World of Earth Science | South America

The South American continent stretches from about 10° above the equator to almost 60° below it, encompassing an area of 6,880,706 sq mi (17,821,028 sq km). This is almost 12% of the surface area of the earth. It is about 3,180 mi (5,100 km) wide at its widest point, and is divided into 10 countries. The continent can be divided into three main regions with distinct environmental and geological qualities: the highlands and plateaus of the east, which are the oldest geological feature in the continent; the Andes Mountains, which line the west coast and were created by the subduction of the Nazca plate beneath the continent; and the riverplain, between the highlands, which contains the Amazon River. The South American climate varies greatly based on the distance from the equator and the altitude of the area, but the range of temperatures seldom reaches 36°F (20°C), except in small areas.

The Eastern highlands and plateaus are the oldest geological region of South America, and are thought to have bordered on the African continent at one time, before the motion of the earth's crust and continental drift separated the continents. The Eastern highlands can be divided into three main sections, the Guiana Highlands, the Brazilian Highlands, and the Patagonian Highlands. The Guiana Highlands are found in the Guianan states, south Venezuela, and northeastern Brazil. Their highest peak, Roraima, reaches a height of 9,220 ft (2,810 m). This is a moist region with many waterfalls; it is in this range, in Venezuela, that the highest waterfall in the world, Angel Falls, is found. Angel Falls plummets freely for 2,630 ft (802 m).

The Brazilian Highlands make up more than one half of the area of Brazil, and range in altitude between 1,000 and 5,000 ft (305–1524 m). The highest mountain range of this region is called Serra da Mantiqueira, and its highest peak, Pico da Bandeira, is 9,396 ft (2,864 m) above sea level.

The Patagonian Highlands are in the south, in Argentina. The highest peak reaches an altitude of 9,462 ft (2,884 m), and is called Sierra de Cordoba.

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 and its 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 western 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° south latitude. The complexity of plate tectonics in this region sparks 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 three major areas in which volcanoes are concentrated. The first of these appears between latitude 6° north and 2° south, straddles Colombia and Ecuador, and contains active volcanoes. The second, and largest region, lies between latitudes 15° and 27° south; 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. The volcanic activity, however, is low and it is generally geysers that 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° south.

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° south, 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. Columbia 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.

The Amazon basin is the largest river basin found in the world, covering an area of about 2.73 million sq mi (7 million sq km). The second largest river basin, which is the basin of the River Zaire in the African Congo, is less than half as large. The water resources of the area are spectacular; the volume of water that flows from the basin into the sea is about 11% of all the water drained from the continents of the earth. The greatest flow occurs in July, and the least is in November. While there are many rivers flowing through the basin, the most important and well known of these is the Amazon. The width of the Amazon ranges from about 1 mi (1.6 km) to as wide as 5–6 mi (5–6 km), and although it is usually only about 20–40 ft (6–12 m) deep, there are narrow channels where it can reach a depth of 300 ft (100 m).

The Amazon basin was once an enormous bay, before the Andes were pushed up along the coasts. As the mountain range grew, they held back the ocean and eventually the bay became an inland sea. This sea was finally filled by the erosion of the higher land surrounding it, and finally a huge plain, crisscrossed by countless waterways, was created. Most of this region is still at sea level, and is covered by lush jungle and extensive wetlands. This jungle region contains the largest extant rain forest in the world. Despite the profusion of life that abounds here, the soil is not very rich; the fertile regions are those which receive a fresh layer of river silt when the Amazon floods, which occurs almost every year.

The climate of South America varies widely over a large range of altitudes and latitudes, but only in isolated regions is the temperature range greater than about 36°F (20°C). The coldest part of the continent is in the extreme southern tip, in the area called Tierra del Fuego; in the coldest month of the year, which is July, it is as cold as 32°F (0°C) there. The highest temperature of the continent is reached in a small area of northern Argentina, and is about 108°F (42°C). However, less than 15 days a year are this warm, and the average temperature in the same area for the hottest month of the year, which is January, is about 84°F (29°C).

