How Did It Happen?

How Did It Happen?. . , At 200 feet tall, the Natural Bridge is estimated to weigh 36,000 tons - as much as 2,500 school buses! How does something like this come about? The answer is in the limestone all around you., Most of the rock in and under the park is limestone. Limestone slowly dissolves when in contact with carbonic acid, which is made when water and carbon dioxide mix. Places underlain by limestone may contain caves, underground rivers, and sinkholes because wherever carbonic acid forms it wears away this type of rock., Around one million years ago, Cedar Creek was swallowed by a sinkhole that turned it into an underground river. It eventually reached the James River by means of a cave that slowly developed through the limestone deposit you are standing in now. The forces at work were small, but on the grand scale of several hundred thousand years, they carved out the walls around you., This Cedar Creek-made cave collapsed, leaving the Natural Bridge standing at the narrowest point in the chasm., (Sidebar):, Measuring Up, Taller than the Statue of Liberty (151 feet tall without her base) and Niagara Falls (167 feet tall), Natural Bridge is the tallest limestone arch in all of North America. That is less than half as tall as the Washington Monument (555 feet tall), but the rock formation before you is still nearly 19 stories tall!