The Nazca plate or Nasca plate , named after the Nazca region of southern Peru , is an oceanic 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 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 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 million years ago. The oldest rocks of the plate are about 50 million years old.
43-797: A triple junction , the Chile Triple Junction , occurs on the seafloor of the Pacific Ocean off Taitao and Tres Montes Peninsula at the southern coast of Chile . Here, three tectonic plates meet: the Nazca plate, the South American plate , and the Antarctic plate . The eastern margin is a convergent boundary subduction zone under the South American plate and the Andes Mountains , forming
86-635: A date arrived at by interpreting 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 . 15°S 85°W / 15°S 85°W / -15; -85 Triple junction A triple junction
129-412: A dozen cases where such bends were undone the results were substantially identical with continental reconstructions deduced by other means. Recognition of oroclinal bending provided strong support to the subsequent theory of plate tectonics . Examples [ edit ] [REDACTED] A composite relief image of South America. The Bolivian Orocline can be seen in the middle of the picture next to
172-448: A few are stable through time ( stable in this context means that the geometrical configuration of the triple junction will not change through geologic time). The meeting of four or more plates is also theoretically possible, but junctions will only exist instantaneously. The first scientific paper detailing the triple-junction concept was published in 1969 by Dan McKenzie and W. Jason Morgan . The term had traditionally been used for
215-425: A history of producing massive earthquakes , including the largest ever recorded on earth, the moment magnitude 9.5 1960 Valdivia earthquake . 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
258-457: A seaward-convex bend in the Andes. Cantabrian Orocline and Gibraltar Orocline, Spain. Carpathian Orocline, Romania. Balkan Orocline, Romania, Bulgaria and Serbia. Northern Apennines Orocline, Southern Apennines Orocline and Calabrian Orocline, Italy Western Alps Orocline, Italy, France and Switzerland. Oroclines in cratons [ edit ] Bothnian oroclines in
301-454: A single point, for the triple junction to exist stably. These lines necessarily are parallel to the plate boundaries as to remain on the plate boundaries the observer must either move along the plate boundary or remain stationary on it. The point at which these lines meet, J, gives the overall motion of the triple junction with respect to the Earth. Using these criteria it can easily be shown why
344-456: Is believed to have caused the formation of the Pacific plate about 190 million years ago. By assuming that plates are rigid and that the Earth is spherical, Leonhard Euler 's theorem of motion on a sphere can be used to reduce the stability assessment to determining boundaries and relative motions of the interacting plates. The rigid assumption holds very well in the case of oceanic crust , and
387-514: Is demonstrated below – as the perpendicular bisectors of the sides of a triangle always meet at a single point, the lines ab, bc and ca can always be made to meet regardless of relative velocities. RTF junctions are less common, an unstable junction of this type (an RTF(a)) is thought to have existed at roughly 12 Ma at the mouth of the Gulf of California where the East Pacific Rise currently meets
430-405: Is retained with time as the plates involved move. This places restrictions on relative velocities and plate boundary orientation. An unstable triple junction will change with time, either to become another form of triple junction (RRF junctions easily evolve to FFR junctions), will change geometry or are simply not feasible (as in the case of FFF junctions). The inherent instability of an FFF junction
473-485: Is tearing as well as deforming as it is subducted (Barzangi and Isacks). The subduction has formed and continues to form the volcanic Andes Mountain Range. Deformation of the Nazca plate even affects the 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 M w {\displaystyle M_{w}} , which at that time
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#1732841958297516-423: Is the point where the boundaries of three tectonic plates meet. At the triple junction each of the three boundaries will be one of three types – a ridge (R), trench (T) or transform fault (F) – and triple junctions can be described according to the types of plate margin that meet at them (e.g. fault–fault–trench, ridge–ridge–ridge, or abbreviated F-F-T, R-R-R). Of the ten possible types of triple junctions only
