The islands ofJapanare primarily the result of several large ocean movements occurring over hundreds of millions of years from the mid-Silurianto thePleistocene,as a result of thesubductionof thePhilippine Sea Platebeneath the continentalAmurian PlateandOkinawa Plateto the south, and subduction of thePacific Plateunder theOkhotsk Plateto the north.

The islands of Japan were separated from mainland Asia byback-arc spreading.

Japan was originally attached to the eastern coast of theEurasiancontinent. The subducting plates, being deeper than the Eurasian plate, pulled Japan eastward in the process ofback-arc extension,opening theSea of Japanaround 15 million years ago.[1]TheStrait of Tartaryand theKorea Straitopened much later.

Japan is situated in avolcaniczone on thePacific Ring of Fire.Frequent low intensity earth tremors and occasional volcanic activity are felt throughout the islands. Destructiveearthquakes,often resulting intsunamis,occur several times per century. The most recent major quakes include the2024 Noto earthquake,the2011 Tōhoku earthquake and tsunami,the2004 Chūetsu earthquake,and theGreat Hanshin earthquakeof 1995.

The geological features and bedrock composition of the Japanese main islands

Geological history

edit

Orogeny phase

edit
Japanese archipelago relief (including submerged parts)

The breakup ofRodiniaabout 750 million years ago formed thePanthalassaocean, with rocks that eventually became Japan sitting on its eastern margin.[2]In theEarly Silurian(450 million years ago),[3]the subduction of the oceanic plates started, and this process continues to the present day, forming a roughly 400 km wideorogenyat theconvergent boundary.Several (9 or 10) oceanic plates were completely subducted and their remains have formedpaired metamorphic belts.The most recent complete subduction of a plate was that of theIzanagi Plate95 million years ago. Currently the Philippine Sea Plate is subducting beneath the continental Amurian Plate and the Okinawa Plate to the south at a speed of 4 cm/year, forming theNankai Troughand theRyukyu Trench.The Pacific Plate is subducting under the Okhotsk Plate to the north at a speed of 10 cm/year. The early stages of subduction-accretion have recycled the continental crust margin several times, leaving the majority of the modernJapanese archipelagocomposed of rocks formed in thePermianperiod or later.

Island arc phase

edit

Around 23 million years ago, western Japan was a coastal region of the Eurasia continent. The subducting plates, being deeper than the Eurasian plate, pulled parts of Japan which become modernChūgoku regionandKyushueastward, opening the Sea of Japan (simultaneously with theSea of Okhotsk) around 15–20 million years ago, with likely freshwater lake state before the sea has rushed in.[4]Around 16 million years ago, in theMioceneperiod, a peninsula attached to the eastern coast of theEurasiancontinent was well formed. About 11 million years before present, the parts of Japan which become modernTōhokuandHokkaidowere gradually uplifted from the seafloor, and terranes ofChūbu regionwere gradually accreted from the colliding island chains. The Strait of Tartary and the Korea Strait opened much later, about 2 million years ago. At the same time, a severe subduction ofFossa Magnagraben have formed theKantō Plain.[5]

Current state

edit

General information

edit

Overall, the geological composition of Japan is poorly understood. The Japanese islands are formed of several geological units parallel to the subduction front. The parts of islands facing oceanic plates are typically younger and display a larger proportion of volcanic products, while the parts facing the Sea of Japan are mostly heavily faulted and folded sedimentary deposits. In northwest[vague]Japan, the thickQuaternarydeposits make determination of the geological history especially difficult.[6]

Geological structure

edit

The Japanese islands are divided into three major geological domains:

Research

edit

The Geology of Japan is handled mostly byGeological Society of Japan[ja],with the following major periodicals:

Geological hazards

edit

Japan is in a volcanic zone on the Pacific Ring of Fire. Frequent low intensity earth tremors and occasional volcanic activity are felt throughout the islands. Destructive earthquakes, often resulting in tsunamis, occur several times a century. The most recent major quakes include the 2011 Tōhoku earthquake and tsunami, the 2004 Chūetsu earthquake and the Great Hanshin earthquake of 1995.

See also

edit

References

edit
  1. ^Barnes, Gina L. (2003)."Origins of the Japanese Islands: The New" Big Picture ""(PDF).University of Durham.Archived fromthe original(PDF)on April 28, 2011.RetrievedAugust 11,2009.
  2. ^Wakita, Koji (2013-08-10)."Geology and tectonics of Japanese islands: A review – The key to understanding the geology of Asia".Journal of Asian Earth Sciences.Geological Evolution of Asia.72:75–87.Bibcode:2013JAESc..72...75W.doi:10.1016/j.jseaes.2012.04.014.ISSN1367-9120.
  3. ^Bor-ming Jahn(2010)."ACCRETIONARY OROGEN AND EVOLUTION OF THE JAPANESE ISLANDS—IMPLICATIONS FROM A Sr-Nd ISOTOPIC STUDY OF THE PHANEROZOIC GRANITOIDS FROM SW JAPAN"(PDF).American Journal of Science.310(10). American Journal of Science, Vol. 310, December, 2010, P. 1210–1249, DOI 10.2475/10.2010.02:1210–1249.Bibcode:2010AmJS..310.1210J.doi:10.2475/10.2010.02.S2CID129989718.Archived fromthe original(PDF)on August 9, 2017.RetrievedOctober 10,2017.
  4. ^Barnes, Gina L. (2003)."Origins of the Japanese Islands: The New" Big Picture ""(PDF).University of Durham.Archived fromthe original(PDF)on April 28, 2011.RetrievedAugust 11,2009.
  5. ^"Formation history of the Japanese Islands (4) -- GLGArcs".glgarcs.rgr.jp. Archived fromthe originalon December 1, 2017.RetrievedJuly 16,2017.
  6. ^"Geology of Japan|Geological Survey of Japan, AIST| sản tổng nghiên địa chất điều tra tổng hợp センター / Geological Survey of Japan, AIST".gsj.jp.RetrievedJuly 16,2017.
  7. ^"Yurie SAWAHATA, Makoto Okada, Jun Hosoi, Kazuo Amano," Paleomagnetic study of Neogene sediments in strike-slip basins along the Tanagura Fault ".confit.atlas.jp.RetrievedJuly 16,2017.
  8. ^[email protected]."Southwest Japan".geo.arizona.edu. Archived fromthe originalon October 10, 2017.RetrievedJuly 16,2017.
  9. ^A. Taira, H. Okada, J. H. McD. Whitaker & A. J. Smith, The Shimanto Belt of Japan: Cretaceous-lower Miocene active-margin sedimentation
  10. ^"Sanbagawa belt (Sambagawa metamorphic belt), Shikoku Island, Japan".mindat.org.RetrievedJuly 16,2017.
  11. ^"Chichibu belt from geo.arizona.edu".geo.arizona.edu. Archived fromthe originalon December 5, 2017.RetrievedJuly 16,2017.

Further reading

edit
  • Hashimoto, M., ed. (1990).Geology of Japan.Dordrecht: Kluwer Academic Publishers.ISBN9780792309093.
  • T. Moreno; S.R. Wallis; T. Kojima; W. Gibbons, eds. (16 March 2016).Geology of Japan (Geological Society of London)(2015).ISBN978-1862397439.

by - (Author),

  • Takai, Fuyuji; Tatsurō Matsumoto; Ryūzō Toriyama (1963).Geology of Japan.University of California Press.
edit
External image
Statistical map of location, size and depth of earthquakes near Japan