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chilled below the freezing point at night, while plains made to yield a wealth twice as much per the diurnal and seasonal extremes in the lofty capita as that of any other portion of the United deserts of Central Asia are much greater. Thus States. desert-regions are most effective in producing The North American Cordilleran region emland and sea breezes and monsoon winds in con- braces the whole of our continent between the sequence of the marked periodical changes in at- Great Plains and the Pacific north of the Isthmospheric density. Another effect is the mirage mus of Tehuantepec. Of the grander scenery of (q.v.), a phenomenon which, combined with the the world none is more varied and beautiful than great loneliness that oppresses the occasional that of this region. From its northern end in traveler, probably accounts for the widespread far-away Alaska to the jump-off of the Mexican superstitions peopling deserts, above all other Plateau of the South it presents a marvelous places, with evil and malicious spirits. The panorama of form, color and sculpture. A few dreaded sand-storm or simoom is a kind of tor- of these features are familiar by name, but the nado or whirlwind which raises the sand in tall glories of the Cordilleras as a whole have not rotating columns sweeping over the surface with been written, for even the professional geogtremendous velocity. Sand-dunes, sometimes rapher has but an incomplete idea of the region several hundred feet in height, are raised by as an entirety, or of its parts and their relations. steady winds, and gradually shift their position. In fact, much of the Cordilleran region is still Desert vegetation is extremely scanty, consisting so poorly mapped, that there is not yet a chart mainly, of hard prickly, plants, of the cactus, that gives a correct presentation of its great euphorbia, and spinose kinds, whose surface ex- mountains and valleys. Most people, therefore, hales little moisture. Animal life is correspond- have but vague ideas of the Rocky Mountains, ingly restricted both in variety and number of the Great Deserts, the western and eastern individuals. The camel is par excellence the Sierra Madre, the California sierras, and the beast of burden for conducting traffic across arid Coast ranges — any one of which is as extensive wastes. When an overflowing river, such as the and unique a geographic unit as the great ApNile, traverses a desert, the land becomes richly palachian region. fertile in its immediate neighborhood, and wher- The Cordilleran region is likewise one of ever springs bubble up through the sand there contrasting, extremes. Within it are found are oases, bearing palm-trees and grass. Arti- every condition of climate, altitude, vegetation ficial irrigation, especially the sinking of artesian and productivity. The rainfall varies from the wells, has done much to reclaim tracts of desert greatest in the United States (in Washington) for agriculture in the Sahara and to a less extent to the least in the world (in the Death Valley in Australia, while the area of arid land in the and the Yuma Desert). Its altitudes range from western part of the United States, once con- the highest peaks on our continent (over 17,000 sidered irreclaimable, is being rendered by irri- feet) to depressions 300 feet below sea-level. gation increasingly productive.
Its vegetation presents the contrast of forests of Geological considerations show that arid des- the largest and most beautiful trees in the world erts are not permanent features of the earth's and vast stretches of desert plain with the feesurface. The most level expanses have once blest mantle of struggling bush and thorn. The formed part of the ocean bed, or at least great region is the motherland of our longest rivers, inland seas. The orographical changes which the Missouri, the Columbia, the Colorado and the cut off these seas and created inland drainage Rio Grande; yet it has a million square miles areas probably at the same time modified the without as much running surface water as the rainfall of the locality. Excessive evaporation smallest New England township. It has in dried up the great lakes, leaving at present a places mines which yield from a single acre series of diminishing salt lakes without outlet, more wealth than whole counties in many Eastreceiving rivers which dwindle down by evapora. United States; yet again there are hundreds of
ern States, and it produces every mineral of the tion as they flow. The only commercial commodities yielded by deserts are the salts (common miles of barren malpais as worthless as any salt (borax, sodium carbonate, and sometimes ground the sun shines on. Some of its acres of sodium nitrate) left in the dried-up lake beds. agricultural soil are the most productive on These salt lakes are subject to alternate long earth, yielding under intensified and scientific periods of desiccation and flooding; during the culture the finest and most abundant crops of former the area of the desert extends, during fruit, grain and tubers; and upon others even the the latter it contracts. These periods have been cactus will not grow. traced out in the case of the Great American distinct groups, which are so aligned as to con
The forested Cordilleras occur in several Basin by a series of most interesting researches stitute marginal chains of mountains bordering' on the part of the United States Geological Sur- the Eastern and Pacific sides of the Cordilleran vey. See GOBI; SAHARA.
region, between which lie the deserts and plaDesert, The Great American. The North teaus. The chief of these groups are, (1) the American deserts possess all the physiographic, Montana and Colorado groups of New Mexico, geologic and climatic elements which distinguish and the eastern Sierra Madre of Mexico, formthe African desert of Sahara. The chief dif- ing the eastern ranges of the Cordilleran region; ference between the two regions is the relatively and (2) the Sierra Nevada, Cascade and Coast larger area of the Sahara, the arrangement of ranges of the extreme western United States, the topographic units and the occurrence in the and the western Sierra Madre of Mexico, conGreat American Desert of a wealth of mineral stituting the Pacific or western ranges. resources which the Sahara does not possess. The remainder of the Cordilleran region, inThrough the application of modern mechanical cluding the vast stretches lying between the agencies by American energies and brain, its Sierra Nevada of California and the eastern wastes have become inhabited by an intelligent Cordilleran ranges (Rocky Mountains) in the and progressive people, and its arid hills and United States, and between the Pacific Ocean
and the eastern Sierra Madre of Mexico, con- or Nevadan, Desert occupies much of the area stitutes the Great American Desert.
