Chapter II: Preface (2)

This mass 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 cañon, 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 mass. The glaciers in the United States are at present comparatively small, but once these icy masses 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.

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 asserting 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.

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 cañon 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 mass 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 passed 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.

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 débris along the side of a glacier is known as a marginal moraine. A similar ridge, formed by the accumulation 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.

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 canals, 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 associated 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 passed 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 space 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 shore 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 passes down through them in large quantities.

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? Note the effect produced by drops of water falling upon a hot stove. Each one, as it strikes, is partly changed to steam with a slight explosive sound. The result is similar when water is turned into the hot and nearly empty boiler of a steam-engine--an explosion is sure to follow.

When the pressure of steam suddenly formed within the earth is too great, a volcanic explosion takes place at some point where the overlying rocks are weakest, probably on or near one of the lines of fracture about which we have been speaking. The explosion is accompanied by thundering noises, tremblings of the earth, and the hurling of rock and molten lava into the air. That the rocks of the earth's crust are elastic is shown by the rebounding of a pebble thrown against a large boulder. If a file be drawn across the edge of a sheet of tin upon which sand has been sprinkled, the tin vibrates over its whole extent, as is shown by the jumping of the sand grains. Because of like elasticity in the materials which make up the surface of the earth, the vibrations produced by an explosion are carried through the solid earth for hundreds of miles.

The records of earthquakes show that they are much more violent and occur oftener where the crust of the earth is being disturbed by folding. We have seen that there are two main causes of earthquakes: the slipping of portions of the earth past each other along a fissure, and the contact of water with very hot rocks far below the surface. It is probable that the earthquakes which occur so often in the western portion of the United States are due to the first of these causes. The numerous extinct volcanoes show that at one period this region was frequently shaken by explosive eruptions.

From Salt Lake City]

Mono Lake (see Fig. 42, page 99), at the eastern base of the Sierra Nevada Range, has been a centre for explosive eruptions, which were extremely violent at one time. The islands which rise in the lake are shattered, while Black Point, upon the northern shore, has been uplifted by an explosion from beneath, which split the rocks apart and formed deep fissures.

It is an interesting fact that in the Cordilleran region the mountains have been increasing in height in very recent years. We might almost say that they are growing to-day. In this region, then, we can actually see how mountains are made; we do not have to depend upon descriptions of the manner in which they are supposed to have been made thousands of years ago.

At the foot of the Wasatch Range, Utah]

Any good map will show that the mountains of the Cordilleran region have in general a north and south direction. Their direction was determined by fissures formed long ago in the crust of the earth. Movements have continued to take place along many of these fissures up to the present time, and probably will continue for some time to come.

In order to become better acquainted with these remarkable mountains, let us examine some of them, taking first the Wasatch Range in eastern Utah. The range has an elevation of nearly eleven thousand feet, rising gradually upon the eastern side, but presenting a bold and picturesque front upon the west, toward the plain of Great Salt Lake. A short drive from Salt Lake City brings us to the foot of the range, at the mouth of Little Cottonwood Cañon.

A peculiar bluff which extends for a number of miles along the base of the mountains at once attracts our attention. The steep face of the bluff, which is from fifty to seventy-five feet high, appears to have been formed by a rising of the land upon the side next the mountains, or a dropping upon the valley side. There are reasons for believing that the formation of the bluff was due to the occurrence of an earthquake some time within the last century. The bluff is closely related to the mighty mountains behind it. It was formed by the last of a series of movements in the earth which raised the great block known as the Wasatch Range to an elevation of six thousand feet above the plains at its base. Is it to be wondered at that disturbances of the earth which result in the erection of mountains of such height are frequently so severe as to destroy the strongest buildings?

Now let us go westward across the various parallel ranges of the Great Basin to Owens Valley at the eastern base of the Sierra Nevada mountains. This is the highest and longest continuous mountain range in the United States. For a distance of more than one hundred miles its elevation is from twelve thousand to over fourteen thousand feet.

