The Grand Canyon lies in the southwestern portion of the Colorado Plateau, which occupies a large area of the southwestern United States and consists essentially of horizontal layered rocks and lava flows. The broad, intricately sculptured chasm of the canyon contains between its outer walls a multitude of imposing peaks, buttes, gorges, and ravines. It ranges in width from about 175 yards (160 metres) to 18 miles (29 km) and extends in a winding course from the mouth of the Paria River, near Lees Ferry and the northern boundary of Arizona with Utah, to Grand Wash Cliffs, near the Nevada state line, a distance of about 277 miles (446 km); the first portion of the canyon—from Lees Ferry to the confluence with the Little Colorado River—is called Marble Canyon. The Grand Canyon also includes many tributary side canyons and surrounding plateaus.
The greatest depths of the Grand Canyon lie more than a mile (some 6,000 feet [1,800 metres]) below its rim. The deepest and most spectacularly beautiful section, 56 miles (90 km) long, is within the central part of Grand Canyon National Park, which encompasses the river’s length from Lake Powell (formed by Glen Canyon Dam in 1963) to Lake Mead (formed by Hoover Dam in 1936). The North Rim, at approximately 8,200 feet (2,500 metres) above sea level, is some 1,200 feet (365 metres) higher than the South Rim. In its general colour, the Grand Canyon is red, but each stratum or group of strata has a distinctive hue—buff and gray, delicate green and pink, or, in its depths, brown, slate-gray, and violet.