Izanagi Plate

The Izanagi Plate (named after the Shinto god Izanagi) was an ancient tectonic plate, which began subducting beneath the Okhotsk Plate 130–100 Ma years ago. The rapid plate motion of the Izanagi Plate caused north-west Japan and the outer zone of south-west Japan to drift northward. High-pressure metamorphic rocks were formed at the eastern margin of the drifting land mass in the Sanbagawa metamorphic belt, while low-pressure metamorphic rocks were formed at its western margin in the Abukuma metamorphic belt. At approximately 95 Ma, the Izanagi Plate was completely subducted and replaced by the western Pacific Plate, which also subducted in the north-western direction. Subduction-related magmatism took place near the Ryoke belt. No marked tectonics occurred in the Abunkuma belt after the change of the subducted plate.

The discovery of an extinct Jurassic–Cretaceous spreading system in the north-west Pacific led to the introduction of the extinct Kula Plate in 1972. The Izanagi Plate was subsequently introduced in 1982 to explain the geometry of this spreading system.[1] Knowledge of the now-subducted Izanagi Plate is limited to Mesozoic magnetic lineations on the Pacific Plate that preserve the record of this subduction.[2]

See also

References

Notes
  1. ^ Woods & Davies 1982, Abstract
  2. ^ Seton et al. 2012, Izanagi Plate, pp. 225–227
Sources
  • Seton, M.; Müller, R. D.; Zahirovic, S.; Gaina, C.; Torsvik, T.; Shephard, G.; Talsma, A.; Gurnis, M.; Maus, S.; Chandler, M. (2012). "Global continental and ocean basin reconstructions since 200Ma" (PDF). Earth-Science Reviews. 113 (3): 212–270. doi:10.1016/j.earscirev.2012.03.002. Retrieved 23 October 2016.
  • Woods, M. T.; Davies, G. F. (1982). "Late Cretaceous genesis of the Kula plate". Earth and Planetary Science Letters. 58 (2): 161–166. doi:10.1016/0012-821X(82)90191-1.

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Farallon Plate

The Farallon Plate was an ancient oceanic plate that began subducting under the west coast of the North American Plate—then located in modern Utah—as Pangaea broke apart during the Jurassic period. It is named for the Farallon Islands, which are located just west of San Francisco, California.

Over time, the central part of the Farallon Plate was completely subducted under the southwestern part of the North American Plate. The remains of the Farallon Plate are the Juan de Fuca, Explorer and Gorda Plates, subducting under the northern part of the North American Plate; the Cocos Plate subducting under Central America; and the Nazca Plate subducting under the South American Plate.The Farallon Plate is also responsible for transporting old island arcs and various fragments of continental crustal material rifted off from other distant plates and accreting them to the North American Plate.

These fragments from elsewhere are called terranes (sometimes, "exotic" terranes). Much of western North America is composed of these accreted terranes.

Geology of Japan

The islands of Japan are primarily the result of several large ocean movements occurring over hundreds of millions of years from the mid-Silurian to the Pleistocene as a result of the subduction of the Philippine Sea Plate beneath the continental Amurian Plate and Okinawa Plate to the south, and subduction of the Pacific Plate under the Okhotsk Plate to the north.

Japan was originally attached to the eastern coast of the Eurasian continent. The subducting plates, being deeper than the Eurasian plate, pulled Japan eastward, opening the Sea of Japan around 15 million years ago. The Strait of Tartary and the Korea Strait opened much later.

Japan is situated 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. Hot springs are numerous and have been developed as resorts.

Izanagi

Izanagi (Japanese: イザナギ, recorded in the Kojiki as 伊邪那岐 and in the Nihon Shoki as 伊弉諾) is a deity born of the seven divine generations in Japanese mythology and Shinto, and his name in the Kojiki is roughly translated to as "he-who-invites". He is also known as Izanagi-no-mikoto or Izanagi-no-Ōkami.

Japan Median Tectonic Line

Japan Median Tectonic Line (中央構造線, Chūō Kōzō Sen), also Median Tectonic Line (MTL), is Japan's longest fault system. 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 Inland Sea from the Kii Channel and Naruto Strait to Shikoku along the Sadamisaki Peninsula and the Bungo Channel and Hōyo Strait to Kyūshū.The sense of motion on the MTL is right-lateral strike-slip, at a rate of about 5–10 mm/yr. This sense of motion is consistent with the direction of oblique convergence at the Nankai Trough. The rate of motion on the MTL is much less than the rate of convergence at the plate boundary, making it difficult to distinguish the motion on the MTL from interseismic elastic straining in GPS data.

Kula Plate

The Kula Plate was an oceanic tectonic plate under the northern Pacific Ocean south of the Near Islands segment of the Aleutian Islands. It has been subducted under the North American Plate at the Aleutian Trench, being replaced by the Pacific Plate.

The name Kula is from a Tlingit language word meaning "all gone". As the name suggests, the Kula Plate was entirely subducted around 48 Ma and today only a slab in the mantle under the Bering Sea remains.

List of tectonic plates

This is a list of tectonic plates on the Earth's surface. Tectonic plates are pieces of Earth's crust and uppermost mantle, together referred to as the lithosphere. The plates are around 100 km (62 mi) thick and consist of two principal types of material: oceanic crust (also called sima from silicon and magnesium) and continental crust (sial from silicon and aluminium). The composition of the two types of crust differs markedly, with mafic basaltic rocks dominating oceanic crust, while continental crust consists principally of lower-density felsic granitic rocks.

Yanshanian

The Yanshanian movement were first recognized by Weng WH (1927,1929) in the Yansan area of China (116°-119.5°N, 40°-42°E). Since then, the Yanshanian has been used as a local term in China for tectonic events which occurred mainly during the Jurassic Period. Later, Ding WJ (1929), Huang JQ (1945,1960) and Zhao ZF (1959) extended the term to cover tectonic events which occurred throughout China during the Jurassic and Cretaceous tectonic periods. However, it was soon realized that tectonic and magmatic events in the Jurassic and Cretaceous were very different. In the Jurassic there are NNE-NE trending folds and thrusts related to transpressional tectonics, and WNW trending normal faults with some strike-slip movement and widespread calc-alkaline magmatism, while the Cretaceous is characterized predominantly by extensional tectonics with NE-NNE trending normal faults, WNW trending folds and thrusts and highly alkaline acid magmatism located along faults, or at fault intersection.

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