Valley and Ridge Physiography Topics

1. Regional Setting
2. Extent and Boundaries
3. Characteristic Features
4. Drainage
5. Scenic Tour
• Introduction to Physiography
• Coastal Plain
• Piedmont
• Mesozoic Basins
• Blue Ridge
• Valley and Ridge
• Appalachian Plateaus
• Virginia's Rivers

 

Scenic Tour of the Valley and Ridge (Part 3)

Natural Bridge

• Natural Bridge is located in the Valley and Ridge of southern Rockbridge County.  This famous western Virginia landmark was surveyed by George Washington and owned by Thomas Jefferson.

Natural Bridge, the “eighth wonder of the world.” Actually, arches like Natural Bridge are found in karst areas throughout the world. Image on the right shows an early drawing of Natural Bridge. (Photograph by Robert Whisonant; Drawing courtesy of Royster Lyle, Jr.)

• The bridge is a 200-foot-high stone arch formed in dolomite of the Ordovician
505 to 438 million years ago
Beekmantown Formation. The bridge formed when the roof of most of a cavern system collapsed, leaving the single surviving arch we call Natural Bridge.

Natural Bridge is part of an ancient cave system. Cedar Creek flowed along the floor of the cave. The cave roof eroded away except for the stronger rock in the Natural Bridge arch. The arch probably survived because of the presence of thick, flat-lying dolomite beds. (Photograph by Lori Combs)

















• Natural Bridge continues to erode, especially along the many fractures and bedding planes in the rock. Eventually, the arch itself will collapse.

The fate of Natural Bridge is to disappear. Pieces of the bridge are broken loose by freeezing and thawing water and other forces. Eventually, Natural Bridge will disappear. (Photograph by Karen Cecil)


















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