The Western United States Part 2

[Footnote 2: _lapilli_, volcanic ashes, consisting of small, angular, stony fragments.]

[Ill.u.s.tration: FIG. 9.--PITT RIVER CAnON, NORTHERN CALIFORNIA

The plateau is built of layers of lava]

The volcanoes at last ceased to grow any higher, for the lava, if the eruptions continued, formed new craters at their bases.

It is probable that all these great peaks have been extinct for several thousand years, although some are much older and more worn away than others. One of these volcanoes has completely disappeared, and in its place lies that wonderful sheet of water known as Crater Lake. It is thought that the interior of this mountain was melted away during a period of activity, and that the outer portion fell in, leaving a crater five miles across and nearly a mile deep.

The streams of lava, as they flowed here and there building up the plateau, frequently broke up the rivers and turned them into new channels. As time went on the eruptions were less violent, and the rivers became established in the channels which they occupy to-day. The Columbia River, winding about over the plateau, sought the easiest path to the sea. It soon began to dig a channel, and now has hidden itself between dark walls of lava.

But other forces besides the streams were now at work in this volcanic region. The lava plateau began slowly to bend upward along the line of the great volcanoes, lifting them upward with it. In this manner the Cascade Range was formed. The Columbia River, instead of seeking another way to the sea, continued cutting its channel deeper and deeper into the growing mountain range, and so has given us that picturesque canon which forms a most convenient highway from the interior of Was.h.i.+ngton and Oregon to the coast.

Take a sheet of writing paper, lay it upon an even surface, then slowly push the opposite edges toward each other. This simple experiment will aid one in understanding one of the ways in which mountain ranges are made. Besides the upward fold of the plateau which made the Cascade Range, another was formed between the Blue Mountains in eastern Oregon and a spur of the Rocky Mountains in northern Idaho. This fold lay across the path of the Snake River, but its movement was so slow that the river kept its former channel and in this rising land excavated a canon which to-day is more than a mile deep. The upper twenty-five hundred feet of the canon are cut into the lava of the plateau, and the lower three thousand into the underlying granite. The canon is not so picturesque as the Colorado, for it has no rocks with variegated coloring or castellated walls. Its sides are, however, exceedingly precipitous and it is difficult to enter.

[Ill.u.s.tration: FIG. 10.--SHOSHONE FALLS, SNAKE RIVER, IDAHO]

Along portions of the lower Columbia and Snake rivers, navigation is obstructed by rapids and waterfalls. The presence of these falls teaches us that these streams are still at work cutting their channels deeper. The Snake River in its upper course has as yet cut only a very shallow channel in the hard lava, and the beautiful Shoshone Falls marks a point where its work is slow. These falls, which are the finest in the northwest, owe their existence to the fact that at this particular spot layers of strong resistant lava cover the softer rocks.

There are other canons in the plateau region which are fully as remarkable as those which have been mentioned. That of the Des Chutes River in central Oregon is in places a thousand feet deep, with almost vertical walls of lava.

We have already seen how mountains have been formed upon the Columbia plateau, by a bending of the earth upward. Other mountains of the plateau are due to fractures in the solid rocks, often many miles long. Upon one side of these fractures the surface has been depressed, while upon the other it has been raised. The amount of the uplift varies from a few hundred to thousands of feet. The mountains thus formed have a long, gentle slope upon one side and a very steep incline upon the other. They are known as "block mountains," and those upon the Columbia plateau are the most interesting of their kind in the world.

With the exception of a few large rivers, the greater portion of the Columbia plateau is remarkable for its lack of surface streams. 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 canons which have been mentioned intercept some of these underground rivers, so that their waters pour out and down over the sides of the canons in foaming cascades.

The greatest of these cascades is that known as the Thousand Springs in the Snake River canon. The waters of the Blue Lakes in the canon 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.

[Ill.u.s.tration: FIG. 11.--CAnON OF CROOKED RIVER NEAR THE DES CHUTES RIVER

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 Was.h.i.+ngton and northern Oregon the plateau becomes one vast grain-field. It is difficult to irrigate the plateau because the streams flow in such deep canons, but above the point where the canon of the Snake River begins there is an extensive system of ca.n.a.ls 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 CAnONS OF THE SIERRA NEVADA MOUNTAINS

The western half of our country contains the deepest and most picturesque canons in the world. Those of the Colorado and Snake rivers form trenches in a comparatively level but lofty plateau region. The canons 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 canons 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 canons 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.

