Part 9 (1/2)

[Ill.u.s.tration: FIG. 52.--SCENE ON GREAT SALT LAKE]

Although decreasing in area so rapidly, Great Salt Lake is still the largest body of water in the western part of the United States, and the largest salt lake within its boundaries. It has a length of seventy miles and a maximum width of nearly fifty miles.

Desolate, indeed, must have appeared the surroundings of the lake, with its salt-incrusted borders, as the Mormon emigrants gained the summit of the Wasatch Range and looked out over the vast expanse to the west. But as the slopes at the foot of the mountains seemed capable of producing food for their support, they stopped and made their homes there. Now in this same region, after half a century, one can ride for many miles through as beautiful and highly cultivated a country as the sun ever looked down upon. In the early days the barren plains were broken only by mountains almost as barren, which rose from them like the islands from the surface of the Great Salt Lake. The only pleasing prospect was toward the east, where stood the steep and rugged Wasatch Range, with its snow-capped peaks.

From its deep canons issued large streams of pure, cold water, which flowed undisturbed across the brush-covered slopes, then unbroken by irrigating ditches, and at last were lost in the salt lake.

One might think that streams of water apparently so pure would at last freshen the lake, but in reality they are carrying along invisible particles of mineral matter which add to its saltness day by day. The dry air steals away the water from the lake as fast as it runs in, but cannot take the minerals which it holds in solution.

Great Salt Lake is still considered very large, but at one time it was ten times its present size, while still longer ago there was no lake at all. Without a basin there can be no lake, and at that far-away time, as we have already learned, the Great Basin did not exist, and the streams, if there were any, ran away to the ocean without hindrance.

When the Great Basin was formed by a breaking and bending of the crust of the earth, many a stream lost its connection with the ocean and went to work filling up the smaller basins, thus giving rise to the lakes which have already been described. The largest of these bodies of water, and in some respects the most interesting, is Great Salt Lake.

[Ill.u.s.tration: FIG. 53.--OLD Sh.o.r.e LINE OF LAKE BONNEVILLE

Foot of the Wasatch Range]

This lake, lying close to the lofty Wasatch Range, received so much water from numerous streams during the Glacial period that it slowly spread over thousands of square miles, overrunning the desert valleys and making islands of the scattered mountain ranges.

It extended from north to south across Utah, into southern Idaho and almost to the Arizona line, until this body of water, which arose from so small beginnings, had become a veritable inland sea, three hundred miles long, one hundred miles wide, and one thousand feet deep.

By the time the lake had covered an area of twenty thousand square miles the lowest point in the rim of the basin was reached and the overflow began. No map will tell you where the outlet was, for no river exists there now. If you could explore the sh.o.r.e lines of this ancient lake, which has been called Bonneville after the noted trapper, you would find two low spots in the mountains which hem the waters in, one upon the south, facing the Colorado River, the other on the north toward the Snake River. The one on the north happened to be a little lower, so that the break occurred there.

First as a little, trickling stream, then as a mighty, surging river, the water poured northward down the valley of a small stream, widening and deepening it until, pa.s.sing the spot where now the town of Pocatello stands, it joined the Snake River.

This old outlet is now known as Red Rock Pa.s.s, and it forms an easy route for the Oregon Short Line from Salt Lake City to the plains of southern Idaho. The old river-bed is marked by marshes and fertile farms.

With an outlet established, Lake Bonneville could rise no higher, and its waves began the formation of a well-defined terrace or beach, just as waves are sure to do along every sh.o.r.e. The level of the water could not remain permanently at the same height, for the rocks at the outlet were being worn away by the large volume of water which flowed over them. In the course of years the level of the lake was lowered four hundred feet. The sinking was not uniform, but took place by stages, while at each period of rest the waves made a new beach line. The lake during all this time must have been a beautiful sheet of fresh water filled with fish.

Its sh.o.r.es, also, must have been much richer in vegetation than they are now.

[Ill.u.s.tration: FIG. 54.--RED ROCK Pa.s.s, SOUTHERN IDAHO

Outlet of Lake Bonneville]

The water remained for a long time at the level of four hundred feet below its highest stage. This fact is evident from the width of the wave-cut terrace, which is the most prominent of all those that mark the old levels along the sides of the mountains. Finally, for some reason the climate began to change, the streams supplied less water to the lake, and the evaporation from its surface became greater because the air was drier. As a result the lake was lowered to such an extent that it lost its outlet. The mighty river flowing down through Red Rock Canon grew smaller and at last dried up altogether.

In this manner the lake was again cut off from the ocean, as it had been during its earlier history. The waters still continued to recede, but not at a uniform rate. During periods of greater rain its level remained stationary, so that the waves added new terraces to those already formed.

As the lake had no outlet and was decreasing in volume, the water became salty, for the minerals brought by the streams could no longer be carried away. The fish either died or pa.s.sed up into the purer waters of the inflowing streams.

The water of the present lake is so salt that in every four quarts there is one quart of salt, and the preparation of this commodity by a process of evaporating the water in ponds has become an important industry. The water is the strongest kind of brine and it is impossible for a bather to sink in it. One floats about upon it almost as lightly as wood does upon ordinary water. After bathing it is necessary to wash in fresh water to remove the salt from the body.

The dry bed of the former Lake Bonneville stretches far to the south and west of the present lake, and forms one of the most barren and arid regions in the United States. It is sometimes called the Great American Desert.

Why is the lake receding now? Some people think that the climate is growing still more arid, and that the lake will eventually disappear.

Others think that its shrinkage is the result of irrigation, for a large part of the water from the streams which supply it is now taken out and turned upon the land. There is still another reason which may account for the low water. The lake is known to rise and fall during a series of wet and dry years. When first mapped, in the middle of the last century, it was about as low as it is now. Then it gradually rose for a number of years and lately has again been falling.

The story of Great Salt Lake has been much more complicated than the statement given above, but this is sufficient for our purpose.

Irrigation has made a garden spot of a large part of the old bed of Lake Bonneville, but much of the beauty and attractiveness of this region would be lost if the present lake should give place to a bed of glistening salt. Let us hope that it will remain as it is.

THE SKAGIT RIVER