Theetymology of the wordAndes has been debated. The majority consensus is that it derives from theQuechua wordanti "east"[1] as inAntisuyu (Quechua for "east region"),[1] one of the four regions of theInca Empire. Others suggest that it is in fact from the wordanta (meaningcopper) of the olderAymara language.[2]
The termcordillera comes from theSpanish wordcordel "rope"[3] and is used as a descriptive name for several contiguous sections of the Andes, as well as the entire Andean range, and the combinedmountain chain along the western part of the North and South Americancontinents.
The Andes mountain range, the longest continental mountain system in the world,[4] extends approximately 7,000 km (4,300 mi) along the western edge ofSouth America, spanningseven countries. Its width varies from 200 km (120 mi) to 700 km (430 mi), encompassing a series of parallelcordilleras,high plateaus, and deep intermontane valleys. Prominent peaks such asAconcagua at 6,961 metres (22,838 feet) in Argentina,Huascarán at 6,768 metres (22,205 feet) in Peru, andIllimani 6,438 metres (21,122 feet) in Bolivia illustrate the extreme elevations and rugged relief that define the range.[5]
The Andes encompass a wide variety of climatic and ecological zones, ranging from humid cloud forests on the eastern slopes to the arid high plains of theAltiplano and the glaciated summits of the southern Andes. These sharp environmental gradients have strongly influenced human settlement and the development of major highland cities such as Bogotá, Cusco, La Paz and Quito.
The Northern Andes inColombia,Ecuador, andVenezuela. The northern Andes are separated into three branches.
At the northern end of the Andes, the separateSierra Nevada de Santa Marta range is often, but not always, treated as part of the Northern Andes.[6]
TheLeeward Antilles islandsAruba,Bonaire, andCuraçao, which lie in theCaribbean Sea off the coast ofVenezuela, were formerly thought to represent the submerged peaks of the extreme northern edge of the Andes range, but ongoing geological studies indicate that such a simplification does not do justice to the complex tectonic boundary between theSouth American andCaribbean plates.[7]
Aerial view ofValle Carbajal in theTierra del Fuego. The Andes range is about 200 km (124 mi) wide throughout its length, except in theBolivian flexure where it is about 640 kilometres (398 mi) wide.
The Andes are anorogenic belt of mountains along thePacific Ring of Fire, a zone ofvolcanic activity that encompasses the Pacific rim of the Americas as well as theAsia-Pacific region. The Andes are the result oftectonic plate processes extending during theMesozoic andTertiary eras, caused by thesubduction ofoceanic crust beneath theSouth American Plate as theNazca Plate and South American Plate converge. These processes were accelerated by the effects of climate. As the uplift of the Andes created a rain shadow on the western fringes ofChile,ocean currents and prevailing winds carried moisture away from theChilean coast. This caused some areas of the subduction zone to be sediment-starved, which in turn prevented the subducting plate from having a well lubricated surface. These factors increased the rate of contractional coastal uplift in the Andes.[8] The main cause of the rise of the Andes is the contraction of the western rim of theSouth American Plate due to the subduction of theNazca Plate and theAntarctic Plate. To the east, the Andes range is bounded by severalsedimentary basins, such as theOrinoco Basin, theAmazon Basin, theMadre de Dios Basin, and theGran Chaco, that separate the Andes from the ancientcratons in eastern South America. In the south, the Andes share a long boundary with the formerPatagonia Terrane. To the west, the Andes end at thePacific Ocean, although thePeru–Chile Trench can be considered their ultimate western limit.
The Andean orogen has a series of bends ororoclines. TheBolivian Orocline is a seaward-concave bending in the coast ofSouth America and the Andes Mountains at about 18° S.[9][10] At this point, the orientation of the Andes turns from northwest inPeru to south inChile andArgentina.[10] The Andean segments north and south of the Orocline have been rotated 15° counter-clockwise to 20° clockwise respectively.[10][11] TheBolivian Orocline area overlaps with the area of the maximum width of theAltiplano Plateau, and according to Isacks (1988) the Orocline is related tocrustal shortening.[9] The specific point at 18° S where thecoastline bends is known as theArica Elbow.[12] Further south lies the Maipo Orocline, a more subtleorocline between 30° S and 38°S with a seaward-concave break in the trend at 33° S.[13] Near the southern tip of the Andes lies the Patagonian Orocline.[14]
The formation of the modern Andes began with the events of theTriassic, whenPangaea began the breakup that resulted in developing severalrifts. The development continued through theJurassic Period. It was during theCretaceous Period that the Andes began to take their present form, by theuplifting,faulting, andfolding ofsedimentary andmetamorphic rocks of the ancient cratons to the east. The rise of the Andes has not been constant, as different regions have had different degrees of tectonic stress, uplift, anderosion.
