Alexx Sanchez
asanch16@uwyo.edu
A large opening in the Earth, now being referred to as “The Crack” or “The Gash.” was found by hunters in the Big Horn Mountains.
According to Wyoming Public Radio, “The Crack” is about 750 yards long and 50 yards wide.
There has been much concern about what could have caused such a large crack in the Earth. After the article was posted on Facebook, people have commented their thoughts on the possible causes behind “The Crack,” such as fracking, earthquakes or volcanic activity under Yellowstone. Others have suggested the picture of “The Crack” is a fake. There were even a few wild speculations that aliens were behind “The Crack”.
Despite the wide range of speculations, “The Crack” is very real, and there is a logical explanation to how it was formed. The Wyoming State Geological Survey (WSGS) stated that a slow-moving landslide formed “The Crack”.
Tom Drean, director of the WSGS, discussed on Wyoming Public Radio why the landslide does not look like a typical landslide.
“It was more of a block that slid. Quite often what you see in landslides, you see a whole broken up surface that moves down. In this case, it looks like a block of the Earth that moved down or slid down a slope,” Drean said.
Landslides are not an uncommon occurrence in Wyoming, especially with water running down steep mountain slopes. According to the WSGS website, over 30,000 landslides have been mapped in Wyoming.
There are many factors that contribute to the occurrence of a landslide.
One contributing factor is sub-surface water content. According to the WSGS report on “The Crack,” there is evidence of ephemeral springs near surface water tables, which is near where “The Crack” formed.
Dr. Brandon McElroy, UW assistant geology professor of sedimentology, explained the significance of the presence of water in the area where “The Crack” formed.
“Essentially the water when it fills up the pores between the grains, it gives some buoyancy to the materials that are making those pore spaces,” McElroy said. “It slightly reduces the weight of the overlying material as felt by those grains.”
In other words, water from the near-surface water table reduced the weight of the sub-surface material, the sub-surface material being the rock beneath the surface. With the weight of the rock reduced, it makes it easier for the rock to move downhill, thus creating the landslide.
Another contributing factor is the type of rock beneath the surface. When looking at a picture of “The Crack,” McElroy said there are types of rock that can be seen now that the sub-surface has been exposed.
He said there is clearly a large layer of mudstone along with layers of soil and some wind-blown sediment, or broken up pieces of rocks. These types of rocks and sediments allow water to fill up in the pore spaces in between the grains of the rocks, causing the buoyancy as discussed above.
Other rocks such as sandstone would not be conducive to creating a landslide because the water would flow through the rock as opposed to making the grains buoyant.
With these contributing factors and the presence of a steep enough slope, eventually the forces keeping the rock from sliding downhill were overcome and “The Crack” formed, McElroy said.
According to the WSGS report, since “The Crack” is in a remote location there is not much concern for future damage to infrastructures or properties. The current concern is the possibility of people or livestock falling into “The Crack” from the unstable edges or the landslide suddenly moving. However, the report continued by stating that the landslide “catastrophically failing” is not likely.
