1902 Encyclopedia > United States > The Cordilleran System

United States
(Part 16)


Part 16. The Cordilleran System

For convenient description, this system may be divided into the following six regions: - I. the Rocky Mountains; II. the Great Basin and the Basin ranges; III. the Northern or Columbian plateau; IV. the Southern or Colorado plateau; V. the Sierra Nevada and Cascade ranges; VI. The Pacific Coast ranges.

I. The Rocky Mountains form the eastern border of the Cordilleran region, - a border made up of many subordinate ranges. They may be divided into two parts – the north and south trending portion, and the north-west and south-east trending portion. Between these two subdivisions there is a marked orographic break, in the form of a high plateau region, over which the Union Pacific Railroad passes at an elevation of about 8000 feet. On the north of this plateau are the Sweetwater and the much higher Wind River Mountains, which latter form the culminating region of the continent, since in them head the three great river-systems of the country, - the Missouri, the Columbia, and the Colorado.

(A) The southern or north and south trending division is about 600 miles in length from north to south, and about 300 in breadth. Its eastern edge is extremely well market, the ranges rising abruptly from a very gently sloping plateau. Looking at this division in the most general way, we find on its eastern edge a double range of mountains, quite distinctly marked in Colorado, or between the parallels of 36 and 41°, where they enclose a system of high plateau-like valleys, known as the North, Middle, South, and San Luis Parks, which have an elevation of from 6000 to 10,000 feet, the enclosing ranges rising 3000 to 4000 feet higher. These so-called parks are drained by the head waters of the Platte, Colorado, and Arkansas, with the exception of the San Luis Park or Valley, in which lies the upper course of the Rio Grande, whence it finds its way southward, through New Mexico, having a pretty well marked and lofty range on its eastern side, and more broken ones on the west, the two representing the Front and Park ranges of Colorado.

The Front of Colorado range proper, beginning as a junction at the south of the Medicine Bow range and the Laramie Hills, which are low inconspicuous ranges closing in the plateau above noticed as separating the two divisions of the Rocky Mountain system, is a broad, lofty mass, continuous from about 41° N. lat as far as Pike’s Peak, about lat. 38° 45’, when it runs out into the plain. The best known points in the Rocky Mountains – Long’s peak (14,271 feet) and Pike’s Peak (14,147 feet) – are in this range; both are visible from the plains, and are conspicuous landmarks. Gray’s Peak (14,341 feet) is the highest point in this range; but, although on the continental divide, it is too far west to be visible from the plains. This divide, which separates the Atlantic waters from those of the Pacific, follows the Front range as far as Gray’s Peak, where it is deflected westward for 20 miles to the Sawatch range, which it follows for about 75 miles. In this deflection the divide passes between Middle and South parks, the lowest pass in this part being that called the Tennessee (10,418 feet), which leads from the head of the Arkansas to the Grand river branch of the Colorado.

The Sawatch range is one of the highest and best-marked chains in the Rocky Mountains. It lies west of the head of the Arkansas; and its dominating peaks, along the whole range, exceed 14,000 feet. The most northerly of these, the mountain of the Holy Cross (14,176 feet), was so named on account of the existence on its eastern flank of a large snow-field lying in two ravines which intersect each other at right angles, in the form of a cross, and which in summer is conspicuously visible from a great distance. The highest point is Mount Harvard (14,375 feet), and the passes range from 12,000 to 13,000 feet. The continental divide follows the Sawatch range to its southern end, in lat. 38° 20’, and then runs in a south-westerly direction for about 75 miles, over a high region without any distinctly marked range. Here it turns, and, running south-easterly, follows the crest of the San Juan range, which at many points rises above 13,000 feet. This range forms the western border of the San Luis park, and, from its north-western end, in going either north, north-west, or west the explorer finds a very elevated and exceedingly broken country, which finally merges in the plateau or "mesa" region of western Colorado. Uncompahgre Peak (14,235 feet), a magnificent isolated summit of volcanic materials is the culminating point.

West of the Sawatch range is that of the Elk Mountains, a volcanic mass of sharp pinnacles, the culminating point of which – Castle peak – is over 14,000 feet. Between the Elk Mountains and the Uncompahgre rise the various branches which unite to form the Gunnison river.

The entire western portion of Colorado is a high plateau region of sedimentary rocks, of late geological age, cut deeply into by numerous streams, giving rise to canons or ravines alternating with mesas or plateaus, the whole forming a labyrinthine succession of depression and elevation. The mesas are sometimes so nearly eroded away that the remaining portion of the flat surface is hardly wide enough for a bridle path, while at other times there is a broad area of nearly level surface, bordered on each side by tremendous precipices. The small valleys on the streams, where there is an area of level land large enough to be a feature in the topography, are called "parks" or "holes." The area occupied by these, in Colorado, west of the continental divide, is extremely small as compared with the whole area of the region.

When the "parks" are spoken of in describing the Rocky Mountains, it is usually the more conspicuous ones-the North, Middle, South, and San Luis Parks-that are intended. The North Park is a tolerably level area, about 40 miles by 20, and quite walled in by high ranges rising at points above 12,000 feet. This park is a favorite resort for hunters. In it rises the North Fork of the Platte. Middle Park, which is drained by the branches of Grand river (not to be confounded with the Rio Grande), is much more broken by elevations than North Park. The continental divide surrounds it on every side excepting the west. There are but few points in this park under 7000 feet. South Park is about 40 miles in length and 15 to 20 in breadth; it is more nearly level than the North or the Middle Park, and has a higher elevation than either (about 10,000 feet at its northern end, and declining gradually southward to about 8000). The San Luis Park, or Valley, is much larger than the more northern parks, and is closed in by high mountain ranges. On its north-eastern side it has a boundary the Sangre de Cristo range, of which the culminating point is Blanca Peak, the highest point in the Rocky Mountains (14,463 feet). The Sangre de Cristo range is almost a continuation of the Sawatch, having the same trend and similar geological characters, the two being separated by the broad depression known as Poncho Pass (about 9000 feet). The north-western portion of the San Luis Valley is closed in by the Garita Hills, which are a part of the great irregular volcanic mass continued north-westerly by the Uncompahge and south-westerly by the San Juan range. The San Luis Valley is traversed by the Rio Grande, which enters it from the west, rising in the above-mentioned volcanic region. In the northern and wider portion of the valley the mountain streams sink or are lost by evaporation before reaching the Rio Grande, and most of this portion of the valley is sandy, and unfit for cultivation except where it can be artificially irrigated.

