Rocky Mountains, a name applied indefinitely to a long series of mountain ranges west of the Mississippi, of a great variety of form and structure. The term Stony mountains was originally used without the intention of applying it to any one range or group of ranges. From the eastern slope, westward, we pass over range after range for 1,000 m. or more, until we descend the western slope of the Coast range to the Pacific. At least two thirds of the United States, an area of over 2,000,000 sq. m., lies west of the Mississippi, and this vast area may be defined as the Rocky mountain region. This great group of ranges extends southward through Mexico and Central America to the isthmus of Darien, and northward into British America and Alaska to the Arctic ocean. The great chain of the Andes of South America is an extension of the same group, and in a general view they all form one great system. Not till within the present century was there any definite understanding of the geography of the Rocky mountains. Upon the old maps the mountain ranges were shown by a single line of hachures, with a few minor ranges branching off, the whole trending nearly N. and S., or rather W. of N. and E. of S. The first important government expedition was that of Lewis and Clarke, which in 1804-'6 passed up the Missouri river to its source, crossed the main divide of the Rocky mountains, and followed the Columbia to its entrance into the Pacific ocean.
Although this expedition was a great achievement in a geographical point of view, taking into consideration the time and the means at its command, yet much of the information it obtained was very vague and limited to a narrow belt across the northern portion of the country. Lewis and Clarke, however, fixed pretty well the positions of the Missouri and Columbia rivers. The next explorer was Major Z. M. Pike, who in 1805-'7 crossed the country further south, and discovered the head waters of the Arkansas and the lofty peak which now bears his name. He crossed the divide into the Great Basin. In 1819-20 S. H. Long was sent out by the government with a well equipped party, comprising not only topographers, but also geologists and naturalists, including Thomas Say. After Long came Bonneville, Ross Cox, Schoolcraft, Nicollet, Fremont, and others, all of whom added to the store of knowledge in regard to this great area. From 1844 to 1860 more than 20 expeditions were sent out, with the object of determining the best route for a railroad to the Pacific. In 1853 congress passed the bill making appropriations for the determination of the most practicable route for a railroad from the valley of the Mississippi to the Pacific coast.
No expense was spared in equipping expeditions, which traversed the country from E. to W., at various points from lat. 49° to the southern boundary of the United States. The information thus obtained was embraced in a large series of maps and reports (13 vols. 4to). Yet up to 1865 no portion of the great Rocky mountain region had been examined with such care and detail as to render the maps anything more than approximately correct. The information thus obtained could only be placed on a map projected on a small scale, where an error of five or ten miles would be overlooked. Within the past ten years several expeditions have been organized with the object of working out certain areas with considerable detail, including topography, geology, and natural history; and more definite knowledge of the Rocky mountain region has been obtained within that period than in all the previous years. - To convey an idea of the plan and growth of the development of the great area west of the Mississippi, it is only necessary to suppose it to have been originally a vast plateau, out of which have been evolved the different ranges of mountains as if they had been lifted by volcanic action.
Indeed they appear as wrinkles on the earth's surface, and were probably produced by the contraction of its crust in the process of cooling. This may be understood more clearly by examining some of the barometrical profiles which have already been constructed across the continent. In proceeding westward along the Missouri river, the ascent is gradual, at first not more than one foot in a mile, but steadily increasing until the base of the mountains is reached, when the rise becomes suddenly 50 to 100 ft. or more in a mile. The profile of the Pacific railroad shows that Omaha on the Missouri river is 1,060 ft. above sea level, while at Columbus, 91 m. by rail westward, the elevation is 1,470 ft., showing an ascent of about 4 1/2 ft. in a mile. At Cheyenne, 516 m. W. of Omaha, the elevation is 6,075 ft., showing an ascending grade from Omaha of nearly 10 ft. in a mile. This entire distance is over an apparently level plain, most of the way by the valley of the Platte. From Cheyenne to the highest point along the line of the railroad, at Sherman, 8,271 ft., the distance is 33 m., when the grade suddenly increases to over 66 ft. in a mile. The profile along the Kansas Pacific railroad, from Kansas City on the Missouri to Denver, shows similar results.
At Kansas City the elevation is 764 ft.; at Denver, 639 m. W., 5,197 ft., making an average ascent of nearly 7 ft. per mile across an apparently level, treeless plain. A few miles W. of Denver, the great Colorado or Front range seems to rise abruptly out of the plains, its summits reaching the line of perpetual snow. - The great mass of the rocky chain lies W. of the 105th meridian. The united ranges trend about 20° W. of N. Along the eastern slope the smaller or minor ridges have a trend more to the northwest, so that they constantly die out in the plains, giving to the eastern side the appearance of an echelon arrangement. As the small ridges run out, they often present a fine example of an anticlinal, as seen on the Cache à la Poudre river. From the notches in the outline of the ranges, the Platte, Arkansas, and many other rivers open into the plains. About the source of the Missouri the main chain is 9° of longitude further W. than in Colorado. In this broad space and to the eastward are numerous outliers, as the Black hills, Big Horn, Bear's Paw, Judith groups, etc, all more or less distinctly connected with the main chain.
