COLORADO RIVER, or COLORADO OF THE WEST, a great river of the United States and Mexico, formed at about lat. 38° N. and long. 110° W., by the junction of the Green and Grand rivers. The Green River rises in the RocIcy Mountains in the west of Wyom ing, receiving in its southwestern course the waters of the Bear, the White, the Uintah and San Rafael. From Flaming Gorge, a point in the northwest of Colorado, where the Uintah Mountains rise, the Green River cleaves its way rapidly through canyons, the walls of which tower up to a height of nearly 1,500 feet. The Grand River rises in the RocIcy Mountains, west of Denver, Colo., receiving in its south western course the South Fork or Gunnison, the San Miguel and Dolores. After the junc tion the Colorado flows southwest through Utah, joined on the east by the San Juan, on the west by the Dirty Devil and Escalante; southwest through the north of Arizona, till its waters are increased by the Colorado Chiquito, or Little Colorado of Arizona. Near the in flow of this tributary is the Marble Canyon, 3,600 feet deep and about rone-third the length of the greater canyon below.
From the mouth of the Little Colorado the river bends west and for inore than 200 miles flows through the wonderful Grand Canyon. The successive divisions of the canyon are known as the Kaibab section, the ICanab sec tion, the Uinlcaret section and the Sheavwitz section. The walls of this water-worn trench are often vertical, or nearly so, for a distance of thousands of feet at a time; sometimes they slope steeply, or constitute magnificent terraces. The cliffs or rock-walls attain a height of from 4,000 to 7,000 feet above the stream. (For heights of particular points, see CANYON). There are frequent whirlpools and waterfalls. Below the canyon the valley opens, and there is much fertile bottom-land on one or both sides of the river. Numerous tributaries pierce the high plateau on either side, the whole present ing a strangely intersected topography. Escap ing from the Grand Canyon, the river flows southwest to the borders of Nevada, receiving from the west the Paria, Tapeat, the Kanat (of Arizona) and the Virgen (of Nevada).
Above Callville, Nev., the Colorado, with its tributaries, again bores its way through deep canyons, the sides of which, in some places, present walls of solid rock nearly 7,000 feet high. The plateaus at the top of these rock masses, generally treeless, are again surmounted by terraces 1,000 feet or more high. These lower and higher terraces are both piled with mas sive ruins, once the walled towns and cities of a race said to be represented by the present Moqui Indians in the northeast of Arizona and the Nahuas of Mexico. Below Callville the river is again shut in by the last of the canyons, the Black Canyon, 25 miles long, and from 1,000 to 1,500 feet high. Shortly after re ceiving the Virgen, the Colorado talces a southerly course, severing Anzona and Sonora on the east from Nevada, California and Lower California on the west, and receiving on the east Bill Williams' Fork and the Gila. After
absorbing the latter the river sweeps round in a westerly direction for 7 or 8 miles, and soon expands to a width of 1,200 feet. Thence it pursues a tortuous course of 180 miles, the last portion being through Mexican territory, to its mouth in the Gulf of California. There is a vast delta or flood plain formed by the waste from rock erosion. From the sources of the Green River the Colorado measures a total length of about 2,000 miles. It is navigable for steamers as far as Callville, 612 miles from its mouth, and can be made so, it is thought, to the foot of the Grand Canyon, 57 miles higher. The first attempt to navigate the upper part of the Colorado was made in 1891. In 1893 the stream was proved navigable for 130 miles between Green River and Cataract Canyon.
The investigation of geologists dispelled the theory once held that the Grand Canyon was a fracture of the earth's crust. It is now clear that a long period of erosion through plateaus successively uplifted has produced this remark able gorge. At the bottom of the canyon throughout a considerable part of its course the Archaean system is laid bare. The Algonkian beds with their high coloring give brilliancy to that portion of the canyon where they can be traced. The Cambrian beds are found above the Algonkian, but in places rest directly on the Archanan. The.thickness of the Cambrian (here known as the Tonto formation) is in places 1,000 feet. The upper part of the cation walls consists of carboniferous formations (Red Wall formation below, Aubrey limestone and sandstone above). It has been estimated that all the Eocene, Cretaceous, Jurassic and per haps Triassic beds and the greater part of the Permian were worn away from the plateau region during the period of erosion. The Marble Canyon platform, like that of the Grand Canyon, consists of carboniferous strata with a considerable number of Permian remnants scat tered over it.
In 1540 the Colorado was visited by a de tachment of Coronado's expedition and another of his exploring parties gave the first descrip tion of the Grand Canyon as seen by white men. About the same time Fernando Alarcon as cended the stream in boats for a long distance. Catholic missionaries subsequently traveled through these regions. For about 300 years, nothing more was learned concerning the Col orado. Much light was thrown on the subject by the investigations of Ives in 1858. In 1869 Powell explored the region and made the descent through the whole course of canyons to the mouth of the Rio Virgen, a distance of more than 1,000 miles. Dutton made geological studies of the Grand Canyon in 1875. In 1889 the canyons were explored by a party of en gineers sent out to make surveys.
Powell, 'Exploration of the Colorado River) (1875) ; David, W. M., (An Expedition to the Grand Carlon of the Col
; Dutton,