Editing Geography of Japan (section)

==Geology==
[[File:Japan separation.png|thumb|upright=1.3|The islands comprising the [[Japanese Archipelago]] were separated from the Asian continent by [[back-arc spreading]].]]
[[File:Tectonic map of Japan-fr.png|thumb|upright=1.3|Tectonic map of Japan (French)]]
{{main|Geology of Japan}}

===Tectonic plates===
The Japanese archipelago is the result of subducting [[tectonic plates]] over several 100 million years, from the mid-[[Silurian]] (443.8 Mya) to the [[Pleistocene]] (11,700 years ago). Approximately {{convert|15000|km|mi|abbr=on}} of oceanic floor has passed under the Japanese archipelago in the last 450 million years, with most being fully subducted. It is considered a mature [[island arc]].

The islands of Japan were created by tectonic plate movements:
* [[Tohoku]] (upper half of Honshu), Hokkaido, the Kuril Islands, and Sakhalin are located on the [[Okhotsk Plate]]. This is a minor tectonic plate bounded to the north by the [[North American Plate]].<ref>Seno et al., 1996 Journal of Geophysical Research; https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/96JB00532{{Dead link|date=December 2022 |bot=InternetArchiveBot |fix-attempted=yes }}</ref><ref>Apel et al., 2006 Geophysical Research Letters; http://onlinelibrary.wiley.com/wol1/doi/10.1029/2006GL026077/full</ref> The Okhotsk Plate is bounded on the east by the [[Pacific Plate]] at the Kuril–Kamchatka Trench and the Japan Trench. It is bounded on the south by the [[Philippine Sea Plate]] at the [[Nankai Trough]]. On the west, it is bound by the [[Eurasian Plate]], and possibly on the southwest, by the [[Amurian Plate]]. The northeastern boundary is the [[Ulakhan Fault]].<ref>http://www.stephan-mueller-spec-publ-ser.net/4/147/2009/smsps-4-147-2009.pdf {{Webarchive|url=https://web.archive.org/web/20180721230444/https://www.stephan-mueller-spec-publ-ser.net/4/147/2009/smsps-4-147-2009.pdf |date=2018-07-21 }} {{Bare URL PDF|date=March 2022}}</ref>
* The southern half of Honshu, Shikoku, and most of Kyushu are located on the Amurian Plate.
* The southern tip of Kyushu and the Ryukyu islands are located on the [[Okinawa Plate]].
* The Nanpō Islands are on the [[Philippine Sea Plate]].

The Pacific Plate and Philippine Sea Plate are [[subduction]] plates. They are deeper than the Eurasian plate. The Philippine Sea Plate moves beneath the continental Amurian Plate and the Okinawa Plate to the south. The Pacific Plate moves under the Okhotsk Plate to the north. These subduction plates pulled Japan eastward and opened the Sea of Japan by [[back-arc spreading]] around 15 million years ago.<ref name="Barnes">{{cite web |url=http://shinku.nichibun.ac.jp/jpub/pdf/jr/IJ1501.pdf |last=Barnes |first=Gina L. |title=Origins of the Japanese Islands: The New "Big Picture" |publisher=[[University of Durham]] |year=2003|access-date=August 11, 2009|archive-url=https://web.archive.org/web/20110428043510/http://shinku.nichibun.ac.jp/jpub/pdf/jr/IJ1501.pdf|archive-date=April 28, 2011|url-status=dead}}</ref> The [[Strait of Tartary]] and the [[Korea Strait]] opened much later. [[La Pérouse Strait]] formed about 60,000 to 11,000 years ago, closing the path used by mammoths, which had earlier moved to northern Hokkaido.<ref name="brit" /> The [[eastern margin of the Sea of Japan]] is an incipient subduction zone consisting of thrust faults that formed from the compression and reactivation of old faults involved in earlier rifting.<ref name="Tamaki85">{{cite journal |last1=Tamaki |first1=Kensaku |last2=Honza |first2=Eiichi |title=Incipient subduction and deduction along the eastern margin of the Japan Sea |journal=[[Tectonophysics (journal)|Tectonophysics]] |date=20 October 1985 |volume=119 |issue=1–4 |pages=381–406 |doi=10.1016/0040-1951(85)90047-2 |bibcode=1985Tectp.119..381T }}</ref>

