I visited Tallulah Gorge a few years before I started writing this blog, so at the time I didn’t think to write down my observations. I can’t remember where I put the photos I took of that trip or if I even took any. However, I found plenty of Tallulah Gorge photos online. I do remember walking down a long flight of manmade stairs to the bottom of the gorge and on the way down coming face to face with a black vulture that was perched on a ledge. I saw blueberry and blackberry growing on the canyon wall. And I recall swimming in a very cold reservoir nearby. Lately, I’ve been reading a new book, Roadside Geology of Georgia, by Pam Gore and William Witherspoon. Their page on Tallulah Gorge reminded me of my trip there. I didn’t realize Tallulah Gorge had such a fascinating geological history.
Location of Habersham County. Tallulah Gorge is in this county.
The headwaters of the Tugaloo River eroded backwards upstream from the Tugaloo and captured the Tallulah and Chattooga Rivers both of which formerly flowed into the Chattahoochee River.
Tallulah Gorge is the 4th deepest gorge east of the Mississippi.
Tallulah Falls. The sudden drop in elevation when the Tugaloo River eroded backward into the Gainesville Ridge created these falls.
The Gainesville Ridge separates the Chattahoochee River drainage from that of the Savannah River. All streams on the west side of the ridge empty into the Chattahoochee River, while all streams on the east side of the ridge flow into the Savannah River or its tributaries. Formerly, the Chattooga and Tallulah rivers were tributaries of the Chattahoochee River. But the headwaters of the Tugaloo River eroded upstream into the Gainesville Ridge capturing the Tallulah and Chattooga Rivers. These 2 rivers changed course making a sharp right angle turn through the Tugaloo River which empties into the Savannah River. It’s a classic example of what geologists refer to as stream capture. Geologists believe this stream capture event occurred “recently”, but I haven’t been able to find any studies of the exact age of the event, and I think scientists have not determined the exact timing of this dramatic occurrence. Recently in geological time could be 10 million years. Nevertheless, scientists believe the steepness of the gorge is evidence the stream capture occurred relatively recently. Some of the cliffs are 600 feet high. Geologists believe the gorge is geologically young because not enough time has passed for the high cliffs to erode away. In older river and stream incisions, water eventually erodes the sides back, creating broad gently sloped valleys. But at Tallulah Gorge, not enough time has passed for this to happen.
The rock along Tallulah Gorge is made of erosion resistant quartzite which is sandstone that has been metamorphized. There is no Chattooga River gorge because the rock along that river is less resistant to erosion. When the Tugaloo River eroded backwards and captured these 2 tributaries, the elevation suddenly lowered, creating the falls. This change in elevation is the reason the Chattooga river is known for its white water rafting.
There are 2 types of environments in the vicinity of the Tallulah Gorge. The cliffs provide nesting habitat for many species of birds (See http://markgelbart.wordpress.com/2013/05/19/piedmont-cliff-ecology/). In pre-Columbian times bald and golden eagles and peregrine falcons likely nested here. An acidic pine/oak woodland and forest grow on the rim of the gorge. Plant species composition includes white pine, Virginia pine, table mountain pine, pitch pine, shortleaf pine, southern red oak, rock chestnut oak, scarlet oak, blackjack oak, red maple, sourwood, persimmon, mountain laurel, rhododendron, blueberry, and greenbrier. This is the southernmost range limit of the Carolina hemlock. Monkey-faced orchid and persistent trillium are rare plants that favor this moist, water-splashed environment.
The Soque River may be a remnant of the Chattooga and Tallulah Rivers before they were diverted from the Chattahoochee River Drainage to the Savannah River Drainage. This is a beautiful small river with little public access.
This non-native brown trout was caught in the Soque River. I didn’t know trout in Georgia got this big. Native brook trout don’t get nearly this big. I hypothesize that brook trout occured farther south in Georgia during the Ice Age because water temps were cooler then.
Deep Creek and the Soque River are likely remnants of the Chattooga and Tallulah Rivers before they were diverted from the Chattahoochee River Drainage. There are many species of mussels common to both the Chattahoochee and Savannah Rivers. The Tugaloo stream capture event must explain how bivalves from the Chattahoochee Drainage colonized the Savannah. For a while during this stream capture event, water must have flowed from the Savannah to the Chattahoochee as well because mussels originating from the former also made it to the latter. However, it’s not clear how thie mussel exchange from the Savannah to the Chattahoochee occurred.