Natural Tunnel State Park

Natural Tunnel State Park is a state park in the U.S. state of Virginia. It is named after the Natural Tunnel, a large natural cave. The tunnel is so big that a railroad goes through it. The park is in the Appalachian Mountains, near the town of Duffield in Scott County. The Natural Tunnel is 200 feet (61 meters) wide and 80 feet (24 meters) high. It began forming more than one million years ago. Rainwater mixed with carbonic acid went into small cracks in the rock. This water slowly dissolved limestone and dolomite, two types of rock. Over time, a small river—now called Stock Creek—went underground. It kept cutting through the rock and helped make the tunnel bigger. The walls of the tunnel show signs of very old life. Many fossils have been found in the creek and in the tunnel walls. References