559-592: The Mid-Atlantic Ridge , and an associated aulacogen , the Benue Trough , in the Niger Delta region of Africa. RRR junctions are also common as rifting along three fractures at 120° is the best way to relieve stresses from uplift at the surface of a sphere; on Earth, stresses similar to these are believed to be caused by the mantle hotspots thought to initiate rifting in continents. The stability of RRR junctions
602-679: 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 Galapagos Rise . The subduction of the Nazca plate under southern Chile has
645-662: The Philippine and Pacific plates , with the Philippine plate also overriding the Pacific. Here the Japan Trench effectively branches to form the Ryukyu and Bonin arcs . The stability criteria for this type of junction are either ab and ac form a straight line or that the line bc is parallel to CA. Orocline Aspect of geology An orocline — from
688-556: The San Andreas Fault zone. The Guadeloupe and Farallon microplates were previously being subducted under the North American plate and the northern end of this boundary met the San Andreas Fault . Material for this subduction was provided by a ridge equivalent to the modern East Pacific Rise slightly displaced to the west of the trench. As the ridge itself was subducted an RTF triple junction momentarily existed but subduction of
731-705: The Svecofennian Domain in Finland and Sweden. Inari orocline including the Lapland Granulite Belt in Finland, Norway and Russia. Lachlan Orocline, eastern Australia Dabashan Orocline, China See also [ edit ] Syntaxis (geology) Notes [ edit ] ^ Carey 1955 , p. 257. Note that the initial formation does not have to be straight. ^ Carey 1955 , p. 257. ^ Carey 1955 , p. 255. ^ Isacks, Bryan L. (1988), "Uplift of
774-647: The Central Andean Plateau and Bending of the Bolivian Orocline" (PDF) , Journal of Geophysical Research , 93 (B4): 3211–3231, Bibcode : 1988JGR....93.3211I , doi : 10.1029/jb093ib04p03211 ^ Kley, J. (1999), "Geologic and geometric constraints on a kinematic model of the Bolivian orocline", Journal of South American Earth Sciences , 12 (2): 221–235, Bibcode : 1999JSAES..12..221K , doi : 10.1016/s0895-9811(99)00015-2 ^ Beck, Myrl E. (1987), "Tectonic rotations on
817-488: The Euler poles are distant from the triple junction concerned. The definitions they used for R, T and F are as follows: For a triple junction between the plates A, B and C to exist, the following condition must be satisfied: where A v B is the relative motion of B with respect to A. This condition can be represented in velocity space by constructing a velocity triangle ABC where the lengths AB, BC and CA are proportional to
860-637: The FFF triple junction is not stable: the only case in which three lines lying along the sides of a triangle can meet at a point is the trivial case in which the triangle has sides lengths zero, corresponding to zero relative motion between the plates. As faults are required to be active for the purpose of this assessment, an FFF junction can never be stable. McKenzie and Morgan determined that there were 16 types of triple junction theoretically possible, though several of these are speculative and have not necessarily been seen on Earth. These junctions were classified firstly by
903-469: The Greek words for "mountain" and "to bend" — is a bend or curvature of an orogenic (mountain building) belt imposed after it was formed. The term was introduced by S. Warren Carey in 1955 in a paper setting forth how complex shapes of various orogenic belts could be explained by actual bending, and that understanding this provided "the key to understanding the evolution of the continents". Carey showed that in
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#1732841958297946-847: The Miocene to Recent geodynamic evolution in the central Chilean Andes" (PDF) , Andean Geology , 40 (3): 419–437 ^ Jara-Muñoz, Julius; Melnick, Daniel; Dominik, Brill; Strecker, Manfred R. (2015), "Segmentation of the 2010 Maule earthquake rupture from a joint analysis of uplifted marine terraces and seismic cycle deformation", Quaternary Science Reviews , 113 : 171–192, doi : 10.1016/j.quascirev.2015.01.005 ^ Gutiérrez-Alonso, G.; Johnston, S.T.; Weil, A.B.; Pastor-Galán, D.; Fernández-Suárez, J. (2012). "Buckling an orogen: The Cantabrian Orocline" (PDF) . GSA Today . 22 (7): 4–9. doi : 10.1130/GSATG141A.1 . ^ Faccenna C., Piromallo C., Crespo-Blanc A., Jolivet L., Federico Rossetti F.(2004) Lateral slab deformation and
989-694: The Pacific Ocean. Further south it also possible to hint the less pronounced Maipo Orocline. The Bolivian Orocline is a seaward concave bending in the coast of South America and the Andes mountains at about 18° S. At this point the orientation of the Andes turns from Northwest in Peru to South in Chile and Argentina . The Andean segment north and south of the orocline have been rotated 15° to 20° counter clockwise and clockwise respectively. The orocline area overlaps with
