The Andes Mountain Range is the main mountain system in South America. Being geologically-young, it is the longest mountain range in the world, with more than 7,000 km in length, extending from Venezuela all the way down to the extreme southern tip of South America. It also features the highest peak in the American continent, which is Mount Aconcagua (6,961 m). The Andes are the most important climatic barrier on the continent, isolating the entire east from the influence of the Pacific Ocean and the west from the influence of the Atlantic. Thus, the South American continental divide runs along the Andes, and from the Andes flow the beginnings of the sources and tributaries of the Amazon as well as the tributaries of the Orinoco, the Paraguay, the Paraná, and the rivers of Patagonia. This mountain system is known as Cordillera de los Andes in Spanish.
The Andes have an average height of 4,000 m and a maximum width of 700 km. This young mountain system is divided into many sub-ranges by intervening depressions. Numerous high plateaus nestle among its high, snow-capped peaks, where the population depends on husbandry for a living, with llamas and vicuñas being their main livestock. The extent of the Andes and their altitude are the causes of major landscape differences in individual areas. With an altitude of 3,750 m, the Altiplano Plateau, which is located in Bolivia, is the world’s second-highest plateau, right after the 4,500-m high Tibetan Plateau in Asia. In Bolivia, a significant portion of the population is concentrated on this high plateau of the Andes. Also, the world's highest active and dormant volcanoes are found in this mountain system.
Orographically, the Andes consist of parallel, predominantly meridional ranges between which the interior highlands and depressions lie. Geomorphological structural features differ in individual sections of the Andes. The major ones (from north to south) are the Caribbean, northwestern, Ecuadorian, Peruvian, Central, Chilean-Argentinian, and Patagonian Andes. The Central Andes are the widest (700–800 km) and most complex segment of the Andes. The entire central portion is formed by the broad internal plateau, called the Puna de Atacama in Chile (with an elevation of around 4,000 m), and Altiplano in Bolivia, tectonic and residual lakes (Titicaca, Poopó, Coipasa), and enormous salars. The Puna is enclosed between the ridges of intrusive peaks and volcanoes that rise up to 5,500–6,700 m high on the west, and by high folded-block ranges and medium-altitude folded sub-andean chains in the east.
Geology
The orogeny (formation) of the Andes began about 50 million years ago, during the Tertiary period of the Cenozoic era. The general uplift and folding of South America's western portion to high altitude has been caused by the collision and subduction of the Nazca plate against the South American plate, with the former pushing against the latter, sliding beneath it. When this happened, already-existing, much older geological rocks were raised and folded to high altitude and were exposed in different geological strata, which were formerly arranged horizontally before the Tertiary orogeny, but, when the uplifting began, they were set up slantingly and, sometimes, almost vertically by the violence of the tectonic collision. Therefore, the geological structure of the Andes is quite diverse and complex.
Along the eastern edge of the Andes, the Hercynian folded system stretches between 10° and 30° Southern latitude. The puna/altiplano plateau, which is part of this folded system, is composed of Paleozoic rock (from the Cambrian to the Permian) and breached by granodiorites. The Andean system itself is one of the major systems of alpine folding. The geological materials had already being formed on a Paleozoic and partially Baikalian (Upper Precambrian) folded basement. Although the geosynclinal troughs of the Andes were formed in the Triassic period (Mesozoic) and were filled with thick sedimentary and volcanic beds, their uplifting and folding process began at the beginning of the Tertiary period (Cenozoic).
The various geological structures contain the useful minerals usually associated with them. The major oil deposits—the depressions of Maracaibo, Magdalena, the Andean foothills of Venezuela, Peru, Bolivia, and Argentina—are confined to the foredeeps and intermontane troughs. Tin, silver, lead, zinc, tungsten, vanadium, antimony, bismuth, arsenic, and other ores are located in the eastern Paleozoic structures and in the vents of ancient volcanoes in Peru and Bolivia. The copper ore deposits (Chile) are associated with the intrusions of the Andes. There are also deposits of gold, platinum, and emeralds in Colombia, sodium nitrate in northern Chile, and other minerals.
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| Above, Mt Aconcagua, the highest peak in the American continent, with 6,961 m high, lying in Mendoza, Argentina. |
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| Map of South America showing the Andes Mountains extending from north to south along the western portion of that continent. |