General Information

The Grand Canyon is an exceptionally deep, steep-walled canyon in northwestern Arizona excavated by the Colorado River. The entire canyon is extremely beautiful, containing towering buttes, mesas, and valleys within its main gorge. Acclaimed as nature's greatest example of sculpture, a spectacular section of the canyon is preserved in the Grand Canyon National Park, which receives about four million visitors a year.

The Grand Canyon is about 446 km long, up to 29 km wide, and more than 1500 m deep. It cuts steeply through an arid plateau region that lies between about 1500 and 2700 m above sea level. The Kaibab Plateau, which forms the northern rim of the canyon, is about 365 m higher than the Coconino Plateau, which forms the southern rim. 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. 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.

Although other factors have also influenced its development, the downward cutting erosion of the Colorado River, which flows through the canyon’s lowest portions, has been the greatest force influencing the sculpture of the Grand Canyon. Jointing and faulting has broken nearly all the rocks from the canyon region. These fractures have contributed to the rapid erosion of the gorge.

The canyon extends in a winding course from the mouth of the Paria River, near the northern boundary of Arizona, to Grand Wash Cliffs, near Nevada. Grand Canyon National Park, covering 493,076 hectares, was first established in 1919. Its area was greatly enlarged in 1975 by the addition of adjoining lands so that it now extends from Lake Powell to Lake Mead.

The north and south rims of the canyon are connected by a paved road and by a trans-canyon trail. However, more traditional mule-pack trips and river rafting are popular ways of viewing and experiencing the beauty of the vast canyon.

Formation

The Grand Canyon is of relatively recent origin; apparently the river began its work of erosion about six million years ago. Coupled with the downward cutting of the river has been a general rising or upwarping of the Colorado Plateau, which has added its effect to the action of the river.

Although the canyon itself is of comparatively recent origin, the rocks exposed in its walls are not. Most of the strata were originally deposited as marine sediment, indicating that for long periods of time the canyon area was the floor of a shallow sea. In a typical section of the canyon, toward its eastern end, nine separate rock layers can be seen, dating back to the dawn of the Paleozoic Era, 570 million years ago. No other place on Earth compares with the mile-deep Grand Canyon for its record of geological events. Some of the canyon's rocks date back about 4 billion years.

Wildlife & Vegetation

There are magnificent forests on the north rim of the canyon where the soil is moist and deep. There are also drought-resistant plants, including numerous species of cactus. Vegetation along the valley walls consists principally of such desert plants as agave and Spanish bayonet. However, willow trees and cottonwoods can be found at the bottom of the canyon where there is plenty of water.

The canyon is also home to many types of squirrels, coyotes, foxes, deer, badgers, bobcats, rabbits, chipmunks, and kangaroo rats.

History

The first Europeans to see the canyon were members of a group headed by the Spanish explorer Francisco Vásquez de Coronado in 1540. However, because of the inaccessibility of the canyon, it was not until more than three centuries later that it was fully explored. Beginning about 1850, a series of expeditions commanded by officers of the United States Army surveyed the canyon and the surrounding area. In 1869, the American geologist John Wesley Powell and ten companions made the first difficult journey through the length of the gorge in four rowboats. To this day, his account remains a classic story of American travel.

Historical Development

The construction of the Glen Canyon Dam in Arizona in 1963 dramatically reduced the natural flow of sand and nutrients down the Colorado River and into the Grand Canyon. In March 1996 the federal government released more than 380 billion liters of water from Glen Canyon Dam. This artificial flood added more than three feet to some beaches and cleared fish spawning grounds of debris and sediment.