Proceeding westward from the San Juan range, in lat. 38°, we soon enter the plateau region which extends to the Colorado. This plateau region is bounded on the north-east by the volcanic masses of the San Juan, Uncompahgre, and Elk Mountains, at the western base of which spread the great tables or mesas of Cretaceous and Tertiary rocks, often capped by volcanic materials, and which thus already begin to exhibited the characteristic features of the plateau region. Here the principal branches of Grand river and of the Gunnison have their sources. The Grand itself rises in the Front range on the western slope of Long’s Peak, while the Gunnison heads near Mount Harvard, the two uniting near the western boundary of Colorado, near 39° N. lat.

Directly west of North Park, and separated from it by the mass of the Park range, and also by a broad belt of high mesa country, is the Uintah range, remarkable as having an east and west trend, and thus forming a sort of connecting ink between the eastern edge of the Rocky Mountain system and its western border, of which the Wahsatch range is the most strongly marked division. Starting from the eastern side of the Wahsatch, where it inosculates with it, it runs east for a distance of 150 miles, when it sinks and becomes lost in the tertiary and Cretaceous mesas lying west of the Park range. It has the Bridger basin on the north – a continuation of the Laramie Plains, - the two together forming an important member of the orographic break between the north and south divisions of the Rocky Mountain system already indicated. The Bridger basin is underlain by rocks of Eocene Age, and has an elevation of 6000 to 7000 feet, Fort Bridger itself being 6,753 feet above the sea. South of the Uintah range is the Uintah Valley, also underlain by Tertiary rocks, forming the north-westernmost division of the Colorado plateau region. The Uintah range itself is of very simple geological structure, being a low flattened anticlinal, complicated by one or more faults on the northern edge. The Tertiary and Cretaceous strata have been so much eroded away on the higher portion of the flattened arch that the chief rock exposed in the body of the range is the underlying Carboniferous. The highest points, as given by the Fortieth Parallel Survey, are Gilbert’s Peak (13,687), Tokewanna (13,458), and Wilson’s peak (13,235 feet). The southern slope of this range is drained by the affluents of Green river, which unites with the Grand, about 175 miles farther south, to form the Colorado.

The Wahsatch range is one of the most conspicuous of the Rocky Mountain system, and, as it borders the Great Basin on its eastern side, it may properly be considered as forming the western limit of the Rocky Mountain southern division of he Cordilleran system. This range has a nearly north and south trend, rising with a hold escarpment to a height of nearly 12,000 feet in the portion of the range just east of Salt Lake City, but falling off gradually towards the north and not being recognizable as a distinct range beyond Bear river. This stream rises on the northern slope of the Uintah range, in nearly the same latitude as that of Salt Lake City, then flows northward for more than 100 miles, to lat. 42° 40’, when it turns and follows an almost exactly opposite course, finding its way round the north end of the Wahsatch range and emptying into Great Salt Lake. In the loop thus made by Bear River range, in which North Logan Peak rises to 10,004 feet, and others are of nearly equal altitude. The whole of the Wahsatch region – the range of that name as well as the parallel ranges and spurs on the east – is one of difficult and complicated topography. It forms the connection between the north and south divisions of the Rocky Mountains, and connects by spurs and irregular lines of elevation with the Wind River range, the range of the Tetons, and the Snake River Mountains.

Although Bear river runs for more than a hundred miles in a northerly direction before crossing the Wahsatch range, the Weber river, which rises in the Uintah range, three or four miles of the head of Bear river, runs with a pretty direct north-westerly course across that range, breaking through it where it is from 8000 to 9000 feet in elevation, and affording an easy route for the railroad from the Birdger and Green river basin to Salt Lake.

(B) The northern division of the Rocky Mountains has been much less fully explored than the southern. It also is made up of a large number of ranges, having a general though by no means uniforms north-west south-east trend. As a whole, thisdivision is lower and less impressive from the grandeur of the masses than the southern; and as we advance north-westerly we find more monotony in the scenery, more uniformity in the height of the ranges, and an almost entire absence of dominating peaks. Striking exceptions to this condition are offered by the Wind River and the Yellow-stone geyser region.

The Northern pacific Railroad, by which access is had from the east to this portion of the Cordilleras, strikes across the plains from the western end of Lake Superior, directly west to the Missouri, which it crosses in 101° long., at Bismarch, near the center of Dakota. From this crossing it runs in almost a straight line to the Yellowstone river, which it follows for a distance of 340 miles. It then crosses to the Missouri at Gallatin, and follows that stream to near Helena, a distance of about 100 miles. From here the ascent of the main divide of the Rocky Mountains is made by way of Mullan’s Pass, the summit being crossed by a tunnel 3850 feet long, at an elevation of 5548 feet. Thence the line follows Hell-Gate river, the Missouri, and Clark’s Fork, to lake Pend d’Oreilles (2059 feet),which it curves round on the north, and then strikes directly south-west to the junction of Snake river with the main Columbia.

The Rocky Mountains, in their north-western portion in Montana and Idaho, are more irregular in their development than they are farther south. There is, however, a similar tendency in both regions to the formation of those mountain –enriched valleys which are so generally known in this region as "parks," although not infrequently called "prairies." These parks are mostly destitute of timber, excepting the cotton-woods along the banks of the streams. The mountains are more or less covered with coniferous trees, not of great size, but sufficiently large for ordinary building purposes. As the ranges themselves are lower than in Colorado and in the southern division generally, so the high enclosed valleys are also proportionally lower. Portions of them have a soil suitable for cultivation; other portions are covered with bunch grass and well adapted for grazing. There is considerable uncertainty in the nomenclature of the various individual ranges. The name Bitter Root is most frequently given to an important range, which in a portion of its course forms the main divide between the Mossouri and the Columbia, but which, farther to the north-west, separates the waters tributary to the Snake from those which unite of form the Clarke’s Fork. The Lapwai and Coeur d’Alene ranges lie west and north-west of the Bitter Root Mountains, and unite the Rocky Mountains with the Blue Mountains, an important, but little-known group of ranges occupying a considerable portion of the region lying west of Snake river. There are also various groups of mountains, more or less isolated in position, and lying to the east of the main range of the Rocky Mountains in this portion of their extension. The Crazy Mountains form an isolated group immediately north of the Yellowstone river. They occupy an area about 40 miles long and 15 wide; the highest point is Crazy Peak (11,178 feet), and there are numerous others approaching 11,000 feet. The mass is formed by immense outbursts of volcanic rocks through horizontally lying strata consisting of sandstones and shales of Cretaceous age. The Judith Mountains form another more or less isolated group farther north-east, in 109°-110° W.