The Black hills are connected with the Laramie range, near the Red Buttes, by an anticlinal valley, while the Big Horn is related in the same way, showing that they are all the product of one uniform cause. The Black hills are in Dakota territory, extending into Wyoming, E. of the Big Horn range, between lat. 43° and 45°, and lon. 103° and 105°, and are quite isolated from the main chain; they are a sort of huge puff from out of the plains, occupying an area of about 100 m. in length and 60 m. in breadth. The mass is elliptical, and the major axis trends about 20° W. of N. The base of the hills is 2,500 to 3,000 ft. above the sea, while the highest peaks are not more than 6,000 or 7,000 ft. They are covered with a dense growth of pine, which gives them a black appearance in the distance. The two forks of the Cheyenne embrace the Black hills, and have their origin in the plains far to the westward; hence they give rise to no important stream. The nucleus of the hills is composed of feldspathic granites and slates surrounded with the full series of the sedimentary strata known in this region, inclining at various angles from the central mass, as if originally their sedimentary beds had formed an unbroken communication across the entire area; or in other words, they form a fine example of an anticlinal on a large scale.
There is some good pasture and timber land in the vicinity of the Black hills, but the mineral resources have been extravagantly overrated. Like the Black hills, the Big Horn range does not give rise to any important stream. The largest river in this region, which gives name to the mountains, rises in the Wind River range, passes through the Big Horn mountains, and flows into the Yellowstone about 70 m. to the northward. The central mass of this range is coarse granite also, with a series of Silurian, carboniferous, Jurassic, cretaceous, and tertiary strata, inclining from the sides. The highest peak is Cloud peak, supposed to be about 7,300 ft. We may separate the nuclei of the mountain ranges roughly into three divisions: those with a granitic and those with an igneous nucleus, and those with a combination of the two. Usually the volcanic material has come up through the granitic mass and flowed over it, in some instances almost entirely concealing it. Still further W. is the Wind River chain, the loftiest peak of which Fremont, whose name it bears, found to be 13,570 ft. The central mass of the mountains is also a coarse, massive granite, overlaid by metamor-phic slates, in which the gold mines are found.
This chain forms a portion of the main divide. - To the north of the Wind River mountains, in the N. W. corner of Wyoming territory, is one of the most interesting and remarkable regions in the world. The Yellowstone national park occupies an area of 65 m. from N. to S. and 55 m. from E. to W., or 3,575 sq. m., the whole of which is more than 6,000 ft. above the sea. The Yellowstone lake, the source of the Yellowstone river, is 22 m. long and 12 to 15 m. wide, and is 7,788 ft. above the sea. The ranges of mountains that hem it in on every side are all of volcanic origin, and are covered with snow all the year. There is frost here every month of the year, and in June, July, and August the thermometer frequently sinks to 25°. (See Wyoming.) In a geographical point of view this park will always be of the highest interest, as constituting the apex of the continent, and giving origin to three of the largest rivers in North America. On the N. side are the sources of the Yellowstone; on the W. those of the three forks of the Missouri; on the S. W. and S. those of Snake river, flowing into the Columbia and thence into the Pacific ocean, and those of Green river, rushing southward to join the great Colorado, and finally emptying into the gulf of California; while on the E. side are the numerous sources of Wind river. - Southward from the Wind River chain, the mountainous character of the divide is "interrupted for a short distance by comparatively level plateaus, while to the east are the Laramie plains, bounded by a comparatively low range, of which Laramie peak is about 10,000 ft. high, and, on account of its isolation and the insignificance of the mountains in the vicinity, is one of the great landmarks of the west.
Still further S. are the remarkable mountain regions and the parks of Colorado. The Colorado or Front range rises up before the traveller on the plains like a gigantic wall, with Long's peak at the north and Pike's peak at the south, as high bastions. West of this range are three great depressions, North, Middle, and South parks. In the Front range are several peaks over 14,200 ft. high (according to the latest surveys): Long's, 14,-271 ft.; Evans, 14,330 ft.; Rosalie, or Rosa, 14,340 ft.; and Gray's and Torrey's, twin peaks with an interval of less than a mile, 14,341 and 14,336 ft. In this range are the oldest known silver and gold mines of Colorado. On the W. side of the parks is the Park range, in which are several peaks of over 13,000 ft., and a few, as Mt. Lincoln, of over 14,000 ft. In this range are many important gold and silver mines. From Mt. Lincoln, on the W. side of the South park, one can look down into the valley of the Upper Arkansas and across to the Sahwatch range, one of the most remarkable in the west. At its N. end is the Holy Cross group, in lat. 39° 30', lon. 106° 33', composed of gneiss and coarse massive granite.
