Page:The New International Encyclopædia 1st ed. v. 17.djvu/234

* KOCKY MOUNTAINS. 210 ROCKY MOUNTAINS. this inouiitainous iilatoau of Wyoming, and sup- plied principally by the melting of the snow on the lofty ranges, the Yellowstone Kiver flows eastward to join the Missouri, and the Snake River flows westward and luiites with the Colum- bia : the many head-branches of these two impor- tant waterways adjoin along the continental di- vide. In central Idalio there is a great region of sharp, serrate peaks, the character of which is ex- pressed by the name of the main or Sawtooth range, by estimate about 13,000 feet high. Topo- graphically this rugged region extends northwest and is known in part as the Bitter Root and the Ca?ur d'Alene ilountains, which, although not re- markable for their height, are of great extent and important on account of their mines, forests, and fine scenery. In Montana there are also several distinct and important ranges, among which there are not less than 23 peaks that exceed 10,000 feet in height above the sea and rise from (3000 to 8000 feet above the neighboring valleys. To the east of the Big Horn Jloiintains and separated from them by a portion of the Great Plateaus, 150 miles wide, are the Black Hills, which in a general view are included in the Rocky Mountains. These hills are due to a dome- like elevation of the generally horizontal rocks underlying the Great Plateaus, measuring about 80 by IfiO miles, which if uneroded would have a height of some 7000 feet above the surrounding plain. Erosion has cut deeply into the uplift, however, and produced a rugged topography, es- pecially in its central part, where granitic rocks ai'e exposed. The culminating summit, Harney Peak, has .an elevation of 7216 feet and rises about 2700 feet above the surrounding plain. The Park Mountains, situated to the south of the Wyoming Plateau, are composed of many distinct ranges having a north and south trend, to which, however, a marked exception is fur- nished by the Uintah range in southwest Wyo- ming and northeast Utah, which consists of a deeply dissected east and west fold or broadly uplifted plateau. Intervening between several of the adjacent ranges, especially in Colorado, there are wide, nearly flat-bottomed valleys which owe their leading characteristics to the depth of the deposits of debris swept into them from the bordering uplands by streams and the wind. These valleys are known as 'parks' and suggested the name for the mountain system in which they occur. Typical examples are furnished by North, Middle, South, and San Luis parks in central Colorado, the broad generally level floors of which have elevations ranging from 7000 to 8000 feet. Among the numerous ranges of the Park Mountains in Colorado are the Front or Colorado range, in view from Denver, the Saguache. Elk, San .Juan ranges, etc. A conspicuoiis feature in the relief is the generally great elevation and the large number of lofty summits. The area above an elevation of 10,000 feet is much larger than any other region with a similar altitude in North America. Among the host of magnificent moun- tain peaks there are more than 30 which exceed 14.000 feet, but the'ir height is seldom fully ap- preciated, owing to the elevation of the neighbor- ing valleys, which reduces their vixtml hrifiht to about one-half of their total elevation above the sea. Of this luultitude of magnificent individual mountains or peaks, as many of them are termed, the best known and perhaps most representative are, with their elevations expressed in feet: Gray's Peak, 14,341; Mount Harvard, 14,325; Mountain of the Holy Cross, 14,000; Mount Lin- coln, 14,2U7; Long's Peak, 14,271; Mount Prince- ton, 14,1UU; Pike's Peak, 14,108; Uncompahgi'e Peak, 14,28U: and Mount Yale, 14,187, In the opinion of many observers the most ni.aguificent mountain mass in the Park Mountains, largely on account of its isolation, is Sierra Blauca, in soutlieast Colorado, 14,405 feet. The Park iXountains extend west into Utah and there include the bold Vasatch range, with a culminating summit nearly 12,000 feet above the sea, Tliis range is iti view from Ogden and Salt Lake City and presents a wonderfully bold escarpment to the west, Avhich sharply defines the west border of the Kocky Mountains for a distance of some 200 miles. To the southwest of the as yet indefinitely de- termined border of the Park ^Mountains is a series of high plateaus termed collectively the Colorado Plateaus, situated principallj' in Ari- zona, western New Mexico, and southern Utah, which iiave elevations ranging from 7000 to 8000 feet, and have been deeply dissected by the Colorado River and its tributaries. The explora- tions of J. S. Newberry, J, W, Powell, and C. E. Button in this land of remarkable canons have made it one of the best known and to geologists and geographers most instructive portions of the Rocky Mountain region. In New Jlexico the moinitains are lower than in Colorado, and the several ranges and numerous isolated volcanic mountains are separated by broad deeply filled valleys. These same charac- teristics of the relief extend southward into Mexico, where the Rocky ilountains terminate and are succeeded by a series of lofty volcanoes, and by the western portion of the Antillean Cor- dillera, in which the major structural features are folds and faults, trending east and west. Geologically the Rocky iloimtains present a wide range in reference especially to the age of the rocks and to the structure of the numerous ranges. All of the larger divisions of geological history from the Arch^Eean to recent times are represented. Granite, gneiss, schist, and related rocks usually referred to the Archaean occur es- pecially in the axial portion of many of the ranges, as the Front or Colorado range, the Saguache, etc,, in Colorado, the Black Hills, Big Horn, Teton, etc. The older recognized sedi- mentary rocks belong to the Algonkian period and consist largely of quartzites. In the Lewis and Livingston of ilontana rocks of this age have yielded interesting remains of large crustaceans related to Etirt/pterus. which belong to the oldest kno™ fauna of the earth. In sandstone of Ordovician (Lower Silurian) age near Caiion City, Colo., the oldest known fossil fishes have been found. Carboniferous rocks, principally ma- rine limestone, occur widely throughout both the Stony and Park Mountains. At several localities in Colorado and Wyoming rocks of Jura-Trias age have yielded large quantities of bones belong- ing to gigantic extinct reptiles. Marine sedi- ments of Cretaceous age. particularly in ]SIon- tana, are frequently crowded with beautifully preserved shells, anil particularly a great variety of eephalopods. Tertiary rocks, consisting prin- cijially of the sediments of lakes and occurring for the most part in the valley, contain the bones of many genera of extinct mammals, some of