The Western United States: A Geographical Reader. Harold W. Fairbanks
The water which reaches the borders of the plateau from the surrounding mountains often sinks into the gravel between the layers of lava and forms underground rivers. The deep cañons which have been mentioned intercept some of these underground rivers, so that their waters pour out and down over the sides of the cañons in foaming cascades. The greatest of these cascades is that known as the Thousand Springs in the Snake River cañon. The waters of the Blue Lakes in the cañon of the same river below Shoshone Falls also come from underneath the lava. They are utilized in irrigating the most picturesque fruit ranch in southern Idaho.
Eroded in the Columbia plateau
The climate of the plateau is dry, and its eastern portion is practically a desert. Toward the west, however, the rainfall is greater, and in central Washington and northern Oregon the plateau becomes one vast grain-field. It is difficult to irrigate the plateau because the streams flow in such deep cañons, but above the point where the cañon of the Snake River begins there is an extensive system of canals and cultivated fields. With a sufficient water supply, the lava makes one of the richest and most productive of soils. Along the Snake and Columbia rivers, wherever there is a bit of bottom land, orchards have been planted. Little steamers ply along these rivers between the rapids, gathering the fruit and delivering it at the nearest railroad point.
Mining is carried on only in the mountains which rise above the lava flood, for the mineral veins are for the most part older than the lava of the plateau. We are certain that many very valuable deposits of the precious metals lie buried beneath the lava fields.
It is thought that the volcanic history of the Columbia plateau has been completed. Now the streams are at work carrying away the materials of which it is composed and may in time uncover the old buried land surface.
THE CAÑONS OF THE SIERRA NEVADA MOUNTAINS
The western half of our country contains the deepest and most picturesque cañons in the world. Those of the Colorado and Snake rivers form trenches in a comparatively level but lofty plateau region. The cañons of the Sierra Nevada Range, on the contrary, take their rise and extend for much of their length among rugged snowcapped peaks which include some of the highest mountains in the United States. All these cañons are the work of erosion. The rivers did not find depressions formed ready for them to occupy, but had to excavate their channels by the slow process of grinding away the solid rock.
The streams of the Sierra Nevada mountains begin their course in steep-walled alcoves under the shadows of the high peaks, where they are fed by perpetual snow-banks. Soon they bury themselves between granite walls, which at last tower three thousand feet above their roaring waters. After many miles the cañons widen, the walls decrease in height, and the streams come out upon the fertile stretches of the Great Valley of California.
Nature works in many ways. Her tools are of different kinds, but the most important one is running water. The forms which she produces are dependent upon the kind of rock upon which she works. Where the surface of the earth is soft the results of her labor are not very interesting, but if the crust is hard the forms which she produces are often so remarkable that they arouse our wonder and admiration.
In shaping the Sierra Nevada mountains Nature had a grand opportunity. Here she produced the Yosemite Valley, which has a setting of cliffs and waterfalls that attract people from all over the world. Hetch-Hetchy Valley at the north of the Yosemite, and Tehipite and King's River cañons at the south, are interesting places, but not so majestic and inspiring as the Yosemite.
Nature never seems satisfied with her work. After she has created a piece of wonderful scenery she proceeds to destroy it. The great cliffs of the Yosemite will sometime lose their grandeur and be replaced by gentle slopes down which the streams will flow quietly. The mountains of the Laurentian highlands in the northeastern portion of the continent undoubtedly were once lofty and picturesque, but there were no people upon the earth at that time to enjoy this scenery. Now these mountains have become old and are nearly worn down.
The head of the King's River
In one portion of the earth after another, Nature raises great mountain ranges and immediately proceeds to remove them. This continent was discovered and California was settled at the right time for the Sierra Nevadas to be seen in all their grandeur.
When the pioneers came in sight of the Sierra Nevada (snowy range), they little dreamed of the cañons hidden among these mountains. Gold, and not scenery, was the object of their search. The great cañons were outside of the gold regions, and so inaccessibly situated that no one except the Indians looked upon them until 1851. In that year a party of soldiers following the trail of some thieving Indians discovered and entered the Yosemite Valley, but it was not explored until 1855. For many years the valley could be reached only by the roughest trails, but as its advantages became more widely known roads were built, and there are now three different wagon routes by which it may be entered.
The history of the Yosemite Valley is like that of all the other cañons of the Sierra Nevada mountains. Long ago there were no high mountains in eastern California. If there had been explorers crossing the plains in those days, they would have found no rugged wall shutting them off from the Pacific. There came a time, however, when the surface of the western portion of America was broken by violent earthquake movements, and hundreds of fissures were formed. Some of the earth blocks produced by these fissures were shoved upward, while others were dropped. One enormous block, which was to form the Sierra Nevada, was raised along its eastern edge until it stood several thousand feet above the adjoining country. The movement was like that of a trap-door opened slightly, so that upon one side—in this case the western one—the slope was long and gentle, while upon the east it was very abrupt.
Nature, the sculptor, took this mountain block in hand, and with the aid of running water began to carve its surface into a most intricate system of cañons and ridges. The streams first flowed over the easiest slopes to the Great Valley of California, but soon they began to cut their way down into the granite, while along the crests of the ridges the more resistant rocks began to stand out as jagged peaks.
Thus Nature worked until the mountains promised before long to be well worn down. The cañons had widened to valleys and the rugged slopes had given place to gentle ones. Toward the northern end of the range the work was even farther advanced, for the streams, now choked with gravel and sand, flowed over broad flood plains. In this gravel was buried a part of the wealth of California. The rocks over which the streams flowed contained veins of quartz with little particles of gold scattered through it, and as the surface rock crumbled and was worn away, the gold, being much heavier, slowly accumulated in the gravel at the bottom of the streams. This gold amounted in value to hundreds of millions of dollars.
The forces within the earth became active again. Apparently Nature did not intend that the gold should be forever buried, or that the country should always appear so uninteresting. Internal forces raised the mountain block for a second time, tilting it still more to the westward. Volcanoes broke forth along the summit of the range near the line of fracture, and floods of lava and volcanic mud ran down the slopes, completely filling the broad valleys of the northern Sierras and burying a great part of the gold-bearing gravel.
The eruptions turned the streams from their channels, but on the steeper slope of the mountains the rivers