Sewanee Natural Bridge

Useful Information

Location:	Sewanee forest, Sewanee, Tennessee, 37375. Sewanee SR 56 south 4 km, turn left Natural Bridge Road, parking at the end of the road, 300 m/5 minutes hike. (35.1536502, -85.9213951)
Open:	no restrictions. [2024]
Fee:	free. [2024]
Classification:	Natural Bridge Erosional Cave
Light:	n/a
Dimension:	W=15 m, H=7.6 m.
Guided tours:	self guided
Photography:	allowed
Accessibility:	no
Bibliography:
Address:	South Cumberland Recreation Area, 11745 US 41, Monteagle, TN 37356, Tel: +1-931-924-2980. Division of Natural Areas, William R. Snodgrass Tennessee Tower, 312 Rosa L. Parks Avenue, 2nd Floor, Nashville, TN 37243-0447, Tel: +1-615-532-0431.
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History

1976	area given to the Tennessee Conservation Department by the University of the South.

Description

Sewanee Natural Bridge is a natural bridge in sandstone, which is the result of erosion caused by a small intermittent spring. It is located at the edge of a huge sinkhole structure named Lost Cove, and is 15 m wide and 7.6 m high. The spring flows during snow melt and after heavy rains, and the water emerges from a small cave, then crosses the natural bridge and flows into the sinkhole. The bridge looks quite fragile, but is massive enough to allow people to cross it. As the bridge is quite narrow, you should not be afraid of heights and should be sure-footed. We recommend not crossing the bridge when the ground is wet as it can be slippery.

The name is derived from the nearby town Sewanee, about 4.5 km to the north. This town is best known as the home of the University of the South, and this site with the natural bridge was once owned by this university. Some say it was named after the university, which is colloquially called Sewanee. Today it is located in a small State Natural Area with three acres (1.2 ha).

The water from the spring erodes the sandstone, it causes not only mechanic stress by flowing and transporting sand and gravel, it also transports loosened material away. And the water causes frost erosion, when water in cracks freezes, it expands, as ice has a higher volume than water. As a result, the rock cracks and crumbles. It is quite obvious that the spring is responsible for the formation of a shelter, locally called a rock house, and the front part of this small cave was separated from the rear part by a collapse of the ceiling. This type of natural bridge is actually quite common.

The place is located on a dissected section of the Cumberland Plateau. Karstified limestone is covered by sandstone layers which form the plateau. The sandstone is the Warren Point Sandstone of Pennsylvanian age, which forms escarpments all around the Cumberland Plateau. The karst cave below is called Lost Cove Cave, and when it collapsed it formed a huge sinkhole. The sandstone obviously has an impermeable layer which creates a small aquifer, the water from the surface is dammed by the impermeable layer and flows on top of this layer to the next spring. Emerging from the spring, the brook flows across the small doline which was caused by the collapse of the erosional cave. So this is actually not a karst feature, it was created by mechanical weathering or erosion. Then it flows through the natural bridge and into the sinkhole, where it disappears into Lost Cove Cave. The water reappears as Crow Creek from Buggytop Cave, which is located in Mr. & Mrs. Harry Lee Carter State Natural Area, about 6 km to the south.