Spreading across countries Argentina, Bolivia, Chile, Colombia, Ecuador, Peru and Venezuela, Andes is the world's longest continental mountain range. In length wise, the Andes is split into several ranges, which are separated by intermediate depressions. It is a continual range of highlands along the western coast of South America. This range is about 7,000 km long, about 200 km to 700 km wide and of an average height of about 4,000 m. Its highest peak, Mt. Aconcagua, rises to an elevation of about 6,962 m above sea level. The peak of Mt. Chimborazo in the Ecuadorean Andes is farther from the centre of the Earth than any other location on the Earth's surface. This is because of the equatorial bulge that results from the Earth's rotation. The world's highest volcanoes are in the Andes, including Ojos del Salado on the Chile-Argentina frontier which rises to 6,893 m and over 50 other volcanoes that rise above 6,000 m.
The Andes can be divided into three sections as the Southern Andes in Argentina and Chile, the Central Andes including the Chilean and Peruvian cordilleras and parts of Bolivia and the Northern Andes in Venezuela, Colombia, and Ecuador that consists of two parallel ranges, the Cordillera Occidental and the Cordillera Oriental. In Colombia, north of its the border with Ecuador, the Andes split in three parallel ranges, the western, central, and eastern ranges. The eastern range of Colombia is the only one that extends to Venezuela. In the northern part of the Andes, the isolated Sierra Nevada de Santa Marta range is often considered to be part of the Andes.
The Andes are a Mesozoic – Tertiary orogenic belt of mountains along the Pacific Ring of Fire, a zone of volcanic activity that encompasses the Pacific rim of the Americas as well as the Asia-Pacific region. The Andes are the result of plate tectonics processes, caused by the subduction of oceanic crust beneath the South American plate. The main cause of the rise of the Andes is the compression of western rim of the South American Plate due to the subduction of the Nazca Plate and the Antarctic Plate. To the east, the Andes range is bounded by several sedimentary basins such as Orinoco, Amazon Basin, Madre de Dios and Gran Chaco which separates the Andes from the ancient cratons in eastern South America. In the south the Andes shares a long boundary with the former Patagonia Terrane. To the west, the Andes end at the Pacific Ocean, although the Peru-Chile trench can be considered its ultimate western limit. From a geographical approach the Andes are considered to have their western boundaries marked by the appearance of coastal lowlands and a less rugged topography.
The Andes has many active volcanoes, which are distributed in four volcanic zones separated by areas of inactivity. The Andes also has large ore and salt deposits and some of its eastern fold and thrust belt acts as traps for commercially exploitable amounts of hydrocarbons. In the forelands of the Atacama Desert some of the largest porphyry copper mineralization occurs making Chile and Peru the 1st and 2nd largest exporters of copper in the world. The dry climate in the central western Andes have led to the creation of extensive saltpeter deposits which were extensively mined until the invention of synthetic nitrates. Yet another result of the dry climate are the salars of Atacama and Uyuni, the first one being the largest source of lithium at present day and the second the world’s largest reserve of the element.
The climate in the Andes varies greatly depending on location, altitude, and proximity to the sea. Temperature, atmospheric pressure and humidity decrease in higher elevations. The southern section is rainy and cool, the central Andes are dry. The northern Andes are typically rainy and warm, with an average temperature of 18 °C (64 °F) in Colombia. The Andes of Chile and Argentina can be divided in two climatic and glaciological zones; the Dry Andes and the Wet Andes. Since the Dry Andes extends from the latitudes of Atacama Desert to the area of Maule River, precipitation is more sporadic and there are strong temperature oscillations. The line of equilibrium may shift drastically over short periods of time, leaving a whole glacier in the ablation area or in the accumulation area.
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 hot spot. The small tree Cinchona pubescens, a source of quinine which is used to treat malaria, is found widely in the Andes as far south as Bolivia. Other important crops that originated from the Andes are tobacco and potatoes. The high-altitude Polylepis forests and woodlands are found in the Andean areas of Colombia, Ecuador, Peru, Bolivia and Chile. It remains unclear if the patchy distribution of these forests and woodlands is natural, or the result of clearing which began during the Incan period. The Andes’ fauna consists of almost 3,500 species, of which roughly 2/3 are endemic to the region, the Andes is the most important region in the world for amphibians.
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 and for their meat and wool. The nocturnal chinchillas, two threatened members of the rodent order, inhabit the Andes' alpine regions. The Andean Condor, the largest bird of its kind in the Western Hemisphere, occurs throughout much of the Andes but generally in very low densities. Other animals found in the relatively open habitats of the high Andes include the huemul, cougar, foxes in the genus Pseudalopex, and, for birds, certain species of tinamous, Andean Goose, Giant Coot, flamingos, Lesser Rhea, Andean Flicker, Diademed Sandpiper-plover, miners, sierra-finches and diuca-finches.
Lake Titicaca hosts several endemics, among them the highly endangered Titicaca Flightless Grebe and Titicaca Water Frog. Birds of humid Andean forests include mountain-toucans, quetzals and the Andean Cock-of-the-rock, while mixed species flocks dominated by tanagers and Furnariids commonly are seen - in contrast to several vocal but typically cryptic species of wrens, tapaculos and antpittas.
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