Andes Mountains

The Andes Mountains (Cordillera de Los Andes) are the longest continental mountain range in the world. They form a continuous highland along the western coast of the South American continent for a distance of more than 7,000 km (4,350 mi), separating a narrow western coastal area from the rest of the continent.

The Andes is the highest mountain range outside Asia and consists of a vast series of extremely high plateaus surmounted by even higher peaks, with an average height of about 4,000 m (13,000 ft) asl.

The highest mountain is Mount Aconcagua at 6,959 m (22,831 ft) asl, on the border of Argentina and Chile. The summit of Mount Chimborazo in the Ecuadorian Andes is the point on the Earth's surface most distant from its center, because of the equatorial bulge.

The Andes mountains are also part of the American Cordillera, a chain of mountain ranges that consist of an almost continuous sequence of mountain ranges that form the western "backbone" of North America, Central America, South America and Antarctica; also known as the Continental Divide.

The Andes range extends north and south through seven countries: Venezuela, Colombia, Ecuador, Peru, Bolivia, Chile and Argentina. The islands of Aruba, Bonaire and Curaçao, which lie in the Caribbean Sea off the coast of Venezuela, represent the submerged peaks of the extreme northern edge of the Andes range.

Some geologists consider the Antarctandes, also known as the Antarctic Peninsula cordillera, the southernmost continuation of the Andes system in Antarctica.

The Andes are bounded by many sedimentary basins, including the Amazon Basin and Orinoco Basin in the east, the Patagonia Terrane in the south, and the Pacific Ocean in the west.

_{South America topographic map, Andes system along the western coast}

Geology

The Andes are a Mesozoic-era orogenic belt of mountains along the Pacific Ring of Fire. The mountain range is the result of plate tectonics processes, caused by the subduction of oceanic crust beneath the South American Plate.

It is the result of a convergent plate boundary between the Nazca Plate and the South American Plate. The boundary between the two plates is marked by the Peru-Chile oceanic trench.

The main cause for the rise of the Andes range is the compression of the western rim of the South American Plate due to the subduction of the Nazca Plate and the Antarctic Plate.

Tectonic forces along the subduction zone along the entire west coast of South America produce an ongoing orogenic event resulting in minor to major earthquakes and volcanic eruptions

The world's highest volcanoes are in the Andes, including Ojos del Salado on the Chile-Argentina border, which rises to 6,893 m (22,615 ft). Cotopaxi, the second-highest summit in Ecuador at 5,897 m (19,347 ft), is one of the highest active volcanoes in the world.

Geography

To the east, the Andes range is bounded by several sedimentary basins, such as Orinoco, Amazon Basin, Madre de Dios and Gran Chaco, that separate the Andes from the ancient cratons in eastern South America. In the south, the Andes share a long boundary with the former Patagonia Terrane.

To the west, the Andes Mountains end at the Pacific Ocean, although the Peru-Chile trench can be considered their ultimate western limit. From a geographical approach, the Andes are considered to have their western boundaries marked by the appearance of coastal lowlands and less rugged topography.

Throughout their length, the Andes Mountains are divided into many ranges by intervening depressions. Consisting of a vast series of extremely high plateaus, surrounded by even higher peaks, the Andes can be divided into three geographical sections.

^{Topography of the Andes from a Digital Elevation Model}

Northern Andes

Venezuelan Andes

The Venezuelan Andes can be divided into two sections:

• Cordillera de Mérida: commonly considered the proper Venezuelan Andes

• Serranía del Perijá: a much smaller section, located along the border with Colombia at the western extreme of Venezuela in Zulia state

The Colombian Andes

The Colombian Andes system is composed of three parallel mountain chains (Cordilleras). These ranges, which trend generally north and south are known as the Occidental (western), Central (middle) and Oriental (eastern).

The Ecuadorian Andes

The Ecuadorian Andes mountain system is essentially a 600 km- (375 mi-) long narrow plateau, bordered by primarily two parallel chains that contain numerous volcanoes. Several transversal mountain spurs, known as nudos, cut across the plateau.

Central Andes

The Peruvian Andes

The Peruvian Andes, part of the greater Andes mountain system of South America, are formed by three ranges of mountains with fertile river valleys, high plains and deep canyons.

The Bolivian Andes

The Bolivian Andes are composed primarily of two ranges or cordilleras. In western Bolivia, the Cordillera Occidental is characterized by volcanic activity, making up the natural border with Chile. The much older Cordillera Oriental enters Bolivia on the north side of Lake Titicaca and extends southeastward to the Argentine border.

