Editing Andes (section)

==Geology==
{{Geology of the Andes}}
The Andes are an [[Orogeny|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 [[tectonic plate]] processes extending during the [[Mesozoic]] and [[Tertiary]] eras, caused by the [[subduction]] of [[oceanic crust]] beneath the [[South American Plate]] as the [[Nazca 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 of [[Chile]], [[ocean current]]s and prevailing winds carried moisture away from the [[Chilean 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.<ref>{{cite journal |url=https://doi.org/10.1038/nature02049 |doi=10.1038/nature02049 |title=Cenozoic climate change as a possible cause for the rise of the Andes |year=2003 |last1=Lamb |first1=Simon |last2=Davis |first2=Paul |journal=Nature |volume=425 |issue=6960 |pages=792–797 |pmid=14574402 |bibcode=2003Natur.425..792L |s2cid=4354886}}</ref> The main cause of the rise of the Andes is the contraction of the 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 basin]]s, such as the [[Orinoco Basin]], the [[Amazon Basin]], the [[Madre de Dios River|Madre de Dios]] Basin, and the [[Gran Chaco]], that separate the Andes from the ancient [[craton]]s in eastern South America. In the south, the Andes share a long boundary with the former [[Patagonia#Geology|Patagonia Terrane]]. To the west, the Andes 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. The Andes also contain large quantities of [[iron ore]] located in many mountains within the range.

The Andean orogen has a series of bends or [[orocline]]s. The [[Bolivian Orocline]] is a seaward-concave bending in the coast of [[South America]] and the Andes Mountains at about 18° S.<ref name="Isacks1988" /><ref name="Kley1999">{{Citation |last=Kley |first=J. |title=Geologic and geometric constraints on a kinematic model of the Bolivian orocline |journal=[[Journal of South American Earth Sciences]] |volume=12 |issue=2 |year=1999 |pages=221–235 |doi=10.1016/s0895-9811(99)00015-2 |bibcode=1999JSAES..12..221K}}</ref> At this point, the orientation of the Andes turns from northwest in [[Peru]] to south in [[Chile]] and [[Argentina]].<ref name="Kley1999" /> The Andean segments north and south of the Orocline have been rotated 15° counter-clockwise to 20° clockwise respectively.<ref name="Kley1999" /><ref name="Beck1987">{{Citation |last=Beck |first=Myrl E. |title=Tectonic rotations on the leading edge of South America: The Bolivian orocline revisited |journal=[[Geology (journal)|Geology]] |volume=15 |issue=9 |year=1987 |pages=806–808 |doi=10.1130/0091-7613(1987)15<806:trotle>2.0.co;2 |bibcode=1987Geo....15..806B}}</ref> The [[Orocline|Bolivian Orocline]] area overlaps with the area of the maximum width of the [[Altiplano|Altiplano Plateau]], and according to Isacks (1988) the Orocline is related to [[crustal shortening]].<ref name="Isacks1988">{{Citation |last=Isacks |first=Bryan L. |title=Uplift of the Central Andean Plateau and Bending of the Bolivian Orocline |journal=[[Journal of Geophysical Research]] |volume=93 |issue=B4 |year=1988 |pages=3211–3231 |url=http://geomorphology.sese.asu.edu/Papers/Isacks_Uplift_Andean_Plateau_1988.pdf |doi=10.1029/jb093ib04p03211 |bibcode=1988JGR....93.3211I}}</ref> The specific point at 18° S where the [[coast]]line bends is known as the [[Arica]] Elbow.<ref name="PrezziVilas">{{cite journal |last1=Prezzi |first1=Claudia B. |last2=Vilas |first2=Juan F. |date=1998 |title=New evidence of clockwise vertical axis rotations south of the Arica elbow (Argentine Puna) |journal=[[Tectonophysics (journal)|Tectonophysics]] |volume=292 |issue=1 |pages=85–100 |doi=10.1016/s0040-1951(98)00058-4 |bibcode=1998Tectp.292...85P}}</ref> Further south lies the Maipo Orocline, a more subtle [[orocline]] between 30° S and 38°S with a seaward-concave break in the trend at 33° S.<ref name="Arriagada2013">{{Citation |last1=Arriagada |first1=César |last2=Ferrando |first2=Rodolfo |last3=Córdova |first3=Loreto |last4=Morata |first4=Diego |last5=Roperch |first5=Pierrick |title=The Maipo Orocline: A first scale structural feature in the Miocene to Recent geodynamic evolution in the central Chilean Andes |journal=[[Andean Geology]] |volume=40 |issue=3 |year=2013 |pages=419–437 |url=http://www.scielo.cl/pdf/andgeol/v40n3/art02.pdf}}</ref> Near the southern tip of the Andes lies the Patagonian Orocline.<ref name="Charrieretal2006">{{cite book |last1=Charrier |first1=Reynaldo |last2=Pinto |first2=Luisa |last3=Rodríguez |first3=María Pía |author-link=Reynaldo Charrier |editor-last=Moreno |editor-first=Teresa |editor2-last=Gibbons |editor2-first=Wes |title=Geology of Chile |publisher=Geological Society of London |date=2006 |pages=5–19 |chapter=3. Tectonostratigraphic evolution of the Andean Orogen in Chile |isbn=978-1-86239-219-9}}</ref>