Colombia borders Venezuela, Brazil, Ecuador, and Peru, and encompasses an area of 440,831 sq mi (1,141,748 sq km). It is found where Panama of Central America meets the South American continent, and its location gives it the interesting feature of having coastal regions bordering on both the Atlantic and the Pacific oceans. It is a country of diverse environments, including coastal, mountain, jungle, and island regions, but in general can be considered to consist of two major areas based on altitude: the Andes mountains and the lowlands.

The Andes in Colombia can be divided into three distinct ranges, which run approximately from north to south in parallel ridges. The Cordillera Occidental, or westernmost range, attains a maximum altitude of about 10,000 ft (3,000 m). The Cordillera Oriental, which is the eastern range, is much higher, and many of its peaks are covered with snow all year round. Its highest peak is about 18,000 ft (5,490 m) high, and it has many waterfalls, such as the Rio Bogota, which falls 400 ft (120 m). The Cordillera Central, as its name implies, runs between the Occidental and Oriental Cordilleras. It contains many active volcanoes as well as the highest peak in Colombia, Pico Cristobal Colon, which is 19,000 ft (5,775 m) high.

The lowlands of the east cover two thirds of Colombia's land area. It is part of the Orinoco and Amazon basins, and thus is well watered and fertile. Part of this region is covered with rich equatorial rain forest. The northern lowlands of the coastal region also contain several rivers, and the main river of Colombia, the Magdalena, begins there.

Venezuela covers an area of 352,144 sq mi (912,0250 sq km). It is the most northern country of South America, and can be divided up into four major regions. The Guiana Highlands in the southeast make up almost half of Venezuela's land area, and are bordered by Brazil and Guyana. It is here that the famous Angel Falls, the highest waterfall in the world, is found. The Northern Highlands, which are a part of the Andes Mountains, contain the highest peak in Venezuela—Pico Bolivar, which reaches a height of 16,427 ft (5,007 m). This range borders on much of the coastal region of Venezuela, and despite its proximity to both the Caribbean and the equator, it has many peaks that are snow-covered year-round. The Maracaibo basin, one-third of which is covered by Lake Maracaibo, is found in the northwest. It is connected to the Caribbean Sea, and although it contains fresh water at one end of the lake, as it nears the ocean it becomes more saline. Not surprisingly, most of the basin consists of wetlands. The Llanos de Orinoco, which borders on Colombia in the southwestern part of Venezuela, is watered by the Orinoco River and its tributaries. The Orinoco has a yearly discharge almost twice as large as that of the Mississippi, and from June to October, during the rainy season, many parts of the Llanos are inaccessible due to flooding.

Ecuador received its name from the fact that it straddles the equator. Its area is 103,930 sq mi (269,178 sq km), making it the smallest of the Andean countries. Its eastern and western lowlands regions are divided by the Andes Mountains, which run through the center of the country. This part of the Andes contains an active volcano region; the world's highest active volcano, Cotopaxi, which reaches an altitude of 19,347 ft (5,897 m), is found here. The western lowlands on the coast contain a tropical rain forest in the north, but become extremely dry in the south. The eastern lowlands are part of the Amazon basin, and are largely covered by tropical rainforest. The rivers Putumayo, Napo, and Pastaza flow through this area.

Ecuador also claims the famous Galapagos Islands, which lie about 650 mi (1,040 km) off the coast. These 12 islands are all volcanic in origin, and several of the volcanoes are still active. The islands are the home of many species unique to the world, including perhaps the most well-known of their numbers, the Galapagos tortoise.

