ANDES, Wei, the great mountain mass, or, as Humboldt called it, ((the largest mountain chain of the extending along the entire western coast of South America and turning toward the east in the regions between the equator and lat. N. Prolongations of the chain still farther eastward and, on the other hand, toward the extreme south, cannot be dis cussed conveniently in this place; it is, how ever, essential to note the deflection below the Caribbean Sea and the interposition of the Antillean• continent (compare article CENTRAL. AMERICA) between the Andean Cordillera and the quite distinct and separate mountain sys tems of western North America. :n regard to the derivation of the name Humboldt wrote: in the Quichua language (which lacks the consonants d, f and g), Antis, or Ante, appears to me to be made from the Peruvian word onto, signifying copper or metal in general." In the recent work by Professors Pirsson and Schuchert we find a condensed statement that supplies an outline of the geological story of the Andes as a whole: °Toward the close of the Cretaceous, the Andes had been elevated and folded throughout the length of South America (4,500 miles), and during most of Tertiary time an extensive pene plain (in places it was a postmature surface) was being developed in the central Andes. Vertical uplift began in later Tertiary time, ele vating this peneplain from 3,000 to 7,000 feet. This was in turn eroded to mature slopes and then was rapidly warped in Pliocene and early Pleistocene time, so that now the deeply dis sected erosion surface of the old peneplain stands at an average elevation of 12,000 feet, though locally it varies between 6,000 and 15, 000 feet. Upon it in the west rest immense lava flows and lofty volcanic cones, some of which attain a height of .21,000 feet above the sea. These are part of a great volcanic field whose development began in the early Tertiary and was completed soon after the Pliocene up lift began. The central Andean plateau is the second highest in the world, being exceeded only by that of western Tibet to the north of the Himalayas of India, where the intermontane plains range from 14,000 to 17,000 feet above the sea." We shall now endeavor to obtain clear views of the five chief divisions of this great uplifted region, namely, the far southern, the south central, the central, the equatorial and the northern.
The mountain region of Argentine Pata gonia, which first claims attention in the far southern division, is very different from the Pampa region in topography, climate and vege tation. The rainfall is very much heavier and all the conditions of the country are changed accordingly. Sheep-raising, which is the great industry of the Pampas, is not practicable in the forested Cordillera, as the feed is not suited to sheep, whereas cattle-raising, which is un successful in the drier part of the Pampas, will always be a principal industry in the Cordillera. Forests, of which there is no vestige in the Pampas, clothe the mountain slopes of the Andes. In the Pampas running streams are rare, but in the Andes they constitute one of the principal natural features and, gathering in beautiful lakes or in great rivers, determine the future of the region to be one of manu facturing industries based on water-power (Compare the extended and excellent study of this region by Mr. Willis, one of the best of recent works in this field. In several of the following paragraphs a few items of permanent interest from the same source are given, with minor changes).