===Orogeny===
{{main|Andean orogeny}}
The western rim of the [[South American Plate]] has been the place of several pre-Andean [[orogeny|orogenies]] since at least the late [[Proterozoic]] and early [[Paleozoic]], when several [[terrane]]s and [[microcontinent]]s collided and amalgamated with the ancient [[craton]]s of eastern South America, by then the [[South American Plate|South American part]] of [[Gondwana]].

The formation of the modern Andes began with the events of the [[Triassic]], when [[Pangaea]] began the breakup that resulted in developing several [[rift]]s. The development continued through the [[Jurassic]] Period. It was during the [[Cretaceous]] Period that the Andes began to take their present form, by the [[Tectonic uplift|uplifting]], [[Fault (geology)|faulting]], and [[Fold (geology)|folding]] of [[sedimentary rock|sedimentary]] and [[metamorphic rock|metamorphic]] 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, and [[erosion]].

Across the {{convert|1000|km|mi|-wide|sp=us|adj=mid}} [[Drake Passage]] lie the mountains of the [[Antarctic Peninsula]] south of the [[Scotia Plate]], which appear to be a continuation of the Andes chain.

The far east regions of the Andes experience a series of changes resulting from the Andean orogeny. Parts of the [[Sunsás orogeny|Sunsás Orogen]] in [[Amazonian craton]] disappeared from the surface of the earth, being [[thrust fault|overridden]] by the Andes.<ref>{{cite journal |last1=Santos |first1=J.O.S. |last2=Rizzotto |first2=G.J. |last4=McNaughton |first4=N.J. |last3=Potter |first3=P.E. |last5=Matos |first5=R.S. |last6=Hartmann |first6=L.A. |last7=Chemale Jr. |first7=F. |last8=Quadros |first8=M.E.S. |date=2008 |title=Age and autochthonous evolution of the Sunsás Orogen in West Amazon Craton based on mapping and U–Pb geochronology |journal=[[Precambrian Research]] |volume=165 |issue=3–4 |pages=120–152 |doi=10.1016/j.precamres.2008.06.009 |bibcode=2008PreR..165..120S}}</ref> The [[Sierras de Córdoba]], where the effects of the ancient [[Pampean orogeny]] can be observed, owe their modern uplift and relief to the [[Andean orogeny]] in the [[Tertiary]].<ref>{{cite book |last1=Rapela |first1=C.W. |last2=Pankhurst |first2=R.J |last3=Casquet |first3=C. |last4=Baldo |first4=E. |last5=Saavedra |first5=J. |last6=Galindo |first6=C. |last7=Fanning |first7=C.M. |author-link2=Robert John Pankhurst |date=1998 |editor2-last=Rapela |editor2-first=C.W. |editor1-last=Pankhurst |editor1-first=R.J |chapter=The Pampean Orogeny of the southern proto-Andes: Cambrian continental collision in the Sierras de Córdoba |chapter-url=http://sp.lyellcollection.org/content/142/1/181.full.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://sp.lyellcollection.org/content/142/1/181.full.pdf |archive-date=2022-10-09 |url-status=live |title=The Proto-Andean Margin of Gondwana |series=Geological Society, London, Special Publications |volume=142 |issue=1 |pages=181–217 |doi=10.1144/GSL.SP.1998.142.01.10 |s2cid=128814617 |access-date=7 December 2015}}</ref> Further south in southern [[Patagonia]], the onset of the Andean orogeny caused the [[Magallanes Basin]] to evolve from being an [[extensional tectonics|extensional]] [[back-arc basin]] in the [[Mesozoic]] to being a contractional [[Andean Foreland Basin|foreland basin]] in the [[Cenozoic]].<ref>{{cite journal |last=Wilson |first=T.J. |date=1991 |title=Transition from back-arc to foreland basin development in the southernmost Andes: Stratigraphic record from the Ultima Esperanza District, Chile |journal=Geological Society of America Bulletin |volume=103 |issue=1 |pages=98–111 |doi=10.1130/0016-7606(1991)103<0098:tfbatf>2.3.co;2 |bibcode=1991GSAB..103...98W}}</ref>