Formed by a great fracture in the earth's crust]

Owens Valley was in 1872 the centre of one of the most severe and extensive earthquakes ever recorded in the United States. The little village of Lone Pine, situated in the valley below Mount Whitney, was utterly demolished, twenty people were killed and many injured. A portion of the valley near the village sank so low that the water flowed in and formed a lake above it. The land was so shaken up that the fields of one man were thrust into those of his neighbor. For a distance of several hundred miles to the north along the base of the mountains the earth was fractured, and bluffs from ten to forty feet high were formed as a result either of the dropping of the surface of the valley upon the eastern side, or of the raising of the mountains upon the west.

This slipping of the earth which gave rise to the earthquake bluffs was the most recent of a long series of similar events which have raised the precipitous eastern wall of the Sierra Nevada mountains to a height of two miles above Owens Valley. If you will go out into the centre of the valley and look west toward the mountains, you will see three bluffs or scarps. The first, which is twenty feet high, was made at the time of the last earthquake; the second, known as the Alabama Hills and rising about four hundred feet, was formed at an earlier time; the third, rising back of the others, is that of the main Sierra.

Similar cliffs appear at the bases of other ranges of mountains in the Great Basin. Springs abound along these fractures in the earth, for the surface waters have an opportunity to collect wherever the rocks are broken. Numerous fertile valleys mark the line of earthquake movements, for the broken rocks and abundant springs favor rapid erosion.

Among the Coast Ranges of California there appears a series of fractures in the earth which form a line nearly four hundred miles long. They extend from a point near San Bernardino in a northwesterly direction to the neighborhood of San Francisco. Severe earthquakes have taken place along this line since the country was settled. The pressure and grinding of the earth upon opposite sides of the fissures has formed long low ridges of earth. Small valleys have been blocked, and the old stage road from Los Angeles to Bakersfield, which followed the course of the fissures for a number of miles, has been almost obliterated.

Occupying a valley primarily due to earthquake movements]

Hundreds of cliffs and mountain scarps throughout the West have come into existence as the results of movements such as we have been describing. Where the disturbances have been recent the mountains are bold and picturesque. Those produced in earlier times are in many instances so worn away that it is difficult to tell with certainty how they were made.

THE LAST VOLCANIC ERUPTIONS IN THE UNITED STATES

There are more volcanoes in our country than is generally supposed. Some are very small and some rank among the greatest of mountain peaks, but all together there are many hundreds, perhaps thousands, of them. At present they are all silent and apparently dead. We are accustomed to speak of them as extinct volcanoes, but of this we must not be too sure.

They stand dark and cold, giving no clue to the nature of the forces which made them, except perhaps by the presence of an occasional hot spring and the appearance of the rocks of which they are composed. The slag-like character of these rocks we have learned to associate with intense heat. Some of these volcanoes are very old and have been nearly worn away; others are new and almost as perfect as when they were first made.

Where shall we go to find these volcanoes? Are there any upon the Atlantic coast or neighboring highlands? Though you may travel over all that portion of our country, you will find none, although you will discover in places, as for instance in the palisades of the Hudson, lavas which came from very ancient volcanoes, worn down so long ago that their very sites are lost to view.

If we search the Mississippi basin we find there even fewer traces of volcanic action than upon the eastern highlands. The greater portion of the vast area embraced by the Mississippi River and its tributaries has had a very uneventful history, although at times earthquakes may have occurred and the sky may have been darkened by ashes from eruptions in distant parts of the earth.

The groovings in the lava show that it was squeezed out in a half-solid condition]

It is in the country west of the Rockies, the region last to be explored and settled, that the objects of our search come to light. Here are volcanoes and lava fields so extensive as almost to bury from sight the older surface of the earth. Some of them appear as if but yesterday they had been glowing with heat.

In the Cordilleran region Nature has carried on her work with a master hand. She has lifted the earth's crust to form a great plateau. Portions of the plateau she has broken, projecting the fragments upward to form lofty mountains, while along the fissures thus created she has squeezed out fiery molten matter from the interior of the earth. This molten material has spread out in fields of lava or has piled itself about small openings, forming volcanic cones, which in some cases have overtopped the loftiest mountain ranges of the continent. It is believed that a number of these volcanic eruptions have occurred in the Cordilleran region of the United States since the discovery of America, and that one took place within the lifetime of many persons now living.

