Aside from the lessons of interest to the geologist and geographer so plainly engraved on the surfaces of the plateaus crossed by the Colorado, the region has a wonderful fascination for the purely æsthetic feelings more or less latent in every human breast. To one traversing the open pine forests, in places clothing the plateaus and inclosing many grassy glades and flower-decked parks, in which timid deer may frequently be seen feeding in the early morning, and emerging on the brink of the Grand Cañon, the scene that meets the eye is marvellous beyond all description. C. E. Dutton, to whom we owe some of the most graphic and inspiring descriptions of natural scenery ever written, states that those who have long and carefully studied the Grand Cañon of the Colorado do not hesitate for a moment in pronouncing it the most sublime of all earthly spectacles. "If its sublimity," writes Dutton, "consisted only in its dimensions, it could be sufficiently set forth in a single sentence. It is more than 200 miles long, from 5 to 12 miles wide, and from 5,000 to 6,000 feet deep. But it is not magnitude alone that gives this marvellous cañon its prominence; it is the gorgeous and varied colouring of its mighty walls, the endless details in the sculpturing of its battlements and towers, the ever-changing atmospheric effects of its profound depths, and the wonderful stimulus to the imagination with which it feeds the mind. Standing on the brink of the Grand Cañon, the prosaic search for causes and effects for a time at least must be laid aside, and give place to the emotions."
Wonderfully grand as are the scenes beheld in traversing this region of high plateaus, with its magnificent cliffs and profound cañons, one is constantly reminded that it is an arid land. The higher portions of the plateau, it is true, are in places forested, but over vast areas the rocks are bare. Water is everywhere scarce except in the bottom of the larger excavations. Thirsty, and perhaps perishing, the traveller, Tantalus like, looks down on the shining silvery threads of water in the cañons, hundreds and even thousands of feet below, but separated from them by impassable barriers. To the south the plateaus descend to the desolate valleys of southern Arizona, where strange gigantic cactus-plants and scattered clumps of thorny shrubs alone break the dreary monotony of the hot gravelly deserts. Agriculture is there impossible without irrigation, but where the life-giving waters can be utilized, as in the Gila Valley, marvellous productiveness follows.
To the west of the Rocky Mountain belt in the United States there exists a region embracing about 210,000 square miles, which sends no stream to the ocean. This vast and in large part desert tract is known as the Great Basin. The climate is characterized by its aridity. The annual precipitation is small and evaporation active. All the water reaching the land is returned to the air by evaporation, either directly or from the streams and lakes. Many of the lakes do not overflow and are more or less alkaline and saline, while some of them, as Great Salt Lake, Utah, and Mono and Owens Lakes, California, are dense with mineral matter in solution.
The Great Basin is not a single level-floored depression, as one might infer from its name, but is traversed by rugged mountain ranges, which divide it into a large number of minor valleys. Some of these secondary basins have lakes and streams which escape from them into lower depressions, but in many instances under present climatic conditions they have no surface water, all the moisture that reaches them being absorbed by the thirsty soil or evaporated without forming lakes. The Great Basin proper, as it may be termed, embraces nearly the whole of Utah and Nevada, together with small portions of the southern parts of Idaho and Oregon and a large area in southeastern California. While the drainage conditions limit the application of the name to this group of associated basins which send no tribute to the sea, the climatic and to a less extent the topographic and geological conditions that characterize it have much wider, although indefinite boundaries. This wider region which resembles the Great Basin proper, extends from British Columbia southward to beyond the city of Mexico, and includes the eastern half of Washington and Oregon, a large part of Idaho, and much of Arizona, New Mexico, and western Texas. In this outer region both to the north and south of the Great Basin proper there are drainless valleys, as those of central Mexico, in which the conditions characteristic of the desert valleys of Utah and Nevada are repeated.
The greater region of arid valleys and desolate mountains surrounding the Great Basin proper is crossed at the north by the Columbia and in the central part by the Colorado. Each of these large rivers has its source in the Rocky Mountains and flows to the Pacific.
The most obvious features of the Great Basin and of the northward and southward extensions of the belt of country having much in common with it, depend on climatic conditions. The rainfall is small throughout the entire belt from the Canadian boundary to south-central Mexico. The average mean annual precipitation, judging from such observations as are available, is probably less than 15 inches, but this broad statement does not truly represent the diverse conditions. The rainfall is confined almost entirely to the winter season, and frequently comes in short heavy downpours. During the summer season, the valleys especially, become so parched that only such plants can grow as are adapted to long-continued droughts. The topography is rough and diversified by many mountain ranges, and the precipitation is more abundant on the uplands than in the valleys. Over large areas in Nevada and southeastern California the mean annual rainfall is less than 5 inches. The author, while carrying on geological work in this region, was informed by some of the older settlers that at times for fully eighteen consecutive months no rain whatever fell in certain of the valleys. From the accounts of travellers in central Mexico, it seems as if some of the interior basins in that region must be fully as arid as those just referred to.
