Twin Arches in the Big South Fork National River & Recreation Area

By Ann Farrar and Dick Ketelle

​The Big South Fork National River and Recreation Area (BSFNRRA) was authorized as part of the 1974 Water Resources Development Act and encompasses 125,000 acres of the Cumberland Plateau in Tennessee and Kentucky. The Big South Fork of the Cumberland River passes through 90 miles of scenic gorges and valleys. There are so many sandstone bluffs, and some of our favorites are the Twin Arches and surrounding rock houses. For us, it is about a two hour drive  to the trailhead (I-40 W, US Hwy 127, TN Hwy 154, gravel roads to trailhead). The map below shows the location of this particular trailhead (in the red rectangle) . 

We like to hike a loop trail that includes the Twin Arches, numerous other rock houses and bluffs, Jakes Place, a side trail to Slave Falls, and past Charit Creek Lodge. The hiking loop is shown below, highlighted in red. The Twin Arches are two of the largest arches in the eastern United States and the most spectacular geologic formation in the Big South Fork area. Nowhere else are there two arches so close together and nearly aligned end to end. 

The pictures are from our last hike there which was before Christmas. 
​This is a picture of the side of the South Arch. It is the largest on the Cumberland Plateau, with a span of 135' and a clearance of 70'.  This day, we were lucky enough to have the arches to ourselves! So we could take time to capture the composition we wanted. 

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​The size of the arches and the nearby trees makes getting good photographic compositions a challenge.

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Dick likes to make panorama sequences while under the many rock-house ceilings to capture the feel of the places. This rock-house had nice illumination from the near-solstice winter sun. If you search, you will see Ann sitting in the sun.

That Native Americans used these rock-houses before European settlers invaded the area is evidenced by the presence of "hominy holes". These are small indentations in some of the scattered boulders where mortar and pestel type activities to crush acorns and probably other nuts to prepare them for cooking for food.

​There is a coal seam that lies at the base of this massive sandstone bed. Water seeps through the coal, which is naturally very fractured, and in some areas water trickles across the ground and through the rocks. Interesting plants can survive in these isolated wetland pockets in the otherwise dry, sandy soils.

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​The weathering surfaces, and inter-layered sandstone beds create endlessly interesting faces on the rock-house bluffs.

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​The weathering patterns consisting of holes and pockets are referred to as "tafoni" that form through complex physical and chemical weathering processes in the granular sandstones.

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The apparently massive sandstone comprises a wide range of depositional features that provide clues to the environments at the time the sand was laid down. Here we see relatively flat beds at the bottom of the bluff with some cross bedding indicative of deposition in a low to moderate flow current environment. Overlying the bottom layers, and cutting into them, lies the big, nearly featureless brown sandstone bed. That bed is indicative of a cross-cutting channel that eroded down into the underlying sand beds and then was infilled with sand that exhibits little sign of the beds within its thick body. These are among the things that geologists ponder when wandering the woods.

It was cold the day we hiked and we loved seeing the icicles, as well as the arches!! 

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