San Francisco Mountain, in northern Arizona, is the loftiest volcanic peak of a region dotted with volcanoes and lava flows. This great volcano, like most of its neighbors, has long been extinct, although a few miles to the eastward there appears a group of small but very new cones.

A ride of fifteen miles from the town of Flagstaff, across the forest-covered plateau, brings us to Shadow Mountain and the fields of lava and volcanic sand lying at its base. The mountain, throughout its height of over one thousand feet, is a conical aggregate of loose lapilli which give way under the feet and make climbing the peak very tiresome.

The lapilli and scoriæ are slag-like fragments of lava which have been blown out of the throat of the volcano while in a hot or semi-molten condition. These fragments, as they fall back to the earth, collect about the opening and in time build up the volcano, or cinder cone, as such a mountain is frequently called. The finer particles, which have the appearance of dark sand, fall farther away and form a layer over the surface for some miles upon every side. These products of an explosive volcano are sometimes called cinders and ashes, because of their resemblance to the slag and refuse of furnaces.

In the case of the volcano which we are studying, the lapilli are so black that they give the cone the appearance of being darkened by the shadow of a cloud, and on this account the peak is named Shadow Mountain. As the days are usually bright here, the shadow effect is very striking.

Near Shadow Mountain]

There are several smaller craters, east of the main one, which also threw out volcanic sand and lapilli. The surrounding hills are of volcanic origin, although very much older than Shadow Mountain. These hills are covered with pine forests; but trees or plants have gained only slight hold upon the newer surfaces of the cinder cones, which present a picture of almost complete desolation.

There have been two other eruptions since the making of the cinder cones, and these were marked by flows of molten lava. Although the rough and rugged surface of the older flow has not yet begun to crumble and form soil, as it must do in time, yet a few trees are found here and there, reaching their roots down for the scanty nourishment to be drawn from the crevices of the rocks.

The last flow of lava, which was very small, ran into a depression in the other flow just described. This lava appears so fresh that we almost expect to find the rocks still warm. What a contrast between the wooded hillside adjoining, with its carpet of soft volcanic sand, and the jagged surface of the lava! Care must be taken in climbing over the lava, for the sharp points and angles are ever ready to tear one's shoes and hands. It cannot be many years since these hard, cold rocks formed a glowing mass of molten matter creeping quietly out of some hidden fissure which reached far down into the earth. The lava hardened as it became cold, just as does molten iron when led from the furnace to make a casting.

At one spot in the lava field stand the remains of rude stone houses built into caverns in the lava. About them are scattered pieces of broken pottery. These rude dwellings were probably occupied by some of the prehistoric people whose homes are also found along many of the streams, and in the caves of the plateau region. We can see no reason for their coming to this desolate place, so far from a water supply, unless it was that the rugged lava offered some protection from their enemies.

Now let us imagine ourselves transported to northern California. Near Lassen Peak, the southernmost of the great volcanoes of the Cascade Range, there lies another field of recent volcanic activity of even greater interest than the first. The centre of attraction is Cinder Cone, similar to Shadow Mountain in its manner of formation as well as in materials, but more symmetrical in form. Upon one side is a field of black lava several miles in extent, while volcanic sand has been spread over all the adjacent country.

As nearly as can be determined, only a little more than two hundred years ago the valley now occupied by Cinder Cone and the lava fields gave no indication of ever becoming a new centre of volcanic action. It has been thousands of years since the ancient volcanic peaks and cinder cones of this mountainous region became extinct. The glaciers had come, and torn and ground away the surface of the lava, and afterward dense forests had hidden all the rocky slopes, while lakes had occupied many of the valleys. Far below, however, the fires had not gone out. In many places there were boiling springs from which the steam, upon cold mornings, rose in dense white clouds.

Then, for some reason which we do not understand, the forces beneath the surface increased their activity. The force of the steam and other gases was too great to be restrained, and at a weak spot in the overlying rocks they broke through. Molten lava accompanied them, and a new volcano came into life in the valley where Cinder Cone now raises its dark, symmetrical slopes.