One conspicuous result of the lack of moisture is the absence of forests. Except on the mountains mainly at the north the Great Basin and its extensions, as defined above, is nearly destitute of trees. The valleys are in many instances thickly covered with desert shrubs, notably the sage-brush, but the floors of the driest basins are in many instances almost absolutely without vegetation, and are frequently white with saline incrustations.
Many of the depressions in the Great Basin, as well as some of the outlying valleys referred to, have rivers and lakes which exhibit certain interesting features that are unfamiliar to people dwelling in humid lands. The streams are fed in part by the small precipitation on the desert valleys, and by springs, frequently of heated water, but mainly by the rain and melting snow on the mountains. Many rills and rivulets are born on the valley sides of a single storm, but are absorbed by the thirsty soil or evaporated during the succeeding hours of sunshine. Other streams have a greater lease of life and flow down to valleys and basins, suffering evaporation and absorption as they progress, which cause them to diminish in volume, and finally to vanish. The stronger streams, such as Sevier and Bear Rivers in Utah, the Humboldt River in Nevada, and the Truckee River in California, maintain their existence throughout the year, and expand into lakes in which the inflow is balanced by evaporation.
The lakes of the Great Basin present even greater diversity than the streams. Some of those situated principally in the mountains are of pure, limpid, wholesome water, supplied by cool, sweet brooks and rills or by the melting of the winter's snows, and overflow throughout the year. These lakes, usually of small size, are similar in all respects to the ordinary lakes of humid lands. In eastern Utah, adjacent to the west base of the Wasatch Mountains, the Provo River and other streams supply Utah Lake, the outlet of which, the Jordan River, empties into Great Salt Lake. Utah Lake is well within the Great Basin, and situated at a low elevation for the region, namely, 4,500 feet, or about 280 feet (in 1873) above the level of lake of brine into which it discharges. This is the largest of the fresh lakes in the valleys of the Great Basin, and owes its existence to the fact that a depression there occurs which is filled to overflowing by the streams from the mountains. Bear Lake, in northeastern Utah, is another exceptional example of a fresh lake of considerable size at a comparatively low altitude, in the same region. On the western rim of the Great Basin, at an elevation of 6,247 feet, and surrounded by the forested peaks of the Sierra Nevada, lies Lake Tahoe, "the gem of the Sierra," a water body of remarkable purity, which discharges through Truckee River into Pyramid and Winnemucca Lakes. These lower lakes, situated in desert valleys at an elevation of 3,780 feet above the sea, are without outlets and alkaline and bitter. The most characteristic lakes of the Great Basin, however, are those that do not overflow, and on account of concentration by evaporation are more or less highly charged with mineral matter in solution. These saline and alkaline lakes may be divided into two classes, in reference to their duration, but the line of separation is indefinite. Certain of them have maintained their existence for many years, and probably have not been evaporated to dryness for several centuries, and may be classed as perennial lakes; others are evaporated to dryness each year, or during certain exceptionally dry and hot seasons, and may be termed ephemeral lakes. In many instances the beds of the ephemeral lakes are normally in a state of desiccation, and appear as broad, level, mud plains, usually with a white fringe of saline matter. Frequently these mud plains, or playas, as they are termed, are transformed into shallow lakes during a single storm, but the waters are absorbed by the clays beneath or evaporated within a few days or perhaps a few hours after the rain ceases. The largest and most characteristic of the perennial saline water bodies is Great Salt Lake, the counterpart in many ways of the Dead Sea. The streams discharging into this salt sea have the usual purity of river-waters, and carry but a small fraction of one per cent of saline matter in solution. The lake is supplied also in part, but to an unimportant extent, by springs, the most of which are of essentially fresh water. The source of the salts which make the waters of the lake a brine is evidently, therefore, the small percentage of mineral material brought in by the tributary streams. After reaching the lake these fresh waters, in the ordinary meaning of the term, are concentrated by evaporation. This is the explanation of the leading facts in the chemistry of all of the saline and alkaline lakes of the Great Basin region, such as Pyramid, Winnemucca, and Walker Lakes in Nevada, Mono and Owens Lakes in California, and the saline lakes of Mexico.
The volume of a lake without an outlet, or an "inclosed lake," is determined mainly by the ratio of the inflow (including the rain falling directly on its surface and the tribute from springs) and evaporation. Its volume, and consequently its area, fluctuates from season to season, and frequently varies also during periods embracing several years. With variations in volume there are fluctuations in the percentage of saline matter in solution, even if precipitation of one or more of the contained salts does not take place during the periods of more than usual concentration. In most instances inclosed lakes are concentrated by evaporation in summer seasons, and perhaps become nearly saturated solutions, but are diluted during the rainy winter seasons. Fluctuations in volume, area, depth, salinity, etc., are thus characteristic of inclosed water bodies. They are sensitive to climatic changes which ordinary weather records fail to detect, and are modified in a conspicuous manner when the country about them becomes inhabited and irrigation is practised.
