Читать книгу Wealth of the World's Waste Places and Oceania - Jewett C. Gilson - Страница 13

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Nowhere else on the face of the globe is one so vividly impressed by the vastness of the work of corrasion as in the northwestern part of Arizona. Here the mutilated breast of Mother Earth discloses a chasm from three thousand feet to seven thousand feet deep, cut through horizontal strata of sandstone, shale, limestone, and granite, chiefly by the agency of water.

This stupendous chasm is the Grand Canyon of the Colorado River. It is more than two hundred miles long; and from rim to rim its walls measure in places twenty miles across. It is not a clean-cut open channel from wall to wall, but, on the contrary, it is filled with castellated peaks, buttes, pinnacles, ridges, seams, and lesser canyons. Down deep in its lowest part, hurrying onward with impetuous speed, is the river itself.

Geologists tell us that this stream was an ancient river before the Mississippi was born and that it formerly watered a valley as fertile.

Ages ago when Time was young the river found its channel closed by an obstruction—just how, or where, or by what, no one knows. So it spread out into a great lake, or, perhaps, into an inland sea several thousand feet deep. The rock waste carried into its basin hardened into sandstone—red, pink, and white of many shades.

After this great inland sea had become dry the Colorado River was born—just how, or when, or because of what, one can only guess. But when it was born it began to undo what its predecessor had done. It cut a channel in the surface of the sandstone and then began business in earnest. It loosened little pieces of sharp flint from the sandstone and swept them along with such force that each became a tiny mallet and chisel combined to cut and carry away other rock. And so it kept on until it had carved a passage not only to the original granite bed rock but in places a thousand feet or more into it. A few localities excepted, the canyon does not form a single gash; nor has it the usual V-shape of canyons in regions of plentiful rainfall. On the contrary, its cross-section takes the form of a succession of steps and terraces, as though the river cut the channels successively in decreasing widths. And because the region through which it flows is one of very slight rainfall, all the landscape outlines are bold and sharply angular.

All told, an area comprising two hundred thousand square miles has been denuded to the depth of six hundred feet, and the material borne southward by the Colorado and its tributaries, while the land through which they flow has been literally drained to death. Even the tributaries have formed deep lateral canyons that meet the level of the main stream. It staggers the mind to try to grasp the time expressed in countless eons since the youth of this now senile river.

The Grand Canyon of the Colorado LINK TO IMAGE

As early as 1540 Spanish explorers made known to the world the fact that a deep and impassable gorge existed in one part of the Colorado River, and again in 1776 a Spanish priest revived a knowledge of its existence.

Then, for many years afterward, the canyon claimed but little attention because it was so difficult of access, and so little was known of its colossal dimensions and the marvellous carvings within its walls.

Just above the Grand Canyon and continuous with it is Marble Canyon, so called because of the immense beds of marble that form a part of its walls. In both canyons the limestone sometimes takes the form of marble, or gypsum, or alabaster—crystallized forms of limestone which take a fine polish.

This remarkable river with its canyons was first explored by Major Powell in 1869. With nine men and four boats he started from a landing on Green River in Utah, floated down Green River to its junction with the Grand, and thence down the Colorado below the mouth of the Virgin to the Grand Wash. There he landed after having passed through the entire length of the canyon.

The time spent in this voyage was ninety-eight days, and the distance travelled was upward of one thousand miles. Four of his men left him when the voyage was but partly finished, being frightened by the perils that beset them. They were killed by Indians. The others, after many accidents and hair-breadth escapes, succeeded in getting through in safety.

In addition to the rapidity of the current the river has many rapids and water-falls with jagged projecting rocks which make boating extremely hazardous. All these perils were conjectured but unknown to Major Powell's party, and every new bend of the river was liable to disclose a cataract more dangerous than any encountered before. Then the reverberating sound of the roaring river as it struck the sides of its lofty prison walls together with the deep gloom of the mighty abyss was calculated to terrify the bravest. Thus, facing death at every turn of the stream, the men were kept constantly in a tense state of excitement.

