The Western United States Part 3

A continual struggle is going on between the forces within the earth and the sculptor working upon its surface. First one, then the other, gains the advantage. Where the mountains are steep and high, often the forces within have recently been active. Where they are low and the slopes are gentle, the sculptor has long held sway. She begins by making the surface as rough and picturesque as possible, but after a time she destroys her own handiwork.

AN OREGON GLACIER

There are records all about us of events which took place upon the earth long before there were any human inhabitants. These records have been preserved in the rocks, in the geographic features of the land and water, and in the distribution of the animals and plants. On every hand appear evidences of changes in the surface of the earth and in the climate.

Through all the central and northern United States, if we except some of the mountains of the West, the winter snows entirely disappear long before the coming of summer. But the climate of this region has not always been so pleasant and mild. Lands now densely peopled were once buried under a thick mantle of ice which lasted through many thousands of years.

Scattered over the surface of the northern United States are vast numbers of boulders and rock fragments which are not at all like the solid rocks beneath the soil. The history of these materials takes us back to the Glacial period, which can be best understood from a study of some one of the glaciers now existing upon the mountains of the northwestern part of our country.

Among the lofty mountain ranges of the Cordilleran region there are many peaks upon which perpetual snow-banks nestle, defying the long summer days. Where the winters are long and cold and the storms are severe, immense drifts of snow collect in the hollows and canons of the mountain slopes. Each summer all or a part of this snow melts. Upon the northern slopes the melting process is slower, and if there happens to be a large basin upon that side, an extensive field of snow remains until the winter storms come again. Each winter new snow is added to the surface, while the older snow, becoming hard and firm through repeated freezing and thawing, at last turns to ice.

This ma.s.s of snow and ice does not remain stationary, as might be expected from its apparent solidity. Under the influence of its own weight and of alternations of heat and cold, it flows down the incline like a very thick liquid. During the winter the ice melts but little, and the movement is slow, but in the summer, under the influence of the warm days and cool nights, both the melting and the rate of flow of the ice are increased. A moving body of snow and ice of this sort is called a "glacier." It creeps down the mountain slope and into some canon, until, in the warmer air of the lower mountains, the rate of advance is exactly balanced by the rate of melting at the lower end of the ma.s.s. The glaciers in the United States are at present comparatively small, but once these icy ma.s.ses stretched over the mountains and lowlands of a large portion of the continent.

In the southern Sierra Nevada mountains no permanent snow exists below an elevation of about eleven thousand feet, but as we go north snow-fields are found lower and lower, until in the fiords of Alaska enormous glaciers reach down to the sea.

A glacier worthy of our study may be found upon the Three Sisters, a group of lofty and picturesque volcanic mountains rising from the summit of the Cascade Range in central Oregon. There is a deep depression between two of the peaks, which slopes down to the north and is thus particularly well adapted to catch and retain the drifting snows. Consequently the glacier to which it gives rise is of exceptional size, being nearly three miles long and half a mile wide.

[Ill.u.s.tration: FIG. 16.--THE THREE SISTERS, FROM THE NORTH

Showing snow-fields and glacier. Fields of recent lava appear in the foreground]

The easiest path to the Three Sisters is by way of the McKenzie River from Eugene, Oregon. The McKenzie is a noted stream and one of the most beautiful in the state. The river courses through dense forests, and its clear, cold water is filled with trout. So tempestuous is the weather about the Cascade range that July is almost the only month in which one can visit the Three Sisters without danger of being caught in severe storms.

The traveller leaves the river a few miles above McKenzie Bridge, where a small tributary known as Lost Creek joins it. Lost Creek flows under the lava from a lake near the Three Sisters, while another stream, coming from the glacier of which we are in search, flows down the same valley upon the surface of the lava and almost directly over the hidden stream.

Upon the summit of the Cascade Range the dense forests of the river valley give place to more open woods interspersed with park-like meadows. A few miles away to the south rise the volcanic peaks of the Three Sisters, clear and cold in the mountain air, wrapt about with a mantle of white except where the slopes are too precipitous to hold the snow.

An indistinct trail leads through the tamarack forest and over a field of rugged lava to the base of the peaks. Here we come upon a swiftly flowing stream of a strange milky color. This appearance is due to the presence of fine mud, the product of the work of the glacier at the head of the stream as it slowly and with mighty power grinds away the surface of the rocks over which it moves.

