3 No One Knows What Caused Them

First thought to be caused by exploding gas, scientists are now tackling the idea of pingos causing these craters. Pingos are plugs of ice that form over time and have small mounds on top. If it melts quickly, it could cause the ground to collapse and form a crater. However, this still doesn’t explain the dirt or rocks found around the rim of the craters. The holes seem to be caused by an explosion as opposed to a collapse. Natural gas stored in permafrost previously held under pressure by pingos may have caused an explosion. However, methane is said to be only found in land permafrost at 740 feet or deeper, a depth that the 50-foot deep craters did not reach.