Across the 1,000-kilometer-wide (620 mi)Drake Passage lie the mountains of theAntarctic Peninsula south of theScotia Plate, which appear to be a continuation of the Andes chain.
The amount, magnitude, and type of seismic activity varies greatly along the subduction zone. These differences are due to a wide range of factors, including friction between the plates, angle of subduction, buoyancy of the subducting plate, rate of subduction, and hydration value of the mantle material. The highest rate of seismic activity is observed in the central portion of the boundary, between 33°S and 35°S. In this area, the angle of subduction is very low, meaning the subducting plate is nearly horizontal. Studies of mantle hydration across the subduction zone have shown a correlation between increased material hydration and lower-magnitude, more frequent seismic activity. Zones exhibiting dehydration instead are thought to have a higher potential for larger, high-magnitude earthquakes in the future.[18]
The mountain range is also a source of shallow intraplate earthquakes within the South American Plate. The largest such earthquake (as of 2024)struck Peru in 1947 and measured Ms 7.5. In the Peruvian Andes, these earthquakes display normal (1946), strike-slip (1976), and reverse (1969, 1983) mechanisms. The Amazonian Craton is actively underthrusted beneath the sub-Andes region of Peru, producing thrust faults.[19] In Colombia, Ecuador, and Peru, thrust faulting occurs along the sub-Andes due in response to contraction brought on by subduction, while in the high Andes, normal faulting occurs in response to gravitational forces.[20]
Sol de Mañana, an area of intense geothermal activity withfumaroles andgeysers, BoliviaThis photo from theISS shows the high plains of the Andes Mountains in the foreground, with a line of young volcanoes facing the much lower Atacama Desert
The Andes range has many active volcanoes distributed in four volcanic zones separated by areas of inactivity. The Andean volcanism is a result of thesubduction of the Nazca Plate and Antarctic Plate underneath the South American Plate. The belt is subdivided into four main volcanic zones that are separated from each other by volcanic gaps. The volcanoes of the belt are diverse in terms of activity style, products, and morphology.[21] Although some differences can be explained by which volcanic zone a volcano belongs to, there are significant differences inside volcanic zones and even between neighboring volcanoes. Despite being a typical location forcalc-alkalic and subduction volcanism, the Andean Volcanic Belt has a large range of volcano-tectonic settings, such as rift systems, extensional zones,transpressional faults, subduction ofmid-ocean ridges, andseamount chains apart from a large range of crustal thicknesses andmagma ascent paths, and different amount of crustal assimilations.
The Andes Mountains host largeore andsalt deposits, and some of their easternfold and thrust belts act as traps for commercially exploitable amounts ofhydrocarbons. In the forelands of theAtacama Desert, some of the largestporphyry copper mineralizations occur, making Chile and Peru the first- and second-largest exporters ofcopper in the world.[22][23] Porphyry copper in the western slopes of the Andes has been generated byhydrothermal fluids (mostly water) during the cooling ofplutons or volcanic systems. The porphyry mineralization further benefited from the dry climate that reduced the disturbing actions ofmeteoric water. The dry climate in the central western Andes has also led to the creation of extensivesaltpeter deposits that were extensively mined until the invention of syntheticnitrates. Yet another result of the dry climate are thesalars ofAtacama andUyuni, the former being the largest source oflithium and the latter the world's largest reserve of the element.[citation needed] Early Mesozoic andNeogene plutonism in Bolivia's Cordillera Central created theBolivian tin belt as well as the famous, now mostly depleted, silver deposits ofCerro Rico de Potosí.