Southern Andes

The Chilean Andes and Argentine Andes

The Chilean Andes and Argentine Andes form most of the border between the countries of Chile and Argentina and make up the highest section of the mountain range.

_{3D map of South America and the Andes Mountain range}

Andean Region

The Andean region cuts across several natural and floristic regions. The region extends from Caribbean Venezuela to cold, windy and wet Cape Horn; passing through the hyperarid Atacama Desert. Tropical and temperate rain forests encircle the Northern Andes.

The Central Andes comprise a region of abrupt environmental contrasts: arid along the west coast, with a steep ascent to volcanoes and glacierized massifs above 5,000 m (16,400 ft) and an equally abrupt descent eastward to the tropical rain forests of the Amazon.

The line of permanent snow becomes higher in elevation with decreasing latitude in the Southern Andes. A line of active volcanoes along with enormous ice fields and numerous lakes form fertile valleys called vegas. Magnificent and impenetrable forests grow on both sides of these cordilleras.

Flora and Fauna

About 30,000 species of vascular plants live in the Andes, with roughly half being endemic to the region, surpassing the diversity of any other hotspot.

Fauna and flora in the Andean Region are as varied as the altitude of the different geographic zones, the complex topography and the varied climates.

In Bolivia alone, there are estimated to be 1,950 to 2,500 tree species, 1,200 species of moss, 1,500 species of ferns, 16 species of gymnosperm, and 11,000 species of angiosperm.

The Andean Region is rich in fauna, of which approximately 2/3 are endemic to the region. Diversity is high, with almost 600 species of mammals (13% endemic), more than 1,700 species of birds (about 1/3 endemic), more than 600 species of reptiles (about 45% endemic), and almost 400 species of fish (about 1/3 endemic).

Mammals

The vicuña and guanaco can be found living in the Altiplano, while the closely related domesticated llama and alpaca are widely kept by locals as pack animals as well as for their meat and wool. Cougars are also found in the region and play an important role in many Andean cultures, together with the llama.

The nocturnal chinchillas, two threatened members of the rodent order, inhabit the Andes alpine regions but are also common in captivity. Another domestic animal that originates from the Andean region is the guinea pig. Other wild mammals found in the relatively open habitats of the high Andes include the huemul deer and fox in the genus Pseudalopex.

Although very rich in flora and fauna, few large mammals are found in the Andean cloud forests, including the Yungas and parts of the Chocó, with exceptions being the threatened mountain tapir, spectacled bear, and yellow-tailed woolly monkey.

Birds

The Andean condor, the largest flying land bird in the Western Hemisphere, occurs in small numbers throughout much of the Andes. Numerous other birds are found in open habitats, including certain species of tinamous (notable members of the genus Nothoprocta), Andean goose, torrent duck, giant coot, flamingos, lesser rhea, Andean flicker, diademed sandpiper-plover, miners, sierra-finches and diuca-finches.

A few species of hummingbirds can be found at altitudes above 4,000 m (13,100 ft) asl but a much higher diversity can be found at lower elevations, especially in the humid Andean cloud forests growing on slopes in Colombia, Ecuador, Peru, Bolivia, and far northwestern Argentina. Other birds of humid Andean forests include mountain toucans, quetzals, and the Andean cock-of-the-rock.

Waterbirds are diverse, ranging from giant coot, Andean goose, and other waterfowl in lakes, torrent ducks in fast-flowing rivers, and Andean avocet along with flamingos in hypersaline lakes.

A number of species such as the royal cinclodes and white-browed tit-spinetail are associated with Polylepis woods and consequently also threatened.

Climate

Along their length, the Andes are split into several ranges, separated by intermediate depressions. These ranges are in turn grouped into three major divisions based on climate.

The climate in the Andes varies greatly depending on location, altitude and proximity to the sea. The mountains have a large effect on the temperatures of nearby areas. The snow line depends on the location.

The southern section is rainy and cool, and the central Andes are dry with large variations in temperature. The northern Andes are typically rainy and warm.

Tropical Andes

The Tropical Andes runs through Venezuela, Colombia, Ecuador, Peru and Bolivia.

Dry Andes

The Dry Andes is one of the two subregions of the Argentine and Chilean Andes (from the Atacama Desert in northern Chile and northwestern Argentina south to latitude 35°S in Chile. In Argentina the Dry Andes reaches 40°S due to the leeward effect of the Andes).

Wet Andes

The Wet Andes is one of the two subregions of the Argentine and Chilean Andes (from latitude 35°S to Cape Horn at 56°S).

_{Map of the climatic regions of the Andes: Dry Andes in yellow, Wet Andes in blue, and Tropical Andes in green}