Some of the lakes of the Great Basin are dense brines from which various substances are being precipitated. The economic importance of these natural reservoirs of brine and of various soda salts is great, and will become more and more important as transportation facilities increase. Great Salt Lake, it has been estimated, contains 400,000,000 tons of common salt and 30,000,000 tons of sodium sulphate in solution. During the past ten years about 40,000 tons of common salt have been harvested from it annually. Mono Lake contains some 245,000,000 tons of saline matter in solution, of which about 92,000,000 tons are sodium carbonate and bicarbonate. Owens Lake is similar to Mono Lake in composition, and is now the basis of a large soda industry.
A marked difference between a region which drains to the ocean and one where the streams enter inclosed basins where their waters are evaporated is that in the former the waste from the land carried by the streams as an invisible load in solution or as a visible load consisting mainly of silt and sand in suspension is contributed to the ocean and widely distributed before being deposited—much of the material in solution, in fact, may be said to be a permanent contribution to the salinity of sea-water; but in most instances where streams enter inclosed basins all of the material contributed both in solution and suspension is sooner or later precipitated. The area within an inclosed basin, on which the inflowing streams lay down their loads, is as a rule less extensive than the area that is being denuded to supply the material. The receiving basins are thus filled in or aggraded, and there is a concentration both of the mechanical wash from the land and of the substances taken in solution by the waters of streams and springs. A marked result of this process of concentration, particularly of the fine waste of the uplands and mountains, is seen in the approximately level floors of inclosed valleys. Throughout the Great Basin the valleys have been filled to a depth in many instances of hundreds of feet. Some of the lower mountain ranges in Utah have been so nearly buried beneath these valley deposits that only their summits, termed lost mountains, appear above the even surface of the desert plains. This débris, deeply filling the valleys referred to, is usually a fine yellowish dust-like material, similar in many ways, and probably in mode of origin, to the loess of China in which geologists have taken much interest. With the concentration and deposition of the fine mechanical wash of the uplands there has also been a concentration of the more soluble saline constituents of rocks, which causes the soils of arid regions to differ in an important way from those of humid lands. The leached and characteristically red-tinted soils of warm humid countries, consisting of the oxidized residue of deeply weathered rocks, are absent from arid regions; in their place we find minutely disintegrated, usually light-coloured, and not chemically impoverished soils. In warm humid regions chemical decay of the rocks is the conspicuous feature; in equally warm arid lands mechanical disintegration is carried to an extreme, without the removal of the more soluble constituents. In fact, concentration of saline matter, notably common salt, sodium sulphate, gypsum, etc., is one of the functions, so to speak, of arid climates, when the requisite evaporation basins are present. Among the important industries of the Great Basin region is the gathering and purifying of the various salts contained in the existing water bodies and in the basins of desiccated lakes.
In addition to the characteristics of the region referred to above, which are mainly the result of climatic conditions, the Great Basin has certain geological features, in the main, so far as North America is concerned, peculiar to itself. The leading structural features of the rocks, so far as they find expression in the surface relief, is the presence of a large number of extensive faults trending in general about northeast and southwest. These faults are breaks or cracks along which the rocks have been moved up and down. One side of a fault sometimes stands higher than the opposite side, and forms a narrow and frequently high and rugged mountain range. The number of these faults within the Great Basin is as yet unknown, but they certainly number many hundreds. In a cross profile of the region between the Wasatch Mountains on the east and the Sierra Nevada on the west the number of mountain ridges due to faulting is at least a score. The precipitous western border of the Wasatch Mountains is itself a great fault scarp, as is also the eastern border of the Sierra Nevada. The faults that determine the steeper sides of these mountain ranges are not to be considered as single clean-cut gashes, but as irregular and intersecting fractures traversing a narrow belt of country. The faults referred to divide rocks of all ages, and are evidently due to the most recent disturbances that have affected the region. It is not probable that the break in any given instance was formed all at once. Such vast convulsions would be out of harmony with the rules of nature. But rather many small movements and adjustments of pressure have occurred along the same belt of fracture. This conclusion is sustained by the fact that many of the faults have experienced movements in very recent times. In places fault scarps a score or more feet in height cross the alluvial cones at the mouths of the small high-grade valleys in the mountains. These scarps in loose unconsolidated gravel and similar material, even under an arid climate, could not be expected to preserve their freshness for many years. At times the breaks cross the courses of streams and cascades, and rapids are formed by the waters flowing down escarpments thus produced in loose material. One characteristic fault scarp in Inyo Valley, California, is known to have been formed during an earthquake that shook that portion of the country in 1872. The many small earthquakes that have been felt in the Great Basin region are believed to have been caused by slight movements along the breaks that traverse the region. This and other evidence indicates that the faults to which so much of the characteristic scenery of the Great Basin is due have grown by repeated minor displacements, and that such movements are a common cause of earthquakes.
The most conspicuous topographic features of the better known portion of the Great Basin are long, narrow, and frequently sharp-crested ridges, with a gentle slope on one side and a steep escarpment on the other. The steeper side in a large number of instances is known to be the upraised side of a fault. Each of these basin ranges, as they are termed, may be considered as the upturned edge of a block of the earth's crust, in general from 60 to 100 or more miles long, and 10 to perhaps 20 miles wide. The crest-lines of the tilted blocks are frequently serrate, on account of differences in the hardness and texture of the rocks and the effects of weathering. There is frequently, however, an older structure revealed in them, showing that the region was folded and otherwise disturbed previous to the later movements which produced the leading features in the present topography. It is probable that this older structure in some instances has had an important bearing on the forms of some of the ranges, but our knowledge in this direction is too limited to warrant presentation in a popular treatise.