The eruptions were violent. With explosive force the molten lava was torn into fragments, and sand, lapilli, and bombs were hurled out into the air. The finer particles were carried by the air currents far over the surrounding country. The lapilli, scoriæ, and bombs fell around the throat of the volcano, finally building up the cone to its present proportions. The great bombs, some of them five feet in diameter, are among the most remarkable products of this eruption. They lie scattered about upon the surface of the ground at the foot of the cone, and, although they are often irregular in shape, they might almost be mistaken for huge cannon-balls. The eruption killed and burned the trees in the near-by forests, burying them under six or seven feet of fine sand or ashes. After the cone had been built and the explosive eruptions had nearly stopped, a stream of molten lava burst from the base of the cone and filled a portion of the valley.

Now followed a long period of quiet. Trees began to grow upon the sand and gradually to encroach upon the barren wastes about Cinder Cone. It appeared as if there were to be no more eruptions. But the volcano was only resting. At about the time, perhaps, when the gold seekers began to pour across the continent to California, there was another eruption; but this time it took the form of a lava flow and was so quiet as to create no disturbance in the surrounding country.

The trees were killed by the last eruption of volcanic ashes]

A stream of thick, viscous lava flowed slowly out of an opening at the southern base of Cinder Cone. As the lava crept down the gentle slopes of the valley, it crusted over, forming a black, slag-like surface. The surface was from time to time broken up and mixed with the softer portions beneath, so that the movement of the flow was still further retarded. At the lower end of the valley the lava occupied a portion of a body of water now known as Lake Bidwell; its rugged front made a dam across the valley above, forming Snag Lake. The stumps of the trees which were killed by the water when the lake was first formed are still standing.

At Cinder Cone, California. It formed a dam across a valley, thus creating Snag Lake]

One's feet sink deep into volcanic sands, and walking is tiresome. The lava field resulting from the last eruption is free from sand, but its rough surface, formed of broken blocks, is difficult to cross.

A few charred stumps rise out of the sand, pathetic remnants of the forest trees that were growing at the time of the first eruption. Most of the trees have completely disappeared, leaving shallow pits where they once stood.

It is exceedingly difficult to climb the cone, which rises over six hundred feet, for the slopes, composed of loose lapilli, are so steep that one slips back at every step nearly as far as he advances. From the summit a remarkable sight meets the eye. Within the rim of the main crater is a second crater with a rim nearly as high as the first, while the cavity within has a depth of about two hundred and fifty feet.

Because of the loose character of the material of which it is built, no streamlets have yet worn channels down the slopes of Cinder Cone, and except for the presence of two small bushes which cling to its side, it is just as bare and perfect in form as when first completed.

Little by little the forests are encroaching upon the sand-covered slopes about the cone, and in time these slopes, the black fields of lava, and the cone itself, will be covered with forests like the older lava fields and cinder cones which appear upon every hand.

THE MUD VOLCANOES OF THE COLORADO DESERT

The Colorado Desert is a strange, weird region. Here is a vast basin at the head of the Gulf of California which was once a part of the gulf, but is now separated from it by the delta of the Colorado River. With the drying up of the water, the centre of the basin was left a salt marsh more than two hundred and fifty feet below the level of the ocean. In summer the air quivers under the blazing sun, and it seems as if no form of life could withstand the scorching heat, but in winter the atmosphere is cool and full of life-giving energy.

Around this desert rise the mountains, some old and nearly worn down, their tops barely rising out of the long slopes of sand and gravel; others rugged and steep, lifting their crests far above the burning desert into the cold, clear sky.

Curious forms of plants and animals find their homes upon the slopes about the basin, where they adapt themselves to the heat and dryness. But toward the centre the soil is bare clay, for when the water dried up so much alkali and salt were left that nothing could grow.

However we do not now intend to study the plants or the animals, interesting though they are, but rather a group of mud volcanoes, which forms almost the only relief in the monotony of the bare plain. These volcanoes are in no way related to real volcanoes except in shape, for water and mud, instead of fire and lava, have been concerned in their building.

