7/27/2015 South America ­ AccessScience from McGraw­Hill Education South America Article by: Salazar, Deborah A. Department of Geography, Oklahoma State University, Stillwater, Oklahoma. White, C. Langdon Formerly, Stanford University, Palo Alto, California. Publication year: 2014 DOI: http://dx.doi.org/10.1036/1097­8542.638200 (http://dx.doi.org/10.1036/1097­8542.638200) Content Regional characteristics Physiographic features Biotic features Deforestation and environmental contamination Bibliography Additional Readings The southernmost of the New World or Western Hemisphere continents, with three­fourths of it lying within the tropics. South America is approximately 4500 mi (7200 km) long and at its greatest width 3000 mi (4800 km). Its area is estimated to be about 7,000,000 mi2 (18,000,000 km2). South America has many unique physical features, such as the Earth's longest north­south mountain range (the Andes), highest waterfall (Angel Falls), highest navigable freshwater lake (Lake Titicaca), and largest expanse of tropical rainforest (Amazonia). The western side of the continent has a deep subduction trench offshore, whereas the eastern continental shelf is more gently sloping and relatively shallow. See also: Continent (/content/continent/158900) Regional characteristics South America has three distinct regions: the relatively young Andes Mountains located parallel to the western coastline, the older Guiana and Brazilian Highlands located near the eastern margins of the continent, and an extensive lowland plains, which occupies the central portion of the continent. The regions have distinct physiographic and biotic features. The Andes represent the highest and longest north­south mountain system on Earth. Altitudes often exceed 20,000 ft (6000 m) and perpetual snow tops many of the peaks, even along the Equator (Fig. 1). So high are the Andes in the northern half of the continent that few passes lie below 12,000 ft (3600 m). Over most of their length the Andes are not just a single range but two or three parallel ranges. Within the parallel peaks lie a vast series of intermontane basins and plateaus. Ecuador contains a string of 10 such basins. Bolivia has the Altiplano, an extensive basin about 400 mi (640 km) long and up to 200 mi (320 km) wide that is almost entirely surrounded by rugged and lofty peaks. The http://www.accessscience.com/content/south­america/638200 1/11 7/27/2015 South America ­ AccessScience from McGraw­Hill Education Altiplano is cold and high, averaging 12,000 ft (3600 m), and is mostly level. The Altiplano is distinctive in that it possesses the highest navigable freshwater body, Lake Titicaca, measuring approximately 3488 mi2 (8965 km2 ) at 12,497 ft (3750 m) elevation and approximately 918 ft (275 m) in depth. Fig. 1 Andes Mountains, Chile. The Andes, which parallel the Pacific coast, constitute one of the Earth's most majestic features. Only the Himalayas exceed them in elevation and mass. (United Press International) On the northeastern and eastern continental periphery lie the Guiana and the Brazilian Highlands. These vast areas of hilly uplands and low mountains are separated from each other by the Amazon River drainage (Fig. 2). Together these two plateaus form the geologically oldest part of South America. Rocks of ancient igneous and metamorphic origin are partially covered by younger sedimentary beds and sandstones. The vegetation and animal life associated with the flat­topped mesas of the highlands, called tepuis, show a high proportion of endemicity (in­situ speciation) resulting from long periods of isolation and ecosystem stability. http://www.accessscience.com/content/south­america/638200 2/11 7/27/2015 South America ­ AccessScience from McGraw­Hill Education Fig. 2 Representative view of the hilly uplands and low mountain country of the Guiana Highlands. One of five waterfalls on the Canaima River, Gran Sabana in southern Venezuela. (Venezuelan Information Service) More than 65% of South America's total area is characterized by lowland plains under 1000 ft (300 m) in elevation. Some 40% of the continent is less than 650 ft (200 m) above sea level. The plains lie from about 8°N to 40°S between the lofty Andean backbone on the west coast and the Guiana and the Brazilian Highlands on the east coast, and between the Río Orinoco in the north and the Río Colorado in the south. Also in this region are the Llanos of Venezuela and Colombia, the Amazon plain of Brazil, the Paraguayan Chaco, and the Pampas of Argentina. Some of these areas are quite flat while others are undulating. Some, such as the Llanos and Chaco, are alternately flooded and baked. Physiographic features The three Andes regions, the lowlands, and the eastern highlands are composed and bounded by many physiographic features, including mountains, intermontane basins, extensive