The Andes Mountains is connected to the climate of South America, particularly through the hyper-arid conditions of the adjacentAtacama Desert. The Atacama Bench, a prominent low-relief feature along the Pacific seaboard, serves as a key geomorphological record of the long-term interplay between Andean tectonics and Cenozoic climate. While the initial uplift and shortening of the Andes were driven by the subduction of the Nazca Plate beneath the South American Plate, arid climate acted as an important feedback mechanism. Reduced erosion rates in the increasingly arid Atacama region may have effectively stopped tectonic activity in certain parts of the mountain range. This lack of erosion could have facilitated the eastward propagation of deformation, leading to the widening of the Andean orogen over time. Thus, the Atacama Desert and its geological features, like the Atacama Bench, offer critical insights into the coupled evolution of the Andes Mountains and the changing regional climate.[24]
The Andes Mountains, initially inhabited byhunter-gatherers, experienced the development ofagriculture and the rise of politically centralizedcivilizations, which culminated in the establishment of the century-longInca Empire. This all changed in the 16th century, when the Spanishconquistadors colonized the mountains in advance of themining economy.
In the tide ofanti-imperialist nationalism, the Andes became the scene of aseries of independence wars in the 19th century, when rebel forces swept through the region to overthrowSpanish colonial rule. Since then, many former Spanish territories have become five independent Andean states.
The climate in the Andes varies greatly depending on latitude, altitude, and proximity to the sea. Temperature, atmospheric pressure, and humidity decrease in higher elevations. The southern section is rainy and cool, while the central section is dry. The northern Andes are typically rainy and warm, with an average temperature of 18 °C (64 °F) inColombia. The climate is known to change drastically in rather short distances.Rainforests exist just kilometers away from the snow-covered peak ofCotopaxi. The mountains have a large effect on the temperatures of nearby areas. Thesnow line depends on the location. It is between 4,500 and 4,800 m (14,800 and 15,700 ft) in the tropical Ecuadorian, Colombian, Venezuelan, and northern Peruvian Andes, rising to 4,800–5,200 m (15,700–17,100 ft) in the drier mountains of southern Peru and northern Chile south to about30°S before descending to 4,500 m (14,760 ft) on Aconcagua at32°S, 2,000 m (6,600 ft) at40°S, 500 m (1,640 ft) at50°S, and only 300 m (980 ft) inTierra del Fuego at55°S; from 50°S, several of the larger glaciers descend to sea level.[25]
The Andes of Chile andArgentina can be divided into two climatic and glaciological zones: theDry Andes and theWet Andes. Since the Dry Andes extend from the latitudes of theAtacama Desert to the area of theMaule 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 theablation area or in theaccumulation area.
In the high Andes ofCentral Chile andMendoza Province,rock glaciers are larger and more common than glaciers; this is due to the high exposure tosolar radiation.[26] In these regions, glaciers occur typically at higher altitudes than rock glaciers.[27] The lowest active rock glaciers occur at 900 m a.s.l. inAconcagua.[27]
Though precipitation increases with height, there are semiarid conditions in the nearly 7,000-metre (22,966 ft) highest mountains of the Andes. This drysteppe climate is considered to be typical of the subtropical position at 32–34° S. The valley bottoms have no woods, just dwarf scrub. The largest glaciers, for example the Plomo Glacier and the Horcones Glaciers, do not even reach 10 km (6.2 mi) in length and have only insignificant ice thickness. At glacial times, however,c. 20,000 years ago, the glaciers were over ten times longer. On the east side of this section of the Mendozina Andes, they flowed down to 2,060 m (6,760 ft) and on the west side to about 1,220 m (4,000 ft) above sea level.[28][29] The massifs ofAconcagua (6,961 m or 22,838 ft),Tupungato (6,550 m or 21,490 ft), andNevado Juncal (6,110 m or 20,050 ft) are tens of kilometres away from each other and were connected by a joint ice stream network. The Andes' dendritic glacier arms, components of valley glaciers, were up to 112.5 km (69.9 mi) long and over 1,250 m (4,100 ft) thick, and spanned a vertical distance of 5,150 m (16,900 ft). The climatic glacier snowline (ELA) was lowered from 4,600 m (15,100 ft) to 3,200 m (10,500 ft) at glacial times.[28][30]
The Andean region cuts across severalnatural and floristic regions, due to its extension, fromCaribbean Venezuela to cold, windy, and wetCape Horn passing through the hyperaridAtacama Desert.Rainforests andtropical dry forests[31] used to[when?] encircle much of the northern Andes but are now greatlydiminished, especially in theChocó and inter-Andean valleys of Colombia. Opposite the humid Andean slopes are the relatively dry Andean slopes in most of western Peru, Chile, and Argentina. Along with severalInterandean Valles, they are typically dominated bydeciduous woodland, shrub andxeric vegetation, reaching the extreme in the slopes near the virtually lifelessAtacama Desert.