The subduction zone is where the [[oceanic crust]] slides beneath the [[continental crust]] or other oceanic plates. This is because the oceanic plate's litosphere has a higher density. Subduction zones are sites that usually have a high rate of volcanism and earthquakes.<ref>{{Cite journal |last=Martínez-López, M.R., Mendoza, C. |year=2016 |title=Acoplamiento sismogénico en la zona de subducción de Michoacán-Colima-Jalisco,México |journal=Boletín de la Sociedad Geológica Mexicana |language=es |volume=68 |issue=2 |pages=199–214 |doi=10.18268/BSGM2016v68n2a3|doi-access=free|bibcode=2016BoSGM..68..199M }}</ref> Additionally, subduction zones develop [[orogen|belts]] of [[deformation (geology)|deformation]].<ref>{{cite web |url=http://snl.no/orogenese |title=Orogenese |access-date=July 2, 2014 |date=February 14, 2009 |website=[[Store norske leksikon]] |language=no |archive-date=July 14, 2014 |archive-url=https://web.archive.org/web/20140714212710/http://snl.no/orogenese |url-status=live }}</ref> The subduction zones on the east side of the Japanese archipelago cause frequent low-intensity earth tremors. Major earthquakes, volcanic eruptions, and tsunamis occur several times per century. It is part of the Pacific Ring of Fire.<ref name="Barnes" /> Northeastern Japan, north of the [[Tanakura fault]], had high volcanic activity 14–17&nbsp;million years before the present.<ref name="atlas">{{cite web |url=https://confit.atlas.jp/guide/event-img/jpgu2016/SGL36-P01/public/pdf?type=in |publisher=confit.atlas.jp |title=Yurie SAWAHATA, Makoto Okada, Jun Hosoi, Kazuo Amano, "Paleomagnetic study of Neogene sediments in strike-slip basins along the Tanakura Fault |access-date=July 16, 2017 |archive-date=October 20, 2022 |archive-url=https://web.archive.org/web/20221020122154/https://confit.atlas.jp/guide/event-img/jpgu2016/SGL36-P01/public/pdf?type=in |url-status=live }}</ref>

=== Median Tectonic Line ===
[[Image:Tectonic map of southwest Japan.png|thumb|upright=1.3|left|The red line represents the Median Tectonic Line. The orange-shaded region is Fossa Magna, bounded by the [[Itoigawa-Shizuoka Tectonic Line]] (western blue line).]]
The [[Japan Median Tectonic Line]] (MTL) is Japan's longest [[Fault (geology)|fault]] system.<ref name="d">{{cite encyclopedia |encyclopedia=Dijitaru Daijisen |title=中央構造線 |url=http://rekishi.jkn21.com/ |access-date=2012-09-21 |year=2012 |publisher=Shogakukan |location=Tokyo |language=ja |trans-title=Japan Median Tectonic Line (MTL) |oclc=56431036 |url-status=dead |archive-url=https://web.archive.org/web/20070825113418/http://rekishi.jkn21.com/ |archive-date=2007-08-25}}</ref><ref name="n">{{cite encyclopedia |encyclopedia=Nihon Daihyakka Zensho (Nipponika) |title=中央構造線 |url=http://rekishi.jkn21.com/ |access-date=2012-09-21 |year=2012 |publisher=Shogakukan |location=Tokyo |language=ja |trans-title=Japan Median Tectonic Line |oclc=153301537 |url-status=dead |archive-url=https://web.archive.org/web/20070825113418/http://rekishi.jkn21.com/ |archive-date=2007-08-25}}</ref> The MTL begins near [[Ibaraki Prefecture]], where it connects with the [[Itoigawa-Shizuoka Tectonic Line]] (ISTL) and the Fossa Magna. It runs parallel to Japan's volcanic arc, passing through central Honshū to near [[Nagoya]], through [[Mikawa Bay]], then through the Seto Inland Sea from the [[Kii Channel]] and [[Naruto Strait]] to Shikoku along the [[Sadamisaki Peninsula]] and the [[Bungo Channel]] and [[Hōyo Strait]] to Kyūshū.<ref name="n" />