=== Seismic activity ===
Tectonic forces above the [[subduction zone]] along the entire west coast of South America where the [[Nazca Plate]] and a part of the [[Antarctic Plate]] are sliding beneath the [[South American Plate]] continue to produce an ongoing [[Orogeny|orogenic event]] resulting in minor to major [[earthquake]]s and [[volcanic eruption]]s to this day. Many high-magnitude earthquakes have been recorded in the region, such as the [[2010 Chile earthquake|2010 Maule earthquake]] (M8.8), the [[2015 Illapel earthquake]] (M8.2), and the [[1960 Valdivia earthquake]] (M9.5), which as of 2024 was the strongest ever recorded on seismometers.

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.<ref>{{Cite journal |last1=Rodriguez Piceda |first1=Constanza |last2=Gao |first2=Ya-Jian |last3=Cacace |first3=Mauro |last4=Scheck-Wenderoth |first4=Magdalena |last5=Bott |first5=Judith |last6=Strecker |first6=Manfred |last7=Tilmann |first7=Frederik |date=2023-03-17 |title=The influence of mantle hydration and flexure on slab seismicity in the southern Central Andes |journal=Communications Earth & Environment |language=en |volume=4 |issue=1 |page=79 |doi=10.1038/s43247-023-00729-1 |issn=2662-4435 |doi-access=free |bibcode=2023ComEE...4...79R}}</ref>

The mountain range is also a source of shallow intraplate earthquakes within the South American Plate. The largest such earthquake (as of 2024) [[1947 Satipo earthquake|struck Peru in 1947]] and measured {{M|s}} 7.5. In the Peruvian Andes, these earthquakes display normal ([[1946 Ancash earthquake|1946]]), strike-slip (1976), and reverse ([[1969 Huaytapallana earthquake|1969]], 1983) mechanisms. The Amazonian Craton is actively underthrusted beneath the sub-Andes region of Peru, producing thrust faults.<ref>{{cite journal |last1=Dorbath |first1=L. |last2=Dorbath |first2=C. |last3=Jimenez |first3=E. |last4=Rivera |first4=L. |title=Seismicity and tectonic deformation in the Eastern Cordillera and the sub-Andean zone of central Peru |journal=Journal of South American Earth Sciences |date=1991 |volume=4 |issue=1–2 |pages=13–24 |doi=10.1016/0895-9811(91)90015-D |bibcode=1991JSAES...4...13D |url=https://core.ac.uk/download/pdf/39863456.pdf}}</ref> 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.<ref name="Suárez83">{{cite journal |last1=Suárez |first1=Gerardo |last2=Molnar |first2=Peter |last3=Burchfiel |first3=B. Clark |title=Seismicity, fault plane solutions, depth of faulting, and active tectonics of the Andes of Peru, Ecuador, and southern Colombia |journal=Journal of Geophysical Research: Solid Earth |date=1983 |volume=88 |issue=B12 |pages=10403–10428 |doi=10.1029/JB088iB12p10403 |bibcode=1983JGR....8810403S}}</ref>

In the extreme south, a major [[transform fault]] separates [[Tierra del Fuego]] from the small [[Scotia Plate]].

