Editing Nazca plate

{{Short description|Oceanic tectonic plate in the eastern Pacific Ocean basin}}
{{Infobox tectonic plate
| image = File:NazcaPlate.png
| type = [[List of tectonic plates#Minor plates|Minor]]
| area = 15,600,000 km<sup>2</sup><ref>{{cite web |url=http://geology.about.com/library/bl/blplate_size_table.htm |title=Sizes of Tectonic or Lithospheric Plates |work=About.com Geology |access-date=4 January 2016 |archive-date=9 February 2007 |archive-url=https://web.archive.org/web/20070209033841/http://geology.about.com/library/bl/blplate_size_table.htm |url-status=dead }}</ref>
| move_direction = north-east
| move_speed = 40-53 mm/year
| geo_features = [[Pacific Ocean]]
}}

The '''Nazca plate''' or '''Nasca plate''',<ref>{{Cite book |title=Oxford Atlas of the World 26th Ed. |publisher=Oxford University Press |year=2019 |isbn=978-0-19-006581-2 |location=New York, NY |pages=74}}</ref> named after the [[Nazca]] region of southern [[Peru]], is an oceanic [[list of tectonic plates|tectonic plate]] in the eastern [[Pacific Ocean]] basin off the west coast of [[South America]]. The ongoing [[subduction]], along the [[Peru–Chile Trench]], of the Nazca plate under the [[South American plate]] is largely responsible for the [[Andes|Andean]] [[orogeny]]. The Nazca plate is bounded on the west by the [[Pacific plate]] and to the south by the [[Antarctic plate]] through the [[East Pacific Rise]] and the [[Chile Rise]], respectively. The movement of the Nazca plate over several [[Hotspot (geology)|hotspots]] has created some [[volcanic islands]] as well as east–west running [[seamount]] chains that subduct under [[South America]]. Nazca is a relatively young plate in terms of the age of its rocks and its existence as an independent plate, having been formed from the breakup of the [[Farallon plate]] about 23&nbsp;million years ago. The oldest rocks of the plate are about 50&nbsp;million years old.<ref>{{cite web |title=Sea Floor Spreading in the Pacific (Plate Boundaries Shown) |first=Steven |last=Dutch |url=https://www.uwgb.edu/dutchs/GeolColBk/PacificSFS-PB.HTM |url-status=dead |archive-url=https://web.archive.org/web/20100317130720/https://www.uwgb.edu/dutchs/GeolColBk/PacificSFS-PB.HTM |archive-date=17 March 2010 |date=10 August 2009 |publisher=University of Wisconsin – Green Bay}}</ref>

==Boundaries==

===East Pacific and Chile Rise===
{{Main|East Pacific Rise|Chile Rise}}

A [[triple junction]], the [[Chile triple junction]],<ref>{{cite web |url=http://www.nsm.buffalo.edu/courses/gly481-581/McGuire05_2.pdf |title=Tectonics of South America: Chile Triple Junction |date=8 April 2004 |author=Kelly McGuire |access-date=27 February 2016 |archive-date=19 January 2020 |archive-url=https://web.archive.org/web/20200119100719/http://www.nsm.buffalo.edu/courses/gly481-581/McGuire05_2.pdf |url-status=live }}</ref> occurs on the seafloor of the [[Pacific Ocean]] off [[Taitao Peninsula|Taitao]] and [[Tres Montes Peninsula]] at the southern coast of [[Chile]]. Here, three [[tectonics|tectonic]] plates meet: the Nazca plate, the [[South American plate]], and the [[Antarctic plate]].

===Peru–Chile Trench===
{{See also|Peru–Chile Trench}}

The eastern margin is a [[convergent boundary]] [[subduction]] zone under the South American plate and the [[Andes Mountains]], forming the [[Peru–Chile Trench]]. The southern side is a [[divergent boundary]] with the Antarctic plate, the [[Chile Rise]], where [[seafloor spreading]] permits [[magma]] to rise. The western side is a divergent boundary with the [[Pacific plate]], forming the [[East Pacific Rise]]. The northern side is a divergent boundary with the [[Cocos plate]], the [[Cocos–Nazca spreading centre]].

The subduction of the Nazca plate under southern Chile has a history of producing massive [[earthquake]]s, including the largest ever recorded on earth, the [[moment magnitude scale|moment magnitude]] 9.5 [[1960 Valdivia earthquake]].

==Intraplate features==

===Hotspots===
{{Main|Easter hotspot|Juan Fernández hotspot|Galápagos hotspot}}

A second triple junction occurs at the northwest corner of the plate where the Nazca, Cocos, and Pacific plates all join off the coast of [[Colombia]]. Yet another triple junction occurs at the southwest corner at the intersection of the Nazca, Pacific, and Antarctic plates off the coast of southern [[Chile]]. At each of these triple junctions an ''[[:wikt:anomaly|anomalous]]'' microplate exists, the [[Galapagos microplate]] at the northern junction and the [[Juan Fernandez microplate]] at the southern junction. The [[Easter Plate|Easter Island microplate]] is a third microplate that is located just north of the Juan Fernandez Microplate and lies just west of [[Easter Island]].

