View source for Geology of Chile

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[[File:Llaima eruption2.jpg|thumb|upright=1.25|alt=Flaming volcano overlooking a city|[[Llaima]] volcano in eruption]]

The '''geology of Chile''' is a characterized by processes linked to [[subduction]], such as [[volcanism]], [[earthquake]]s, and [[orogeny]]. The [[terrane|building blocks]] of Chile's geology were [[accretion (geology)|assembled]] during the [[Paleozoic|Paleozoic Era]] when Chile was the southwestern margin of the supercontinent [[Gondwana]]. In the [[Jurassic]], Gondwana began to split, and the ongoing period of [[crustal deformation]] and [[mountain building]] known as the [[Andean orogeny]] began. In the [[Cenozoic|Late Cenozoic]], Chile definitely separated from Antarctica, and the Andes experienced a significant rise accompanied by a cooling climate and the onset of [[glaciation]]s.

The subduction interactions shaped four main [[wikt:morphostructure|morphostructures]] of Chile: the [[Andes]], the [[Chilean Central Valley|Intermediate Depression]], the [[Chilean Coast Range|Coast Range]], and the [[Peru–Chile Trench]] off the coast. Since Chile is on an active [[continental margin]], it has many [[volcano]]es. Almost the entire country is subject to earthquakes arising from strains in the [[Nazca plate|Nazca]] and [[Antarctic plate]]s or shallow [[strike-slip fault]]s. Northern Chilean mineral resources are a major economic resource, and the country is the leading producer of [[copper]], [[lithium]] and [[molybdenum]]. Most of these mineral deposits were created from [[Magmatic water|magmatic]] [[Hydrothermal circulation|hydrothermal]] activity, and the water required to form those deposits derived from the subducted slab of the oceanic crust beneath the Andes.

The Chilean [[Easter Island]] and [[Juan Fernández Archipelago]] are volcanic [[hotspot (geology)|hotspot]] islands in the eastward-moving Nazca plate. The geology of the [[Chilean Antarctic Territory]] has various commonalities with that of mainland Chile.

==General characteristics==
{{See also|Geography of Chile}}
The three primary morphological features derived from the Andes are the Andes Mountains proper, the Chilean Coast Range and the Chilean Central Valley, also known as the Intermediate Depression and the Longitudinal Valley. The mountains run parallel in a north–south direction from [[Morro de Arica]] to [[Taitao Peninsula]], making up most of Chile's land surface. South of Taitao, only the Andes Mountains are present.

North of the Taitao Peninsula, the Peru–Chile Trench [[subduction]] zone is the boundary between the South American and Nazca plates. At Taitao, the [[Chile triple junction]] and the [[Nazca plate]] subduct the South American plate.

===The Andes===
[[File:Miscanti Lagoon near San Pedro de Atacama Chile Luca Galuzzi 2006.jpg|thumb|right|alt=Stark mountains in background, with salt flats in foreground|The Andes are generally higher in northern Chile.]]

In [[Norte Grande]] the mountains form a series of [[plateaus]], such as [[Puna de Atacama]] and the [[Altiplano]]. At a south latitude of 27 degrees, Chile's highest mountain ([[Ojos del Salado]]) reaches a height of {{convert|6893|m}}. Below 42 degrees south, the Andes split into a [[fjord]] landscape and the highest mountain is [[Monte San Valentín|Monte San Valentin]] at {{convert|4058|m||abbr=}} at north of [[Northern Patagonian Ice Field]]. As the mountains ebb, the [[snow line]] lowers; in the [[Llanquihue Lake|Llanquihue]] it is at {{convert|1200|m}}, and {{convert|900|m}} in the [[Magallanes Region|Magallanes]].

===Intermediate Depression===
{{main|Chilean Central Valley}}

The Intermediate Depression, a series of faults running north to south, separates the Andes from the Coast Range with a steady decrease in altitude as the latitude increases. In [[Norte Grande]] the Intermediate Depression is partially covered by a series of [[Salt pan (geology)|salt flat]]s, and has the world's largest [[potassium nitrate]] deposits. In [[Norte Chico, Chile|Norte Chico]], the depression disappears briefly before reappearing in a narrow valley at [[Santiago, Chile|Santiago]]. From the narrows southward the valley widens until it is interrupted near [[Loncoche]] by the [[Bahía Mansa Metamorphic Complex]] (part of the Coast Range), then widening at [[Los Llanos, Chile|Los Llanos]] (near [[Paillaco]]). In central and southern Chile (33°–42° south), the landscape is partially covered with glacial [[sediments]] from the Andes. In [[Zona Austral]] (south of 42° south) the depression dips below [[sea level]], appearing occasionally in islands such as [[Chiloé Island|Chiloé]]. Its southern end is the [[Isthmus of Ofqui]].