1032-535: The RRF configuration could be stable under certain conditions. An RRR junction is always stable using these definitions and therefore very common on Earth, though in a geological sense ridge spreading is usually discontinued in one direction leaving a failed rift zone . There are many examples of these present both now and in the geological past such as the South Atlantic opening with ridges spreading North and South to form
1075-622: The arc of the Western Alps and Alps-Apennines transition in the light of new geophysical data on the lithospheric architecture around the Ligurian knot, EGU Conference Vienna Apennines_transition_in_the_light_of_new_geophysical_data_on_the_lithospheric_architecture_around_the_Ligurian_knot ^ Lahtinen, R.; Sayab, M.; Johnston, S.T. (2016). "Inari orocline – progressive or secondary orocline". Institute of Seismology, University of Helsinki Report S-65 . Lithosphere 2016 Ninth Symposium on
1118-560: The area of maximum width of the Altiplano Plateau . According to Isacks (1988) the orocline is related to crustal shortening . The specific point at 18° S where the coastline bends is known as the Arica Elbow . The Maipo Orocline or Maipo Transition Zone is an orocline located between 30° S and 38°S in the Andes with a break in trend at 33° S. The Arauco Orocline a subtle orocline located at 37° S in south-central Chile. It marks
1161-658: The coast of southern Chile . At each of these triple junctions an anomalous microplate exists, the Galapagos microplate at the northern junction and the Juan Fernandez microplate at the southern junction. The Easter Island microplate is a third microplate that is located just north of the Juan Fernandez Microplate and lies just west of Easter Island . The Carnegie Ridge is a 1,350-kilometre-long (840 mi) and up to 300-kilometre-wide (190 mi) feature on
1204-410: The geological details but simply by defining the properties of the ridges , trenches and transform faults involved, making some simplifying assumptions and applying simple velocity calculations. This assessment can generalise to most actual triple junction settings provided the assumptions and definitions broadly apply to the real Earth. A stable junction is one at which the geometry of the junction
1247-426: The intersection of three divergent boundaries or spreading ridges. These three divergent boundaries ideally meet at near 120° angles. In plate tectonics theory during the breakup of a continent, three divergent boundaries form, radiating out from a central point (the triple junction). One of these divergent plate boundaries fails (see aulacogen ) and the other two continue spreading to form an ocean. The opening of
1290-522: The junction of Qinling Orogen, Yangtze Craton and Tibetan Plateau: implications for the formation of the Dabashan Orocline and the growth of Tibetan Plateau" . Geophysical Journal International . 205 (3): 1670–1681. doi : 10.1093/gji/ggw096 . References [ edit ] Carey, S. Warren (1955), "The Orocline Concept in Geotectonics, Part I" (PDF) , Papers and Proceedings of
1333-685: The leading edge of South America: The Bolivian orocline revisited", Geology , 15 (9): 806–808, Bibcode : 1987Geo....15..806B , doi : 10.1130/0091-7613(1987)15<806:trotle>2.0.co;2 ^ Prezzi, Claudia B.; Vilas, Juan F. (1998). "New evidence of clockwise vertical axis rotations south of the Arica elbow (Argentine Puna)". Tectonophysics . 292 (1–2): 85–100. Bibcode : 1998Tectp.292...85P . doi : 10.1016/s0040-1951(98)00058-4 . ^ Arriagada, César; Ferrando, Rodolfo; Córdova, Loreto; Morata, Diego; Roperch, Pierrick (2013), "The Maipo Orocline: A first scale structural feature in
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1376-485: The ocean floor of the northern Nazca plate that includes the Galápagos archipelago at its western end. It is being subducted under South America with the rest of the Nazca plate. The absolute motion of the Nazca plate has been calibrated at 3.7 cm/year (1.5 in/year) east motion (88°), one of the fastest absolute motions of any tectonic plate. The subducting Nazca plate, which exhibits unusual flat slab subduction ,
1419-930: The origin of the western Mediterranean arcs, Tectonics, 23: (1) 1-21 [1] ^ Shaw J., Johnston S. T., The Carpathian–Balkan bends: an oroclinal record of ongoing Arabian–Eurasian collision, Journal of the Virtual Explorer, 43(4) [2] ^ Finetti et al, 2005, Crustal geological section across C Italy from the Corsica Basin to the Adriatic Sea based on geological and CROP Seismic data [ https://www.researchgate.net/publication/256305887_Crustal_geological_section_across_central_Italy_from_the_Corsica_Basin_to_the_Adriatic_Sea_based_on_geological_and_CROP_seismic_data/citation/download} ^ Edi Kissling E., Romain Bousquet R., Ford M., Schmid S. M. (2012) Formation of