Many of the basin ranges are imposing on account of their height and ruggedness, when seen from the adjacent, deeply filled valleys, although scarcely more than half of their actual elevation above the sea is revealed from such points of view. Exceptions to this general statement occur, however, in southeastern California, where, in Death Valley, the land is 480 feet below sea-level. This is the only region in North America which, like the basin of the Dead Sea, is below the level of the ocean's surface. On the border of Death Valley the mountain ranges rise from 6,000 to 10,000 feet, and the highest summit, known as Telescope Peak, is reported to have an elevation of nearly 11,000 feet above the sea. In the central and northern portions of the Great Basin the valley floors have a general elevation of from 5,000 to 6,000 feet. The mountains rise from these valleys to a height of from a few hundred to 4,000 or 5,000 feet. Among the highest, if not actually the culminating peaks well within the Great Basin are White Mountain, on the California-Nevada boundary, about 30 miles southeast of Mono Lake, which has a summit elevation of 13,000 feet, and Jeff Davis Peak, in eastern Nevada, which rises 13,100 feet above the sea and 8,000 feet above the adjacent valleys.
The numerous sharp-crested ranges of the region under review are frequently remarkable for the richness of the colours of the naked rocks. The mountain slopes and towering angular summits when outlined against the morning or evening sky are frequently as brilliantly dyed as are the New England hills when clothed in the harlequin foliage of autumn. Before sunrise and after sunset each serrate crest-line is the sharply cut border of a silhouette of the deepest and richest purple. The diversity of scenery in the Great Basin is increased by mountains of volcanic origin, including several modern craters, some of which hold lakes, and by lava-flows of recent date, and by great alluvial fans or detritus cones which stream out into the valleys from the mouths of gorges in the bordering mountains.
The Great Basin proper, with its rugged topography and arid climate, is not an agricultural region. Small portions of it, however, when water can be had for irrigation, have been transformed into fruitful farms and gardens which yield bountiful returns. But even a century hence, when all has been accomplished in the way of reclaiming the arid valleys that can be done by utilizing the available water for irrigation, only a small per cent of the whole will be under cultivation.
To the west of the Great Basin, and extending from southern California northward to beyond the United States-Canadian boundary, there is a lofty and extremely rugged belt of mountains consisting of two ranges—the Sierra Nevada at the south and the Cascade Mountains at the north. Topographically, these two ranges form a single elevated belt of country, but custom, and as is now generally understood the geological structure and history, draws a dividing line between them in northern California. The Sierra Nevada-Cascade range extends far into Canada, and is there known as the Coast Range. No adjustment of the nomenclature in use on the two sides of the international boundary has been made, and in order to conform with current usage, it is necessary to consider separately the two portions of the range on opposite sides of the forty-ninth parallel.
The Sierra Nevada has its southern terminus at Tejon Pass, in southern California, and extending from there northward to Lassen Peak, in the northern part of the same State. With the exception of a small area to the east and north of Lake Tahoe, the entire range is included within the boundaries of California. This is geographically one of the best defined of the larger mountain ranges in the United States. Its eastern border especially is easy to trace, as for the most part it is determined by a great escarpment, corresponding to the fault scarp which borders one side of so many of the basin ranges. The Sierra Nevada, in fact, may be considered as one of the basin ranges of great size and forming the western wall of the region of interior drainage lying to the eastward. This abrupt eastward-facing mountain slope is in reality a great fault scarp, formed mainly by the upheaval of the west side of an intersecting system of fractures. It is not known, however, how much of the escarpment is due to the upheaval of the west side of the belt of fracture, or how much to the sinking of the eastern side. There have no doubt been many up and down movements along this belt, of which the present mountain wall is the algebraic sum. The escarpment rises in general from 5,000 to 6,000 feet above the desert valleys to the eastward, and reaches a maximum of about 14,000 feet in the vicinity of Death Valley. It is exceedingly precipitous and rises to an irregular serrate crest-line, from which the general slope westward to the Great Valley of California is gentle.
The best idea of the generalized topographic form as well as of the origin of the Sierra Nevada, which the reader may be asked to hold in mind, is that the range consists of a block of the earth's crust about 500 miles long and from 70 to 100 miles broad, which has been upraised along its eastern edge so as to give its surface a westward inclination. From this vast monolith the profound cañons and multitude of sharp tapering spires which give to the range its magnificent scenery have been sculptured. Like most generalized pictures of great geographical features, however, this outline of the form and structure of the great mountain range of California has to be modified when studied in detail. From extensive and most painstaking studies by H. W. Turner, of the United States Geological Survey, the conclusion is reached that "the Sierra Nevada may be described as a monogenetic range, composed of highly compressed schists and slates with large areas of associated igneous rocks, chiefly granite and diabase, upon which lie uncomfortably a series of later Cretaceous and Tertiary sediments and volcanic rocks."
