The Grand Canyon, located in northern Arizona, is a gorge formed by the downward erosion of the Colorado River during several million of years. The sideward erosion is the result of other natural forces like rain, snow and wind. The Grand Canyon is 277 miles (445 km) long, 1 mile (1.6 km) deep and, on average, 10 miles (16 km) wide. The oldest layers of exposed rock at the bottom of the gorge dates from 2,000 million years ago.