To the south-east, again, are the Big Horn Mountains, an extensive range forming an advance guard, as it were, of the main chain, between 43° and 46° N. lat. Still farther east, and in entire isolation from the main range, is the large and important group known as the Black Hills, in 103° to 105° W. long., embracing a region which has lately become of considerable importance on account oval shape, about 120 miles in length and from 40 to 50 in width; the average elevation is from 2000 to 3000 feet above the surrounding country; but the highest point – Mount Harney-reaches 9700 feet. Deadwood, the principal mining settlement, has an elevation of 4630 feet. The geological structure of this range is comparatively simple, and typical of that of a very considerable portion of the Rocky Mountains, especially of the ranges of the northern division. The central or axial mass is of an oval form, about 70 miles in length by 40 broad, and is made up of crystalline rocks,- granitic, gniessoid, and schistose in character. The sedimentary rocks rest upon it uncomfortably, folded like a mantle around its base, and everywhere dipping from it, at a higher angle near the axial mass, and at a lesser one as we recede from it. The lowest fossiliferous rock is the Potslam sandstone, from 200 to 300 feet in thickness. On this rests conformably a series of beds of Carboniferous age, 600 to 700 feet in thickness, and this group is succeeded by the series of deep-red sandy gypsiferous strata, the "Red Beds" of the Rocky Mountain geologists, a very conspicuous feature of the geology through a large portion of this region, and the more so because often eroded into peculiar fantastic and picturesque forms. These beds are considered to be of Triassic age. In the Black Hills their total thickness varies from 300 to 400 feet. Above the Red Beds lies the Jurassic, which here has a quite uniform character, and is made up of grey or ash-colored marls, marly limestones, and soft sandstones. The thickness of this group in the central region f the Black Hills is about 200 feet, increasing to the north, and attaining in Belle Fourche Valley a maximum of 600 feet. In the Wind River range the Jurassic is more largely developed, and farther to the south and south-west, through the Rocky Mountains and in the ranges south of the Great Basin, it is still thicker. Above the Triassic and Jurassic, and conformable with them, are the various members of the Cretaceous series, so largely developed in this region, varying in lithological character, the upper 600 feet composed of soft, easily eroded materials, and containing many characteristic Cretaceous fossils. The position of these various groups of strata, some quite hard and others very soft, wrapped concentrically around the axial mass, and cut through by a radial drainage, has given rise to an interesting topography, easily understood from its simplicity, and little obscured by any covering of forest vegetation. A remarkable feature of the landscape, on the western bank of the Belle Fourche, is the Bear Lodge, or Devil’s Tower, "a great rectangular obelisk of trachyte, with a columnar structure, giving it a vertically striated appearance," rising 625 feet from its base, the summit being entirely inaccessible.

II. The Great Basin is the name now given to a region embracing an area of about 225,000 square miles, and having no drainage to the sea. Its shape is roughly triangular, the apex of the triangle being near the mouth of the Colorado river, and its base extending in an irregular line, approximately east and west in direction, from near the north-eastern corner of California to a point on the northern slope of the Uintah range, where, as already mentioned, Bear river has its source. The length of the east side of the triangle thus designated is approximately 600 miles. From the northern side or base the drainage is into Snake river; on the south-eastern side rise various branches of the Colorado; and the south western is very distinctly marked, for the greater part of its length, by the crest of the Sierra Nevada.

The Great Basin is an elevated plateau, traversed by numerous ranges of mountains, having a general north and south trend, and a very considerable elevation above the intervening valleys. While there is a marked tendency in these ranges to isolation from each other, and to separation by deep and persistent valleys, there is still so much inosculation of one range with another, and so much irregularity in their development, that it is extremely difficult to define their number or to group them. Starting from the crest of the Sierra Nevada, at a point west of Pyramid Lake, and going in a direction a little north of east of Salt Lake, the traveler would cross about twenty mountain chains, mostly very distinctly marked, and separated by deep valleys of from 4 to miles in width. The height of the plateau from which these chains rise is greatest in its central portion, and it declines eat and west and also towards the south, where considerable areas are actually below the level of the sea. The most important centers towards which the drainage converges are Salt Lake, about 4250 feet above the sea, and the sink of the Humboldt and Carson, very nearly at the same elevation. The head of the Hmuboldt river is near Cedar Pass (6263 feet), about 100 miles west of Salt Lake. This river therefore marks a distinct line of depression near the northern edge of the Great Basin, and in going south from this we rise in the various valleys to heights of from 5000 to 7000 feet. The Humboldt Sink not only receives the surplus drainage of the northern portion of the Basin, but is on the same level, and after a wet season in actual continuous connection, with the Carson Sink, into which quite an extensive portion of the eastern slope of the Sierra Nevada is drained. Throughout the Great Basin the valleys between the ranges are themselves usually sinks, the lower portion being frequently occupied by bodies of water which vary in size according to the atmospheric precipitation of the preceding winter, and in many cases are hardly more than saline incrustations resting upon a more or less muddy bottom. In general the valleys are nearly bare of vegetation in their lower portions; higher up they are covered with a growth of desert shrubs. There are, in occasional favored localities, small sedge grass meadows. There is a rapid falling off in elevation of the Basin region towards its south-western corner, and here portions are below the sea-level. Death Valley, the sink of the Armagosa river, is one of these depressed regions, and along the line of the Southern Pacific Railroad is another depression, a little over 60 miles in length, he lowest portion of which is 263 below the level of the sea. Of the ranges traversing the Great Basin, with a trend approximately north and south, some are short and inconspicuous , while others maintain an almost unbroken crest for 100 miles or more. Their parallelism in certain portions of the Basin is very striking. The loftiest range is that called the East Humboldt- or more frequently simply the Humboldt; this rises about the middle of the Basin, its southern end being in 115° 30’ W. long, and runs north-north-east for about 100 miles to near the head of the Humboldt river. At the north end of this range is Mount Bonpland (11,321 feet), the culminating point of the Basin ranges. The Pah-Ute range, about 150 miles west of the Humboldt, is another very persistent line of elevation, although rather irregular in trend, and not very high. The West Humboldt range is also a conspicuous one near the western side of the basin; its culminating point is Star Peak (9925 feet). The mountain ranges of the Basin are characterized by the almost entire absence of forest vegetation, trees being abundant only in their higher portion in the deeply hidden canons. The rocks are everywhere exposed along the ridges and flanks. The valleys are deeply filled with detrital materials, which rise sometimes along the flanks of the ranges to a very considerable height, with a steep but gradually diminishing slope, indicating the former greater energy of erosive agencies.

