Photo by @MaxwellTheTige1; click to see the original. Click the photo to see the kink at full size.
I studied alongside mining engineers during my days at Crazy Go Nuts University, and yeah, they were into some pretty weird stuff.
But seriously…
Click the photo to see it at full size.
I’ll leave the explaining to the Kentucky Geological Survey:
“Kinks” and “kink zones” are fracture zones that form after mining, usually along the center of an entry, from compressive forces that cause the immediate roof strata (in shale roofs) to impinge upon each other or “kink.”