For 80 m. to the southward this range literally bristles with peaks, many of which rise over 14,000 ft.; Harvard, Yale, and Princeton are respectively 14,384, 14,150, and 14,199 ft., and many others are over 13,000 ft. The rocky mass is mostly granite, intersected with igneous dikes. The general trend of this range is about 20° W. of N., and it forms one of the most gigantic anti-clinals in the entire Rocky mountain region. Vast ranges of massive granitic rock, capped with limestone and sandstone, incline from either side, with broad valleys intervening. The proofs of ancient glacial action on both sides of the range are wonderful. In the valley of Roches Moutonnés creek, which flows into Eagle river from its N. E. base, are very remarkable rounded masses of granite, such as have long been called sheep backs or roches moutonnés in the glacial regions of central Europe. Here they are shown on a grand scale. In the valley of the Arkansas and the Gunnison are marvellous examples of lateral and terminal moraines, and there are numerous lakes whose basins have been scooped out by some extended glacial action. The Twin lakes are beautiful sheets of water on the E. side of the Sahwatch range, 2 to 3 m. in diameter and about 80 ft. deep. These are true glacial lakes.
The proofs of glacial action are common throughout the Rocky mountain region, but they are nowhere shown to such a marked extent E. of the Sierra Nevada as in the vicinity of the Sahwatch range. From the W. side of this range flow the Gunnison river and southern branches of the Grand, which, after cutting deep cañons or gorges, unite near the western boundary of Colorado; and cutting a still deeper cañon, the stream flows into the great Colorado of the West. - West of the Sahwatch or great "Mother" (Madre) range is another remarkable group in the drainage that leads to the great Colorado, called the Elk range. It is about 50 m. in length, with a trend about N. W. and S. E., and differs from any of the others mentioned both in form and structure. In this range are seven peaks of the first order, rising to an elevation of nearly 14,000 ft., and many others ranging from 12,000 to 13,000 ft. The geological structure is very peculiar. It appears that the vast thickness of sedimentary strata once rested upon a floor of igneous granite in a pasty or semi-pasty condition, and that these high peaks were thrust up through the overlying beds, in many instances completely overturning them for miles in extent.
There are faults 2,000 ft. in extent, and dikes without number, where the igneous material seems to have been squeezed through fissures in the thousands of feet of overlying strata, vertically as well as horizontally. Deep gorges and amphitheatres meet the eye on every side. Snow Mass peak, 13,961 ft. high, is so called from the immense mass of perpetual snow on its sides. At its immediate base, on all. sides, are beautiful lakes. The surface is remarkably rugged, and as far as the eye can reach on every side are high peaks with deep gorges in one continuous succession, while the sedimentary rocks are thrown into chaos. On the N. W. end of the range is a remarkable peak which forms an excellent landmark, known among the miners and prospectors for years as Sopris peak, 12,972 ft. high. From this point the land slopes off into the remarkable plateau country bordering on the Colorado river, literally gashed as it were by the little streams which have cut innumerable cañons through it. There is probably no country in the world that presents more obstruction to the traveller. - At first glance the Park range appears to be connected with the Sangre de Cristo range, which bounds the E. side of the San Luis valley, but the former is separated from the latter by the Arkansas valley, and really lies parallel with it.
It begins in lat. 38° 26', lon. 106°, trends S. 30° E., and shows on its summit a continuous series of sharp peaks. Parallel to it, on the east and bordering the plains, is the Wet mountain range. The interval is known as the Wet mountain valley and Huerfano park, one of the most beautiful and fertile districts in Colorado. These mountains extend far down into New Mexico. Southward the Sierra Blanca and Spanish peaks are lofty landmarks. Fort Garland, an old military post in the San Luis valley, is near the base of the Sierra Blanca. The San Luis valley, though nearly surrounded with high ranges, is not a park, but a valley 30 to 50 m. wide, through which the Rio Grande flows after emerging from the San Juan mountains, cutting a gorge through its basaltic floor 1,000 to 1,500 ft. in depth for 60 to 80 m. - Immediately W. of the upper portion of the San Luis valley, in S. W. Colorado, is a most interesting as well as lofty group of mountains, forming what is now called the San Juan district. These mountains form the sources of a great number of streams.
