One of my favorite out of the way waterfalls in the Great Smoky Mountains is this small one found in White Oak Sink. White Oak Sink is an area within Great Smoky Mountain National Park that is lower in elevation than the surroundings. There are larger areas like this in the area called coves - Cades Cove being among the most well known. These topographic depressions are areas where erosion has eaten through the hard metamorphic rocks and into the softer sedimentary rocks beneath. The boundary between the metamorphic rocks and the sedimentary rocks is the Great Smoky Thrust Fault. The Great Smoky Thrust is fairly horizontal in geometry through this area, and areas where erosion has reached through it to the rocks underneath are called windows. The Great Smoky Thrust has over 400 km of displacement, so the rocks above it have moved a long way to arrive at their current location in eastern TN. One of the best places to see the Great Smoky Thrust is here at White Oak Sink, behind a small waterfall. The fault is visible as a horizontal line in the rocks, with the older Precambrian rocks above sitting on top of younger Ordovician rocks. The Precambrian rocks are metamorphosed, but they were originally deposited as sedimentary rocks in the Late Neoproterozoic. They were later metamorphosed to phyllites in the Ordovician, the same time period during which the Ordovician Knox limestone was deposited. The Precambrian phyllites were not thrust over the Knox until much later during the Alleghanian Orogeny in the Pennsylvania Period. Because the Ordivician Knox Group is made of carbonate rocks, caves form within it, as well as sinkholes and other features associated with karst. Here where this small creek enters the sink, it flows into a cave and disappears underground. This is a great location to bring students, and the hike from parking along the road is quite nice. Below are three photos I took of the waterfall and the thrust fault while on a trip with students in the spring of 2014.
This first image was taken with a 1/2 second shutter speed, f/8.0, 24 mm, ISO 100. This image was selected as the Earth Science Picture of the Day for May 22, 2014. My goal with this image was to highlight the dipping foliation within the phyllite, which leads the eye up to the waterfall.
For this next image, I chose a vantage point where I could look up at the falls and the fault. This image was shot with similar settings as the first, but with a wider angle (18 mm focal length).
One last image, photographed from another vantage point. The thrust fault can be seen where the color of the rocks changes from a dark black to a dark tan color. Settings: 0.5", f/9.0, ISO 100, 20 mm.
I am grateful to Don Byerly, Professor Emeritus at Univ. Tennessee, for providing me with the location of this excellent spot a number of years ago.