Peru covers an area of 496,225 sq. mi (1,285,216 sq. km), making it the largest of the Andean countries. Like Ecuador, it is split by the Andes Mountains into two distinct sections. The eastern coastal region is mostly covered with mountains, and in many places, the ocean borders on steep cliffs. In the northern part, however, there is a relatively flat region that is suitable for agriculture. In the east, the lowlands are mostly covered by the thick tropical rain forest of the Amazon basin. The southern part of the Andes in Peru contain many volcanoes, some of which are still active, and Lake Titicaca, which is shared by Bolivia. Lake Titicaca is remarkable for, among the large lakes with no ocean outlet, Titicaca is the highest in the world. It is 125 mi (200 km) at its largest length and 69 mi (110 km) at its largest breadth, which is not quite half as large as Lake Ontario; but it lies at an altitude of 12,507 ft (3,812 m) above sea level.

Bolivia has an area of 424,164 sq mi (1,098,581 sq km), and is the only landlocked country in South America besides Paraguay. The western part of the country, which borders on Ecuador and Chile, is covered by the Andes Mountains, and like most of this part of the Andes, it contains many active volcanoes. In the southern part of the range, the land becomes more arid, and in many places salt marshes are found. Among these is Lake Poopo, which lies 12,120 ft (3,690 m) above sea level. This saline lake is only 10 ft (3 m) deep. In the northern part of the range, the land becomes more habitable, and it is here that Lake Titicaca, which is shared with Peru, is found.

The eastern lowlands of Bolivia are divided into two distinct regions. In the north, the fertile Llanos de Mamore is well watered and is thickly covered with vegetation. The southeastern section, called the Gran Chaco, is a semiarid savanna region.

Chile is the longest, narrowest country in the world; although it is 2,650 mi (4,270 km) long, it is only about 250 mi (400 km) wide at its greatest width. It encompasses an area of 284,520 sq mi (736,905 sq km). The Andes divides into two branches along the eastern and western edges of the country. The eastern branch contains the highest of the Andean peaks, Aconcagua, which is 20,000 ft (6,960 m), and the highest point on the continent. The Andes in Chile has the greatest concentration of volcanoes on the continent, containing over 2,000 active and dormant volcanoes, and the area is plagued by earthquakes.

In the western coastal region of north and central Chile, the land meets the ocean in a long line of cliffs which reach about 8,800 ft (2,700 m) in altitude. The southern section of this coastal mountain range moves offshore, forming a group of about 3,000 islands extending in a line all the way to Cape Horn, which is the southernmost point on the continent. The coast in this area is quite remarkable in appearance, having numerous fjords. There are many volcanic islands off the coast of Chile, including the famous Easter Island, which contains some unusual archeological remains.

The southern part of the coastal region of Chile is a temperate area, but in the north it contains the Atacama Desert, which is the longest and driest desert in the world. Iquique, Chile, which lies in this region, is reported to have at one time suffered 14 years without any rain at all. The dryness of the area is thought to be due to a sudden temperature inversion as clouds move from the cold waters off the shore and encounter the warmth of the continent; this prevents water from precipitating from the clouds when they reach the shoreline. It has been suggested also that the sudden rise of the Andes Mountains on the coast contributes to this effect.

Argentina, the second largest of the South American countries, covers an area of 1,073,399 sq mi (2,780,092 sq km). The Andes Mountains divide western Argentina from Chile, and in the south, known as Tierra de Fuego, this range is still partly covered with glaciers.

A large part of Argentina is a region of lowlands and plains. The northern part of the lowlands, called the Chaco, is the hottest region in Argentina. In the northwestern part of Argentina near the Paraguayan and Brazilian borders, are found the remarkable Iguassa Falls. They are 2.5 mi (4 km) wide and 269 ft (82 m) high. As a comparison, Niagara Falls is only 5,249 ft (1,599 m) wide and 150–164 ft (46–50 m) high. The greatest part of the lowland plains is called the Pampa, which is humid in the east and semiarid in the west.

The southern highlands of Patagonia, which begins below the Colorado River, is a dry and mostly uninhabited region of plateaus. In the Tierra del Fuego the southernmost extension of the Andes is found. They are mostly glaciated, and many glacial lakes are found here. Where the mountains descend into the sea, the glaciers have shaped them so that the coast has a fjord-like appearance.

