The Grand Canyon is an exceptionally deep, steep-walled canyon in northwestern Arizona, excavated by the Colorado River. The Grand Canyon is 446 km (277 mi) long, up to 29 km (18 mi) wide, and more than 1,500 m (5,000 ft) deep.
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The Grand Canyon. Video hosted on Google. The entire canyon is extremely beautiful, containing towering buttes, mesas, and valleys within its main gorge. A spectacular section of the canyon, together with plateau areas on either side of it, are preserved as the Grand Canyon National Park, which receives about four million visitors a year. The Grand Canyon cuts steeply through an arid plateau region that lies between about 1,500 and 2,700 m (about 5,000 and 9,000 ft) above sea level. This region, although lacking year-round streams in recent years, is sharply eroded, showing such characteristic forms as buttes; it is interspersed with old lava flows, hills composed of volcanic debris, and intrusions of igneous rock. The plateau area has a general downward slope to the southwest and in its upper reaches is sparsely covered with such evergreens as juniper and piñon. Parts of the northern rim of the canyon are forested. Vegetation in the depths of the valley consists principally of such desert plants as agave and Spanish bayonet. In general the entire canyon area has little soil. The climate of the plateau region above the canyon is severe, with extremes of both heat and cold. The canyon floor also becomes extremely hot in summer, but seldom experiences frost in the wintertime.
The Grand Canyon has been sculpted in general by the Colorado River, which now flows through the canyon’s lowest portions more than 1,500 m (more than 5,000 ft) below the canyon’s rim. About 6 million years ago the river began its work of erosion, gradually cutting through the numerous rock layers of the Colorado Plateau. The geologic uplifting that formed the Colorado Plateau and the Rocky Mountains also tilted the land. This tilting amplified gravitational forces, adding to the river’s erosion power as it rushed along its course from high in the mountains of present-day Wyoming to the Gulf of California (an arm of the Pacific Ocean). Other factors have also played a part in the formation of the canyon. The Kaibab Plateau, which forms the northern canyon rim, is about 365 m (about 1,200 ft) higher than the Coconino Plateau, which forms the southern rim. Water from the northern side has flowed into the canyon, forming tributary valleys, while the streams of the southern plateau flow away in a southerly direction without carving valleys in the canyon walls. The underlying rock beds also have a southwestern slant, with the result that groundwater from the north finds its way into the canyon, but water from the south does not. In the entire canyon region, the rocks have been broken by jointing and faulting, and fractures in the rocks resulting from these processes have contributed to the relatively rapid erosion of the gorge.
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