[Ill.u.s.tration: FIG. 12.--SAN JOAQUIN RIVER EMERGING UPON THE PLAIN OF THE GREAT VALLEY]

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 canons 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.

[Ill.u.s.tration: FIG. 13.--WHERE THE CAnONS BEGIN UNDER PRECIPITOUS PEAKS

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 canons hidden among these mountains.

Gold, and not scenery, was the object of their search. The great canons 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 canons 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.

[Ill.u.s.tration: FIG. 14.--THE YOSEMITE VALLEY]

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 canons 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 canons 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 acc.u.mulated 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 went energetically to work making new beds. They cut down through the lava and the buried gravel until they finally reached the solid rock underneath. Into this rock, which we call "bed-rock," they have now worn canons two thousand feet deep. The beds of gravel that lay under the old streams frequently form the tops of the hills between these deep canons. Here they are easily accessible to the miners, who by tunnels or surface workings have taken out many millions of dollars' worth of gold.

The important canons of the northern Sierras, where the gold is found, have been made by the American and Feather rivers. Farther south are the deeper and more rugged canons of the Tuolumne, Merced, King's, and Kern rivers, which open to us inviting pathways into the mountains.

It might be supposed that the mantle of snow and ice which at that time covered most of the surface of the earth would have protected it from further erosion, but this was not the case. In the basin at the head of each stream the snow acc.u.mulated year after year until it was more than a thousand feet deep. Under the influence of the warm days and cold nights the snow slowly turned to ice, and moved by its own weight, crept down into the canons. The solid rock walls were ground and polished, and even now, so long a time after the glaciers have melted, some of these polished surfaces still glisten in the sunlight. The glaciers deepened and enlarged the canons, but running water was the most important agent in their making.

Upon the disappearance of the glaciers, the streams went to work again deepening their canons. From their starting-points, under the lofty crags, they first ran through broad upland valleys, then tumbled into the canons; but until they had reached the lower mountain slopes, to which the glaciers had not extended, they pa.s.sed through a dreary and desolate region devoid of almost every sign of life.

The glaciers had swept away all the loose rock and soil, and it was many long years before the surface again crumbled so that forest trees could spread over it once more.

The grandeur and attractiveness of the Yosemite is partly due to the precipitous cliffs enclosing the valley, some of which are nearly four thousand feet in height, partly to the high waterfalls, and partly to the green meadows and forest groves through which the Merced River winds.

Although the glaciers had little to do with the making of the Yosemite Valley, yet they added to its attractiveness. The valley is situated where a number of smaller streams join the Merced River. Erosion was more rapid here because the granite was soft, while the vertical seams in the rock gave the growing valley precipitous walls. When the glacier came it pushed out the loose rocks and boulders, and dropping a portion of them at the lower end, made a dam across the Merced River. At first a shallow lake filled the valley, but after a time the silt and gravel which the streams were continually bringing in filled the lake, and formed marshy flats. Finally, gra.s.ses and trees spread over these flats and gave the valley the appearance which it has to-day.

Besides the meadows, the glaciers gave us two of the waterfalls.

Yosemite Creek, which comes down over the walls twenty-seven hundred feet in three successive falls, was turned into its present channel by a dam which a glacier had left across its old course. A glacier also turned the Merced River at its entrance to the main valley so as to form the Nevada Fall.

[Ill.u.s.tration: FIG. 15.--THE CAnON OF BUBB'S CREEK, A BRANCH OF THE KING'S RIVER CAnON]

After the valley had been made and clothed in vegetation, it was discovered by a small tribe of Indians who came here to make their home, secure from all their enemies. There were fish in the streams and animals in the woods. The oaks supplied acorns, and in early summer the meadows were covered with strawberries. Legends were a.s.sociated with many of the cliffs and waterfalls, for the Indians, like ourselves, are impressed by the wonders of Nature.

Hetch-Hetchy Valley, twenty-five miles north of the Yosemite, has been formed upon much the same plan, but a portion of its floor is marshy and there are few waterfalls. King's River Canon has no green meadows and no high waterfalls, while its great granite walls are not so precipitous as those of the Yosemite. Next to the Yosemite, in the wildness of its scenery, is Tehipite Canon.

This canon is situated upon the middle fork of King's River, about a hundred miles south. For many miles its walls and domes present ever changing views.