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South America - The Andes

region plate plates chile

The great mountain range of South America is the Andes Mountains, which extends more than 5,500 mi (8,900 km) all the way down the western coast of the continent. The highest peak of the Andes, called Mount Aconcagua, is on the western side of central Argentina, and is 22,828 ft (6,958 m) high.

The Andes were formed by the motion of the earth's crust, which is cut up into different tectonic plates. Some of them are continental plates, which are at a greater altitude than the other type of plate, the oceanic plates. All of these plates are in motion relative to each other, and the places where they border each other are regions of instability where various geological structures are formed, and where earthquakes and volcanic activity is frequent. The west coast of South America is a subduction zone, which means that the oceanic plate, called the Nazca plate, is being forced beneath the adjacent continental plate. The Andes mountains were thrust upwards by this motion, and can still be considered "under construction" by the earth's crust. In addition to the Nazca plate, the South American and Antarctic plates converge on the west coast in an area called the Chile Triple Junction, at about 46°S latitude. The complexity of plate tectonics in this region makes it a locality of interest for geologists.

The geological instability of the region makes earthquakes common all along the western region of the continent, particularly along the southern half of Peru.

The Andes are dotted with volcanoes; some of the highest peaks in the mountain range are volcanic in origin, many of which rise above 20,000 ft (6,100 m). There are 3 major areas in which volcanoes are concentrated. The first of these appears between latitude 6°N and 2°S, and straddles Colombia and Ecuador. The second, and largest region, lies between latitudes 15° and 27°S; it is about 1,240 mi (2,000 km) long and 62-124 mi (100-200 km) wide, and borders Peru, Bolivia, Chile, and Argentina. This is the largest concentration of volcanoes in the world, and the highest volcanoes in the world are found here; but it is an area of low volcanic activity, and it is generally geysers which erupt here. The third region of volcanic concentration is also the most active. It lies in the central valley of Chile, mostly between 33° and 44°S.

The climate in the Andes varies greatly, depending on both altitude and latitude, from hot regions to Alpine meadow regions to the glaciers of the South. The snowline is highest in southern Peru and northern Chile, at latitude 15-20°S, where it seldom descends below 19,000 ft (5,800 m). This is much higher than at the equator, where the snowline descends to 15,000 ft (4,600 m). This vagary is attributed to the extremely dry climate of the lower latitude. In the far south of the continent, in the region known as Tierra del Fuego, the snowline reaches as low as 2,000 ft (600 m) above sea level.

The Andes are a rich source of mineral deposits, particularly copper, silver, and gold. In Venezuela, they are mined for copper, lead, petroleum, phosphates, and salt; diamonds are found along the Rio Caroni. Columbia has the richest deposits of coal, and is the largest producer of gold and platinum in South America. It is also wealthy in emeralds, containing the largest deposits in the world, with the exception of Russia. In Chile, the Andes are mined largely for their great copper stores, in addition to lead, zinc, and silver. Bolivia has enormous tin mines. The Andes are also a source of tungsten, antimony, nickel, chromium, cobalt, and sulfur.

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