The Great Basin is an interesting field for the geologist. The most important feature is the entire absence of the marine Cretaceous and Tertiary formations, which play such an important part in the Rocky Mountain division. With the exception of the late frshwaters Tertiary of the Humboldt river and some of the areas farther west, and of the post-Pliocene detrital accumulations of the valleys, there is nothing more recent than Jurassic, and very little of this, the most recent really important fossiliferous formation being the Alpine Trias. The stratigraphical relations of the formations, especially with reference to the building-up of these ranges, are mostly simple, as in the Appalachian and Jura ranges, or even simpler still. Some ranges are simple monoclinals, others anti-clinals, and others again synclinals, or a combination of two or more of these forms of structure. They are rarely or never closely compressed and only moderately faulted. The striking peculiarities of Appaclachian erosion, due in large part to the repetitions of hard and soft strata, are not to be found as important elements in the Great Basin topography. The Basin ranges differ, however, in a marked degree from those of the Applachian and Jura in the almost constant presence, and sometimes overwhelming importance, of the volcanic masses throughout the whole region. In some instances these formations make up the whole range; or at least, the whole interior skeleton of older rocks, if such exist, is concealed by them; in other cases the eruptive materials have been poured forth along the base of the uplift, and there form great plateau-like masses; or they have issued form the summit of the range and spread themselves there in sheets, or flowed down the flanks of the central mass. In this respect the Basin ranges maintain a unity with the other portions of the Cordilleran system, throughout which the exhibition of the results of volcanic energy during the later geological periods is everywhere manifested on a sclae perhaps unequaled elsewhere.

III. The Northern or Columbian plateau embraces the region enclosed between the northern extension of the Rocky Mountains on the east and the Cascade range on the west. It is the basin of the Columbia river, which drains it by means of two principal branches, one of which retains the name Columbia to its source beyond the boundary of the United States, while the other, originally named the Lewis, is now almost universally known as the Snake river. The Columbia itself forks near the boundary line, the main river coming down the north, and being joined by Clarke’s Fork from the south-east. The Columbia and the Snake, after uniting, flow westward for about 100 miles, before breaking through the Cascade range. This area is the portion of the United States of which we have the least topographical knowledge, and therefore only its more striking features can be indicated. The northwesterly trend of the northern division of the Rocky Mountain reduces the width of the Cordilleran system as we go north, since the Cascade range remains unchanged in its direction from the southern line of Oregon to the northern boundary of the country. The area between the two systems is more or less completely filled with mountains of which little is definitely known. Of these there are two principal groups the Blue and Salmon River ranges of which the former lies in the angle made by the Snake in its northerly course before reaching the Columbia, while the latter forms an intricate mass, extending from the westernmost ridge of the Rocky Mountain system westward towards the Snake.

The Columbia river rises only 100 miles north of the boundary line, but runs nearly 200 miles farther in a north-westerly direction before turning to go south again in a course nearly parallel to that it had before. the Okanagan joins it about 70 miles south of the boundary line and from here the course of the Columbia is southerly, parallel with the Cascade range for about 160 miles to the Great Bend, when the river takes a nearly westerly direction, which it keeps until, after having passed through the range, it reaches the Pacific. All the region lying north and west of the river and between that and the Cascade range is mountainous. The topography is very irregular, but there is a general tendency to a north and south trend, which is still more marked in the region between the Columbia and Clarke’s Fork. Here the ranges on each side of the north-flowing Colville rise to from 5000 to 7000 feet in height.

South of the Columbia is a vast area, extending to the edge of the Great Basin, and enclosed between the Rocky and Cascade Mountains, of which the main feature is that a very large portion is deeply covered by volcanic formations, which here extend over larger continuous area than anywhere else in the world, with the possible exception of the Deccan in India. This volcanic plateau like region extends northward into British Columbia and south to near the line of the Central Pacific Railroad in Nevada, from which its dark and frowning walls are visible; it extends up Snake river valley to the base of the Rocky Mountain, and south-west, through California, into the valley of the Sacramento. Along the Columbia river it unites with the great volcanic mass on which Hood, Adams, and St Helens are built up, and still farther north it merged in the eruptive accumulations which reach their greatest elevation and grandeur in Mount Rainier. These lava masses lie in nearly horizontal beds of varying thickness, interesting in their geological relations, but extremely monotonous from the scenographic point of view. They are often cut deeply into by the streams which in some places have sunk their beds below the general level of the country to the depth of more than 500 feet. These are not infrequently precipitated over the edges of the volcanic masses in cataracts, which sometimes are extremely picturesque. The falls of the Pelouse river are striking, but those of the Snake river known as the Shoshone Falls are by far the finest, and among the waterfalls of the United States perhaps come next to Niagara in grandeur. On the volcanic plateau are occasional cones, occurring singly or in groups, but much the larger portion of the overflows seem to have taken place in the form of massive eruptions, by which wide areas were covered very uniformly with lava, and on these nearly horizontal masses the cones have been built up during the dying out of the eruptive agencies. The volcanic rocks cover an area, about the Columbia and its branches, east of the Cascade range, which may be safely estimated at fully 100,000 square miles, - perhaps at considerably more. A large portion of this area was once occupied by bodies of fresh water, the deposits from which, in the form of sands and clays, have been exposed by erosion in various places, and are found to be rich in remains of land and aquatic animals, mostly of late Tertiary age. A considerable number of lakes still occupy portions of the surface, and an extensive group of these, some of which are of large size, although shallow, occupies a corner of Oregon, and an adjacent part of California , east of the Cascade range. Much of the surface is dry and barren. The valleys along the river courses are in many places well adapted for cultivation; but these fertile areas are of comparatively small extent. The mountain ranges around the bases and over the lower portions of which the volcanic materials have been deposited appear to resemble, lithologically and geological, the rocks of the Sierra Nevada. In the Owyhee Mountains there is a central core of granite, on which rest metamorphic slates and sandstones, forming a belt 20 miles wide on the south-western side of the range, and half as much on the other side. In the granitic axis are numerous veins of quartz, carrying free gold and ores of silver. With the exception of occasional hot springs, volcanic activity seems to be extinct, or at least to have been for some time dormant. There seems to have been, about the close of the Tertiary epoch, a period of extraordinary volcanic activity throughout the Sierra Nevada and Cascade ranges, and over a vast extent of country to the east. It does not appear, however, that there has been during the post-Tertiary times any eruption of fluid lava which would harden into solid rock on cooling.

