Discontinuity between Coconino Sandstone and Hermit Shale - seen while hiking down the North Kaibab trail. THe Hermit Shale undermines the sandstone, and eventually big chunks break loose and the canyon grows a little wider.

You can see the Coconino Sandstone is white and forms steep cliffs. THe Hermit Shale is red, and softer. It temds to form a slope and it undercuts the Coconino Sandstone.

Here is an interesting reference www.docstoc.com/docs/652037/GEOLOGY-OF-GRAND-CANYON-NATIO...

My fourth day was pretty long. Since heavy weather was coming in on the North Rim, we decided that we did not want to camp a day there. So, I hiked from Bright Angel out the South Rim. Left at 130, stopped fro breaskfast at Indian Garden, and then up on the South Rim at 8 AM. Got some supplies (and a snack) and then drove over to the North Rim (about 300 km), and then hiked down the North Rim to Cottonwood Camp. It was about 27 km (17 miles).

South2NorthRim day 4