About 30,000 species ofvascular plants live in the Andes, with roughly half beingendemic to the region, surpassing the diversity of any otherhotspot.[32] The small treeCinchona pubescens, a source ofquinine that is used to treatmalaria, is found widely in the Andes as far south as Bolivia. Other important crops that originated from the Andes aretobacco andpotatoes. The high-altitudePolylepis forests and woodlands are found in the Andean areas ofColombia,Ecuador,Peru,Bolivia, andChile. These trees, by locals referred to as Queñua, Yagual, and other names, can be found at altitudes of 4,500 m (14,760 ft) above sea level. It remains unclear if the patchy distribution of these forests and woodlands is natural, or the result of clearing that began during theIncan period. Regardless, inmodern times, the clearance has accelerated, and the trees are now considered highlyendangered, with some believing that as little as 10% of the originalwoodland remains.[33]
The Andes are rich in fauna: With almost 1,000 species, of which roughly 2/3 areendemic to the region, the Andes are the most important region in the world foramphibians.[32] The diversity of animals in the Andes is high, with almost 600 species ofmammals (13% endemic), more than 1,700 species of birds (about 1/3 endemic), more than 600 species ofreptiles (about 45% endemic), and almost 400 species of fish (about 1/3 endemic).[32]
The Andes Mountains form a north–south axis of cultural influences. A long series of cultural development culminated in the expansion of theInca civilization andInca Empire in the central Andes during the 15th century. The Incas formed this civilization throughimperialisticmilitarism as well as careful and meticulous governmental management.[38] The government sponsored the construction ofaqueducts androads in addition to pre-existing installations. Some of these constructions still exist today.
Devastated by European diseases and bycivil war, the Incas were defeated in 1532 by an alliance composed of tens of thousands of allies from nations they had subjugated (e.g.Huancas,Chachapoyas,Cañaris) and a small army of 180 Spaniards led byFrancisco Pizarro. One of the few Inca sites the Spanish never found in their conquest wasMachu Picchu, which lay hidden on a peak on the eastern edge of the Andes where they descend to the Amazon. The main surviving languages of the Andean peoples are those of theQuechua andAymara language families.Woodbine Parish andJoseph Barclay Pentland surveyed a large part of the Bolivian Andes from 1826 to 1827.
In modern times, the largest cities in the Andes areBogotá, with a metropolitan population of over ten million, andSantiago,Medellín,Cali, andQuito.Lima is a coastal city adjacent to the Andes and is the largest city of all Andean countries. It is the seat of theAndean Community of Nations.
La Paz, Bolivia's seat of government, is the highest capital city in the world, at an elevation of approximately 3,650 m (11,975 ft). Parts of the La Paz conurbation, including the city ofEl Alto, extend up to 4,200 m (13,780 ft).
Cities and large towns are connected withasphalt-paved roads, while smaller towns are often connected by dirt roads, which may require afour-wheel-drive vehicle.[39]
The rough terrain has historically put the costs of buildinghighways andrailroads that cross the Andes out of reach of most neighboring countries, even with moderncivil engineering practices. For example, the main crossover of the Andes between Argentina and Chile is still accomplished through thePaso Internacional Los Libertadores. Only recently[when?] have the ends of some highways that came rather close to one another from the east and the west been connected.[40] Much of the transportation of passengers is done via aircraft.