===Chilean Coast Range===
{{main|Chilean Coast Range}}

The [[Chilean Coast Range]] runs southward along the coast (parallel to the Andes) from [[Morro de Arica]] to [[Taitao Peninsula]], ending at the [[Chile triple junction]]. The range, a combined [[horst (geology)|horst]], [[Foreland basin|forearc high]] and [[accretionary wedge]], was separated from the Andes during the [[Tertiary period|Tertiary]] rise due to the [[subsidence]] of the Intermediate Depression.

==Geologic history==
[[File:Pangea animation 03.gif|thumb|alt=Global animation of the breakup of Pangaea into separate continents|[[Pangaea]] separation animation]]
[[File:Parinacota volcano.jpg|thumb|alt=Llamas and alpacas grazing, with snow-capped mountain in background|View of the Altiplano plateau in northern Chile]]
[[File:Cuernos del Paine from Lake Pehoé.jpg|thumb|alt=Lake, with jagged mountains in the background|The mountains at [[Torres del Paine National Park]] have been heavily eroded by the [[Quaternary]] glaciations.]]
[[File:San Rafael Glacier animation.gif|thumb|alt=Animation of a glacier's rapid retreat|Retreat of the [[San Rafael Glacier]] from 1990 to 2000]]

===Paleozoic Era===
The oldest rocks in Chile are [[mica]]ceous [[schist]]s, [[phyllite]]s, [[gneiss]]es and [[quartzite]]s, many examples of which are found in the [[Chilean Coast Range|Coast Range]] of south-central Chile. The schists of [[Zona Sur|southern Chile]] were initially formed by sediment in the proto-Pacific Ocean, and later metamorphosed in the [[forearc]] wedge of the Peru–Chile Trench.

===Mesozoic Era===
{{See also|Antarctic Floristic Kingdom}}

During the [[Triassic]] Period about 250 million years ago Chile was part of the [[supercontinent]] [[Pangaea]], which concentrated the world's major land masses. [[Africa]], [[Antarctica]], [[Australia]] and [[India]] were near Chile. When Pangaea began to split apart during the [[Jurassic]] period, South America and the adjacent land masses formed [[Gondwana]]. Floral affinities among these now-distant landmasses date from the Gondwanaland period. South America separated from Antarctica and Australia 27 million years ago with the development of the [[Drake Passage]]. Across the {{convert|1000|km|adj=on}}-wide Drake Passage lie the mountains of the [[Antarctic Peninsula]], south of the Scotia plate, which appear to be a continuation of the Andes. In the extreme south, the [[Magallanes–Fagnano Fault]] separates [[Tierra del Fuego]] from the small [[Scotia plate]].

The formation of the Andes began during the Jurassic. During the [[Cretaceous]], the Andes began to assume their present form by the uplifting, [[Fault (geology)|faulting]] and [[Fold (geology)|folding]] of [[sedimentary rocks|sedimentary]] and [[metamorphic rocks]] of ancient [[craton]]s. Tectonic forces along the [[subduction]] zone along the west coast of South America continue to their [[Orogeny|orogenesis]], resulting in earthquakes and volcanic eruptions to this day.

===Cenozoic Era===
The [[Altiplano]] [[plateau]] was formed during the [[Tertiary period|Tertiary]], with several mechanisms proposed; all attempt to explain why the topography of the Andes incorporates a large area of low relief at high altitude (high plateau): 
# Existence of weaknesses in the Earth's crust prior to tectonic shortening. Such weaknesses would cause the partition of tectonic deformation and uplift into eastern and western cordillera, leaving the necessary space for the formation of the Altiplano basin.
# Magmatic processes rooted in the asthenosphere might have contributed to uplift the plateau.
# Climate controlled the spatial distribution of erosion and sediment deposition, creating the lubrication along the Nazca plate subduction and hence influencing the transmission of tectonic forces into South America.
# Climate also determined the formation of internal drainage (endorheism) and sediment trapping within the Andes, potentially blocking tectonic deformation in the area between the two cordilleras.

