It is a limestone canyon which is very narrow and deep. A forest road crosses the canyon and a tiny spot of light reflects in the water at the bottom in this photo from the bridge. Tom read on a blog that the canyon is 140 feet deep. It was spooky to look over the edge of the bridge. I dropped a few rocks into the canyon and counted 1001, 1002, 1003, 1004 before each rock hit the water.