Ryukyu Arc: Difference between revisions

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{{Short description|Volcanic island arc between Kyushu and Taiwan}}

[[File:The Ryukyu Arc Map.png|thumb|upright=1.9|Map of the Ryukyu Arc. Red triangles represent volcanoes based on Aster Volcano Archive (NASA-METI) data. Contours in 1 km intervals. Figure made with GeoMapApp (www.geomapapp.org) / CC BY / CC BY (Ryan et al., 2009).<ref name="fig">{{Cite journal|last1=Ryan|first1=William B. F.|last2=Carbotte|first2=Suzanne M.|author-link2=Suzanne Carbotte|last3=Coplan|first3=Justin O.|last4=O'Hara|first4=Suzanne|last5=Melkonian|first5=Andrew|last6=Arko|first6=Robert|last7=Weissel|first7=Rose Anne|last8=Ferrini|first8=Vicki|last9=Goodwillie|first9=Andrew|last10=Nitsche|first10=Frank|last11=Bonczkowski|first11=Juliet|date=March 2009|title=Global Multi-Resolution Topography synthesis|journal=Geochemistry, Geophysics, Geosystems|volume=10|issue=3|pages=n/a|doi=10.1029/2008gc002332|bibcode=2009GGG....10.3014R|issn=1525-2027|doi-access=free}}</ref>]]

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">Kiszaki,{{cite journal |last1=Kizaki |first1=K. (1978). |title=Tectonics of the Ryukyu Island Arc. ''|journal=Journal of Physics of the Earth, |date=1978 |volume=26''( |issue=Supplement), |pages=S301–S307. https://|doi.org/=10.4294/jpe1952.26.Supplement_S301}}</ref><ref name=":2">{{cite journal |last1=Shinjo, |first1=R., & |last2=Kato, |first2=Y. (2000). |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. https://|doi.org/=10.1016/S0024-4937(00)00034-7}}</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. (1998). |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. https://|doi.org/=10.1016/S0040-1951(98)00150-4}}</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., and |last4=Kimura, |first4=M. (1999), |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, ''J.|journal=Journal Geophys.of Res.,Geophysical Research: Solid Earth |date=1999 |volume=104''( |issue=B5), 10591– 10608,|pages=10591–10608 |doi:=10.1029/1999JB900040.}}</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. (2013). |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}}</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. (1986). |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}}</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|metamorphic rocks]], ranging from the [[Paleozoic]] to [[Cenozoic]] in age.

== Geological setting ==

A number of studies defined the extent of the Ryukyu Arc geographically and morphologically into three parts: Northern Ryukyu, which includes the [[Ōsumi Islands]]; Central Ryukyu, which includes [[Amami Islands]] and [[Okinawa Islands]]; Southern Ryukyu, which includes [[Miyako Islands]] and [[Yaeyama Islands]].<ref name=":1" /><ref name=":5" /> The northernmost and southernmost parts of the Ryukyu Arc terminate in Kyushu and Taiwan, respectively.<ref name=":9">{{cite report|last1=Foster,|first1= H. L. (|date=1965). ''|title=Geology of Ishigaki-shima, Ryukyu-retto''. |series=US Geol.Geological Surv.Survey, Prof.Professional Paper.Papers|publisher=US https://pubsGeological Survey|doi=10.usgs.gov3133/pp/0399a/report.pdfpp399A}}</ref>

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">Taira, A., Ohara, Y., Wallis, S. R., Ishiwatari, A., & Iryu, Y. (2016). Geological evolution of Japan: an overview. ''The geology of Japan'', 1–24.</ref><ref name=":26">Takami, M., Takemura, R., Nishimura, Y., & Kojima, T. (1999). Reconstruction of oceanic plate stratigraphies and unit division of Jurassic-Early Cretaceous accretionary complexes in the Okinawa Islands, central Ryukyu Island Arc. ''The Journal of the Geological Society of Japan, 105''(12), 866–880. https://doi.org/10.5575/geosoc.105.866</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" />