How was rainbow bridge formed?

Rainbow Bridge National Monument's history stretches over millions of years. Some 280 million years ago, the area that is now the monument was just sand dunes, mud flats, and a shallow inland sea. Over time, these sands and mud became sandstone and limestone.

Some 130 million years ago the earth rumbled and stretched, forming canyons and upthrusting mesas with the Navajo, Wingate, and Kayenta rock formations. Then the Colorado River came along, carving away the softer layers and leaving the harder rock formations standing.

Erosion continues to shape the landscape today.