Once it required a long journey in wagons or upon horseback to reach the mud volcanoes, but now the railroad takes us within three miles of the spot. We alight from the train before a section house which stands in the midst of the great desert. Far, far away stretches the barren clay floor of the ancient lake. Here and there are scattered stunted shrubs, the only specimens of plant life which have been able to withstand the alkali in the clay.

Seen from the station, the volcanoes appear like dark specks almost upon the horizon, but in reality they are not far away, and an hour's brisk walk will bring us to them. The mud springs, which are scattered over an area of several hundred acres, present many strange and interesting features. There are holes in the earth with bubbling mud at the bottom, cones from the tops of which streams of muddy water issue, and ponds of mud, in some cases as thick as molasses, in others thin and watery. There are little jets of steam, strange odors, and a vista of many mingled colors. Taken altogether, it is a place quite different from any other that we have ever seen.

The ground is soft and marshy, and in some places undermined by the water, so that we have to take great care in walking about. Some of the smaller springs occupy round depressions, sometimes three or four feet across, which look as if they had been made by pressing a large pan down into the clay. The bubbling mud in the bottom of the pan, as well as the hot water in many of the springs, makes it easy to imagine that we are standing upon the top of a great cooking stove in which a hot fire is burning. As the gas with which the water is impregnated comes up through the mud, it forms huge bubbles which finally break and settle down, only to rise again. In this way concentric mud rings, perfect in form, are made to cover the entire surface of the pool.

Where there is little water, the surface of the mud hardens and leaves a small opening, through which the bubbling gas throws small columns of mud at regular intervals. From the large pools, some of which are forty to fifty feet in diameter, there comes a low murmuring sound like the boiling of many kettles. The water is sputtering and bubbling, and in some places it is hot enough to give off thin clouds of steam. Occasionally we get whiffs of sulphur, while about the borders of some of the ponds pretty crystals of this mineral can be found.

More commonly the pools are crusted about with a white deposit of salt, for they all contain more or less of this substance in solution. Around a few of the pools the mud is stained with the red tinge of iron, and red lines mark the paths of the streams as they run off from the pools toward the still lower portions of the desert.

The built-up cones or volcanoes appear in every stage, from the little ones a few inches high to the patriarchs, which in some cases have reached a height of twelve feet. These cones are formed by the hardening and piling up of mud about the openings; but when they have reached the height mentioned, the passages up through their centres, corresponding in each case to the throat of a real volcano, become clogged and new holes are formed in the mud at the base.

With small active one at its side]

Many of these mud volcanoes closely resemble true volcanoes in form and structure. The mud which pours out at the top forms streams down the slopes very like those of molten lava. New cones are built upon the sides or at the bases of the old ones in much the same way as are those in the volcanic regions.

There are no signs of volcanic action in the vicinity of these mud springs, and it is likely that the water is forced to the surface by large quantities of gas produced by chemical changes taking place deep within the clay beds of the old lake. Similar springs occur farther south, nearer the mouth of the Colorado River, in the Yellowstone Park, and near Lassen Peak, but nowhere in America except in the Colorado desert have they formed such large and interesting mounds.

THE HISTORY OF A COAST LINE

The story of our Pacific coast reads more like a tale from the "Arabian Nights" than like a plain statement of events which have actually happened.

The meeting place of the land and ocean is not really so permanent a line as it appears. The shore has been continually moving back and forth throughout the long history of the earth. That which was dry land at one time was at another time deeply buried beneath the ocean. The Pacific border seems never to have been at rest. It has risen and sunk again repeatedly. It has been squeezed, folded, and broken, shaken by earthquakes, and disturbed by volcanic eruptions.

One might be led to think from this statement that it would not be safe to live on the Pacific coast, and that both animals and men would shun the region. The fact is, however, that these changes usually come to pass so very slowly that we are not aware of them. Severe earthquakes and volcanic disturbances take place so rarely in comparison with the length of a man's life, that we may pass our whole lives without experiencing any of these violent disturbances. The Pacific coast region, with its forest-covered mountains, fertile valleys, and beautiful homes, presents so quiet and peaceful an appearance that it is difficult to believe that parts of its history have been so tumultuous.