lowland plains, coastlines, and rivers. M o u n t a i n s Because of the vast extent of the Andes, a greater proportion of South America than of any other continent lies above 10,000 ft (3000 m). The young, rugged, folded Andean peaks stand in sharp contrast to the old, worn­down mountains of the eastern highlands. Although the Andes appear to be continuous, most geologists believe that they consist of several structural units, more or less joined. They are a single range in southern Chile, two ranges in Bolivia, and dominantly three ranges in Peru, Ecuador, and Colombia. Except in Bolivia, where they attain their maximum width of 400 mi (640 km), the Andes are seldom more than 200 mi (320 km) wide. They do not equal the Himalayas in height, but have at least 30 peaks above 20,000 ft (6000 m). The average height of the Andes is estimated to be 13,000 ft (3900 m). However, it is only north of latitude 35°S that the mountains exceed elevations of 10,000 ft (3000 m) [see table]. http://www.accessscience.com/content/south­america/638200 3/11 7/27/2015 South America ­ AccessScience from McGraw­Hill Education Table ­ Principal Andean peaks* Peak Height, ft (m) Aconcagua, Argentina 22,835 (6960) Ampato, Peru 21,702 (6615) Caca Aca, Bolivia 20,329 (6196) Cachi, Argentina 21,326 (6500) Chimborazo, Ecuador 20,577 (6272) Cincel, Bolivia 20,102 (6127) Condoriri, Bolivia 20,043 (6109) Coropuna, Peru 22,802 (6950) Cuzco (Ausangate), Peru 20,187 (6153) Del Acay, Argentina 20,801 (6340) Dos Conos, Argentina 22,507 (6860) Falso Azufre, Argentina­Chile 22,277 (6790) Huascaran, Peru 22,188 (6763) Illampu, Bolivia 21,276 (6485) Illimani, Bolivia 21,282 (6487) Incahuasu, Argentina­Chile 21,720 (6620) Llullaillaco, Argentina­Chile 22,015 (6710) Mercedario, Argentina­Chile 21,884 (6670) Ojos del Salado, Argentina­Chile 22,573 (6880) Payachata, Bolivia 20,768 (6330) Pissis, Argentina 22,245 (6780) Porongos, Argentina­Chile 20,512 (6252) Pular, Chile 20,342 (6200) Sajama, Bolivia 21,390 (6520) Sarmiento, Chile 20,670 (6300) Socompa, Argentina­Chile 19,787 (6031) Tocorpuri, Bolivia­Chile 22,163 (6755) Tortolas, de las, Chile 20,018 (6101) Tres Cruces, Chile 21,720 (6620) Turpungato, Chile 21,490 (6550) Valadero, Argentina 20,735 (6320) * http://www.accessscience.com/content/south­america/638200 4/11 7/27/2015 South America ­ AccessScience from McGraw­Hill Education *The elevations are approximate and some are controversial. Data based mostly on tables in Goode's World Atlas, 12th ed., Rand McNally, 1964. Both active and quiescent volcanic formations are common in southern Colombia, Ecuador, central and southern Peru, and western Bolivia. These volcanic peaks are the surface expression of the subduction of the Nazca tectonic plate beneath the South American plate, forming the offshore Peru­Chile Trench. The Andes were raised up by tectonic forces from 6560 ft (1970 m) to an average 13,120 ft (3940 m) during the Pliocene uplift approximately 5 million years ago, and they continue to rise incrementally each year. As a result of these powerful tectonic forces, there is a spectacular series of volcanic peaks in western Bolivia and on each side of the structural depression in Ecuador. See also: Plate tectonics (/content/plate­tectonics/527000) Stratification of climate and vegetation with altitude can be readily observed in the Andes. At their eastern base is a zone with hot, humid lowland and foothills up to 3300 ft (1000 m), known as tierra caliente. Tierra templada, the zone from 3300 to 6600 ft (1000 to 2000 m), has a relatively mild, frost­free climate and was preferred for European settlement and the production of plantation crops such as coffee and coca. From 6600 to 13,200 ft (2000 to 4000 m) is tierra fria, a montane zone with occasional frosts. Tierra helada, at 13,200 to 19,800 ft (4000 to 6000 m), occupies the zone between the daily frost line and the final zone of permanent snow called tierra nevada. Because of the great north­south extent of the Andes, the processes of their erosion and denudation have varied. Southward from about 40°S, and especially in the far south, the Andes were heavily glaciated during the Ice Age, and an extensive area north of the Strait of Magellan still has a broad mantle of permanent ice. Glaciers descend to the heads of many fiords on the Pacific coast or into lakes on the eastern side of the mountains. Coastal features From the southern tip of Cape Horn north to 41°S latitude, the western coastal zone consists of a broad chain of islands where a mountainous strip subsided and the ocean invaded its valleys. This is one of the world's finest examples of a fiorded coast. Nowhere along the Pacific coast is there a true coastal plain. South of Arica, Chile, the bold, precipitous coast is broken by only a few deep streams, the majority of which carry no water for years at a time.