The MTL moves right-lateral strike-slip at about 5–10 millimeters per year.<ref>Okada, A., On the Quaternary faulting along the Median Tectonic Line, in ''Median Tectonic Line'' (in Japanese with English abstract), edited by R. Sugiyama, pp. 49–86, Tokai University Press, Tokyo, 1973.</ref> The sense of motion is consistent with the direction of the [[Nankai Trough]]'s oblique convergence. The rate of motion on the MTL is much less than the rate of convergence at the [[Nankai Trough|plate boundary]]. This makes it difficult to distinguish the motion on the MTL from interseismic elastic straining in GPS data.<ref>Miyazaki, S. and Heki, K. (2001) Crustal velocity field of southwest Japan: Subduction and arc-arc collision, ''Journal of Geophysical Research'',vo. 106, no. B3.</ref>

===Oceanic trenches===
[[File:Japan_Trench_Map.jpg|thumb|upright=1.3|The map depicts the [[Kuril–Kamchatka Trench]], [[Japan Trench]], [[Izu–Ogasawara Trench]], and [[Mariana Trench]].]]
East of the Japanese archipelago are three oceanic trenches.
* The [[Kuril–Kamchatka Trench]] is in the northwest Pacific Ocean. It lies off the southeast coast of [[Kamchatka Peninsula|Kamchatka]] and parallels the Kuril Island chain to meet the Japan Trench east of Hokkaido.<ref name=USGS>Rhea, S., et al., 2010, ''Seismicity of the Earth 1900–2007, Kuril–Kamchatka arc and vicinity'', U.S. Geological Survey Open-File Report 2010-1083-C, 1 map sheet, scale 1:5,000,000 http://pubs.usgs.gov/of/2010/1083/c/ {{Webarchive|url=https://web.archive.org/web/20171209203950/https://pubs.usgs.gov/of/2010/1083/c/ |date=2017-12-09 }}</ref>
* The [[Japan Trench]] extends {{convert|8000.|km|mi|abbr=on}} from the Kuril Islands to the northern end of the Izu Islands. Its deepest part is {{convert|8046|m|ft|abbr=on}}.<ref>{{cite web |url=https://www.gmrt.org/about/index.php |title=GMRT Overview |last=O'Hara |first=Design by J. Morton, V. Ferrini, and S. |website=www.gmrt.org |access-date=2018-05-27 |archive-date=2023-03-08 |archive-url=https://web.archive.org/web/20230308011339/https://www.gmrt.org/about/index.php |url-status=live }}</ref> The Japan Trench is created as the oceanic Pacific Plate subducts beneath the continental Okhotsk Plate. The subduction process causes bending of the down-going plate, creating a deep trench. Continuous movement on the subduction zone associated with the Japan Trench is one of the main causes of tsunamis and earthquakes in northern Japan, including the [[Megathrust earthquake|megathrust]] 2011 Tōhoku earthquake and tsunami. The rate of subduction associated with the Japan Trench has been recorded at about {{cvt|7.9|–|9.2|cm}}/year.<ref name="revel"/>
* The [[Izu–Ogasawara Trench]] is south of the Japan Trench in the western Pacific Ocean. It consists of the Izu Trench (at the north) and the Bonin Trench (at the south, west of the Ogasawara Plateau).<ref>{{cite web |title=Locator map |url=http://www.soest.hawaii.edu/expeditions/mariana/images/regional_locator.jpg |website=Expedition to the Mariana forearc |publisher=School of Ocean and Earth Science and Technology at the University of Hawaii |access-date=2018-10-01 |archive-date=2016-03-03 |archive-url=https://web.archive.org/web/20160303201252/http://www.soest.hawaii.edu/expeditions/mariana/images/regional_locator.jpg |url-status=live }}</ref> It stretches to the northernmost section of the [[Mariana Trench]].<ref>{{Cite web |url=http://www.agu.org/pubs/crossref/2000/1999JC900324.shtml |title=Deep current structure above the Izu-Ogasawara Trench |access-date=2018-10-01 |archive-date=2012-03-01 |archive-url=https://web.archive.org/web/20120301205341/http://www.agu.org/pubs/crossref/2000/1999JC900324.shtml |url-status=dead}}</ref> The Izu–Ogasawara Trench is an extension of the Japan Trench. There, the Pacific Plate is being subducted beneath the Philippine Sea Plate, creating the Izu Islands and Bonin Islands on the [[Izu–Bonin–Mariana Arc]] system.<ref name="izu-ogasawara-arc">{{cite web |url=http://www.terrapub.co.jp/journals/EPS/pdf/2006e/5808e033.pdf |archive-url=https://web.archive.org/web/20171029065154/http://www.terrapub.co.jp/journals/EPS/pdf/2006e/5808e033.pdf |archive-date=October 29, 2017 |title=Crustal structure of the ocean-island arc transition at the mid Izu–Ogasawara (Bonin) arc margin |publisher=Earth, Planets and Space |access-date=October 2, 2018}}</ref>

