The yellow-red light of early twilight, few minutes after the sunset, illuminates the Grand Canyon. Note the blue-pink glow or antitwilight band that extends the horizon. The glow is separated from the horizon by a dark layer which is the shadow of Earth in the atmosphere. The higher red-pink band is due to back scattering of reddened light from the rising Sun and is named the Belt of Venus. 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.