I finally saw a textbook rock formation fail in real life at the Grand Canyon

I was leading a student group along the Bright Angel Trail last spring, pointing out the classic horizontal layers of the Kaibab Limestone. Right as I was explaining how stable the caprock is, a chunk the size of a car tire just sheared off the cliff face about fifty yards ahead of us. We heard this deep crack and then watched it tumble down. It was pure luck no one was under it, but it totally shook the group's trust in the 'solid' geology I was teaching. Has anyone else had a classic formation do something completely unexpected like that?

2 comments

2 Comments

spencer19912d agoMost Upvoted

A foot of rock just slid sideways... that's terrifying to picture.

the_mary13d ago

My buddy was hiking in Zion last year and swears he saw a section of the Checkerboard Mesa actually shift. He said it was maybe a foot of rock that just slid sideways with this awful grinding sound, like a giant puzzle piece. It left a fresh, pale scar on the cliff face. He said it totally messed with his head because you think of those formations as just being permanent. I mean, it makes sense with erosion and all, but seeing it happen is something else.