By Dr. Nat (Drnat) on Thursday, October 7, 2010 - 09:30 pm:
I’ve seen a few pictures now and watched a TV6 news story about the mystery crack. It is difficult doing geology vicariously. I wish I was there to get a better look at the topography, surrounding rocks, and the crack itself, but I’ll do my best with what I saw.
Depending on the topography of the area, my initial explanation of the rotational slide could still be a possibility. The bedrock of the area, however, is the Trenton Formation, which is dolomite. Dolomite can be dissolved by groundwater, so a collapse along a cave system is also a possible explanation for the crack. Land subsidence caused by groundwater withdrawal could also be the culprit. (In fact, in the American Southwest there are several large cracks in the ground that formed due to water withdrawal and the subsequent subsidence). I have checked with the USGS and no earthquake has been recorded for that area, so I think that explanation can be ruled out.
I will continue checking for more information about the mystery crack and if I find out something interesting, I’ll be sure to let everyone know.
By Capt. Paul (Eclogite) on Thursday, October 7, 2010 - 10:13 pm:
Maybe this should be continued on the Geology Thread.
Just a thought..... J