The Falkland Islands lie off the eastern coast of Argentina. They are a group of about 200 islands consisting of rolling hills and peat valleys, although there are a few low mountains north of the main islands. The sea around the Falkland Islands is quite shallow, and for this reason they are thought to lie on an extension of the continental shelf.

Paraguay, which has an area of 157,048 sq mi (406,752 sq km), is completely landlocked. About half of the country is part of the Gran Chaco, a large plain west of the Paraguay River, which also extends into Bolivia and Argentina. The Gran Chaco is swampy in places, but for the most part consists of scrubland with a few isolated patches of forest. East of the Paraguay River, there is another plain which is covered by forest and seasonal marshes. This region becomes a country of flat plateaus in the easternmost part of Paraguay, most of which are covered with evergreen and deciduous forests.

Uruguay, which is 68,037 sq mi (176,215 sq km) in area, is a country bounded by water. To the east it borders the Atlantic Ocean, and there are many lagoons and great expanses of dunes found along the coast. In the west, Uruguay is bordered by the river Uruguay, and in the south by the La Plata estuary. Most of the country consists of low hills with some forested areas.

With an area of 3,286,487 sq mi (8,511,965 sq km), Brazil is by far the largest country in South America, taking up almost half of the land area of the continent. It can be divided into two major geographical regions: the highlands, which include the Guiana Highlands in the far north and the Brazilian Highlands in the center and southeast, and the Amazon basin.

The highlands mostly have the appearance of flat tablelands, which are cut by deep rifts, and clefts that drain them; these steep river valleys are often inaccessible. In some places, the highlands have been shaped by erosion so that their surfaces are rounded and hill-like, or even give the appearance of mountain peaks. Along the coast, the plateaus plummet steeply to the ocean to form great cliffs, which can be as high as 7,000–8,000 ft (2,100–2,400 m). Except for the far north of Brazil, there are no coastal plains.

The lowlands of Brazil are in the vast Amazon basin, which is mostly covered with dense tropical rain forest, the largest tract of unbroken rainforest in the world. The many rivers and tributaries that water the region create large marshes in places. The Amazon is home to many indigenous peoples and as yet uncounted species of animals and plants found nowhere else in the world.

French Guiana encompasses an area of 35,900 sq mi (93,000 sq km), and is found north of Brazil. The area furthest inland is a region of flat plateaus that becomes rolling hills in the central region of the country, while the eastern coastal area is a broad plain consisting mostly of poorly drained marshland. Most of the country is covered with dense tropical rain forest, and the coast is lined with mangrove swamps. French Guiana possesses a few island territories as well; the most famous of these, Devil's Island, was the former site of a French penal colony.

North of French Guiana lies Suriname, another tiny coastal country that has an area of 63,251 sq mi (163,820 sq km). The southern part of the country is part of the Guiana Highlands, and consists of very flat plateaus cut across by great rifts and steep gullies. These are covered with thick tropical rain forest. North of the highlands is an area of rolling hills and deep valleys formed by rivers and covered with forest. The extreme north of Suriname lies along the coast and is a flat swamp. Several miles of mangrove swamps lie between this region and the coast.

East of Suriname is the country of Guyana, with a land area of 83,000 sq mi (215,00 sq km). The Guiana Highlands are in the western and southern parts of Guyana. As with Suriname and French Guiana, these are cut up deeply by steep and sudden river valleys, and covered with dense rain forest. The western part of the Guiana Highlands are called the Pakaraima Mountains, and are much higher than the other plateaus in Guyana, reaching an altitude of as much as 9,220 ft (2,810 m). The highlands become a vast area of rolling hills in the central part of Guyana due to the effects of erosion; this sort of terrain takes up more than two thirds of the country. In the north along the coast is a swampy region as in Suriname and French Guiana, with many lagoons and mangrove swamps.