===Volcanism===
{{Main|Andean Volcanic Belt}}
[[File:Browncanyonquilotoa.jpg|thumb|upright=1.3|[[Rift valley|Rift Valley]] near [[Quilotoa]], Ecuador]]
[[File:Central Andes Mountains, Salar de Arizaro, Argentina.jpg|thumb|upright|This photo from the [[ISS]] 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 the [[subduction]] 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.<ref>{{Cite journal |last1=González-Maurel |first1=Osvaldo |last2=le Roux |first2=Petrus |last3=Godoy |first3=Benigno |last4=Troll |first4=Valentin R. |last5=Deegan |first5=Frances M. |last6=Menzies |first6=Andrew |date=15 November 2019 |title=The great escape: Petrogenesis of low-silica volcanism of Pliocene to Quaternary age associated with the Altiplano-Puna Volcanic Complex of northern Chile (21°10′-22°50′S) |url=https://www.sciencedirect.com/science/article/pii/S0024493719303196 |journal=Lithos |language=en |volume=346–347 |pages=105162 |doi=10.1016/j.lithos.2019.105162 |bibcode=2019Litho.34605162G |s2cid=201291787 |issn=0024-4937}}</ref> 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 for [[calc-alkalic]] and subduction volcanism, the Andean Volcanic Belt has a large range of volcano-tectonic settings, such as rift systems, extensional zones, [[Transpression|transpressional faults]], subduction of [[mid-ocean ridge]]s, and [[seamount]] chains apart from a large range of crustal thicknesses and [[magma]] ascent paths, and different amount of crustal assimilations.

===Ore deposits and evaporites===
The Andes Mountains host large [[ore]] and [[salt]] deposits, and some of their eastern [[fold and thrust belt]]s act as traps for commercially exploitable amounts of [[hydrocarbon]]s. In the forelands of the [[Atacama Desert]], some of the largest [[porphyry copper]] mineralizations occur, making Chile and Peru the first- and second-largest exporters of [[copper]] in the world.<ref>{{Cite web |title=Trade Map - List of exporters for the selected product in 2023 (Copper ores and concentrates) |url=https://www.trademap.org/Country_SelProduct.aspx?nvpm=1%7C%7C%7C%7C%7C2603%7C%7C%7C4%7C1%7C1%7C2%7C1%7C%7C2%7C1%7C1%7C1&AspxAutoDetectCookieSupport=1 |access-date=2024-08-17 |website=www.trademap.org}}</ref><ref>{{cite book|last=Robb |first=Laurence |title=Introduction to Ore-Forming Processes |edition=4th |year=2007 |publisher=[[Blackwell Science]] Ltd |location=[[Malden, MA]], United States  |isbn=978-0-632-06378-9 |page=104 }}</ref> Porphyry copper in the western slopes of the Andes has been generated by [[hydrothermal fluid]]s (mostly water) during the cooling of [[pluton (geology)|plutons]] or volcanic systems. The porphyry mineralization further benefited from the dry climate that reduced the disturbing actions of [[meteoric water]]. The dry climate in the central western Andes has also led to the creation of extensive [[Chile saltpeter|saltpeter deposits]] that were extensively mined until the invention of synthetic [[nitrate]]s. Yet another result of the dry climate are the [[Dry lake|salars]] of [[Salar de Atacama|Atacama]] and [[Salar de Uyuni|Uyuni]], the former being the largest source of [[lithium]] and the latter the world's largest reserve of the element.{{fact|date=March 2025}} Early Mesozoic and [[Neogene]] plutonism in Bolivia's Cordillera Central created the [[Bolivian tin belt]] as well as the famous, now mostly depleted, silver deposits of [[Cerro Rico|Cerro Rico de Potosí]].

=== Climate ===
The Andes Mountains is connected connection to the climate of South America, particularly through the hyper-arid conditions of the adjacent Atacama 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.<ref>{{Cite journal |last1=Armijo |first1=Rolando |last2=Lacassin |first2=Robin |last3=Coudurier-Curveur |first3=Aurélie |last4=Carrizo |first4=Daniel |date=2015-04-01 |title=Coupled tectonic evolution of Andean orogeny and global climate |url=https://linkinghub.elsevier.com/retrieve/pii/S0012825215000148 |journal=Earth-Science Reviews |volume=143 |pages=1–35 |doi=10.1016/j.earscirev.2015.01.005 |bibcode=2015ESRv..143....1A |issn=0012-8252}}</ref>