IV. Enclosed between the ranges of the Rocky Mountains on the east and Sierra Nevada on the west there are-as has been seen-numerous high plateau-like districts, the beds of old freshwater lakes, some of which were of large dimensions. The strata deposited at the bottom of these lakes have been cut into by erosive agencies in numerous places, so that the geological structure stands fully revealed, while the wealth of organic remains which they contain has made these old lake-beds wonderful attractive of palaeontologists. The drainage, desiccation, and subsequent erosion of these areas have given rise to a remarkable type of scenery, to which the name of Mauvaises Terres was applied by the fur-hunters. These Bad Lands, which lie south and south-west of the Missouri and along its tributaries coming in from that direction, may be considered as the precursors and representatives of lands which, from the agricultural and business point of view, are bad enough, but which to the geological and lover of the picturesque are in the highest degree good, and which are perhaps, on the whole, more striking than anything which the continent elsewhere exhibits. The essential features of their unique and striking type of scenery (of which the Grand Canon of the Colorado is the grandest and most complete example) are these: - a heavy mass of stratified materials, several thousand feet in thickness, and covering many thousand square miles, has been cut into and eroded away, so as to give rise to a labyrinthine series of gorges, or "canons," having a depth of from 1000 to 5000 feet, the walls of which are almost always extremely precipitous and in places perpendicular, and are by no means flat surfaces, but are worn and sculptured into forms almost always peculiar and striking, and often fantastic in the highest degree. And to a variety and complexity of form which seem to find a parallel nowhere on the earth is added the attraction of color, the various groups of strata forming the canon walls presenting a gay adornment of tints of red, yellow, purple, brown, and grey, the depth and brilliancy of which surpass belief.

The region in which these wonderfully picturesque forms of landscape occur lies to the south and east of the Great Basin, between Great Salt Lake and the Colorado, to the west of the Green river branch of that river, extending west, with a gradual disappearance of its characteristic features, to near the border line of California. The Uintah Mountains may with convenience, although somewhat arbitrarily, be taken as the northern limit. But, in point of fact, the characteristic type of scenery begins to be developed in Colorado, where the Book or Roan plateau, which rises to a height of 9000 feet, is deeply cut into by the White river in the north and the Grand river in the south.

The south-westernmost portion of the region, or that portion which includes the Grand Canon and its branches, has a length from north-east to south-west of about 180 miles and a breadth in the opposite direction of about 125 miles. On the west it has as its boundary a grand escarpment which marks the change from "the calm repose of the strata with horizontal surfaces to the turmoil of flexed beds and jagged mountain crests" exhibited in the Sierra and the adjacent ranges on the south-east, in the deserts of southern California. The transition from one type of geological structure to the other on that side is said to be so abrupt that one "might almost hurl a stone from one region to the other." On the north the Grand Canon receives the drainage of four distinct plateaus, the Sheavwits, Uinkaret, Kanab, and Kaibab, east of which lies a fifth (the Paria), which drains into marble Canon, - the prelude to the Grand Canon. The Paria plateau differs from the others in that it lies at a lower level and is covered mainly by Triassic rocks, while the others present an almost unbroken expanse of Carboniferous strata. The southern boundary of the Grand Canon district is a continuation of the western. The same great escarpment which overlooks the Sierra to the west stretches southward across the Colorado, preserving the same features for 30 or 40 miles. Slowly changing its course, it follows a south-easterly course through eastern Arizona, where its edge is known as the Mogollon Mountains. Passing this line to the south-west, the country descends at once from the horizontal platform into a lower country having apparently similar geological features to those presented in the Sierra country to the west. The following are some of the more interesting facts connected with the form and structure of the plateaus making up the Grand Canon district on the north of the Colorado. The Sheavwits has on its western side the so-called "Great Wash," a broad and deep valley to the north of the Colorado. The great escarpment of this plateau is a fault or break, along the course of which the country to the east has been raised several thousand feet. The Uinkaret plateau, which adjoins the Sheavwits on the east, is separated from it geologically by another great fault, the Hurricane Ledge, which marks a rise of the region to the east to the amount of 1600 or 1800 feet, and which is prolonged far to the north. On this plateau are numerous cones and flows of basaltic lava, some of which appear to be of very recent origin. Under some of these are beds of Permian age, lying over the Carboniferous, and preserved from erosion by the harder eruptive material with which they are capped. Another short fault separates the Uinkaret from the Kanab plateau on the east. The Kanab is the broadest of the four plateaus, and has a grand side canon cutting deeply into it, and running to the Colorado. The Kaibab plateau comes next on the east. Flat on the summit, and terminated by lofty battlements upon its eastern and western sides, this is much higher than the other plateaus to the west, being from 7500 to 9300 feet above the sea-level. Its surface is covered in part with forests, grassy parks intervening which in summer are gay with flowers of rare beauty and luxuriance. The total length of this plateau is about 90 miles, and its maximum width about 35. It is a block of ground raised by displacement between two great faults. Farther east and at a much lower altitude is the Paria plateau, "a terrace of Triassic strata scored with a labyrinth of canons," and farther north-east, again, is the Kaiparowits, which, which is nearly equal to the Kaibab both in size and altitude; this is composed of strata of Lower and Middle Cretaceous age. Still farther north is a succession of plateau, separated from each other by lies of dislocation, which, however, gradually close and become less conspicuous in this direction, the topographical features of the region being dependent chiefly for their existence on simple erosion, with the frequent occurrence of curious volcanic formations, and not so much on bodily uplift and depression of great masses of strata by faulting. On the southern side of the Colorado is another vast expanse of plateau land, underlain by nearly horizontal strata, which, with one unimportant exception, are not deeply scored with canons as is the region to the north. "Low mesas, gently rolling, and usually clad with an ample growth of pine, pinon, and cedar, broad and shallow valleys, yellow with sand or grey with sage, repeat themselves over the entire area. The altitude is greater than that of the plateau north of the Colorado, except the Kaibab, being on an average not far from 7000 to 7500 feet. From such commanding points as give an overlook of this region one lonely butte is always visible, and even conspicuous, by reason of its isolation. It stands about 20 miles south of the Kaibab division o the Grand Canon, and is named the Red Butte. It consists of Permian strata lying like a cameo upon the general platform of Carboniferous beds. The nearest remnant of similar beds is many miles away. The butte owes its preservation to a mantle of basalt which came to the surface near the center of its summit…. Fifty or sixty miles south of the river rise the San Francisco Mountains. They are all volcanoes, and four of them are of large dimensions; the largest- San Francisco Mountain, nearly 13,000 feet high-might be classed among he largest volcanic piles of the west. Around these four masses are scattered many comes, and the laws which emanate from them have sheeted over a large area." The length of the Grand Canon of the Colorado, following the meanderings of the river along the middle of its water-surface, is about 220 miles. Where the canon is narrowest it is five miles across from the edge of one wall to the edge of the other. The general depth is 2000 feet; but in the center is a portion 3000 feet deeper, having a width about equal to its depth. The Kaibab division, or that part which has the plateau of that name on the north, is the most stupendous portion of the Canon, a thousand feet deeper than any other, and far more diversified and complex in its structure.