===Aseismic ridges===
{{Main|Nazca Ridge|Juan Fernández Ridge|Carnegie Ridge|}}

The '''Carnegie Ridge''' is a {{convert|1350|km|mi|adj=mid|-long}} and up to {{convert|300|km|mi|adj=mid|-wide}} feature on the ocean floor of the northern Nazca plate that includes the [[Galápagos Islands|Galápagos archipelago]] at its western end. It is being subducted under South America with the rest of the Nazca plate.

==Plate motion==
The absolute motion of the Nazca plate has been calibrated at {{cvt|3.7|cm/yr}} east motion (88°), one of the fastest absolute motions of any tectonic plate. The subducting Nazca plate, which exhibits unusual [[flat slab subduction]], is tearing as well as deforming as it is subducted (Barzangi and Isacks). The subduction has formed and continues to form the [[volcano|volcanic]] [[Andes]] Mountain Range. Deformation of the Nazca plate even affects the [[Geography of Bolivia|geography]] of [[Bolivia]], far to the east (Tinker et al.). The [[1994 Bolivia earthquake]] occurred on the Nazca plate; this had a magnitude of 8.2 <math>M_w</math>, which at that time was the strongest instrumentally recorded earthquake occurring deeper than {{cvt|300|km}}.

Aside from the [[Juan Fernández Islands]], this area has very few other islands that are affected by the earthquakes resulting from complicated movements at these junctions.

==Geologic history==
{{See also|Farallon plate}}

The precursor of the Nazca plate, [[Juan de Fuca plate]], and the [[Cocos plate]] was the [[Farallon plate]], which split in the late [[Oligocene]], about 22.8 [[myr|Mya]], a date arrived at by interpreting [[Geomagnetism|magnetic anomalies]]. Subduction under the South American continent began about 140 Mya, although the formation of the high parts of the Central Andes and the Bolivian [[orocline]] did not occur until 45 Mya. It has been suggested that the mountains were forced up by the subduction of the older and heavier parts of the plate, which sank more quickly into the [[Mantle (geology)|mantle]].<ref>{{cite news |title=Mountains on a plate form the Andes |url=http://www.universityworldnews.com/article.php?story=20120321111927290 |publisher=University World News |date=25 March 2012 |issue=214 |access-date=8 February 2016 |archive-date=13 September 2015 |archive-url=https://web.archive.org/web/20150913114457/http://www.universityworldnews.com/article.php?story=20120321111927290 |url-status=live }}</ref>

==See also==
*[[2010 Chile earthquake]]
*[[Caribbean plate]]
*[[Galápagos Rise]] - fossil spreading centre active 17–5.8 million years ago

==References==
{{Reflist}}

===Bibliography===
* [https://web.archive.org/web/20100211011746/http://www.extremescience.com/PlateTectonicsmap.htm Extreme Science site: "A Lesson in Plate Tectonics"] The basics explained.
* [http://www.earth.columbia.edu/news/2002/story12-05-02.html Galapagos rise junction (map)]
* [http://www.pmel.noaa.gov/vents/s-epr.html Juan Fernandez and Easter microplate (map)]
* Muawia Barazangi and Bryan L. Isacks, "Spatial distribution of earthquakes and subduction of the Nazca plate beneath South America" in ''Geology'' Vol. 4, No. 11, pp.&nbsp;686–692. [https://web.archive.org/web/20120229132304/http://www.gsajournals.org/gsaonline/?request=get-abstract&doi=10.1130%2F0091-7613(1976)4%3C686:SDOEAS%3E2.0.CO%3B2 Abstract]
*Mark Andrew Tinker, Terry C. Wallace, [[Susan L. Beck]], Stephen Myers, and Andrew Papanikolas, "Geometry and state of stress of the Nazca plate beneath Bolivia and its implication for the evolution of the Bolivian orocline" in ''Geology'' '''24'''(5), pp.&nbsp;387–390 [https://web.archive.org/web/20120229132313/http://www.gsajournals.org/gsaonline/?request=get-abstract&doi=10.1130%2F0091-7613(1996)024%3C0387:GASOSO%3E2.3.CO%3B2 Abstract]
* Cahill, T. and B. Isacks (1992). "Seismicity and shape of the subducted Nazca plate." ''Journal Geophysical Research'' '''97''' (12)
* James, D. (1978). "Subduction of the Nazca plate beneath Central Peru." ''Geology'' '''6''' (3) pp 174&ndash;178
* [http://www-odp.tamu.edu/publications/170_SR/VOLUME/CHAPTERS/SR170_07.PDF Martin Meschede and Udo Barckhausen, "Plate tectonic evolution of the Cocos-Nazca spreading center"]

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[[Category:Tectonic plates]]
[[Category:Geology of Chile]]
[[Category:Natural history of Oceania]]
[[Category:Natural history of South America]]
[[Category:Geology of the Pacific Ocean]]