On the north are many branches of the Gunnison, on the east the Rio Grande, and on the south and west the various branches of the Rio San Juan, which flows S. W. and W. and unites with the Colorado. Within an area of about 4,000 sq. m. is the most important and rugged group of peaks in Colorado, and probably in the first division of the Rocky chain. More than 100 points are above 13,000 ft, and about 10 peaks over 14,000 ft. On the N. side of the group is the lofty Un-compahgre or Uncapahgri peak, with its dome-shaped summit rising to a height of 14,235 ft. Large areas here are composed entirely of quartzites, and others wholly of igneous rocks. Toward the south, in southern Colorado and in New Mexico and Arizona, the volcanic action seems to have been very great, and the area covered with igneous rocks increases; sometimes they occupy several thousand square miles, to the exclusion of all others. What are called the broad table lands or mesas of New Mexico are simply floors of basalt. Colorado may be regarded as the culminating area of lofty points in the eastern division of the Rocky chain, as California is in the western, in its Sierra Nevada ranges.
Within the limits of Colorado are 50 or more points exceeding 14,000 ft. in height, and more than 250 of over 13,000 ft., while the number reaching 12,000 ft. is unknown. The average elevation of Colorado is greater than that of any other state or territory in the Union, being 6,600 ft., while California with its magnificent group of peaks in the Sierra Nevada averages only 2,800 ft. - To the west, and walling in the great interior basin on the east, is the Wahsatch range, which is unsurpassed for beauty of form. The scenery in the vicinity of this range has long been celebrated for its grandeur and beauty. Mt. Nebo, one of its prominent peaks and a noted landmark, is 11,992 ft. high. The trend of the range is nearly N. and S., while projecting like a spur toward the east is the Uintah range, with a trend nearly E. and W. and with a number of peaks over 13,000 ft. high. This is one of the most beautiful and symmetrical ranges in the west. The nucleus is composed of quartzites, which are so elevated that the central mass seems to have been lifted up horizontally or nearly so. The entire range is a remarkable example of a huge anticlinal, and on either side of the axis are the numerous pyramidal peaks, rising far above the timber line and covered with perpetual snow.
Three distinct belts may be noted in this range: one above the timber line, revealing only the bare, bleak rocks; below, a dense belt of pine timber; and near the base and sloping off into the plains, another comparatively barren belt. The Wahsatch range has a gray granite nucleus, with a great thickness of sedimentary beds lying on the sides and often rising to the very summits. In the Great Basin, between the Wahsatch mountains and the Sierra Nevada, are many smaller mountain ranges lying nearly parallel with each other, some of which seem to rise abruptly out of the surrounding plateau. This great depression was undoubtedly at no remote period, geologically speaking, a lake of several hundred miles in extent, out of whose waters the summits of the mountains projected like islands. In the Shoshone basin, forming the E. portion of Oregon and the W. part of Idaho, are a great number of similar ranges, all lying parallel with each other, appearing like the waves of the sea after a storm. The Salmon River mountains, Blue mountains, and many others are composed of a series of remarkable regular ridges trending mainly N. and S. - The second division comprises the Cascade, Coast, and Sierra Nevada ranges, fronting the Pacific ocean, which were formerly included under the general term Rocky mountains, and are now called by some geographers the Cordilleras. These mountains, in their extension S. into Mexico, have long been known as the Cordilleras of Mexico, and the main ranges of South America bear the name of Cordilleras or Andes. Still, as all the mountains W. of lon. 105° are plainly a unity in a geographical view, they will fall under the general and quite indefinite term "Rocky mountains." North of lat. 49° but little is known of these western ranges; but it is known that they extend without any permanent interruption to the Arctic ocean, with here and there a lofty peak, which from ignorance of its precise character has been assigned what appears a greatly exaggerated elevation.
The latest measurement by triangulation makes Mt. St. Elias 17,500 ft. high; Mt. Hood in Oregon and Mt. Baker, both of which are enormous extinct volcanic cones, have an elevation respectively of 11,225 and 11,100 ft. The Cascade range is a continuation northward of the Sierra Nevada, and is separated only by the chasm of the Klamath river. Through the entire length of Oregon and Washington territory, the Cascade range runs N. and S. parallel to, and about 100 m. from, the shore of the Pacific. Near the 49th parallel it is bent northwesterly, conforming with the trend of the coast, and in British Columbia is called the Marine range. The average elevation is 5,000 to 6,000 ft. It obtained its name from the cascades of the Columbia, which are formed by the passage of that river through it. The country along the immediate coast is but a narrow belt, much broken, while the shore is indented with great numbers of bays or inlets, of which the estuary of the Columbia, Shoal-water bay, and Gray's harbor are noted.
