A follow-up post from today explains a little bit more about the large opening. “An engineer from Riverton, WY came out to shed a little light on this giant crack in the earth. Apparently, a wet spring lubricated across a cap rock. 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.