While the San Rafael Swell formed as a solid dome, on the eastern side of the dome the earth's crust actually broke, creating a 75 mile long ridge of jagged rock. Some of the early explorers here apparently had spent time at sea, and they saw the earth's uplift as being similar to a reef. They called it San Rafael Reef and the name stuck. Much like other monoclines or anticlines we've discussed here, the Reef is bisected by numerous canyons, some of which are popular with hikers because they don't require special skills or equipment to traverse. The first one I hiked is called Wild Horse Canyon.
To reach the eastern entry to Wild Horse Canyon, one must leave the mesa where the road is located and walk across a broad wash. Depending on where one gets information about the hike, round trip distance is said to be anywhere from 6.3 to 9.7 miles. I really don't know how far I walked, but I did come out on the western end of the canyon, then backtracked to the parking area.
Much of Wild Horse Canyon is open, but there are at least two sections of narrows. I found several pools of water, none presenting any difficulty. All of the canyon was scenic, and not knowing what was ahead made it an adventure.