Promontories and rocky islets are visible everywhere as surviving monuments of the terrific erosion which has swept away entire mountain ranges, leaving at this time only the single group of the Cascade range. - South of Cape Mendocino, in lat. 40° 30', to Point Conception, near lat. 34° 30', the Coast range of California is composed of a succession of parallel ranges, with intervening valleys of great beauty and fertility. Between the Coast range and the Cascades is a longitudinal depression which forms the valley of the Willamette, extending northward to the gulf of Georgia. Similar valleys occur in California, as the San Joaquin and Sacramento. In this northern region the forests are very dense, and the undergrowth so thick that it is difficult to penetrate it. Trees occur of majestic size, of which the yellow fir (abies Dou-glassi) predominates over all others. The cedar (thuja gigantea) is also very abundant. The lumber interests of this country are im-mense. Between the Cascade and the main Rocky chain lies the basin of the Columbia, which is an arid plain covered with artemisia and bunch grass. The surface is cut through by deep cations, through which the large rivers flow between huge walls of basalt.
Although there are great varieties of climate in this division, it is extremely mild on the immediate coast. At Puget sound snow seldom falls, and remains but a short time. Rains are very abundant, reaching 60 inches during the year. According to Mr. J. D. Whitney, the Coast range inosculates with the Sierra Nevada both N. and S. Near Tejon pass, in lat. 35°, the ridges are topographically undistinguishable from each other, and it is only by carefully studying the position of the strata that it can be determined where one system begins and the other ends. The Coast ranges are composed of newer formations than the Sierra, and have been subjected to greater disturbances up to a recent period; and they contain no rocks older than the cretaceous. There are no lofty points in the Coast ranges, according to Whitney, the central portions rarely rising above 4,000 ft., while in approaching the Sierra N. and S. the highest points are as much as 8,000 ft. The well known Monte Diablo is only 3,856 ft. above the sea, although a very conspicuous object from San Francisco. - The Sierra Nevada or Snowy range forms the western border of the great continental plateau, corresponding with the main Rocky chain on the east.
While the base of the eastern mass is everywhere 4,000 to 5,000 ft. above sea level, and the descent to the sea imperceptible to the eye, the Sierra slopes rapidly, so that the sea level is reached within 100 m. So far as now known, the highest peak of the United States is in the Sierra group, viz., Mt. Whitney, 14,887 ft. The scenery of the Sierra group is of surpassing beauty and grandeur. There is not such a vast number of high peaks as in the Colorado group, but it may fairly claim the highest; and inasmuch as the surrounding country has a much lower altitude, there is a massiveness about this magnificent range that even the Sahwatch of Colorado cannot boast. The Sierra chain is about 450 m. in length, and averages about 80 m. in width, supposing its northern terminus to be at Lassen's butte, lat. 40° 30'. The central mass or core is chiefly granite, with metamorphic slates on either side, capped with basaltic and other kinds of lava and heavy beds of ashes and breccia. All these rocks are visible from the Central Pacific railroad between Truckee and Sacramento. The evidences of very modern volcanic action are visible everywhere. Even now there are numerous hot springs and geysers, as well as occasional earthquake shocks.
The height of some of the dominating peaks is as follows: Mt. Shasta, 14,442 ft.; Mt. Tyndall, 14,386 ft.; Mt. Kaweah, 14,000 ft.; Mt. Brewer, 13,886 ft.; Red Slate peak, 13,400 ft.; Mt. Dana, 13,-277 ft. On the mountains snow falls to the depth of 40 or 50 ft., and much of it remains all the year. Enormous glaciers exist here even at the present time, and the evidences of ancient glacial action are wonderful. The worn and rounded granites of the Sierra Nevada were well adapted to preserve the records of the old glaciers, and they everywhere testify to the intensity of their former power. These glaciers have been continued down to the present time in a modified condition. All the glaciers occur on the north side of the mountains, and are very numerous, now estimated at 65. The number known in the Alps is 1,100, of which about 100 may be considered as primary. Some of the Sierra glaciers are nearly as large as the Alpine, as the Lyell, North Ritter, and others not yet named. Although the existence of glaciers in the Rocky mountains is a very modern discovery, enough is already known about them to invest the subject with the highest interest. Moraines and morainal lakes occur in the Sierras in great numbers.