===Composition===
The Japanese islands are formed of the mentioned geological units parallel to the subduction front. The parts of islands facing the [[Pacific Plate]] are typically younger and display a larger proportion of volcanic products, while island parts facing the [[Sea of Japan]] are mostly heavily faulted and folded sedimentary deposits. In northwest Japan, there are thick [[quaternary]] deposits. This makes the determination of the geological history and composition difficult, and it is not yet fully understood.<ref name="gsj">{{cite web |url=https://www.gsj.jp/en/education/geomap-e/geology-e.html |publisher=gsj.jp |title=Geology of Japan{{pipe}}Geological Survey of Japan, AIST{{pipe}}産総研地質調査総合センター / Geological Survey of Japan, AIST |access-date=July 16, 2017 |archive-date=December 1, 2021 |archive-url=https://web.archive.org/web/20211201125222/https://www.gsj.jp/en/education/geomap-e/geology-e.html |url-status=live }}</ref>

The Japanese island arc system has distributed volcanic series where the volcanic rocks change from tholeiite—calc-alkaline—alkaline with increasing distance from the trench.<ref name=":2">{{Cite journal |last=Gill |first=J.B. |date=1982 |title=Andesites: Orogenic andesites and related rocks |journal=Geochimica et Cosmochimica Acta |volume=46 |issue=12 |pages=2688 |doi=10.1016/0016-7037(82)90392-1 |issn=0016-7037}}</ref><ref>{{cite journal |last1=Pearce |first1=J |last2=Peate |first2=D |date=1995 |title=Tectonic Implications of the Composition of Volcanic ARC Magmas |journal=Annual Review of Earth and Planetary Sciences |pages=251–285 |volume=23 |issue=1 |doi=10.1146/annurev.ea.23.050195.001343 |bibcode=1995AREPS..23..251P}}</ref> The [[geologic province]] of Japan is mostly [[structural basin|basin]] and has a bit of [[Crust (geology)|extended crust]].<ref>{{cite web |title=Geologic Province and Thermo-Tectonic Age Maps |url=https://earthquake.usgs.gov/research/structure/crust/maps.php |website=Earthquake Hazards Program |publisher=United States Geological Survey |access-date=6 June 2014 |url-status=dead |archive-url=https://web.archive.org/web/20140607001305/http://earthquake.usgs.gov/research/structure/crust/maps.php |archive-date=7 June 2014}}</ref>