Could the profound valleys carved in the long western slope of the Sierra Nevada be filled so as to restore the conditions as they existed when the mountain block was first upraised and tilted, we would have an inclined plane in which the edges of previously folded rocks would be exposed. In other words, the western slope is a tilted peneplain, bearing on its surface remnants of older uplands. High up on the range there are detached areas of well-worn gravel, which were deposited when the slopes were less inclined than at present, and before the existing peaks and cañons came into existence. Certain of the valleys carved during a portion of the earlier stage of erosion were subsequently filled by lava-floods, which buried gold-bearing gravel beneath thick layers of basaltic rock. Erosion has since cut away the softer beds bordering these ancient lava-sheets, and left them in bold relief as table mountains, underneath which miners have excavated tunnels in order to reach the stream-deposited gravels of the ancient cañons. In these instances valleys have been changed to uplands, owing to the resistance to erosion afforded by the volcanic rocks discharged into them.
The long gentle slope on the west side of the Sierra Nevada has been dissected by westward-flowing rivers, which have sunk their channels 2,000 or 3,000 feet or more into the rocks. Other streams having much shorter courses flow down the steep eastern slope of the range and have also excavated cañons. These two systems of drainage, one leading westward to the Great Valley of California and the other eastward to the valleys of the Great Basin, extended their head branches until they came into rivalry with each other, and cut deep notches in the crest of the range. During a late stage in its history the higher portions of the mountains were covered with a great field of perennial snow, from which glaciers flowed both eastward and westward. These ice-streams, by deepening and broadening the previously water-cut channels, still further increased the diversity of the topography and impressed upon it characteristics such as only glaciers can produce.
The highest and most typical part of the Sierra Nevada is in its south-central portion, and is known as the High Sierra. This region, although at present not accurately defined, is well worthy of recognition. Throughout its entire extent, from the neighbourhood of Lake Tahoe on the north to Tehichipe Pass at the south, a distance of about 240 miles, it is diversified by rugged serrate peaks and narrow stream-cut valleys of great depth. Many of the mountains attain elevations of from 12,000 to over 13,500 feet. The highest summit is Mount Whitney, in the southern part of the range and near its eastern border, which rises 14,522 feet above the sea and has the added distinction of being the highest mountain in the United States, exclusive of Alaska. It is a notable fact that this great mountain-peak should be situated only about 100 miles from Death Valley, the lowest depression on the continent.
Another of the remarkable features of the Sierra Nevada is the great depth and the wonderfully precipitous walls of some of the valleys carved by the westward-flowing rivers. The most famous of these is the sublime Yosemite Valley, now world-renowned. This cleft as it appears in solid light-coloured granite, over a mile deep, is believed by Turner, the last of several geologists to discuss its origin, to be due to stream erosion. The fact seems well established, however, that glacial ice has assisted in the great task. The Yosemite is not such an unique feature as was at one time supposed, but is approached if not equalled in depth and magnificence by Hetch Hetchy Valley, through which flows the Tuolumne River, and is duplicated, in part at least, by other similar stream-cut gulfs.
Among the chief elements in the glorious scenery of the Sierra Nevada is the multitude of lakes left as a rich inheritance by the departed glaciers. These occur not only high up amid the bare peaks where their basins were excavated by the flowing ice, but also in the lower valleys where the ancient ice-streams built morainal dams.
The High Sierra was swept nearly clean of soil and débris by the ancient glaciers, and the hard rocks thus exposed were rounded and burnished by the ice that flowed over them. But little disintegration or decay of the rocks has taken place since an amelioration of climate changed the drainage from a solid to a liquid form. On account mainly of the general absence of soil the forests are less dense than might be expected from the height of the regions where they occur and its general climatic conditions. The more lofty peaks reach far above the forests and are riven and shattered by frost. The crests and cliffs at somewhat lower altitudes are also bare, but in the cañons and on the meadow-like valley bottoms smoothed by the glaciers, open park-like groves of pine and spruce grow in picturesque disorder. On the ledges of the great precipices, and on many of the secondary summits, gardens of alpine flowers blossom in late summer, and at times impart a rich warm glow to the heights that support them. The views of nature, unmarred by the hand of man, which reward the persistent mountaineer in this silent wonderland of the upper world, are not only grand beyond all description, but beautified by a delicacy of decoration where snow-fields and alpine gardens meet, that is undreamed of by the dwellers in the denser air of the plains and seaside. Lovers of nature who are unable to climb the towering summits of the High Sierra and see for themselves the marvellous beauty there so lavishly displayed can at least find a glowing pen picture of it in John Muir's fascinating book The Mountains of California. On the lower western slope of the Sierra Nevada the forests become continuous and luxuriant, the trees are of large size, and the lovely flowers carpeting the valleys and hillsides take on a more familiar appearance than the gorgeous blossoms of the alpine meadows. It is in this region that the gigantic Sequoia still lingers as a remnant of a nearly extinct flora.