There is one railroad that connects Chile with Peru via the Andes, however, and there are others that make the same connection via southern Bolivia.
There are multiple highways in Bolivia that cross the Andes. Some of these were built during aperiod of war between Bolivia andParaguay, in order to transport Bolivian troops and their supplies to the war front in the lowlands of southeastern Bolivia and western Paraguay.
For decades, Chile claimed ownership of land on the eastern side of the Andes. These claims were given up in about 1870 during theWar of the Pacific between Chile and the allied Bolivia and Peru, in a diplomatic deal to keep Peru out of the war. TheChilean Army andChilean Navy defeated the combined forces of Bolivia and Peru, and Chile took over Bolivia's only province on the Pacific Coast, some land from Peru that was returned to Peru decades later. Bolivia has been completelylandlocked ever since. It mostly usesseaports in eastern Argentina andUruguay for international trade because its diplomatic relations with Chile have been suspended since 1978.
Because of the tortuous terrain in places, villages and towns in the mountains—to which travel viamotorized vehicles is of little use—are still located in the high Andes of Chile, Bolivia, Peru, andEcuador. Locally, the relatives of thecamel, thellama, and thealpaca continue to carry out important uses as pack animals, but this use has generally diminished in modern times.Donkeys,mules, and horses are also useful.
The ancient peoples of the Andes such as the Incas have practicedirrigation techniques for over 6,000 years. Because of the mountain slopes,terracing has been a common practice. Terracing, however, was only extensively employed after Incan imperial expansions to fuel their expanding realm. Thepotato holds a very important role as an internally consumed staple crop.Maize was also an important crop for these people, and was used for the production ofchicha, important to Andean native people. Currently,[when?]tobacco,cotton,quinoa, andcoffee are the main export crops.Coca, despite eradication programs in some countries, remains an important crop for legal local use in a mildly stimulatingherbal tea, and illegally for the production ofcocaine.
In unirrigated land,pasture is the most common type of land use. In the rainy season (summer), part of the rangeland is used for cropping (mainly potatoes, barley, broad beans, and wheat).
Irrigation is helpful in advancing the sowing data of the summer crops, which guarantees an early yield in periods of food shortage. Also, by early sowing, maize can be cultivated higher up in the mountains (up to 3,800 m (12,500 ft)). In addition, it makes cropping in the dry season (winter) possible and allows the cultivation of frost-resistant vegetable crops likeonion andcarrot.[41]
The Andes rose to fame for their mineral wealth during theSpanish conquest of South America. Although Andean Amerindian peoples crafted ceremonial jewelry of gold and other metals, themineralizations of the Andes were first mined on a large scale after the Spanish arrival.Potosí in present-dayBolivia andCerro de Pasco in Peru were among the principal mines of the Spanish Empire in the New World.Río de la Plata andArgentina[42] derive their names from the silver of Potosí.
Currently, mining in the Andes ofChile andPeru places these countries as the first and second major producers ofcopper in the world.Peru also contains the 4th-largest goldmine in the world: theYanacocha. The Bolivian Andes principally producetin, although historically silver mining had a huge impact on theeconomy of 17th-century Europe.[citation needed] In Chile in the higher portions of the Andes there are only mining districs dominated by large-scale mining, while medium and small-scale mining is more common at lower altitudes.[43] For mines in the high Andes there are logistical difficulties in the use ofsea water, in addition to increased probabilities ofextreme weather events that may disrupt water supply.[44] The gold deposits of theEl Indio Gold Belt tend to lie along theArgentina–Chile border and next to or below glaciers and gold mining there have thus issues relating to the bi-nationality and theirenvironmental impacts on glaciers.[45]
Mining in the cold conditions in the Andes pose also difficult conditions for outdoor workers such aspallaqueras and for the batteries of electrified machinery.[46][47]
There is a long history of mining in the Andes, from the Spanishsilvermines inPotosí in the 16th century to the vast currentporphyry copper deposits ofChuquicamata andEscondida in Chile andToquepala in Peru. Other metals, including iron, gold, and tin, in addition to non-metallic resources are important. The Andes have a vast supply of lithium; Argentina, Bolivia, and Chile have the three largest reserves in the world respectively.[48]
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