====Quaternary====
The [[Quaternary]] [[glaciation]]s left visible marks in most parts of Chile, particularly [[Zona Sur]] and [[Zona Austral]]. These include [[ice field]]s, [[fjord]]s, [[glacial lake]]s and u-shaped valleys. During the [[Santa María glaciation]] glaciers extended into the Pacific Ocean at 42° south, dividing the [[Chilean Coast Range]] and creating what is now [[Chacao Channel]]. [[Chiloé Island|Chiloé]], part of the Chilean Coast Range, became an island. South of Chacao Channel, Chile's coast is split by fjords, islands and channels; these glaciers created [[moraine]]s at the edges of the Patagonian lakes, changing their outlets to the Pacific and shifting the [[continental divide]]. The remnants of the [[Patagonian Ice Sheet]] which covered large parts of Chile and [[Argentina]] are the [[Northern Patagonian Ice Field|Northern]] and the [[Southern Patagonian Ice Field]]s.

It has been suggested that from 1675 to 1850 the [[San Rafael Glacier]] advanced during the [[Little Ice Age]]. The first documented visit to the area was made in 1675 by the Spanish explorer [[:es:Antonio de Vea|Antonio de Vea]], who entered [[San Rafael Lagoon]] through [[:es:Río Témpanos|Río Témpanos]] ("Ice Floe River") without mentioning the many [[Drift ice|ice floes]] for which the river is named. De Vea also wrote that the [[San Rafael Glacier]] did not reach far into the lagoon. In 1766 another expedition noticed that the glacier did reach the lagoon and had [[Ice calving|calved]] into [[icebergs]]. [[Hans Steffen]] visited the area in 1898, noting that the glacier now penetrated far into the lagoon. As of 2001, the glacier has retreated behind its 1675 border due to climate change.<ref>{{cite journal|title=Historical records of San Rafael glacier advances (North Patagonian Icefield): another clue to 'Little Ice Age' timing in southern Chile?|journal=The Holocene|date=November 2007|volume=17|issue=7|pages=987–998|doi= 10.1177/0959683607082414|last1=Araneda|first1=Alberto|last2=Torrejón|first2=Fernando|last3=Aguayo|first3=Mauricio|last4=Torres|first4=Laura|last5=Cruces|first5=Fabiola|last6=Cisternas|first6=Marco|last7=Urrutia|first7=Roberto|bibcode=2007Holoc..17..987A|hdl=10533/178477|s2cid=128826804 |hdl-access=free}}</ref>

==Pacific islands==
[[File:Moai Rano raraku.jpg|thumb|upright|alt=Statues of heads on Easter Island|Most of the [[moai]] on Easter island are carved from [[volcanic]] [[tuff]].]]

[[Easter Island]] is a [[volcanic island]] consisting of three extinct volcanoes: [[Terevaka]], at an altitude of {{convert|507|m}}, forms the bulk of the island. Two other volcanoes ([[Poike]] and [[Rano Kau]]) form the eastern and southern headlands, giving the island its triangular shape. There are numerous lesser cones and other volcanic features: the crater [[Rano Raraku]], the [[cinder cone]] [[Puna Pau]] and many volcanic caves (including [[lava tubes]]).
 
Easter Island and its surrounding islets, including [[Motu Nui]] and [[Motu Iti (Rapa Nui)|Motu Iti]], form the comminuted apex of a large volcanic mountain rising over {{convert|2000|m}} from the seabed. It is part of the Sala y Gómez Ridge, a mostly-submarine mountain range with dozens of [[seamount]]s. [[Pukao (Seamount)|Pukao]] and [[Moai (seamount)|Moai]] are two seamounts west of Easter Island, extending {{convert|2700|km|mi|abbr=on}} east to the [[Nazca Seamount]]. Pukao, Moai and Easter Island were formed during the last 750,000 years, with the last eruption a little over 100,000 years ago. These are the youngest mountains of the Sala y Gómez Ridge, which was formed by the [[Nazca plate]] floating over the [[Easter hotspot]].<ref>Haase, Karsten & Stoffers, P & Garbe-Schönberg, Dieter. (1997). [https://web.archive.org/web/20110524082519/http://www.oxfordjournals.org/our_journals/petroj/online/Volume_38/Issue_06/html/ega038_gml.html#hd15 The Petrogenetic Evolution of Lavas from Easter Island and Neighbouring Seamounts, Near-ridge Hotspot Volcanoes in the SE Pacific]. Journal of Petrology – J PETROL. 38. 785–813. {{doi|10.1093/petrology/38.6.785}}.</ref> Only on Easter Island is the Sala y Gómez Ridge dry land.