Lake Tenaya, at the head of the Merced river, or a branch of the same name, is a conspicuous example. Traces of the existence of an immense flow of ice are shown here in the valley occupied by the lake, according to Whitney, and the ridges on either side of the trail are so worn by glacial action that the rocks are slippery, rendering travel dangerous. Four pretty well marked belts of forest vegetation have been observed by Whitney. The lowest is the foot hills, with oaks, buckeyes, and small digger pines; the second belt lies between 4,000 and 5,000 ft., and consists of pitch pine (pinus ponderosa), bastard cedar, and Douglas spruce; the third zone, between 7,000 and 9,000 ft., is that of firs, as picea grandis and amabilis, tamarack pine, etc.; and on the highest belt, above 9,000 ft., where vegetation begins to dwindle, a dwarf pine (pinus cris-tata) is seen up to the limit of perpetual snow. There are great numbers of beautiful lakes in the Sierras, fed by the melting of the snows, among which are Lake Tahoe and Donner lake.
The Yosemite valley, so remarkable for its rugged scenery, and which has been set apart by legislative action as a pleasure ground, is in the Sierra. Through this valley flows the Merced river, and at its source is a fine group of peaks, 13,000 ft. high, called the Merced group. - So far as structure and topography are concerned, the great mountain system extending along the western borders of the western hemisphere, from the Arctic ocean to Patagonia, may be regarded as a unit, and due to one great cause. North America has its lofty Rocky group opposite the deep North Pacific ocean, and its small Appalachian group opposite the shallower North Atlantic. So South America has its still higher Andes opposite the deeper South Pacific, and the smaller Brazilian ranges opposite the South Atlantic. This fact, stated by Dana, is founded on a deep-seated structural cause. The elevation of a portion of the earth's crust requires in close proximity a corresponding depression. The Rocky system may be primarily divided into two portions, the Sierra Nevada and Coast ranges fronting the Pacific ocean, and the main Rocky chain which forms the great water divide of the continent.
Each of these chains or groups is made up of a great number of smaller ranges, in the aggregate apparently possessing a considerable degree of regularity, but when studied in detail showing very little regularity or system. Sometimes, as in the Great Basin, the main ranges seem to lie parallel for the most part, but usually the minor ridges branch off in every direction. More commonly the trend is about N. E. and S. W.; but sometimes it is due N. and S. or E. and W. The Wahsatch range in Utah trends nearly N. and S., while the Uintah range, which seems to branch off from it, trends nearly E. and W. The area W. of the Mississippi may be divided into mountain and prairie or plain country. The belt of plains on the E. slope averages about 500 m. in width, and gradually rises to the base of the mountains. The mountain portion has its greatest breadth between the 36th and 41st parallels, where it varies from 800 to 1,000 m. In this belt are the greatest number of lofty peaks, including the highest portion of the Sierra Nevada. - Among the numerous ranges of the Rocky chain are many valleys and plateaus, varying from a few acres to hundreds or even thousands of square miles. Sometimes they are formed by erosion or by depression; many of them are ancient lake basins.
In all the great mountain districts of the west are thousands of these openings, into which settlements have already penetrated. In the San Juan mountains is Baker's park, with an extensive settlement of miners, and in the surrounding mountains are some of the richest silver mines in America. The North, Middle, and South parks, in Colorado, are areas of depression underlaid with sedimentary strata and walled on every side by lofty mountain ranges; they are really old lake basins. The North park has a comparatively level surface,-and an average elevation of 8,000 ft. S. of this, and only separated by a rather low mountain range, is the Middle park, which is much larger and far more rugged; indeed, there is very little of what might be called plain country, but a succession of high ridges, many of which are of volcanic origin. The average elevation is about 7,500 ft. Still further S., but separated by a much wider belt of mountainous district, is the South park, which is mostly a plain, with an average elevation of about 9,000 ft. In these parks there is frost every month of the year. (See Colorado.) San Luis valley, in southern Colorado and northern New Mexico, has an average elevation of 7,000 to 8,000 ft.
The Llano Estacado of Texas and New Mexico averages 3,200 to 4,700 ft. above sea level; the Colorado plateau in Arizona, 5,500 ft.; Salt Lake valley, Utah, 4,200 to 4,500 ft.; Laramie plains, Wyoming territory, 7,000 ft.; Snake river plain, in Idaho, 4,000 to 4,500 ft.; Sevier lake basin, Utah, 4,700 ft.; Humboldt river basin (Lassen's meadows), Nevada, 4,200 ft.; Carson river basin, 3,800 ft.; Walker's river basin, 4,100 ft.; and Mojave river basin, California, 1,100 ft. Comparing the mountain plateaus or basins of the Rocky mountain region with some of those in the Andean region of South America, the difference of elevation is very great. The Antisana plateau of South America is 13,451 ft.; the basin of Santa Fé de Bogota, 8,413 ft.; and the basin near Lake Titicaca, 12,853 ft. Perhaps as great an extent of plateau is comprised in the belt between the 38th and 44th parallels of latitude as in any other portion of the Rocky area. Through this belt the Pacific railroad passes. From Omaha to Cheyenne the track lies nearly all the way on the most modern tertiary formations. From Cheyenne westward the road crosses the Laramie range, the highest point, Sherman, being 8,271 ft. After passing over about 15 m. of granite rocks, it descends into the Laramie plains.