The peculiar interest of the topography of this region is due in part to the manner in which great blocks of strata have been raised or depressed between long faults, which have given rise to differences of level amounting to thousands of feet, and in part to the extraordinary amount of erosion which the region has undergone, first over its whole surface where not protected by overlying masses of harder volcanic material, and, later, in the channels of the streams, which channels have been gradually growing narrower with the lapse of time, the streams diminishing in volume, until during the present epoch they have either shrunk to nothing or have become absolutely insignificant in comparison with what they were in later Tertiary times. In fact, we have in this region the best possible illustration of the progress and effect of that stupendous desiccation of the climate which has long been manifesting itself all over the world, and of which the results may easily be traced far back in geological history. The contrast between the plateau region south and south-east of the Great Basin and that lying to the north-between the region of the Colorado and that of the Columbia- is a most striking one. In the north the volcanic outflows have filled the depressions in the corrugated and folded strata, covering over the whole of the lower portion of the region, from which the older mountain ranges project the islands from the great congealed sea of lava. The rivers could not subsequently cut very deep into these overflow, because the material is so hard and the general level of the region so low. In the Colorado region, on the other hand, the strata have not been crumpled, folded, and metamorphosed, but raised en masse to a high elevation, and not hardened so as effectually to resist erosion; and, possessing just enough variety of lithological character to prevent uniformity of wearing away and give complexity to the resulting forms, they have, under the simple influence of eroding agencies, assumed the wonderful condition in which we now behold them. Here, too, volcanic agencies have been active; but the molten material has been poured out from orifices at a great elevation, and has built up cones, some of which are of nearly as grand dimensions as the mightiest of the Sierra Nevada and Cascade range; but the valleys and lower regions have not been filled up by them, nor have there been in the southern plateau region any such enormous overflows as those which characterize the northern volcanic district.