The [[volcano|volcanic]] [[Juan Fernández Islands]] were created by a [[Hotspot (geology)|hotspot]] in the Earth's mantle penetrating the [[Nazca plate]]. The islands were carried eastward as the plate subducted the [[South America]]n continent. [[Radiometric dating]] indicates that Santa Clara is the oldest of the islands (at 5.8&nbsp;million years), followed by Robinson Crusoe (3.8–4.2&nbsp;million years) and Alexander Selkirk (1.0–2.4&nbsp;million years). Robinson Crusoe is the largest of the islands at {{convert|93|km2|sqmi}}, and its highest peak (El Yunque) is {{convert|916|m}} high. Alexander Selkirk covers {{convert|50|km2|sqmi}}, and its highest peak is Los Innocentes at {{convert|1319|m}}. Santa Clara covers {{convert|2.2|km2|acre}}, reaching an elevation of {{convert|350|m}}.

==Economic geology==

===Mining===
{{see also|Mining in Chile|Copper mining in Chile}}
[[File:Chuqui001 02.jpg|thumb|alt=Truck on road of open-pit mine|[[Chuquicamata]] copper mine in 1984]]

Chile has the world's largest [[copper]] reserves, and is the largest producer and exporter of the metal.<ref name=minas>U.S. Geological Survey (2005). [http://minerals.usgs.gov/minerals/pubs/country/2005/cimyb05.pdf Minerals Yearbook 2005.]</ref> Notable copper mines include [[Chuquicamata]] and [[Escondida]]. Chile accounts for five percent of the Western Hemisphere's [[gold]] production, of which 41 percent is a by-product of [[copper extraction]].<ref name=minas/> The country holds the largest world reserves of [[rhenium]]<ref name=minas/> and [[potassium nitrate]], and its reserves of [[molybdenum]] are estimated to be the third-largest in the world.<ref name=minas/> Most of Chile's mineral resources are in [[Norte Grande, Chile|the north]]; [[Natural gas|gas]], [[coal]] and [[oil]] reserves, in the southern [[Magallanes Region]], are sufficient for local needs. [[Guarello Island]], in the Magallanes Region, has the world's southernmost [[limestone]] mine.

===Geothermal energy===
{{main|Geothermal power in Chile}}

Since 2000, geothermal exploration and concessions have been regulated by the [[Law of Geothermal Concessions]] ({{langx|es|Ley de Concesiones de Energía Geotérmica}}). The Chilean company Geotermia del Pacífico, with support from [[CORFO]], is exploring a location in [[Curacautín]] as a site for a [[geothermal power plant]]. Geotermia del Pacífico's studies indicated that two geothermal fields near Curacautín could be used for energy production, with a combined capacity to supply 36,000 homes in 2010. One area to be developed is located near the [[Tolhuaca]] hot springs, and the other is in Río Blanco Springs.<ref>[http://www.santiagotimes.cl/santiagotimes/index2.php?option=com_content&do_pdf=1&id=10812 "Chile Could Have Geothermal Energy By 2010"]. ''Santiago Times''</ref> Another area under consideration for geothermal production is [[Cordón Caulle]].

===Tourism===
Although geology-focused tourism is rare, there are some sites in which the local geology is a major attraction (for example, the copper mine at [[Chuquicamata]]).

==Geological hazards==
[[File:Plano de Valparaíso-Terremoto 1906.jpg|thumb|upright=1.5|Map of Valparaíso after the earthquake of 16 August 1906<br>
{{Color box|pink|border=darkgray}} Area of the city most affected by earthquake<br>
{{Color box|red|border=darkgray}} City blocks most damaged by fire ]]
[[Earthquake]]s, [[volcanic eruption]]s and [[Mass wasting|mass ground movements]] are frequent occurrences. The subduction zone along Chile's coast has produced the most powerful earthquake ever recorded, the [[1960 Valdivia earthquake]]. Earthquakes are notorious for triggering volcanic eruptions, such as the [[1960 Cordón Caulle eruption]]. Chilean earthquakes have produced tsunamis.

Landslides occur frequently in the Andes, most following earthquakes. The [[2007 Aysén Fjord earthquakes]] produced several landslides along the Fjords Mountains, spawning a tsunami. [[Lahar]]s are among the most lethal volcanic hazards in Chile; a lahar destroyed the original site of [[Coñaripe]].

