Natural Bridge, Virginia
This towering structure is found in the mountains of western Virginia; the arch stands over 60 meters high and the rock is strong enough to support the weight of a road that now sits on top.
The rocks at this site are Ordovician-aged dolomites, formed in shallow seas off the coast of Laurentia after the previous supercontinent broke up and before the assembly of Pangaea. Limestone can erode fairly rapidly when exposed to the natural acidity of rainwater, enabling the growth of caves and valleys. Today only tiny Cedar Creek flows through this arch, but in the past it is thought that a larger creek, Cascade Creek, flowed through this site either through a crack in the limestone or through a cave that has since mostly collapsed. The flow of the larger creek eventually diverted once another nearby stream captured most of the water.
This site was a landmark in the Eastern United States throughout the first 100 years of its history. The 3rd United States President, Thomas Jefferson, purchased this land and built a guest retreat near the site. Many early presidents and other government figures spent nights near here. In 2016, this land was officially added as a Virginia State Park.
-JBB
Image credit: Virginia Parks https://flic.kr/p/MCGGAY
References: https://www.dmme.virginia.gov/commercedocs/RI_13.pdf http://www.naturalbridgeva.com/recreation/bridge-history/