Rock on
John Wesley Powell declaimed that the Grand Canyon was the best geologic cross section in the world. In fact George Bradley, on Powell's first historic river trip/exploration, complained that "If he can only study geology he will be happy without food or shelter but the rest of us are not afflicted with it to an alarming extent".
A cursory study of the rocks keeps the hiker's mind off mundane matters such as blisters, sore muscles, and heat exhaustion.
Click on a formation to learn more about it.