==={{anchor|Background}}Earthquakes===
{{main|List of earthquakes in Chile}}

Major earthquakes in Chile occur in a small number of source areas. Those affecting coastal regions are generally aligned offshore from Concepción southward, with the major epicenters producing a predictable pattern of seismic and tsunami effects.<ref>[[Cinna Lomnitz|Lomnitz, Cinna]]; [https://doi.org/10.1007%2FBF02042278  "Major earthquakes and tsunamis in Chile during the period 1535 to 1955"]; ''[[International Journal of Earth Sciences]]'', Vol. 59, No. 3; abstract.</ref> The first systematic seismological recordings in Chile began after [[1906 Valparaiso earthquake|an earthquake and fire]] devastated Valparaiso in 1906.<ref>Moreno, Teresa. (2006). {{Google books|h4DBQR9jDsoC|''The Geology of Chile,'' p. 264.|page=264}}</ref>

Earthquakes in northern Chile are known to have caused both [[tectonic uplift|uplift]] and [[subsidence]] of the continent. Large earthquakes of [[moment magnitude|Magnitude]] 8 or more are associated with subsidence and drowning of the Chilean coast, except peninsulas and offshore islands. Magnitude 7 to 8 earthquakes with a source area near an internal boundary of the Earth known as the [[Mohorovičić discontinuity|Moho]] are known to result in uplift of the coast. Earthquakes near the Moho may account for permanent [[deformation (geology)|deformation]] of the western edge of [[South American plate]] that accumulates into a long-term net uplift of the continent.<ref>{{cite journal |last1=Melnick |first1=Daniel |date=2016 |title=Rise of the central Andean coast by earthquakes straddling the Moho |journal=Nature Geoscience |volume=9 |issue=5 |pages=401–408 |doi=10.1038/NGEO2683 |bibcode=2016NatGe...9..401M }}</ref>

==={{anchor|Time-span|Conclusions}}Quake clusters===
Although the most powerful six quakes recorded were clustered in two time periods (a 12-year span from 1952 to 1964 and a seven-year span from 2004 to 2011), this is considered a statistical anomaly.<ref name="pappas">Pappas, Stephanie. [http://www.livescience.com/13196-earthquakes-worse.html "Sumatra, Japan, Chile: Are Earthquakes Getting Worse?"]; ''[[LiveScience]]''; 11 March 2011.</ref> The phenomenon of comparably-large quakes on the same (or neighboring) faults within months of each other may be explained by geological mechanisms, but this does not fully demonstrate a relationship between events separated by longer periods and greater distances<ref>Brahic, Catherine; [https://www.newscientist.com/article/mg20928043.000-the-megaquake-connection-are-huge-earthquakes-linked.html  "The mega-quake connection: Are huge earthquakes linked?"]; ''[[New Scientist]]''; UK; 16 March 2011.</ref>

== See also ==
*[[Climate of Chile]]
*[[Geography of Chile]]
*[[List of glaciers of Chile]]
*[[List of volcanoes in Chile]]

==Notes==
{{Reflist}}

==References==
*Brüggen, Juan (1950). ''Fundamentos de la geología de Chile'', Instituto Geográfico Militar.
*Duhart, Paul et al. [http://www.scielo.cl/scielo.php?pid=S0716-02082001000200003&script=sci_arttext El Complejo Metamórfico Bahía Mansa en la cordillera de la Costa del centro-sur de Chile (39°30'-42°00'S): geocronología K-Ar, 40Ar/39Ar y U-Pb e implicancias en la evolución del margen sur-occidental de Gondwana]
* Moreno, Teresa and Wes Gibbons. (2006). ''The Geology of Chile.'' London: Geological Society of London. {{ISBN|9781862392199}}; [https://www.worldcat.org/oclc/505173111 OCLC 505173111]
*Zeil, W. (1964). Geologie von Chile.

==External links==
{{commons category|Geology of Chile}}
*[http://www.ipgp.jussieu.fr/~dechabal/Geol-millon.pdf Geologic map of Chile]
*[https://web.archive.org/web/20151109062356/http://www.geo.arizona.edu/geo5xx/geo527/Andes/tectonicandes.html Tectonical development of Chile and the southern Andes]

{{Geology of Chile}}
{{Chile topics}}
{{South America topic|Geology of}}

[[Category:Geology of Chile| ]]
[[Category:Earthquakes in Chile]]
[[Category:Coasts of the Pacific Ocean]]
[[Category:Seismic zones]]