Old Black comprises Thunderhead sandstone, a type of Precambrian metamorphic rock common throughout the Smokies.

[8] The rock is part of the Ocoee Supergroup, which was formed from ocean sediments nearly a billion years ago.

[9] The mountain was created over 200 million years ago during the Appalachian orogeny, when the North American and African plates collided, thrusting the rock upward.

[13] Laura Thornborough, a writer who made several excursions to the area in the 1930s, recalls the thick spruce forest that dominates in the eastern Smokies: As the A.T. swings around the Tennessee side of Guyot, it passes through what is believed to be the densest stand of spruce and balsam in the Great Smokies.

The trail comes to within less than a 10th of a mile from the summit, but the thickness of the forest atop the mountain will considerably slow any bushwhack attempt and make off-trail navigation difficult.