This edited article about the Grand Canyon originally appeared in Look and Learn issue number 727 published on 20 December 1975.
The Grand Canyon presents one of the most breath-taking scenes of natural beauty in the world. The sides of this jagged gash in the Earth’s surface are sheer precipices, and its rims are crowned with peaks and straight-sided buttes, once joined but now separated by ravines and minor canyons.
At the foot of the canyon, some 7,000 feet (2,133 m) below, flows the Colorado River, winding its way through 217 miles (349 km) of this famous gorge.
In the Grand Canyon the rock formations are laid bare on a scale not seen anywhere else. Layer by layer, they give a striking picture of the way the Earth’s crust has been built up. The colours of the rock strata vary from sombre grey and brown to red, yellow, pink and mauve. Seen in the light of dawn, or at sunset, they provide a brilliant spectacle.
It was probably ten million years ago that the stream that was to become the Colorado first began to flow across this tableland in north-west Arizona. As it did so, the rock on either side was being slowly pushed upwards by subterranean forces. This upthrust increased the rate at which the river cut into the surface. In effect, the river maintained its level, while the land rose on each side.
The process was a very slow one. The river-bed deepened by less than an inch (25 mm.) in 100 years. Meanwhile erosion attacked the upper layers of the rising plateau. Gradually it turned them into the fantastic shapes that appear today.
Some of the rock strata have yielded fossil evidence of prehistoric life. Mostly this is of a very primitive kind, dating from periods when all creatures lived underwater. Plant-life traces range from simple algae to extinct trees.
To descend from the rim of the canyon to the river level is to pass from one climate to another. In the bed of the gorge, temperature, conditions and vegetation are like those of a tropical desert region. The loftier parts of the North Rim, which is up to 2,000 feet (600 m) higher than the south side, has the climate and vegetation of sub-arctic forest land, and is snow-covered in winter.
The gorge is such an impassable barrier that animal life on both sides have developed separately. Where the same species exist, they have in some cases evolved quite separate varieties. For example, the South Rim has grey-tailed squirrels, while those on the north side have white tails. Even the rattlesnakes show differences.
First to navigate the gorge was Major John Wesley Powell, in 1869. He set off downstream with four rowboats and nine men. Ninety-eight days later he emerged from the canyon with two boats and only six men. Three had refused to face the perils of the Wash Cliff rapids at the foot of the gorge, and had set off overland – only to be killed by Indians.
Those rapids are now covered by the waters of Lake Mead, the stretch of water created by the building of the Hoover Dam, which provides irrigation and hydro-electric power over a wide area. In recent years, the voyage down the river, by inflatable raft or power-boat, has become almost an everyday feat.
Tourists can reach the bottom of the gorge by mule trail. The most popular of these is the Bright Angel trail, leading down from the South Rim by way of a natural fault in the rock. The canyon varies in overall width from four to 12 miles (6 to 20 km); but the river gorge itself can be spanned by a suspension bridge, 440 feet (134 m) long, and just wide enough for a mule to cross.
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