The yellow-red light of early twilight, few minutes after the sunset, illuminates the Grand Canyon, and the blue band of rising Earth shadow appears over the east. The first quarter moon is visible on the upper right. The Grand Canyon in northern Arizona 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 or about a mile.