National Park Service's World Heritage Sites: Grand Canyon National Park, Arizona

The Grand Canyon is among the earth's greatest on-going geological spectacles. Its vastness is stunning, and the evidence it reveals about the earth's history is invaluable. About 65 million years ago in the earth's shifting, a huge area of land was lifted a mile and a half above sea level, forming what is now the Colorado Plateau. For the last 5-6 million years, the Colorado River has been slowly carving its way down through the many layers of rock. The river and its tributaries, together with the erosive forces of rain, snow, heat and cold, have formed a spectacular gorge one-mile deep and at some points 18 miles across. The colorful strata of the canyon walls reveal the rock formations of the earth's evolution from nearly 2 billion years ago. The river continues to carve into the earth's surface.