HOME

TheInfoList



OR:

The Kula Plate was an oceanic
tectonic plate Plate tectonics (from the la, label=Late Latin, tectonicus, from the grc, τεκτονικός, lit=pertaining to building) is the generally accepted scientific theory that considers the Earth's lithosphere to comprise a number of large te ...
under the northern
Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the contin ...
south of the
Near Islands The Near Islands or Sasignan Islands ( ale, Sasignan tanangin, russian: Ближние острова) are a group of American islands in the Aleutian Islands in southwestern Alaska, between the Russian Commander Islands to the west and the Ra ...
segment of the
Aleutian Islands The Aleutian Islands (; ; ale, Unangam Tanangin,”Land of the Aleuts", possibly from Chukchi ''aliat'', "island"), also called the Aleut Islands or Aleutic Islands and known before 1867 as the Catherine Archipelago, are a chain of 14 large v ...
. It has been subducted under the
North American Plate The North American Plate is a tectonic plate covering most of North America, Cuba, the Bahamas, extreme northeastern Asia, and parts of Iceland and the Azores. With an area of , it is the Earth's second largest tectonic plate, behind the Pacif ...
at the
Aleutian Trench The Aleutian Trench (or Aleutian Trough) is an oceanic trench along a convergent plate boundary which runs along the southern coastline of Alaska and the Aleutian islands. The trench extends for from a triple junction in the west with the Ulak ...
, being replaced by the Pacific Plate. The name ''Kula'' is from a
Tlingit language The Tlingit language ( ; ''Lingít'' ) is spoken by the Tlingit people of Southeast Alaska and Western Canada and is a branch of the Na-Dene language family. Extensive effort is being put into revitalization programs in Southeast Alaska to re ...
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. There is some evidence of a Resurrection Plate broken off from the Kula Plate and also subducted.


Geological history

The Kula Plate began
subduct Subduction is a geological process in which the oceanic lithosphere is recycled into the Earth's mantle at convergent boundaries. Where the oceanic lithosphere of a tectonic plate converges with the less dense lithosphere of a second plate, the ...
ing under the
Pacific Northwest The Pacific Northwest (sometimes Cascadia, or simply abbreviated as PNW) is a geographic region in western North America bounded by its coastal waters of the Pacific Ocean to the west and, loosely, by the Rocky Mountains to the east. Tho ...
region of North America during the
Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', ...
period much like the Pacific Plate does today, supporting a large
volcanic arc A volcanic arc (also known as a magmatic arc) is a belt of volcanoes formed above a subducting oceanic tectonic plate, with the belt arranged in an arc shape as seen from above. Volcanic arcs typically parallel an oceanic trench, with the arc lo ...
system from northern
Washington Washington commonly refers to: * Washington (state), United States * Washington, D.C., the capital of the United States ** A metonym for the federal government of the United States ** Washington metropolitan area, the metropolitan area centered o ...
to southwestern
Yukon Yukon (; ; formerly called Yukon Territory and also referred to as the Yukon) is the smallest and westernmost of Canada's three territories. It also is the second-least populated province or territory in Canada, with a population of 43,964 as ...
called the Coast Range Arc. There was a
triple junction A triple junction is the point where the boundaries of three tectonic plates meet. At the triple junction each of the three boundaries will be one of three types – a ridge (R), trench (T) or transform fault (F) – and triple junctions can ...
of three ridges between the Kula Plate to the north, the Pacific Plate to the west and the
Farallon Plate The Farallon Plate was an ancient oceanic plate. It formed one of the three main plates of Panthalassa, alongside the Phoenix Plate and Izanagi Plate, which were connected by a triple junction. The Farallon Plate began subducting under the west ...
to the east. The Kula Plate was subducted under the
North American Plate The North American Plate is a tectonic plate covering most of North America, Cuba, the Bahamas, extreme northeastern Asia, and parts of Iceland and the Azores. With an area of , it is the Earth's second largest tectonic plate, behind the Pacif ...
at a relatively steep angle, so that the Canadian Rockies are primarily composed of thrusted
sedimentary Sedimentary rocks are types of rock that are formed by the accumulation or deposition of mineral or organic particles at Earth's surface, followed by cementation. Sedimentation is the collective name for processes that cause these particles ...
sheets with relatively little contribution of continental uplift, while the American Rockies are characterized by significant continental uplift in response to the shallow subduction of the Farallon Plate. About 55 million years ago, the Kula Plate began an even more northerly motion. Riding on the Kula Plate was the Pacific Rim Terrane consisting of
volcanic A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often found where tectonic plates a ...
and
sedimentary rock Sedimentary rocks are types of rock that are formed by the accumulation or deposition of mineral or organic particles at Earth's surface, followed by cementation. Sedimentation is the collective name for processes that cause these particles ...
. It was scraped off and plastered against the
continental margin A continental margin is the outer edge of continental crust abutting oceanic crust under coastal waters. It is one of the three major zones of the ocean floor, the other two being deep-ocean basins and mid-ocean ridges. The continental margi ...
, forming what is today
Vancouver Island Vancouver Island is an island in the northeastern Pacific Ocean and part of the Canadian province of British Columbia. The island is in length, in width at its widest point, and in total area, while are of land. The island is the largest by ...
. By 40 million years ago, the compressional force of the Kula Plate ceased. The existence of the Kula Plate was inferred from the westward bend in the alternating pattern of
magnetic anomalies In geophysics, a magnetic anomaly is a local variation in the Earth's magnetic field resulting from variations in the chemistry or magnetism of the rocks. Mapping of variation over an area is valuable in detecting structures obscured by overlying ...
in the Pacific Plate.


See also

*
Farallon Plate The Farallon Plate was an ancient oceanic plate. It formed one of the three main plates of Panthalassa, alongside the Phoenix Plate and Izanagi Plate, which were connected by a triple junction. The Farallon Plate began subducting under the west ...
*
Kula-Farallon Ridge The Kula-Farallon Ridge was an ancient mid-ocean ridge that existed between the Kula and Farallon plates in the Pacific Ocean during the Jurassic period. There was a small piece of this ridge off the Pacific Northwest 43 million years ago. The r ...
*
Pacific-Kula Ridge The Pacific-Kula Ridge is a former mid-ocean ridge that existed between the Pacific and Kula plates in the Pacific Ocean during the Paleogene period. Its appearance was in an east-west direction and the Hawaiian-Emperor seamount chain had its att ...
* Izanagi Plate


References


External links


Reconstruction of the Kula Plate
* ttp://www.washington.edu/burkemuseum/geo_history_wa/Coast%20Range%20Episode.htm Kula plate when it separates from the Farallon plate {{DEFAULTSORT:Kula Plate Tectonic plates Natural history of North America Historical geology Mesozoic geology Paleogene geology Geology of the Pacific Ocean Bering Sea