Statements of heights and depths, of geological structures, and of topographic forms are perhaps necessary to enable one to form a mental picture of a snow-crowned mountain range which will bear some faint resemblance to the mighty original; but when one threads his way through the resinous forests on the lower slopes of the Sierra Nevada, ascends some one of the profound water-cut rifts in its side, scales the steep cliffs, traverses the crystal surfaces of the small glaciers, and finally stands on a spire-like summit covered only by the dark blue of the dome above, all thoughts of the arches and walls that support the mighty cathedral are lost in wrapt wonder and admiration of the magnificent scene about him. It is this intense feeling for the sublime and beautiful in nature that the student of geography should strive to cultivate, as well as to acquire skill in reading the prosaic history written everywhere on the mountains. This important lesson can seldom be studied to greater advantage than amid the silent awe-inspiring peaks of California.
The Cascade Mountains, as previously stated, are a direct continuation, so far as the relief is concerned, of the Sierra Nevada. The geological structure of the region in northern California, where the two ranges approach each other, has been studied by J. S. Diller, of the United States Geological Survey, who concludes that they present characteristic differences. In the Cascade Mountains in northern California, Oregon, and southern Washington the rocks exposed at the surface are mainly, if not entirely, of volcanic origin, and were poured out in a molten condition as lava-flows, or as fragmental ejections from volcanoes, and in part rose through fissures and formed what are termed fissure eruptions. The rocks thus extruded are mainly composed of dark, heavy basic material, such as basalt and andesite. These outpourings of molten rocks were on a grand scale, and a large number of volcanic mountains were formed which still remain as the dominant peaks of the rugged and densely forested Cascade Range. Although the evidence now available seems to show that there is a striking difference between the Sierra Nevada and the Cascade Mountains, another significant change occurs when one follows the Cascade Mountains into northern Washington. Where the Northern Pacific Railroad crosses the range the volcanic rocks are succeeded northward by granites, schists, serpentine, etc., and Cretaceous and Tertiary sedimentary beds of much the same character as those in the Sierra Nevada.
The study of the Sierra Nevada-Cascade region has not progressed far enough to warrant a decision, but the fact referred to above strongly suggests that the two ranges, as we now term them, are essentially a single uplift, a large portion of which, extending from Lassen Peak, in California, northward across Oregon and into Washington as far as the Northern Pacific Railroad, is buried beneath a great blanket, so to speak, of lava-flows. The tract of elevated and rugged country in northern Washington embraced in the Cascade Mountains, as has been observed by the writer, passes into Canada without a marked change in either its geology or geography, and there is no occasion for a change of name when the international boundary is crossed.
The Cascade Mountains in Oregon and southern Washington, where the surface rocks are mainly and perhaps wholly of volcanic origin, are rugged for two principal reasons: First, volcanic energy has built up great individual peaks; and second, erosion has carved deep valleys and numerous ravines and gorges. The volcanoes are now extinct, or have long been dormant, and their cold summits are in several instances crowned with perennial snow and small glaciers. The forms given to the more prominent elevations by the eruptions which built them have to a great extent been defaced by erosion. As they stand to-day they furnish an instructive series of more or less deeply dissected volcanic mountains.
Not only has erosion changed the characteristic slopes of the peaks built of lava-flows and ejected fragments, but in at least one remarkable instance the volcanic energy itself greatly altered the structure it had previously raised. Mount Mazama, situated in southern Oregon in the summit region of the Cascades, is a truncated volcanic cone in the top of which there is an immense depression now partially filled by the waters of Crater Lake (Fig. 21). The main features in the history of this unique mountain with a lake in its summit, as interpreted by Messrs. Dutton and Diller, of the United States Geographical Survey, are as follows: It once stood as a conical peak, similar to several other mountains of volcanic origin in the same region, some 15,000 feet in height; it was then an active volcano with a summit crater filled with lava, but subsequently, for a time at least, became dormant and was occupied by glacial ice. At a later period an escape for the lava was furnished by a fissure or other opening which admitted of a surface discharge at a more or less distant locality, in a manner similar to the escape of the molten rocks from the great volcanoes of the Hawaiian Islands within historic times. This drawing off of the lava from the crater removed the support afforded its walls from within, and the summit portion of the mountain, embracing about three-fourths of its height above the adjacent valleys, fell in and was engulfed. The mountain was thus truncated, and presents the general appearance of similar cones the upper portions of which are known to have been blown away by explosions. But in the case of Mount Mazama, the hypothesis of truncation by explosion seems to be disproved by the absence of the fragments of the portion removed on the slopes remaining or on the surrounding region. After the falling in of the summit of the mountain comparatively mild volcanic explosions followed which built a cone within the great pit or caldera in the summit of the truncated mountain, but without filling it. The space left vacant is now occupied by water, and thus transformed into a lake. The cone built after the catastrophe referred to now forms Wizard Island, near the southwest border of Crater Lake.
Some idea of the magnitude of the changes wrought in Mount Mazama by the events recorded in its geology and topography may be obtained from the following facts: Crater Lake has a surface elevation of 6,239 feet above the sea, and is nearly 2,000 feet deep in its deepest part; the precipices surrounding it are from 520 to 1,987 feet high. The whole depth of the depression is therefore 4,000 feet. This caldera, as such basins of volcanic origin are termed, is nearly circular, with an east and west diameter measuring 6 miles, and a north and south diameter of 5 miles. The volume of the pit is nearly 12 cubic miles.
