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{{Short description|Island arc between Kyushu and Taiwan}}
[[File:The Ryukyu Arc Map.png|thumb|upright=1.
The '''Ryukyu Arc''' is an [[island arc]] which extends from the south of [[Kyushu]] along the [[Ryukyu Islands]] to the northeast of [[Taiwan]], spanning about {{convert|1200|km|mi}}.<ref name=":1">{{cite journal |last1=Kizaki |first1=K. |title=Tectonics of the Ryukyu Island Arc |journal=Journal of Physics of the Earth |date=1978 |volume=26 |issue=Supplement |pages=S301–S307 |doi=10.4294/jpe1952.26.Supplement_S301|doi-access=free }}</ref><ref name=":2">{{cite journal |last1=Shinjo |first1=R. |last2=Kato |first2=Y. |title=Geochemical constraints on the origin of bimodal magmatism at the Okinawa Trough, an incipient back-arc basin |journal=Lithos |date=2000 |volume=54 |issue=3–4 |pages=117–137 |doi=10.1016/S0024-4937(00)00034-7|bibcode=2000Litho..54..117S }}</ref><ref name=":3">{{cite journal |last1=Park |first1=J.-O. |last2=Tokuyama |first2=H. |last3=Shinohara |first3=M. |last4=Suyehiro |first4=K. |last5=Taira |first5=A. |title=Seismic record of tectonic evolution and backarc rifting in the southern Ryukyu island arc system |journal=Tectonophysics |date=1998 |volume=294 |issue=1–2 |pages=21–42 |doi=10.1016/S0040-1951(98)00150-4|bibcode=1998Tectp.294...21P }}</ref> It is located along a section of the [[Convergent boundary|convergent plate boundary]] where the [[Philippine Sea Plate]] is subducting northwestward beneath the [[Eurasian Plate]] along the [[Ryukyu Trench]].<ref name=":2" /><ref name=":3" /><ref name=":4">{{cite journal |last1=Shinjo |first1=R. |last2=Chung |first2=S.-L. |last3=Kato |first3=Y. |last4=Kimura |first4=M. |title=Geochemical and Sr-Nd isotopic characteristics of volcanic rocks from the Okinawa Trough and Ryukyu Arc: Implications for the evolution of a young, intracontinental back arc basin |journal=Journal of Geophysical Research: Solid Earth |date=1999 |volume=104 |issue=B5 |pages=10591–10608 |doi=10.1029/1999JB900040|bibcode=1999JGR...10410591S |doi-access=free }}</ref> The arc has an overall northeast to southwest trend and is located northwest of the [[Pacific Ocean]] and southeast of the [[East China Sea]].<ref name=":6">{{cite journal |last1=Nakae |first1=S. |title=The radiolarian evidence for the accretion of the Fu-saki Formation with the inferred oceanic plate stratigraphy: A case of weakly-metamorphosed accretionary complex in Ishigaki Jima, southern Ryukyu Arc, Japan |journal=Journal of Asian Earth Sciences |date=2013 |volume=73 |pages=21–30 |doi=10.1016/j.jseaes.2013.04.022|bibcode=2013JAESc..73...21N }}</ref> It runs parallel to the [[Okinawa Trough]], an active volcanic arc, and the Ryukyu Trench.<ref name=":5">{{cite journal |last1=Kizaki |first1=K. |title=Geology and tectonics of the Ryukyu Islands |journal=Tectonophysics |date=1986 |volume=125 |issue=1–3 |pages=193–207 |doi=10.1016/0040-1951(86)90014-4|bibcode=1986Tectp.125..193K }}</ref> The Ryukyu Arc, based on its geomorphology, can be segmented from north to south into Northern Ryukyu, Central Ryukyu, and Southern Ryukyu; the Tokara Strait separates Northern Ryukyu and Central Ryukyu at about 130˚E while the [[Miyako Strait|Kerama Gap]] separates Central Ryukyu and Southern Ryukyu at about 127 ˚E.<ref name=":1" /><ref name=":4" /><ref name=":5" /> The geological units of the arc include [[Igneous rock|igneous]], [[Sedimentary rock|sedimentary]], and [[metamorphic rock]]s, ranging from the [[Paleozoic]] to [[Cenozoic]] in age.
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The geological and structural features of Southern Ryukyu are quite different from those of Northern and Central Ryukyu; Southern Ryukyu, and Northern and Central Ryukyu may have developed in disparate geological settings before the middle [[Miocene]].<ref name=":1" /> [[Accretionary wedge|Accretionary complexes]] in Northern and Central Ryukyu are considered as the extension of the Outer Zone of Southwest Japan,<ref name=":5" /><ref name=":25">{{cite book|last1=Taira|first1= A.|last2= Ohara|first2= Y.|last3= Wallis|first3= S. R.|last4=Ishiwatari|first4= A.|last5= Iryu|first5= Y. |date=2016|chapter=Geological evolution of Japan: an overview|title=The geology of Japan|pages=1–24|doi=10.1144/GOJ.1|editor-first1=T.|editor-last1= Moreno|editor-first2= S. |editor-last2=Wallis|editor-first3= T. |editor-last3=Kojima|editor-first4=W. |editor-last4=Gibbons|isbn=9781862397064|publisher=The Geological Society}}</ref><ref name=":26">{{cite journal |last1=Takami |first1=M. |last2=Takemura |first2=R. |last3=Nishimura |first3=Y. |last4=Kojima |first4=T. |title=Reconstruction of oceanic plate stratigraphies and unit division of Jurassic-Early Cretaceous accretionary complexes in the Okinawa Islands, central Ryukyu Island Arc. |journal=The Journal of the Geological Society of Japan |date=1999 |volume=105 |issue=12 |pages=866–880 |doi=10.5575/geosoc.105.866|doi-access=free }}</ref> whereas metamorphic rocks in Southern Ryukyu are associated with the Inner Zone of Southwest Japan.<ref name=":14" /> The arc might be united into the present configuration in the [[Pliocene]]-[[Pleistocene]] due to different rates of southeastward migration as tectonics proceeded.<ref name=":1" />
[[File:Location of the Ryukyu Islands.JPG|thumb|upright=1.5|Location of the Ryukyu Islands
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The Ryukyu Arc is a site of active [[seismicity]] characterised by shallow earthquakes, given the ongoing convergence between the Philippine Sea Plate and Eurasian Plate.<ref name=":9" /> Seismic data of earthquakes have been used to detect seismic structures below the Ryukyu Arc.<ref name="a">{{cite journal |last1=Roecker |first1=S. W. |last2=Yeh |first2=Y. H. |last3=Tsai |first3=Y. B. |title=Three-dimensional P and S wave velocity structures beneath Taiwan: Deep structure beneath an arc-continent collision |journal=Journal of Geophysical Research: Solid Earth |date=1987 |volume=92 |issue=B10 |pages=10547–10570 |doi=10.1029/JB092iB10p10547|bibcode=1987JGR....9210547R |doi-access=free }}</ref> [[Low-velocity zone|Low seismic velocity zones]], which are possibly associated with the upwelling of magma, have been discovered beneath active volcanoes and the Okinawa Trough.<ref name="a" />
[[File:M≥6.0 (1960-2022) Earthquakes in the Ryukyu Arc.png|thumb|upright=
=== Volcanoes ===
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