ANDES, Fin'dez (Deriv. uncertain, usually ex plained as Copper Mountains. from the Peruvian word anti, copper; cf. in Germany Erz-gebirgc, Ore-Mountains, and Blci-berg, Lead-Mountain). The great mountain chain of South America, extending closely parallel with the Pacific coast, and nowhere far from it, from Cape Horn to the northwest coast of the South American continent. Its length is about 4500 miles, extending in latitude from 56° 30' S. to 11° N. In a way, it may be regarded as continuous with the Cor dilleras of North America, the two forming a well-nigh continuous mountain system 9000 miles in length. stretching from Cape Horn to the Aleutian Islands. The average breadth may be set at 150 miles, although this differs greatly in different parts of the system. Its average height of 12,000 feet is subject to the same qualification. Following the coast, the system trends a little west of south through Colombia and Ecuador, but on entering Peru it turns to the southeast, in which direction it extends through that country and part of Bolivia. Through south Bolivia. Chile, and Argentina, its trend is nearly south, but it swings in a broad the eastward near IN.lagellan Strait.
The mountain system rises abruptly on both sides throughout its course. Everywhere it pre sents a steep wall to the Pacific, and on the east it drops abruptly to the Amazon Valley; farther south, in Argentina, the land rises somewhat to meet it, and there are outlying ridges, but the main ascent is everywhere steep. The south
ern part of the system consists of a single range, with here and there outliers of comparatively little height, hut from northern Chile and Argen tina to Colombia, it consists of a high, broad plateau, capped by two or three ranges, with hundreds of high volcanic peaks, some active, others dormant or extinct.
Geologically, the system is of recent origin, although its age has not been closely determined. The material of which it is composed is in the main granites, with schists, slates, and other metamorphic rocks and the oldest of stratified rocks; here and there upturned beds of more recent formation, up to the Jurassic, lie upon the flanks of the ranges, while in Peru, the eastern range is composed largely of Silurian beds. Over all, in the neighborhood of the volcanic peaks, which are very numerous in all parts of the range. are spread lava, pumice, scoria, and ashes, in many places burying deeply the meta morphic rocks. Near the northern end, in Co lombia and Venezuela. the eastern branches are composed of recent stratified rocks. For de tailed description it will be convenient to refer to the countries traversed by this mountain sys tem, and this order will be followed, commencing at the north.