Map of Colorado Plateau

Map of southern Utah showing the Colorado Plateau, before the Glen Canyon Dam was built.

This region is one of the world’s premier natural showcases for Earth history. Encompassing 240,000 square miles (386,242 km), the Colorado Plateau straddles the region known as The Four Corners, where the states of Arizona, Utah, Colorado, and New Mexico meet. Ancient volcanic mountains, plateaus and buttes, deeply carved canyons, and amazing ranges in color are the region’s defining characteristics. Elevation for the Colorado Plateaus starts at about 610 m (2,000 ft) above sea level, with plateau tops ranging from 1,534 to 2,134 m (5,000 to 7,000 ft) and mountaintops reaching nearly 3,960 m (13,000 ft).

Ancient Precambrian rocks, exposed only in the deepest canyons, make up the basement of the Colorado Plateau. Igneous rocks injected millions of years later form a marbled network through parts of the Colorado Plateaus’ darker metamorphic basement. These rocks formed deep beneath the surface of the earth and were uplifted, eroded, and exposed for eons. By 600 million years ago North America had been eroded to a remarkably smooth surface. It is on this crystalline rock surface that the younger, more familiar layered rocks of the Colorado Plateaus were deposited.