Wherever one meets a stream of this kind, he will probably be safe in a.s.serting that it is fed by a glacier upon some distant mountain peak.

This little stream, the course of which we must follow to reach the glacier, is choked with sand and pebbles brought to it by the moving ice. These are not ordinary stream pebbles, for they have strangely flattened sides which often show scratches, and look as if they had been ground off against a grindstone. They are the tools with which the ice does its work. The ice block takes up the rock fragments which fall upon its surface or which it tears from beneath, and carries them along, grinding every surface which it touches. The fragments are dropped at the end of the glacier, and the smaller pebbles are washed away down the stream that flows from the melting ice.

[Ill.u.s.tration: FIG. 17.--GLACIER ON THE THREE SISTERS]

We follow up the little glacial creek, past icy snow-banks and through groves of fir trees where the warm sunshine brings out the resinous odors. Upon one side of the canon there lies a field of black lava which not many hundreds of years ago forced this glacial creek from an earlier channel into its present bed. Now we come upon what appears at first to be a snow-bank lying across the course of the stream, and from beneath which its waters issue.

Deep cracks in the outer ma.s.s of snow show the clear, pale-green ice below. This is the lower end of the glacier which we have been so long a time in reaching.

A short climb up a steep slope brings us to the top of the glacier.

It forms a perfectly even plain, extending back with a gentle slope to the head of a deep notch between the two northern Sisters, while above and beyond rise the steeper snow-fields, from which this ice is continually renewed.

The glacier does not terminate in the usual manner, with a stream flowing from its centre, for the outlet is at one side, while the middle abuts against a low mound of rock. This mound we find most interesting, for upon reaching its top we look down into a volcanic crater. From this crater flowed the great stream of lava to which we have already referred. The lava ran downward, bending this way and that among the hollows, until it spread nearly to the McKenzie River.

During the Glacial period, before the eruption took place, this glacier was much larger. The summit of the Cascade Range was then covered by glaciers. This fact we know from the presence of grooved and polished rocks wherever the surface has not been worn away or covered with newer lava. The Glacial period had pa.s.sed away and the climate had become much the same as it now is when the volcanic forces broke out at the spot where the crater is situated.

The eruption undoubtedly melted the ice in the vicinity, but after it had ceased and the rocks had become cold, the glacier never gained strength enough to push the loose materials of the volcanic cone out of its path. The ice banked up snugly against the obstruction, and as it melted the water found its way out at the side of the lava.

Although the surface of the glacier appears at first to offer an easy route to the higher mountain slopes, yet there are numerous hidden crevices into which one may fall. The safest arrangement is to tie a company of people together with a stout rope, so that if one falls into a crevice the rope will save him. Toward the middle of the glacier the ice becomes so badly fissured that it is necessary to turn toward the right margin. There are two sets of these fissures, one parallel to the direction in which the glacier is moving, the other at right angles. They are due to the strain to which the ice is subjected as it moves along at an uneven rate and over a surface composed of hollows and ridges.

[Ill.u.s.tration: FIG. 18.--MORAINE AT THE END OF THE GLACIER]

Leaving the glacier, we climb upon a long low ridge of gravel and boulders mixed with fragments of ice. The fragments of rock which have fallen upon the surface of the ice or been torn from the rock over which it is moving, have been heaped up along its sides somewhat as a ridge of snow is raised along each side of the course of a snow-plough. Such a ridge of debris along the side of a glacier is known as a marginal moraine. A similar ridge, formed by the acc.u.mulation of rock fragments at the lower end of the glacier, is a terminal moraine. These ridges and hollows formed by the ice are found all over the northern portion of the United States. The hollows once filled with ice are now occupied by the beautiful lakes of this portion of our country.

As we climb along the moraine at the margin of the glacier, many openings appear in the clear green ice. There is the sound of gurgling waters, and occasionally pieces of ice and rock fall into dimly outlined caverns which are narrow at the top, but far below widen out to the proportion of chambers.

After the head of the glacier is attained there is still a hard climb over the snow-fields, which extend upward so far that they seem to have no end. When at last the gap between the peaks is gained we are completely tired out. The summit of the middle Sister rising directly above us is still a thousand feet higher, but there is not time to-day to reach it.