Thence to the Wahsatch range in Utah no more granitic rocks are met with, only cretaceous or tertiary. In crossing the water divide at Creston, 7,030 ft. high, the stranger would not suspect that he was passing from the Atlantic to the Pacific slope. The road runs through the Wahsatch range at right angles, in the channel of the Weber river, with only 4 m. of granitic rocks, so that from Omaha to Ogden only about 18 m. of metamorphic rocks are met with. Thence the Central Pacific crosses the Salt lake basin, enters the Humboldt valley, and really meets with no mountains until it reaches the Sierra Nevada, where a most formidable obstacle presents itself in a massive granite mountain range, which however is crossed at an elevation of only 7,042 ft. - According to Messrs. Blake and King, there are seven longitudinal zones or belts of mineral deposits in the west, following the prevailing direction of the mountain ranges. Mr. King says: "The Pacific coast ranges upon the west carry quicksilver, tin, and chromic iron. The next belt is that of the Sierra Nevada and Oregon Cascades, which upon their W. slope bear two zones, a foot-hill chain of copper mines, and a middle line of gold deposits.
These gold veins and the resultant placer mines extend far into Alaska, characterized by the occurrence of gold in quartz, by a small amount of that metal which is entangled in iron sul-phurets, and by occupying splits in the upturned metamorphic strata of the Jurassic age. Lying to the east of this zone, along the E. base of the Sierras, and stretching southward into Mexico, is a chain of silver mines, containing comparatively little base metal, and frequently included in volcanic rocks. Through middle Mexico, Arizona, middle Nevada, and central Idaho is another line of silver mines, mineralized with complicated association of the base metals, and more often occurring in older rocks. Through'. New Mexico, Utah, and western Montana lies another zone of argentiferous galena lodes. To the east again the New Mexico, Colorado, Wyoming, and Montana gold belt is an extremely well defined and continuous chain of deposits." It has usually been understood that there is no coal in the true coal measures in the Rocky mountain district; but of late years a few thin seams have been reported as occurring in the south and southwest. In Colorado, Wyoming, Utah, Montana, and New Mexico, vast areas are underlaid by thick beds of coal belonging to the cretaceous and tertiary groups.
In southern Colorado, New Mexico, and the interior of Utah, thick and important beds of coal are found in the cretaceous group, while along the E. slope of the Rocky chain in Colorado, as at Raton hills, Cañon City, Colorado Springs, Golden City, and northward, are numerous coal beds belonging to the lignitic group, eocene tertiary, which are now wrought to a large extent. In the northwest the lignitic area covers at least 100,000 sq. m. Along the Union Pacific railroad are coal beds of the same age, without which the railroad could not exist. Not less than 20,000 tons a month are mined at Evans-ton, Rock Springs, and Carbon, in Wyoming territory, for the use of this road alone. From Coalville, Utah, E. of Salt Lake City, no remarkable beds of coal are found along the immediate vicinity of the Pacific railroad to San Francisco. The scarcity of tree vegetation in the Rocky mountain area renders this coal of vital importance to the present and future industries of the great west. - The timber line or highest limit of tree vegetation does not vary much in the main chain of the Rocky mountains.
In Colorado and Utah it is from 11,000 to 12,000 ft.; in northern Wyoming and Montana, from 8,000 to 11,000 ft.; on Mt. Shasta, California, 8,000 ft.; while as far south as San Francisco mountain, Arizona, between lat. 35° and 36°, it is 11,547 ft. According to the observations made up to this time (1875), the timber line is lower to the far north. Between lat. 45° and 46° in Montana, it varies from 8,800 to 9,600 ft., while from lat. 40° to 35° it is quite uniformly from li,000 to 12,000 ft. These statements may be regarded as approximately accurate, though more observations ought to be made. - The mean elevation along several parallels of latitude has been ascertained approximately. For instance, along the 32d parallel, between lon. 95° and 96°, the mean elevation is 500 ft.; the highest mean between 108° and 110°, in the Sierra Madre plateau, is 5,000 ft.; 35th parallel, first mean 650 ft., highest mean, between lon. 107° and 109°, at Zuñi mountains, 7,000 ft.; 39th parallel, first mean 1,000 ft., highest mean, between lon. 105° and 107°, in the Colorado, Sahwatch, and Elk ranges, 11,000 ft.; 41st parallel, first mean 1,000 ft., highest mean, between lon. 105° and 107°, Laramie range and South park, 8,000 ft.; 45th parallel, first mean 1,000 ft., highest mean, between lon. 108° and 110°, Big Horn mountains and Yellowstone range, 7,000 ft.; 48th parallel, first mean 1,500 ft., highest mean, between lon. 113° and 114°, the main Rocky chain, 4,000 ft.