V. The Sierra Nevada may without hesitation be called the most important and interesting member of the Cordilleran system, not only as a long and elevated mountain chain, - on the whole the most conspicuous within the limits of the United States, - but also for its minerals, its climate, its peculiar geological features, its remarkable forests, its scenery, and the comparative density of the population along its western flank. Its importance and interest are still farther enhanced if (as on the whole seems a reasonable thing to do) we consider the Cascade range as being a continuation. The Sierra Nevada proper forms the western edge of the widest and highest portion of the Cordilleras, or that portion which lies east of the State of California. It is especially conspicuous from the western side, because on this side it falls nearly to the level of the sea, while on the other side it sinks only to the general plateau level. It does not, however, border the Pacific directly, since there is, all along its course, a lower system of mountains, rising directly from the coast- the so-called Coast ranges. With these the Sierra Nevada and the Cascade range are so inosculated in certain portion of their extent that a topographical separation of them is impossible, but for a considerable distance both the Sierra and the Cascade range are distinctly separated from the Coast ranges by broad low valleys, the most extensive of these being the Great Valley of California (for which, as well as for the more important features of the California Sierra, the reader is referred to Ency. Brit. Vol. iv. pp. 696-8). The Sierra Nevada has been already shown to be made up of a core of eruptive granite flanked by rocks of Mesozoic age; the development of these Mesozoic rocks increase towards the north, and in the region lying along the western declivity of the chain, in the central portions of the State, forms the auriferous belt of the Sierra. The gold-producing detrital deposits, formerly so extensively worked, are gravels of Tertiary age covered more or less completely by volcanic materials, which not unfrequently attain a thickness of several hundred feet. As in other portions of the Cordilleran region, the presence of eruptive rocks of Tertiary and post-Tertiary age is a fact of great importance. The volcanic materials in question are seen places in large masses on almost the very highest portion of the Sierra, in its southern extension, in a region where there is very little of this material lower down on the flanks of the range, and where there are no slates and no mining or washing for gold of any importance. Just south of the Mount Whitney group, where the Sierra rapidly falls off in height between the two ranges of which the system is here comprised, there is a region-the valley of the Kern river-in which occur several volcanic cones, which have a very recent look, but which are not know to have been in eruption since the advent of the whites. This region, however, for several years in succession – from 1870 onwards, and perhaps from an earlier date- appears, on good evidence, to have been repeatedly and violently disturbed by earthquakes; and this seems also to have been the portion of the Sierra which was most affected by the great earthquake of March 26, 1872. Midway in Owen’s Valley, on the east side of the Sierra, beginning about 30 miles north of Lone Pine, where this earthquake was most disastrous in its effects, there is a region of volcanic cones and lava- flows, by which the river is crowded over against the invo range, at the foot of which it has only just room to flow. These cones are seemingly as perfect as they ever were; and the flows of basalt have spread themselves out over the sage-brush slope in a manner indicative of a very recent date for their out breaking. Yet all seem now to be entirely dormant. Even solfataric action is almost (if not quite) exclusively manifested at the present time at or near the summits of the highest volcanic cones of ht Sierra and the Cascade range. Farther north more and more volcanic materials cover the western flank of the range; and from about 39° 30’ N lat. much the larger portion of the older rocks is overlain and concealed by modern eruptive materials, through which the streams have worn channels, often of great depth, from the sides of which access is given to the auriferous gravels occupying the bottoms of the channels of the old tertiary but now buried river-systems. In Lassen’s Peak, in 40° 30’ N.lat., we have the first exhibition of the isolated volcanic cone rising high above the adjacent country, which makes to prominent a feature of the range farther north in California and through Oregon and Washington territory. This volcanic mass is 10,537 feet in height, and there are abundant signs of recent volcanic activity on and near it. There are, in this vicinity, several localities where hot springs occur, and where the rock has been so softened by solfataric action as to have given rise to mud lakes, in which jets of hot water and mud are sometimes thrown to a height of several feet. One of these places, about 8 miles from the summit of the peak, is 5976 feet above the sea, and there is here a pool of hot water 600 feet long by 300 broad, in the midst of which miniature mud volcanoes are being constantly formed. There are no such striking indications of dormant volcanic activity as are seen in the vicinity of Lassen’s Peak anywhere to the southward along the crest and flanks of the Sierra. Neither is it known that there has been anything which could be properly called an eruption, whether of lava or ashes, since the region was first visited by the whites, either from Lassen’s Peak or from the much grander volcano to which the name of Shasta is given. at Lassen’s Peak a great change takes place in the character of the range, which is here broken through transversely by a great fault, to the south of which we have the high ranges and deep canons often cut down through the volcanic strata, and sunk deeply into the underlying metamorphic rocks, while to the north is a great depression, comparatively level, and exclusively occupied by volcanic rocks, which stretch off to the north and north-east, in almost unbroken continuance, for many hundred miles, forming a portion of the northern plateau region already described. Seventy miles north-west of Lassen’s Peak rises Mount Shasta (14,440 feet), standing in remarkable isolation on a base between 10,000 and 11,000 feet lower than its summit. There are indications of former volcanic activity near the summit but they are not so marked as those on and near Lassen’s Peak. There is a flat area about 400 feet below the summit, on one side of which are several orifices from which steam and sulphurous gases were constantly escaping at the time of the present writer’s ascent of the mountain (1862).

North of Mount Shasta the mountain mass now called the Cascade range maintain characters similar to those which it has between Lassen’s Peak and Shasta for a distance of fully 500 miles, or until we have passed the northern boundary of the United States. The principal continuous ridge is comparatively low, and on it at irregular intervals rise great volcanic cones, differing considerably from each other in elevation, but all much higher than the surrounding plateau-like base on which they are built up. Unfortunately no portion of the Cascade range has as yet been topographically surveyed. From Mount Shasta northwards there are several prominent peaks, which are apparently volcanic, but which have not the conical form, while other exhibit this peculiar feature in a high degree of perfection. Mount Pitt (9718 feet) is a well-defined cone, about 75 miles north of Shasta. Mount Jefferson, about 150 miles still farther north, is of a similar character; and between Pitt and Jefferson are various prominent peaks, especially the highly picturesque group of five sharp points, known as the Three Sisters, only three of them being visible from the Willamette Valley. All through this portion of the range evidences of comparatively recent volcanic action are present, in the form of regular craters and outflows of lava. Somewhat less than 100 miles north of Mount Jefferson is the grand break made in the Cascade range by the Columbia river, which has cut entirely through the volcanic mass, down almost to the level of the sea, - the Dalles, on the eastern side of the range, having an elevation of only about 100 feet. At the Dalles-so named on account of the great, broad, flat plates or sheets of lava which are there well exhibited on and near the river- is the beginning, in this direction, of the volcanic plateau of the Columbia. Near this point rise three of the best-defined volcanic cones of the range, two – Mount Adams and Mount St Helens – on the north side of the river, and one- Mount Hood – on the south. The last-named has been found by barometric measurement to be 11,225 feet; the other two seem to be of nearly equal height (about 10,500 feet). Mount Rainier (14,444 feet)- about (14,444 feet) – about 75 miles north of the Columbia river – is rivaled in the whole of the Cascade range by Shasta only. The views of Rainier from Puget Sound are magnificent. It is much less accessible than Shasta, as it lies in the midst of a dense forest, far from roads; it is also very much more deeply covered with snow and ice. Still farther north than Rainier, and near the boundary line of the United States, is Mount Baker (10,755 feet), a prominent object in the grand panoramic view from Victoria, Vancouver Island. While evidences of comparatively recent volcanic action are so conspicuous all along the range from Lassen’s Peak north to Mount Baker, it is not easy to reconcile the conflicting evidence with regard to the present condition of the eruptive agencies. The present writer, during several years of exploration, found no evidence whatever of any recent outflow of melted lava, such as would harden into a solid rock on cooling, in any part of the Sierra Nevada or the Cascade range. The eruptive rocks of these ranges are mainly andesites; but the last outflow of molten rock appears to have been basaltic in character. This is certainly true for the Sierra Nevada, and probably to for the Cascade range. Under the basalt we find, in the buried sedimentary strata, abundant remains of vegetation, pronounced by competent authority to be Pliocene in age, with a few species intermingled which have a decidedly Miocene character. The animal remains found under the basaltic lava are all of extinct species, with the single exception of man, whose bones or handiwork have been repeatedly taken from strata occupying this geological position. The age of the sedimentary beds under the basalt is therefore Tertiary, from the combined evidence of both plants and animals. There is no evidence that fragmental lava – ashes, cinders, and the like – has been emitted from any one of the volcanic cones of the Sierra Nevada, since the region became known to the whites; but there is abundant evidence to this effect in regard to some of the high points in the Cascade range. Mount Baker seems to have furnished the most unquestionable proof of activity in recent times. The first known eruption of this volcano appears to have taken place in 1843. In at least three later instances Mount Baker has been in eruption by men of unquestionnaire authority – in 1854, 1858, and 1870. Smoke and steam are said to have been frequently seen rising from the summit of St Helens. It is not easy to reconcile the statements which have been made in regard to the activity of Mount Hood. Eruptions of this mountain have been reported as having taken place; but the present writer in 1867 made inquiries of persons having it in full view, without being able to procure satisfactory evidence of any activity similar to that of Baker and St. Helens, at least within the preceding twenty or thirty years. There is no evidence of any similar activity of Mount Rainier; but, according to Stevens and Van Trump, who were the first to reach the summit of this mighty cone, jets of steam issue from the crater at the summit in sufficient quantity to keep a party warm.