A magnificent vista is spread out upon every hand. Extending north and south along the crest of the Cascade Range there is a line of sharp snowy peaks with summer clouds floating about them. How these peaks contrast with the dark blue of the surrounding forests!

Opposite us, upon the south, is the third Sister, white with snow from top to bottom, while in the basin between this peak and the ridge on which we are standing lie the remnants of a once mighty glacier.

But it is time to return. The cold, foggy clouds are hiding the summits and will soon envelop the spot where we stand. We go down by a different path, but over almost continuous snow-fields, for more than two miles. The return is much easier than the ascent, although if one lost his footing upon some steep slope, it would mean a long slide or tumble. The solid earth is reached without accident. What a relief to have some firm hold for the feet again!

Climbing over a field of rough lava is easier than toiling through soft snow.

[Ill.u.s.tration: FIG. 19.--A BOULDER LEFT BY A GLACIER]

The region about the Three Sisters is just as nature left it, for the home of the nearest settler is many miles away. Although now it has few visitors, this country will become attractive when its wonderful volcanic and glacial phenomena are better known.

SOMETHING ABOUT EARTHQUAKES AND MOUNTAIN BUILDING

Our everyday experiences lead us to feel that nothing is more permanent than the features of the earth upon which we live. Great cities containing costly buildings are built by the water's edge with the expectation that the ocean will remain where it is. The building of railroads and ca.n.a.ls, and the establishment of industries to make the earth more fruitful and better adapted to our use, are based upon the idea that the mountains and valleys with their various, climates will not change.

The study of history, however, makes plain the fact that at different times in the past certain portions of the earth have been visited by destructive changes. Cities have been shaken down by earthquakes, and the ocean has swept in over the land, drowning thousands of people.

Even the mountains, which stand upon broad and firm foundations, sometimes bring disaster, by means of avalanches and land-slides, to the people who live at their bases.

The truth is that the earth's surface is everywhere slowly and quietly changing; but our lives are so short, and the history of even the oldest cities is so brief in comparison with the rate at which most of the changes take place, that we as a rule are aware of only the uncommon and sudden ones.

The occurrence of earthquakes establishes the unmistakable fact that there are forces at work from within disturbing the surface, while land-slides, and even little gullies washed out by the rain, show that other forces are working from without.

The vibration or trembling of the earth which we call an "earthquake"

always arouses alarm, and frequently occasions great destruction and loss of life. Only a few of the various causes that may bring about earthquakes are as yet fully understood. Earthquakes are very interesting, however, because they are often a.s.sociated with the birth and growth of lofty mountain ranges.

Volcanic eruptions, hot springs, and the high temperature which exists toward the bottom of deep mines show us that the interior of the earth is very hot. It is thought that at one time the whole earth glowed with heat, but as ages pa.s.sed it became cold upon the outside and a solid crust was formed.

Every one has observed that fruit becomes wrinkled as the pulp within dries and contracts. The materials of the earth occupy more s.p.a.ce when they are hot than when cold, and as the interior portion is still cooling, the outer layer or crust continues to shrink down upon it, forming folds or wrinkles, as in the case of the skin of an apple.

There is probably no portion of the surface that is fixed in its present position. The land is either rising or sinking continually.

If the area that is pushed upward is large, it becomes a plateau; but if long and narrow like a wrinkle, it forms a mountain range.

We should not be aware of these movements in many cases if it were not for the horizontal shelf cut upon the borders of the land by the ocean waves. Along some coasts old wave-cut cliffs stand hundreds of feet above the present ocean level. Other coasts have sunk, so that the water has flooded the adjoining land and made a new sh.o.r.e line.

When the movements of the land are sudden, they manifest themselves to us through earthquakes. The crust of the earth is not so flexible as the skin of an apple, and when the strain upon it becomes too great it suddenly breaks. The rock walls usually slide past one another along such a fracture. If the rising wall becomes high enough it will form a mountain range.

The great mountain systems border the oceans, for the lines of weakness occur where the land dips steeply down beneath the water.

It sometimes happens that the fractures in the rocks where mountains are being made are situated underneath the water, or in some position where water pa.s.ses down through them in large quant.i.ties.

What do you think would happen if such an underground stream of water came in contact with hot or molten rocks far below the surface?