A wealth of adjectives has been expended in attempting properly to describe the immensity of this great handiwork of nature, and scores of persons have produced fascinating word-paintings of its awe-inspiring grandeur.

Leading back from the river the canyon walls are made up in part of shelving rocks and terraces. These, with peaks, buttes, and myriads of other structures arising from the great gulf, show plainly the different strata of rocks of which they are composed. Many of these rocks are richly colored; the tints as a rule result from the salts of iron and other mineral matter disseminated through them. In some instances the coloring material of the upper strata has been washed down by the storms and has stained the rock of the walls below. This is the case in the Grand Canyon, where the limestone wall is colored red by the iron in an overlying stratum.

When the gigantic forms partly filling the chasm, yet standing apart from each other, are seen near sunrise or sunset with their shifting shadows, they leave on the mind remembrances that will never fade.

To appreciate properly the magnitude and height of these towering masses one should examine them not only by travelling along the brink, but by descending to the river level in order to examine them from below. Then only will the awful grandeur and immensity of this monumental architecture of nature begin to dawn upon the understanding.

To the geologist this chasm is an intensely interesting book which reveals much of the history of the past in world-building.

Some years ago a company was formed in New York to build a scenic railroad through Marble and Grand Canyons. Engineers were sent out not only to make a careful survey of the canyons but also to make a series of photographs which should form a continuous panoramic view of the proposed route. A large sum of money was spent in making the surveys; then the project was abandoned. Possibly at some future time the scheme may be revived and a road be built, using as its motive power electricity generated by the river itself.

The Grand Canyon is now easily reached by the Santa Fé Railway system. From the main line at Williams a branch road extends to El Tovar, Grand Canyon station, which is located near the edge of the canyon. The descent to the bottom of the canyon can be made by several trails. Those noted for easy descent and the best views are Grand View and Red Canyon Trails from Grand View, Bright Angel Trail from El Tovar, and Bass Trail from Bass Camp. Each has its own special charms, and for one limited as to time it is difficult to make a choice.

The course of the Colorado and its tributary, Green River, presents some interesting problems. The latter has cut its channel directly across the Uinta Mountains, and the Colorado has sawed its channel to the base level of a series of plateaus, sometimes called the Sierra Abajo. And the interesting problem is—how was the sawing process accomplished? It needs only a moment's thought to understand that the river could not flow against the base of a mountain range and bore a passage through it, much less clear out an open passage miles in width.

Grand View Trail Looking toward Apache Point from Mystic Spring Plateau. The Grand Canyon of the Colorado LINK TO IMAGE

Major Powell has shown how this mighty work of mountain cutting was accomplished; the sawing process was begun, not at the base of the range, but at its top. It is merely a question of age. The Colorado and its chief tributaries are older than the mountain uplifts which they have severed. Moreover, the level of their channels is much the same now as it was before the mountains were born.

The mountain levels, however, have been changing ever since their uplift began. And when the rock layers of which they are composed began to be pushed upward the uplift was so slow that the rivers cut downward just as rapidly. In time the ranges were pushed upward to their present height; but when the uplift was completed, in each case it was sawed to the bottom by the river. It is in very much the same manner that a huge log is cut in twain as it is pushed against the saw. The mountain range, as it is pushed upward, represents the log; the river, which is stationary, represents the saw.

One might look a long way to find the wealth created by this muddy torrent. But the wealth is there, though it is certainly a long way from the canyon; moreover, the rock waste itself is the wealth, and great wealth it is. The water of the river is very muddy. Dip up a bucket filled to the brim and allow it to stand for ten or twelve hours. There is an inch or two of clear water at the top, while at the bottom there is a thick, muddy paste of sand, clay, and red earth. All this rock waste the current is sweeping along to the Gulf of California.

Every overflow along the banks of its lower course spreads this rich, nutritious rock waste over the flood plain. Imperial Valley is filled with it; and this, together with the flood plain above and below, constitutes an area of productive land about as large as the State of Illinois. Moreover, the area is constantly increasing, because of the enormous amount of rock waste which the river daily bears to the Gulf of California. In time, a long time as years are measured, the gulf will be entirely filled—and what a valley of prairie land there will be.