of Utah, Nevada, Mexico, southern and eastOf the total area of the Cordilleran province, ern California in the United States, and the three eighths are forested mountains, one eighth states of Sonora and Sinaloa in Mexico. The plateau, and one half waterless, treeless, turfless Chihuahuan Desert occupies the vast area of mountain and valley desert. The deserts occur country lying between the eastern and western in Nevada, Utah, eastern and southern Cali- Sierra Madre of Mexico and their northern confornia, Arizona, New Mexico, and all of Texas tinuation into southern New Mexico and Texas west of the Pecos, 550,000 square miles. The west of the Pecos, and is the so-called Mexican American Desert is international, however, for Plateau. in addition to the above area within the United The Great Basin Desert is marked by wide States, it continues southward into Mexico, fatness, and is largely a region of ancient lake where it includes most of the states of Sonora, beds. Its surfaces are in many instances what Chihuahua, Coahuila, San Luis Potosi and Sin- the geologists term constructional, and its flora aloa — another 500,000 square miles — making is mostly sage brush and grease wood; its agria total of 1,050,000 square miles which, although cultural products cereals and tubers; and its one third the area, is as truly a desert in every minerals gold, silver, and copper. The Sonoran natural
as is the Sahara, which em- Desert is of a more complicated geological type, braces an area of 3,500,000 square miles, and has and instead of being land-locked is bordered on a population of 2,500,000 people.
one side by the Pacific Ocean. Some of its Through the area mentioned, the Great surfaces are also the result of what geologists American Desert stretches southward far into term destructional processes. Its Aoral types the tropics, a marvelous country, unique in are the saguara, the palo verde, and the catsevery feature of landscape and vegetation. claw. Its sparse agricultural products are fruit
In its entirety, (with a few exceptional for- and wheat, its mineral resources gold and copested summits) this desert province is one of per. barren, stony mountain ranges, separated by The Chihuahuan Desert, marked by parallel equally barren stretches of desert plain, an ag- plains and ranges, is a relatively higher region; gregation of elongated arid plains and lower its features are a combination of destructional mountain ranges, which mostly follow the axial and constructional processes. Its foral types are line of the Cordilleras. The individual deserts the maguey cactus and yucca; its chief agriculhave many names, and each differs from the tural product maize (corn), and its principal others in some minor aspect.
mineral product silver. From a technical point of view a desert in While the desert plains may be extensive, its ultimate analysis is a region in which the they also have many phases of variation. There rainfall is insufficient to produce run-off. The are the alkali plains, white crystal patches of light rainfall, striking the heated rock surfaces saline efflorescence which vegetation abhors, and and sandy soils, is soon evaporated or drunk in; vast plains of "doby (adobe) -- brownish choceven the large bodies of water which may start olate clay soils through which here and there down the mountain sides as roaring torrents are cut the deep channels of streamless streams. usually die out at the margins of the plains. There are the dreary "tabosa) fats covered by These waters are highly charged with mineral headlike bunches of a woody grass, abhorred by salts derived from the heated rock surfaces, animals and useless to man, through which one and these salts are readily redeposited upon may travel for days. The great white gypsum the surface or in the interstices of the permeable desert of the Tularosa valley of New Mexico is sands. The torrents locally transport the rock one of the most wondrous of all the desert debris -- boulders, pebbles, and powder – from plains. To the eye it is a veritable sea of purest one locality to another, but only for short dis- granular snow, marked with wind waves and tances; and hence the desert plains are usually ripples like the Tropic Ocean, with billows and composed of the debris of the adjacent moun- troughs. Yet it is not snowlike in its torrid tains, which in more humid regions of ample heat, which burns and thirsts more than man can run-off would have been carried to the sea. The tell. In some places there are extensive lakes expansion and contraction from the daily tem- of crystalline salt which the desert inhabitant perature causes the desert rocks to fracture in uses for herd and flock. Sometimes there are situ into the desert waste. This is distributed stretches of dreary brown sand hills, great bilby wind and torrent, and hence the features of lows gathered around the protecting roots of the desert are largely air-made as well as water- the thorny mesquite, the particles blowing with wrought.
each breath of wind, ever seeking a resting place, The scarcity of moisture results in the ab- though seldom finding one. sence of vegetation of the root-twining, soil- The half cannot be told of the many other gathering, and soil-making type that distin- aberrant features of the Great American Desert, guishes the humid region. Every plant and like Death Valley, with which no spot in Sahara species attests the aridity of the country. can compare for sterility and desolation; the Exactly as in the Sahara, these plants are thorny, great "medanos” or white sand dunes just south coriaceous bushes and shrubs of the cactus, aloe, of El Paso, each as high as the national capitol, and acacia families, adapted to withstand their which creep from place to place over the desert droughty environment, and to defend themselves plain; the vast plains of malpais in New Mexico from attack by man or beast.
with their burning, cutting, black, waterless Physiographically there are two sub-provinces surfaces of lava; the four dust” deserts of Jimof the Great American Desert, lying to the east enez and Arizona and Sonora, where the traveler and to the west of the western Sierra Madre is choked with clouds of chalk-white powder; and Colorado Plateau respectively. The west- the Crow Flat with its glare that blinds, the ernmost of these may be termed the Nevadan Jornado del Muerto, with its hundred whirland the eastern the Chihuahuan. The western, winds, the saguara deserts of Sonora, where