The mean elevation of Arizona is 4,200 ft.; of California, 2,800 ft.; of Colorado, 6,600 ft.; of Idaho, 3,800 ft.; of Montana, 3,950 ft.; of Nevada, 4,900 ft.; of New Mexico, 5,400 ft.; of Oregon, 2,700 ft.; of Washington territory, 1,800 ft.; of Wyoming, 6,450 ft. - In almost every state and territory W. of the Mississippi old lake basins exist, and from the sediments that were deposited in the bottoms of these lakes have been obtained the remains of a great variety of extinct animals, including camels, rhinoceroses, elephants, mammoths, crocodiles, huge saurians, turtles, birds, etc. In the vicinity of the Black hills of Dakota is a large area marked on the maps as Mauvaises Terres, or Bad Lands, so called on account of its ruggedness, in which thousands of extinct vertebrate animals were entombed. It was formerly a vast fresh-water lake, probably dating back at least to the beginning of the miocene period, and continuing through the pliocene nearly to the present time. During this time at least two distinct faunal groups appeared on the earth, lived out the period of their existence, and perished. The first group, which lived during the miocene period, left not a single species to the pliocene, and the fauna of the latter furnished no species for our present period.
In the Sweetwater valley, near the three forks of the Missouri, in Oregon, California, Texas, New Mexico, and Colorado, are similar lake basins filled with the remains of these extinct animals. On the Laramie plains, about Fort Bridger, and far S. on Green river, are lake basins of older date, referred to the lower miocene or upper eocene, in the deposits of which have been discovered the abundant remains of hundreds of extinct forms of vertebrate animals, entirely distinct from those just mentioned as of more recent age. Great quantities of fossil insects, fishes, and plants are found in these lake beds. Over 500 species of extinct forms of plants have been found, mostly in connection with the coal, indicating that at a comparatively modern period, geologically speaking, this great region, occupied with mountains and barren plains, was covered with forests as luxuriant as those of the gulf states. These plants belong mostly to the early tertiary period. The present scarcity of timber in the eastern and central portions of the continent is well known.
The principal winds come from the west and northwest, and, as they pass over the summits of the different ranges of mountains from the Pacific coast eastward, laden with moisture, discharge a portion of it from summit to summit, until on the eastern slope the air is almost dry. The absence of timber is due to the absence of moisture, and the inference from the fact of the luxuriant forests existing in the Rocky region during the early tertiary period is that these high summits did not then exist. - The drainage areas of the west are well marked out. The Missouri river and its great branches, the Yellowstone and Platte, have their sources in the eastern portion of the Rocky range, and, gathering their waters from myriads of branches, flow at first E. across the dry plains, and gradually turn S. E. and join the Mississippi; the average rainfall in the upper Missouri drainage is 18 inches. The second drainage is that of the Arkansas further S., which rises in the Sahwatch and Park ranges of Colorado, flows S. to lat. 38° 30' and lon. 106°, then bends E. and flows across the plains to unite with the Mississippi; the average rainfall is 28 inches.
The third system of drainage is still further S., that of the Rio Grande, which rises in the San Juan mountains of southern Colorado, flows S. through New Mexico and between Texas and Mexico, and empties into the gulf of Mexico; average rainfall, 16 inches. West of the last is the drainage of the great Colorado of the West, which, rising far north (in its branches the Green and Grand rivers), near the Yellowstone national park, flows S. and S. W. across Wyoming, Utah, and Arizona, and empties into the gulf of California; the average rainfall in this vast area is only 15 inches. N. and W. of the Colorado drainage is the great interior basin, between the Wahsatch mountains and the Sierra Nevada, with no known outlet, the great rivers sinking; here the average annual rainfall is only 12 inches. To the north is the great drainage of the Columbia, the branches of which rise in the main chain of the Rocky mountains far to the east, in Idaho; the average annual rainfall is only 18 inches. There are several smaller areas of drainage on the Pacific coast. The limited rainfall in all these regions shows that successful agriculture is only possible with the aid of irrigation.
E. of the Sierra Nevada the rains are not frequent, the snows are very light, and the amount not great, so that the supply of water from the melting of the snows is not extensive. The difference between high and low water mark is very great. For a short time in May and June the streams are high and large, but they soon dwindle greatly, and even disappear altogether. So little snow falls on the E. ranges that the streams which flow into the plains from the E. slope will not supply water to irrigate more than one fourth of the agricultural area.