Andes, the range of mountains which extends along the northern and western coasts of South America, from the southern extremity of the continent to the Caribbean sea. It is the most compact mountain system in the world. Skirting the Pacific shore for nearly 4,500 m., with a mean elevation of 12,000 feet and varying in breadth from 40 to 350 m., it covers with its base a surface of more than half a million square miles. Nowhere else does nature present such a continuous, well defined, and lofty chain. It is in strong contrast with the broken and straggling systems of Europe and North America. The Himalayas surpass the Andes in extreme altitude, but as they are situated beyond the tropics and destitute of volcanoes, they do not present that inexhaustible variety of phenomena which characterizes the latter. Though presenting one continuous axis, the Andean range consists of several members, known by the names of the countries in which they occur. The Patagonian section is a single narrow range of moderate elevation, but ascending in several points (Mt. Darwin, Mt. Stokes, and the volcanoes of Yanteles and Minchinmadiva) to 6,400 and 8,000 feet.
It begins in a group of mountainous islands, the archipelago of Tierra del Fuego; and, indeed, the western side throughout its whole length is penetrated by narrow inlets or arms of the sea and bordered by a series of rugged islands. This Pacific side, exposed to the prevailing winds, is of barren rock; but the eastern slope is covered with forests of beech (fagus betu-loides), which reach up to 1,000 or 1,500 feet above the sea level; and beyond this succeeds a belt of dwarfed alpine plants and peat mosses, which continues to the height of 3,500 or 4,000 feet, the limit of perpetual snow. Almost every arm of the sea, says Darwin, which penetrates to the interior higher chain, not only in Tierra del Fuego, but on the coast for 650 m. northward, is terminated by tremendous and astonishing glaciers. Great masses of ice frequently fall from these icy cliffs, and the crash rever-berates like the broadside of a man-of-war through the lonely channels. The glacier furthest from the pole which comes down to the sea, surveyed during the voyages of the Adventure and Beagle, is in lat. 46° 50' S., in the gulf of Penas. - As the Andes enter Chili they begin to recede from the ocean, and a fertile belt of country intervenes, which in lat. 36° is about 100 m. wide.
They still form one immense ridge, but they gain in height and breadth. Though in mean elevation they are inferior to the Andes of the north, they yet contain the gigantic Aconcagua, the culminating point of the whole system, and the highest mountain in the new world. It is frequently called a volcano, but it shows no trace of modern igneous origin, although it is porphyritic. Its height was computed by Capt. Beechey from its angle of elevation at Valparaiso to be 23,910 feet; but the more exact measurement of M. Pissis makes it 22,422. Other Chilian peaks are Tupungato, Antuco, Villariea, Chilian, May-pu, and Osorno, some of which, if not all, are volcanic. The snow line in the latitude of Valparaiso is about 15,000 feet above the sea. "To this line," Darwin observes, "the even summits of the range seemed quite parallel. Only at long intervals a group of points or a single cone showed where a volcano had existed or does now exist. Hence the range resembled a great solid wall, surmounted here and there by a tower, and making a most perfect barrier to the country." - The Bolivian Andes extend from about lat. 24° to 15° S. For some distance there is but one undivided range as in Chili, between which and the Pacific is the vast desert of Atacama, doubtless the bed of an ancient sea.
At the mountain knot of Al-turas de los Lipes, lat. 22°, the chain separates into two great longitudinal ridges, called the Cordillera of the coast and the Cordillera Real, which enclose the wonderful table land of Des-aguadero, the Thibet of the new world. This high valley, elevated 13,000 feet above the sea, extends 500 m. in length and from 30 to 60 in breadth along the top of the Andes. It is so completely walled in that the streams have no apparent outlet, but meet in Lake Titicaca. The surface of this lake is 12,846 feet above the Pacific. It is the largest fresh-water accumulation in South America, covering 4,600 sq. m. and having a depth of at least 120 fathoms. The Rio Des-aguadero connects it with the Laguna Aullagas, 180 m. S., which is about 50 feet lower than Titicaca. The valley enjoys a temperate climate, but it is treeless and cultivation is limited. Yet large cities have flourished at this altitude. Potosi, famed for its silver mines and for being the most elevated city on the globe, two centuries ago contained 150,000 inhabitants. Its altitude is 13,330 feet. The cecro on which it is situated is honeycombed by mining operations, over 5,000 boca-minas being visible. To the N. E. of it is Chuquisaea or Sucre, the capital of Bolivia, in the midst of cultivated fields.
La Paz, a few leagues from the southern extremity of Lake Titicaca, is situated in a que-brada, or ravine, 620 feet below the lake, and still over 12,000 feet above the sea. The water that flows through the quebrada of La Paz winds around the volcano of Illimani, and, flowing northward and uniting with other branches, becomes with them one of the great tributaries of the Amazon. Nine fine bridges cross this ravine in the city. The Cordilleras run parallel to each other, from 200 to 300 m. distant; the eastern range has a mean elevation of 13,500 feet, and the western 14,800. They arc united at various points by enormous transverse mountain dikes or knots. The highest summits in the coast range are Sahama, 22,350 feet; Pa-rinacota and Gualatieri, 22,000 each; Poma-rape, 21,000; and the active volcano Arequipa, 20,300. The loftiest peak in the Cordillera Real is that of Sorata, 21,286 feet; and near by is its rival, Illimani, only 100 feet lower. The Pacific slope of this section of the Andes is sandy and barren.