Not only is Mount Mazama with its wonderful lake one of the most unique natural features of North America, but it has its full share of the artistic details of lake and mountain scenery which appeal so forcibly to the finer instincts within us. The outer slopes of the mountain are clothed with the all-embracing coniferous forests which cover the Cascades as with a mantle throughout their entire extent, while the precipitous inner slopes are for the most part bare precipices of angular and extremely rugged rock. The lake itself is of the most marvellous blue, in which the encircling cliffs, the crater-island, and the sky above are reflected.
Other peaks along the crest-line of the Cascades to be numbered by the score, although with less romantic histories than Mount Mazama, have instructive answers to give when properly questioned. Among the remarkably picturesque summits rising above the dark coniferous forests of western Oregon are the following, with their respective heights above the sea expressed in feet: Mount Pitt, 9,760; Mount Mazama, 8,228; Mount Union, 7,881; Mount Scott, 7,123; Three Sisters, Mount Jefferson, 10,200; and Mount Hood, 11,225. Of these peaks, the best known, on account of its proximity to the city of Portland, and at the same time one of the most picturesque and beautiful, is Mount Hood, situated about 25 miles south of the Columbia River. The concave slopes so characteristic of volcanic cones are no longer conspicuous on the sides of this once symmetrical mountain, and only remnants of its crater remain. The part it played as a safety-valve for the pent-up energy beneath was long since finished, although heated vapours still escape from an opening near the summit. Similar manifestations of heat have also been observed about several other ancient craters in the Cascades, but these occurrences are not considered as indicating that actual connections still exist with reservoirs or bodies of molten rocks below the surface: they are evidently due to the residual heat of the once molten rock in the conduits of the now extinct or dormant volcanoes.
The lava-flows and volcanic mountains typically displayed in the Cascades throughout the breadth of Oregon continue northward and form at least the surface portion of the same range in Washington as far as the Northern Pacific Railroad, or about 100 miles north of the Columbia. The more important volcanic mountains in western Washington are, in their order from south to north; as follows, the height of each being given in feet: Mount Adams, 9,570; Mount St. Helens, 9,750; Mount Rainier, 14,525; Glacier Peak, 10,436; and Mount Baker, 10,877. Only two of these ancient volcanoes, namely, Mount Adams and Glacier Peak, are situated on the crest-line of the Cascade Mountains; the others are to the westward and more or less completely detached from the main range.
The Cascade Mountains are in general parallel with the shore of the Pacific, and rise as a prominent barrier athwart the path of the prevailing westerly winds. Precipitation on their seaward slopes is copious, but their landward sides overlooking the arid plains of central Washington are far less humid. The westward, or rainy slope, is clothed with a magnificent forest of giant trees, while the eastward, or sunny side, is largely without forests, but abounds in natural meadows and pastures. Large portions of the mountains are still almost entirely unknown, and retain their primitive wildness, except that forest fires, particularly near the international boundary, have in places made desolate the once beautiful valleys and precipitous slopes. Elk, deer, bear, the mountain-goat, and mountain-sheep still roam the forests. The large streams abound in salmon, and each cool, clear brook and rushing creek is a favourite haunt of the trout. No more delightful camping-ground for lovers of nature and searchers for recreation can be found than the grassy, park-like valleys on the sunny side of these magnificent mountains.
Many of the details in the scenery of the Cascades are due to the work of ancient glaciers. Numerous lakes, held in rock-basins in the higher portions of the mountains, and many still larger sheets of water retained by morainal dams in the lower valleys, give a superlative charm to many a wild and rugged landscape. The largest and most interesting lake in the entire Cascade region is Lake Chelan, situated in a deep valley on the eastern side of the mountains in north-central Washington. This beautiful sheet of water, a mile or two wide, extending like a placid river for some 70 miles into the mountains, resembles in many of its features the far-famed lakes of northern Italy. The mountains inclosing this hidden gem of the Cascades rise abruptly from the water's edge to great heights, and with one exception are unbroken by deep side-valleys. For fully 50 miles the blue plain of water is overshadowed on each side by crags and precipices from 5,000 to 6,000 or more feet in height. The lower slopes are dark with forests of pine and fir, and the bare serrate spires above are white with snow long after the spring flowers have faded in the lower vales. The water of the lake is clear and sparkling, and has the deep-blue colour of the open ocean. The sounding-line has shown a depth of 1,400 feet, and the bottom is about 300 feet below sea-level. This wonderful lake, clasped in the embrace of the eastward extended arms of the Cascades, is but 2 or 3 miles from the Columbia River, into which it discharges its surplus waters through Chelan River, and may be easily reached from Wenachee, on the Great Northern Railroad, by steamers on the Columbia. Although at present scarcely known to the world of tourists, Lake Chelan is destined to take as an important place in the lives of those who seek rest and recreation as does Lake George in northern New York at the present day.