Perhaps you will ask how we can know so much about the past. It is true that no one was here to witness the events which are supposed to have taken place. But Nature has left a record of her doings which we have only to see and understand in order to learn with certainty many things which happened in the far distant past.

Too many of us go through life seeing and understanding almost as little of the world about us as if we were blind. Our early ancestors were obliged to understand many things about Nature and to cultivate clear and close observation for the sake of self-preservation. The very life of the savage depends upon the training of his eyes. He must be able to tell the meaning of a distant object or an indistinct trail, for his enemies may have passed that way recently. If we could bring the sharp eyes of the savage to our aid, the world would mean much more to us.

In order to learn something of the history of the Pacific shore line, we must see what the waves are doing at the present time. The projecting points of land are being worn away (Fig. 33). The waves form the cliffs against which they beat, and sometimes, as they eat their way slowly into the land, they cut off portions and leave them standing alone as islands.

The pebbles and boulders (Fig. 34) were once angular fragments torn from the cliff. They have been washed about and hurled against the solid rock until they have been worn smooth; and the cliff in turn has had a cave ground out at its base. Above the lower cave there is a remnant of a second one, with pebbles upon its floor. This was made when the land stood ten feet lower than at present.

As the waves wear away the loose earth and the solid rock below it, moving the cliffs inland, they leave a comparatively smooth surface which is partly exposed at low tide. The fact that this surface is not marked by stream channels, as is the land, helps us to realize the great difference between the irregular surface of the latter and the plain-like character of the ocean floor.

The waves are eating their way into the land]

Along the whole coast of California there are many old sea beaches and cliffs which the waves abandoned long ago. The highest of these beaches lies so far up the slopes of the mountains bordering the ocean that it makes us wonder what the geography of California could have been like when the region was so deeply submerged.

The lowest and newest terrace is the one shown in Fig. 35, ten feet above the ocean. Each succeeding terrace is less distinct, and the highest, fourteen hundred feet in elevation, can now be distinguished in only a few places. Where the old sea cliffs are best preserved they form a series of broad, flat steps, rising one above the other. Each bench, or terrace as it is commonly called, is a part of an old plain cut out of the land by the waves when the ocean stood at that level. The steeper slope rising at the back is the remnant of the cliff against which the waves used to beat. If we are fortunate, we shall find at its base some water-worn pebbles and possibly a few fragments of sea-shells. The crumbling of the rocks and the erosive action of the rills are fast destroying the old cliffs, so that in many places they have entirely disappeared.

Pebbles of a former beach are seen above]

Upon the seaward face of San Pedro Hill, in southern California, there are eleven terraces, rising to a height of twelve hundred feet. What an interesting record this shows! Long ago the land stood twelve hundred feet lower than at present, and the waves beat about San Pedro Hill, nearly submerging it. Then the land began to rise, but stopped after a time, and the waves cut a terrace. The upward movement was continued, with repeated intervals of rest, until the land stood higher than it does now.

Point San Pedro, California]

North of San Francisco there stands a terrace fourteen hundred feet above the ocean. Numerous terraces appear along the Oregon coast, but those in Washington are not as high as those in California. It is probable that the land in this region was not so deeply submerged.

The ancient shore lines of British Columbia and Alaska are now deeply buried beneath the ocean, as those of California once were. The fiords, so common in these countries, are old river valleys which have been drowned by the sinking of the land. The islands were once portions of the coast mountains, but have been cut off by the same process.

Let us picture in our minds the changes in the geography of the Pacific coast of the United States which must have been made by a sinking of the land to a depth of only six hundred feet. We will begin upon the north, at the Strait of Fuca.

Puget Sound once opened to the south as well as to the north, so that the Olympic Mountains formed an island. The broad and fertile Willamette Valley was but an arm of the sea, somewhat like Puget Sound to-day. The body of water which once filled this valley has been called Willamette Sound. The ocean overspread the low Oregon coast, and reached far up the valleys of the Umpqua and Rogue rivers. But the boundaries of the Klamath Mountains were not greatly changed, for in many places they rise quite abruptly from the present shore line.

