Glacial Pothole. Glacial meltwater or water at the bottom of the glacier, starts moving in circular motions. The sediment trapped in this movement grinds cylindrical holes into the bedrock through abrasion.
Angular and unsorted rocks show evidence of glaciation. The glacier would not smooth out the rocks and due to the high energy environment, it would leave the rocks behind unsorted. Also, plucking would cause the rocks to be angular and unsorted.
Glacial Polish at Purgatory Chasm. The rock becomes smooth as a result of fined grained material at the bottom of the glacier rubbing against the rock.
Fault plane at purgatory chasm
As stated in Professor Pelto's theory, a fault plane can be identified if the joints on the walls of the chasm do not match up. Therefore, since these joints don't match up, the chasm would be a fault plane.