculation.
Geologist Doug Duncan called it a “common slump.”
“Generally this happens when a stream (or highway construction) erodes the ‘toe’ of a steep slope of loosely cemented rock,” Duncan explained in the comments section. “The slope gives way until it refills the toe and less weight is on top (because it slid down). It can be triggered by rain soaking into the earth that makes the whole thing heavier. It can be triggered by a nearby earthquake, but this crack is not an earthquake fault. In some cases water under pressure can lubricate the failure zone.”
After photos of the area drew so much interest, the guide service had an engineer come out to the site located on state land in the middle of a ranch. The engineer determined the fissure was due to nearby springs reacting to a cap rock.
“Apparently, a wet spring lubricated across a cap rock,” the group reported. “Then, a small spring on either side caused the bottom to slide out. He estimated 15 to 20 million yards of movement. By range finder, an estimate is 750 yards long and about 50 yards wide.
The group also reported further information on its website.