LOGAN -- Kirsten Bahr stands with her back against the cliff wall. Behind her is a triangular crack the size of a car door. Crouching down, she backs slowly into the hole. Five feet back and she is on her knees as the hole shrinks in around her. Bahr backs up another three feet and the floor disappears below her.From here, it's 190 vertical feet and several minutes before her feet are on the ground again.