Andes (said to be derived from the Peruvian anti, copper, metal), a lofty mountain-system of South America, extending north and south along the whole Pacific coast, and really a continuation of the vast and complicated mountain-system of Western North America, though on the Isthmus of Darien the height of the connecting ridges is less than 130 feet. The mountains of the Fuegian Archipelago, south of the mainland of South America, including Cape Horn and Diego Ramirez, must be held to belong to this system. Without allowing for curves, the Andes extend some 4500 miles. The Patagonian portion of the system is much cut by steep ravines, sometimes partly filled with glaciers, and not seldom occupied by deep arms of the sea. On both east and west sides of the ranges vegetation is luxuriant, due to the excessive abundance of the rainfall. Between lat. 42° and 24° S. the main chain of the Andes recedes from the sea-coast, leaving in Chili a tract of country nowhere exceeding 120 geographical miles in breadth. The mountains here reach a mean elevation of 11,830 feet; one of the peaks, Aconcagua, is the loftiest on the American continent, 22,867 feet. Another, Cima del Mercedario, is 22,312 feet. In this region, both to the north and to the south, there is but one main line of peaks; but between these two parts two high parallel ranges occur, having between them a relatively low plateau. The Bolivian Andes occupy perhaps one-third of the area of the republic, and form a vast arid region of great elevation. Amongst them are Gualtieri, 22,000 feet high, and Sorata and Illi-mani, both above 21,000. The east and west Cordilleras of Bolivia enclose the land-locked plateau of the Desaguadero, 13,000 feet in height, and having an area of 30,000 sq. m.

In Peru the maritime Cordillera overlooks the sea in a close succession of volcanic cones. Near lat. 10° S. the chain divides into the seaward Cordillera Negra, and the more eastward Cordillera Nevada, with a deep trough or ravine intervening. The central Cordillera of Peru is the chain which bounds the Titicaca basin on the west. The eastern Andes of Peru form a magnificent succession of grand peaks, with only very local evidences of recent volcanic action. Of the Peruvian peaks the highest are Huascan (22,000 feet) and Huandoy (21,088 feet). The lofty wildernesses of the high Peruvian Andes form a cold and wind-swept region known as the Puna. In the SW. of Ecuador the various ridges of the Andes coalesce, immediately to divide again into two main chains, both characterised by intense volcanic activity. According to Whymper Chim-borazo is 20,498 feet, Cotopaxi 19,613, and Anti-sana 19,335. The Colombian Andes are disposed in three main lines. Only a few of the peaks of the Venezuelan Andes rise above the snow-line. One of the plateaus, Assuay, is 14,500 feet high; the lowest notable pass, Planchon, is 11,455 feet high.

The great bulk of the Andean masses is composed of stratified rocks; upheaval, denudation, and direct volcanic action have been leading factors in building the mountains. Volcanic action is still very great in Ecuador, but less so in the other parts of the chain. Gold, silver, copper, mercury, and other metals abound in nearly every part of the Andes. There are three trans-Andean railways - two In Peru, and a more important one, unfinished in 1004, which connects the Chilian and Argentine railways by a rack-rail line with five tunnels, nearly continuous, about 8 miles long and at a height of between 9000 and 10,000 feet. See Conway, The Bolivian Andes (1901); Fitzgerald, The Highest Andes(1899); Whymper, Travels amongst the Great Andes of the Equator (1892).