Cloudland Canyon State Park–Roadside Geology of Georgia
Cloudland Canyon State Park from Roadside Geology of Georgia
Cloudland Canyon State Park, one of the Seven Natural Wonders of Georgia, is 6.4 miles east of I-59. Turn left (north) onto Cloudland Canyon Park Road and continue 1.5 miles to the overlook parking area.
From the Point you can see Lookout Valley beyond the canyons, with its lush pastures underlain by Ordovician-age carbonate rocks. The ridge in the distance beyond the valley is Sand Mountain.
The layers of sandstone in the bluffs across the canyon are not fully continuous. That’s because there are many independent bodies of sandstone, each the product of a particular even. You can see such a sandstone body, with its convex bottom projecting below nearby sandstone layers, directly across the canyon from the Point.
At the Point you are standing on crossbedded sandstone. What resembles wood grain beneath your feet is actually the eroded top edges of numerous crossbeds. The edges of these former ripples are curved in a U shape because they formed in a stream and were sculpted as they migrated; the concave portion points downstream. On the way back to the parking lot, at the first steps you encounter, look to your left. Here a cross section of the crossbeds is exposed. The orientation of the crossbeds indicates the stream that deposited them flowed south, toward the parking lot.
There is a path to the bottom of the canyon where you can see two waterfalls on Daniel Creek. The complete hike will take about ninety minutes round-trip. From the parking lot, head left along the canyon rim. Continue in the same direction (south) along the Waterfalls Trail and follow the switchback that heads north. Just below the switchback is a long outcrop about 15 feet high, which, where you first see it, is made entirely of crossbedded sandstone. Continuing northward down the path and tracing the crossbedded rock, you’ll see that it ends against a sharp boundary that slopes to the north. Above and north of the boundary is unlayered sandstone. As the trail rounds a corner, the same massive sandstone crops out as a huge overhanging rock, underneath which twenty people might easily take shelter.
The thick sandstone in the overhanging rock is a cross section of an ancient river channel frozen in time. During Pennsylvanian time the river eroded tens of feet down into the older sand deposits (crossbedded sandstone), cutting the large, convex-downward shape of the channel. The absence of obvious internal layering within the channel sandstone indicates that at the end of its life, this channel probably filled rapidly, unlike the layered, crossbedded sandstone surrounding it. Crossbeds form slowly, as the sand in a river or stream channel migrates over time. Studies of modern rivers show that such rapid filling can occur during a major flood. If a natural levee breaks upstream, the flow can cause a river to abruptly change course and abandon a portion of its channel. The pebbles protruding from the bottom of the rock overhang are further evidence that this was a river channel. Pebbles are concentrated on river bottoms, where they tend to roll along in the current. Impressions of fossilized wood (presumably waterlogged as it was carried downstream) are also present.
Both the 50-foot upper falls (Cherokee Falls) and the 90-foot lower falls (Hemlock Falls) on Daniel Creek developed where the stream crosses from erosion-resistant sandstone into easily eroded shale below. The shale is the dark rock with thin beds in the cliffs below the falls. It forms flat chips as it erodes. The shale cliffs behind the waterfall continually crumble away, removing the support for the tough sandstone ledge at the top. As a result, the position of each waterfall retreats upstream over time. The bed of Daniel Creek is filled with sandstone boulders—some nearly house sized—from ledges that have collapsed in the past.
CAPTION: The canyon cut by Daniel Creek. Sand Mountain is visible in the distance.