Justin Sipla ascends a rope 80 feet to reach the mouth of Natural Trap Cave in north-central Wyoming after working on the cave's floor in this July 2014 image. The cave holds the remains of tens of thousands of animals, including many now-extinct species, from the late Pleistocene period, tens of thousands of years ago. Scientists have resumed digging here for the first time in more than 30 years. (Photo by AP Photo/Bureau of Land Management)
|