Front of the Black Mountains--where the valley abruptly meets the mountains.

In this photograph, you see the abrupt main front, and you can see where the fault zone runs--it makes a line which angles up to the left from directly above the letter "u" in "fault". This photo was taken just north of Natural Bridge--in fact, that's the Natural Bridge parking lot on the right side of the photo.

Looking south down the front of the Black Mountains. Alluvial
fans spill out of each of the canyons.