Before attempting to trace the Pacific mountains northward through Canada and Alaska, let us glance at the leading geographical features to the west of the Sierra Nevada-Cascade uplift.
To the west of the Sierra Nevada-Cascade Mountains, and bordered on the west by another and very nearly parallel series of elevations, known in a general way as the Coast Mountains, there is a succession of long, relatively narrow basins, situated end to end, and constituting what may be termed a valley-chain. This series of basins extends from southern California northward far into Canada, and includes, in their order from south to north, the great Valley of California, the Willamette and Cowlitz Valleys in Oregon and Washington, and the Puget Sound basin, together with its great but indefinitely defined northward extension.
The Great Valley of California has a length of about 500 miles and an average width of approximately 40 miles, and is greater in area than either Belgium, Denmark, or Switzerland. It is divided in reference to drainage into two portions, the San Joaquin Valley at the south and the Sacramento Valley at the north, named respectively after the rivers that drain them. These two streams unite and discharge into San Francisco Bay, the outlet of which is through the Golden Gate to the Pacific. This central basin of California has a generally flat bottom composed of a great depth of unconsolidated gravel, sand, and clay, which are believed to owe their deposition mainly to the streams flowing from the bordering mountains, although in part they may have been deposited when the land was more depressed than now and the basin was a great sound, connected with the ocean by a single narrow opening. The rock-waste swept into the valley served not only to add to the accumulations forming its floor, but to give the bottom some irregularities. A portion of its southern end, shut off by alluvial deposits brought down from the Sierra Nevada, is occupied by the shallow alkaline waters of Tulare Lake. When the great valley was first visited by white men it was without trees, except along the immediate borders of some of the streams, and for the most part was a luxuriant meadow of wild grasses and flowers. On the uplands oak-trees grew in scattered park-like groves with gorgeously flower-decked hills and vales between. This favoured land, clothed in its natural beauties, came as near being an Eden as perhaps any portion of the continent. The changes that have followed the settlement and cultivation of this great mountain-inclosed basin are simply marvellous. Cities and villages have been built, orchards and vineyards planted which yield most bountiful harvests, and the once grass-covered plains are now seemingly boundless wheat-fields. The unkept natural garden of half a century ago has become a granary not only for the people of America, but for those of Asia as well.
To the north of the Klamath Mountains, which shut in the central Valley of California at the north, lies the beautiful Willamette Valley, about 150 miles long, drained by the northward-flowing river of the same name, which joins the Columbia where the thriving city of Portland now stands. The depression between the mountains of which the Valley of the Willamette forms a part, extends north of the Columbia, and is there drained by the southward-flowing Cowlitz River. The relation of these two valleys is much the same, although on a smaller scale, as that existing between the San Joaquin and Sacramento Valleys, except that the Columbia, after passing through the Cascade Mountains, receives the Willamette and Cowlitz rivers as tributaries, one from each side of its course. This Willamette-Cowlitz depression is surrounded by densely forested hills and the snow-capped summits of ancient volcanoes. The soil was originally highly fertile, and although now somewhat impoverished, still furnishes a substantial basis for agriculture, and renders the region one of the most productive as well as most beautiful in the United States.
To the geographer the Willamette-Cowlitz Valley seems scarcely distinct from the great depression farther north in the same valley-chain, which now holds the waters of Puget Sound, except that there is a low water-parting between. This divide, as previously suggested, is thought to be due largely to stream and glacial deposits, which have been laid down in the previously nearly level-floored intermontane trough.
The Puget Sound basin has a length from south to north of about 150 miles, and extends from the Olympic Mountains on the west to the Cascade Mountains on the east, a distance of some 60 miles. The sound terminates at the north at the Strait of Fuca (at Port Townsend, in Fig. 23), but the depression in which it lies continues northward, with similar geographical and geological characteristics. In a general way the same depression may be said to extend northward to southeastern Alaska, but is there deeply water-filled, and its western border is discontinuous and broken into many islands.
There are several features in the Puget Sound basin which especially impress the traveller: Next to the magnificence of the lofty volcanic cones that stand like Titan watch-towers along the western slope of the Cascades and the dense forest of gigantic firs and cedars, the most conspicuous feature of the region is the extreme irregularity of the sound itself. Even such general maps of Puget Sound as are usually available indicate that it is exceptional and different from all other water bodies on the continent, not including the extension of the same series of basins northward. Not only is Puget Sound extremely irregular, and inconsistent with any theory that would ascribe its origin to the subsistence and drowning of stream-eroded valleys, but its waters are deep and the channels narrow. The uplands between the waterways are low plateaus composed of clay, gravel, and glacial moraines. The explanation of these unique conditions is that glacial ice formerly occupied the basin and deposited moraines and gravel-plains and clay-plains about its margins; when the branching and irregular sheet of stagnant ice melted its place was taken by the waters of the sea. This simplified outline of the later history of Puget Sound has many modifications, the most important being that there were at least two periods of ice occupation, with an intervening stage of mild climate between, during which the previously formed glacial deposits were forest covered and thick beds of peat formed.