Night in a Dark Canyon

At the bottom of the Grand Canyon, the Colorado River dimly appears by light reflected from the moonlit walls of the canyon. Grand Canyon is the longest canyon on the Earth, a steep-sided gorge carved by the Colorado River steadily in about 17 million year time span. The canyon is 446 km long, ranges in width from about 6 to 29 km and attains a depth of more than 1.6 km (a mile).