The mountain chain of the Andes, attaining altitudes of more than 23,300 feet in its highest peaks, has impressed upon the minds of stu dents the idea of an enormous mountain bar rier, distinctly separating the lowlands of the Pacific coast from the vast low plains of eastern South America. So fixed is the conception that it has affected the deliberations of statesmen and the relations of nations. The conception of a dividing wall, nowhere easy of passage and in many places impassable, was the fundamental idea according to which the boundary between Argentina and Chile was to have been traced (see CHILE). Throughout the greater part of its extent the conception held true, and the engineers traced a well-defined crest which, fol lowing the high summits of the Andes, coincides with the divide of the waters between the Pa cific and the Atlantic. But from lat. south ward the topographic conditions were found to be very' different. In this portion of the Cor dillera it spreads out and divides into parallel mountain ranges. Some of the rivers rising in the extreme west of the mountain-belt flow to the Atlantic; others, rising east even of the eastern Cordillera, in the Pampas themselves, flow westward across the entire zone of the Andes to the Pacific. Here was confusion for the treaty-makers, since their engineers dis covered, in place of a mountain-wall, a laby rinth of heights and valleys pierced in many places by rivers which wound in zigzag courses, now toward one ocean, now toward another; and a boundary as fixed by a line along the highest crest of the Cordillera was found to di verge widely from a boundary traced on the continental divide between the Atlantic and the Pacific. Fortunately for both Argentina and
Chile, the treaty-makers had provided that any dispute should be settled by arbitration. In 1902, after 20 years of discussion, the arbitrator, King Edward of England, gave his award in favor of a compromise line. The foregoing statement makes it evident that the Andes of northern Patagonia constitute not a simple mountain ridge but a broad zone, including both mountains and valleys and traversed by large rivers. The summits whose altitudes most closely approach uniformity have been sculp tured by erosion from the broad plateau-like mass of the older rocks of the Andes, whereas most of the isolated peaks which rise more than 7,333 feet above sea are volcanic cones built up on the plateau. The most renowned of these is El Tronador ((The Thunderer"), 11,533 feet above sea, which received its name from Friar Menendez, about 1791, when he described it as the mountain that is always thundering. At the foot of this great peak lies the most profound canyon and lake of the region, that of Nahuel Huapi. This southern division of the Andes may be subdivided into two distinct areas, and the distinction may be expressed in the simple statement that in one the valleys ex tend east and west across the mountain zone, whereas in the other they range longitudinally from north to south within the Cordillera. The former area comprises the stretch of the Andes from lat. 38° to 41°, from Lago Alumine to Lago Nahuel Huapi. All but one of the streams within it rise in the western Cordillera and flow eastward to join their waters in the Rio Colloncura and the Rio Limay, which flow in the depression that lies along the eastern base of the Andes. Lago Lacar, though its valley once belonged to this Atlantic family, has turned away and now discharges its waters across the western range down the Pacific slope to the Chilean lakes. In this area high trans verse ridges extend eastward between the drain age basins, and some of them attain greater elevations near their eastern extremities than at the western. They divide the area into in dividual basins and more or less effectively ob struct the passage from one to another within the wide belt of the Andean plateau. Where the valley floors range from 2,000 to 2,866 feet in altitude above the sea, one must rise to passes that attain 3,333 or 4,000 feet in order to cross from one valley to the next. Each of the deep transverse valleys harbors one or more lakes, which, like the lakes of Switzerland and north ern Italy, lie in deep basins sculptured by the rock-laden ice of glaciers, descending from the adjacent heights. Their shores are everywhere picturesque and in many places precipitous. About their lower eastern ends are piled the glacial moraines of an ice period which is still represented in the little glaciers that linger about the high summits. In each of these val leys, at a, distance of several kilometres below the moraines just mentioned, is a much older glacial moraine which marks the outermost limit attained by the ice that filled the valleys during a still earlier glacial epoch. Thus these valleys, descending from the western Cordillera to the lowland that intervenes between the An des and the high plateaus of the Pampas, range in character from deep goiges in the mountains to beautiful lake basins and wide stretches of gravel plains. Their waters flow in the direc tion of the western winds, in the direction in which the air currents become dryer as they un load their moisture upon the mountains. The vegetation changes accordingly, and the streams, which gather their headwaters from the deep forest shades of the mountain slopes and which linger in the cold rock-bound lakes of the transverse valleys, flow on in the broad sunlight of the treeless grassy Pampas. Strong historic interests centre about localities in this area. The paso de Villarica, which crosses the Cor dillera in the north, was traversed by Francisco de Villagran in 1553, the year in which Val divia, the conqueror of Chile, after 12 years of struggle with the Indians, was defeated by them, taken prisoner and killed. Villagran was un doubtedly the first European to cross the south ern Cordillera. Subsequently Spanish captains, missionaries and embassies dispatched to nego tiate conditions of peace with the Indians, fought, prayed or held council in the valleys of Lagos Huechulaufquen, Lolog and Lacar.