1462-464: The purely kinematic point of view where the plates are rigid and moving over the surface of the Earth. No knowledge of the Earth's interior or the geological details of the crust are then needed. Another useful simplification is that the kinematics of triple junctions on a flat Earth are essentially the same as those on the surface of a sphere. On a sphere, plate motions are described as relative rotations about Euler poles (see Plate reconstruction ), and
1505-446: The radius of the Earth at the equator and poles only varies by a factor of roughly one part in 300 so the Earth approximates very well to a sphere. McKenzie and Morgan first analysed the stability of triple junctions using these assumptions with the additional assumption that the Euler poles describing the motions of the plates were such that they approximated to straight line motion on a flat surface. This simplification applies when
1548-518: The relative motion at every point along a plate boundary can be calculated from this rotation. But the area around a triple junction is small enough (relative to the size of the sphere) and (usually) far enough from the pole of rotation, that the relative motion across a boundary can be assumed to be constant along that boundary. Thus, analysis of triple junctions can usually be done on a flat surface with motions defined by vectors. Triple junctions may be described and their stability assessed without use of
1591-522: The ridge caused the subducted lithosphere to weaken and 'tear' from the point of the triple junction. The loss of slab pull caused by the detachment of this lithosphere ended the RTF junction giving the present day ridge – fault system. An RTF(a) is stable if ab goes through the point in velocity space C, or if ac and bc are colinear. A TTT(a) junction can be found in central Japan where the Eurasian plate overrides
1634-436: The same velocity space diagrams in the following way. The lines ab, bc and ca join points in velocity space which will leave the geometry of AB, BC and CA unchanged. These lines are the same as those that join points in velocity space at which an observer could move at the given velocity and still remain on the plate boundary. When these are drawn onto the diagram containing the velocity triangle these lines must be able to meet at
1677-443: The south Atlantic Ocean started at the south of the South American and African continents, reaching a triple junction in the present Gulf of Guinea , from where it continued to the west. The NE-trending Benue Trough is the failed arm of this junction. In the years since, the term triple-junction has come to refer to any point where three tectonic plates meet. The properties of triple junctions are most easily understood from
1720-718: The structure, composition and evolution of the lithosphere in Fennosscandia. pp. 69–74. ^ Cayley, R. (2014). "The Lachlan Orocline of Eastern Australia. Giant folds, the geodynamic processes that can form them, and how these new understandings have potential to revolutionise the resource prospectivity game in Eastern Australia" . New Perspectives Workshop, September 2014 . Australian Institute of Geoscientists . Retrieved 4 March 2018 . ^ Chengxin Jiang; Yingjie Yang; Yong Zheng (2016). "Crustal structure in
1763-499: The types of plate boundaries meeting – for example RRR, TTR, RRT, FFT etc. – and secondly by the relative motion directions of the plates involved. Some configurations such as RRR can only have one set of relative motions whereas TTT junctions may be classified into TTT(a) and TTT(b). These differences in motion direction affect the stability criteria. McKenzie and Morgan claimed that of these 16 types, 14 were stable with FFF and RRF configurations unstable, however, York later showed that
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1806-433: The velocities A v B , B v C and C v A respectively. Further conditions must also be met for the triple junction to exist stably – the plates must move in a way that leaves their individual geometries unchanged. Alternatively the triple junction must move in such a way that it remains on all three of the plate boundaries involved. McKenzie and Morgan demonstrated that these criteria can be represented on
1849-550: Was the strongest instrumentally recorded earthquake occurring deeper than 300 km (190 mi). 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. 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 Mya ,
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