Comparison With Other Types of Natural Bridges
Most of the natural bridges of the United States are in the Four Corners region of the Southwest where favorable materials and conditions for bridge-making are to be found. There are two other types of bridges which are entirely dissimilar. Tonto Natural Bridge, in central Arizona, is a “built-up” bridge created by travertine deposited by springs. Natural Bridge, in Virginia—another well-known bridge—apparently was formed when most of the roof of a cavern collapsed.