Saw this incredible rock formation along the Fiery Gizzard Trail in South Cumberland State Park / Grundy Forest about an hour NW of Chattanooga this weekend. Obviously it's erosion from the stream, but it's so strange! What kind of rock is it? Why does it have these distinct "teeth"?

For those who are interested, we hiked approximately 10 miles from the primitive hike-in campground (0.6m from the parking lot) CCW on the Fiery Gizzard Trail, then out-and-back to Raven's Point, then the Dog Hole Trail back to Fiery Gizzard. According to wikipedia, the trail and creek got its name from a story about Davey Crockett burning his tongue on a turkey gizzard while camped out there. Anyway, the trail is rugged and beautiful, with several small waterfalls, and a lovely system of creeks. After the ascent to Raven's Point, there are several nice overlooks. It took us just over 5 hours to hike the loop, but we didn't account for the fact that the trail is in the Central Time Zone, which our phones automatically adjusted to without telling us. We couldn't understand why it was getting so dark so quick! We used our headlamps to complete the last 3 miles.
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