All the large valleys of California were flooded, including the San Joaquin-Sacramento valley, which was then a great sound, open to the ocean in the region of the present Strait of Carquinez. The Coast range was broken up into islands and peninsulas. The islands off the coast of southern California are high and therefore were not entirely submerged. The Gulf of California spread over the Colorado Desert, while from the west the water penetrated inland over the plain of Los Angeles to a point beyond San Bernardino, so that at the San Gorgonio pass only a narrow neck of land connected the San Jacinto Mountains and the Peninsula Range with the mainland.

If California had been inhabited at this time, the state would not have been noted for orchards and grain-fields, but rather for its mineral wealth. There would have been comparatively little low land fit for cultivation, but the mountains, where almost all the precious metals are found, would have appeared nearly as they do to-day.

The surface of the earth may be divided into the ocean basins and the continental masses which rise above them, but we must not make the mistake of thinking that the shore line always corresponds with the border of the continental masses. We have learned that the land is almost always moving slowly up or down, so that the shore is continually changing back and forth. At one time the shore line may be far within the borders of the continent, as we have seen was once the case upon our Pacific coast; at another time, if the land should rise, the shore line might coincide with the real border of the continent. By the real border of the continent we mean the line along which the earth slopes down steeply to the abysmal depths of the ocean.

It is an interesting fact that outside the present shore line of California there is a submerged strip of the continent varying from ten to one hundred and fifty miles in width. This strip of land is like a bench upon the side of the continent, and is known as the continental plateau. The water over the plateau is comparatively shallow. Upon one side the land rises, while upon the other there is a rapid descent into the deep Pacific. The surface of the plateau is in general fairly smooth, but in places mountains lift their summits above the water and form islands.

There was a time, thousands of years earlier than the period when California was so nearly covered by the waters of the Pacific, when this land stood far higher than it does now. The coast line was then much farther west, near the border of the submarine plateau. The Santa Barbara Islands at that time formed a mountain range upon the edge of the continental land. This fact was established by the discovery upon one of the islands of a large number of bones of an extinct American elephant. These animals could have reached the submerged mountains only at a time when there was dry land between them and the present shore line. We should like to know how it came about that these bones were left where they are. Perhaps the land sank so suddenly that the water cut the elephants off from the mainland and compelled them to spend the remainder of their lives upon these islands.

While the land stood so high, some of the larger streams wore deep channels across what is now the submarine plateau. These channels have been discovered by soundings made from the ships of the United States Coast Survey. The largest of the submerged valleys extends through the Bay of Monterey, and runs so close to the shore that it has offered a favorable location for a wharf.

Before the buried valleys upon the northern coast of California were all known, the presence of one of them led to the wreck of a ship. The shore was obscured by fog, but the soundings made by the sailors showed deep water and led them to believe they were a long distance from land, when suddenly the ship drifted in upon the rocks.

The last significant movement of the land of the Pacific border was a downward one. It flooded the mouths of the streams and formed all the large harbors which are of so great commercial importance.

San Francisco Bay occupies a great stretch of lowland at the meeting of several valleys of the Coast Ranges and forms the outlet for the most important drainage system of California. If this region had been settled before the subsidence of the land which let in the ocean through the Golden Gate, how the farmers would have lamented the flooding of their fertile lands! But we can understand how small the loss would have been, compared with the advantages to be gained from the magnificent harbor which now exists here. If the land had not sunk the history of the Pacific coast would have been far different.

Near Anacortes, Puget Sound]

Puget Sound, another very important arm of the ocean, is also a submerged valley, but it has had an entirely different history from that of San Francisco Bay. The valley was at one time occupied by a great glacier which came down from the Cascade Range and moved northwest through the sound and into the Strait of Juan de Fuca, scouring and polishing the rocks over which it passed. A little island near Anacortes (Fig. 36) has been rounded by the action of the ice into a form like a whale's back.

Southern California]