VI. To the west of the Sierra Nevada and the Cascade range is another chain of mountains, which, although greatly inferior to these in some important respects, is still of very considerable interest- the Coast ranges of California and Oregon. They differ in being newer geological, of less elevation, less extensively and regularly broken through by granitic axial masses, and less covered by volcanic overflows. The upheaval of the Sierra took place at the close of the Jurassic epoch, whereas that of the Coast ranges was the result of agencies operating during the later portion of the tertiary, and continuing down to a very recent date – namely, into the post-Pliocene. The greater part of these ranges south of the Bay of San Francisco is of Miocene age, although even there extensive areas of Cretaceous rocks exist, and especially on the eastern side of this mountain belt, in the so-called Monte Diablo range. Farther north, beyond the bay, rocks of this age become more and more predominant, the areas of Tertiary being comparatively narrow and unimportant. A remarkable feature of the geology of the coast ranges is the extent to which these newer formations have been metamorphosed, so that by some observers these altered rocks have been described as belonging to the very oldest part of the geological series. The prevalence of serpentines and obscure serpentinoid rocks in great masses in these altered portions is also a fact of much geological interest. These altered rocks, and especially such of them as have been more or less silicified, are the home of the ore of quicksilver, mines of which metal have been opened and extensively worked at numerous points both south and north of the Bay of San Francisco. Chromic iron is also associated with these magnesian rocks, and at a few points is present in considerable quantity. Gold has been washed at numerous points in southern California, with some success. An important member of the Miocene series south of the Bay of San Francisco is the bituminous slate, which in places is several thousand feet in thickness, and often contains a large quantity of bituminous matter, which, at some localities, especially near Santa Barbara and Los Angeles, has oozed out upon the surface and given rise to areas of semi-liquid material, called "brea" by the Mexican Spanish, which has occasionally hardened and formed large deposits of asphalt. Many attempts have been made to bore into these bituminous rocks for petroleum, but these efforts have never been successful enough to furnish even the home market with a supply of oil suitable for illuminating purposes. Coal is found at numerous points in the Coast ranges, both in California and in Oregon, and of both Cretaceous and Miocene age. The most important mines are those in Washington Territory, near Seattle; and there is also a valuable and quite extensive coal-field on Vancouver Island, near Babaimo, also in the Cretaceous. The most important and best-developed portion of the Coast ranges is that opposite or to the west of the valleys of the San Joaquin and Sacramento rivers. Both south and north of the extremities of these valleys the masses of the Coast and Sierra mountains coalesce, or become topographically so united that any distinction other than geological is impossible. This uniting of the two ranges which takes place in northern California is continued through southern Oregon, where the topography is quite as complicated and difficult as in those parts of California where the two ranges come together. But in the last-named State the structure of the Coast ranges has been pretty well worked out by the California State Geological Survey, although the maps unfortunately remain unpublished, while in Oregon almost nothing has been done in this direction. Where best developed – in California-the Coast ranges have a length of fully 400 miles, and a breadth varying from 40 to 70 according to the varying position of the coast-line. The mass of mountains covering this area is made up of numerous subranges, some of which are very distinct and well-marked, while others are much less so. These all along the north-west and south-east trending portion of the coast, or from Point Conception (34° 15’ N. lat) to Cape Mendocino, run nearly in the same direction as that coast. Their altitude above the intervening valley, in the vicinity of the Bay of San Francisco, varies from a few hundred to 3000 or 4000 feet. Prominent points near that bay are Monte Diablo (3856 feet), (3790). As we go north and south from the region of the Bay of San Francisco, we find the heights of the dominating peaks increasing. Mount Balley, about 150 miles north of SanFrancisco, has an elevation of 6357 feet. About the same distance south of that city is San Carlos Peak (nearly 5000 feet). Portions of the range south of the Bay of San Francisco are of extremely recent date, as great masses of rock of Pliocene age, hundreds of feet in thickness, are seen to be turned up at a high angle. The ranges along that portion of the coast which has an east and west trend, on Santa Barbara Channel, have themselves the same trend, and are high and precipitous. Of these the Santa Inez is the most conspicuous, having along its crest points nearly or quite 4000 feet high. The Santa Monica, another east and west trending range, farther east and south, is remarkable as being made up of Miocene stratified rock, and having a central well-defined linear axial mass of intrusive granite, driven through it like a wedge, by which the range has been raised to a high angle near the eruptive rock, where it is extensively shattered and metamorphosed, and from which, in each direction transverse to the chain, it gradually and rapidly recovers its normal character and nearly horizontal position . Farther south along the coast the ranges are much broken, and central dominating points rise to very considerable elevations. The San Bernandino and San Jacinto Mountains are two of these elevated central masses, each rising to about 11,000 feet. The precise relations of these high masses to be Coast ranges and Sierra cannot as yet be stated. The region of the Coast ranges in California is one of very unequal attractiveness. Portions are rough and for-bidding being covered by a dense thorny undergrowth, locally known as "chaparral"; other portions are in the highest degree fertile and picturesque, and have a remarkably mild and uniform climate. The slopes and hills near the coast, or open to the west winds, have a fairly sufficient rainfall. The interior ranges, especially the portions of them west of the San Joaquin valley, are very dry, and over large areas so much so as to be unfit for cultivation.

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