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Encyclopedia > Continental shelf
     Sediment      Rock      Mantle
     Sediment      Rock      Mantle
     The global continental shelf, highlighted in cyan
     The global continental shelf, highlighted in cyan

The continental shelf is the extended perimeter of each continent and associated coastal plain, which is covered during interglacial periods such as the current epoch by relatively shallow seas (known as shelf seas) and gulfs. Image File history File links Continental_shelf. ... Image File history File links Continental_shelf. ... Image File history File links Download high resolution version (4320x2160, 1907 KB) Summary Global land and undersea elevation. ... Image File history File links Download high resolution version (4320x2160, 1907 KB) Summary Global land and undersea elevation. ... Animated, colour-coded map showing the various continents. ... In geography, a coastal plain is an area of flat, low-lying land adjacent to a seacoast and separated from the interior by other features. ... Variations in CO2, temperature and dust from the Vostok ice core over the last 400 000 years For the animated movie, see Ice Age (movie). ... This article is about the body of water. ... Bay redirects here. ...

Contents

Topography

The shelf usually ends at a point of increasing slope (called the shelf break). The sea floor below the break is the continental slope. Below the slope is the continental rise, which finally merges into the deep ocean floor, the abyssal plain. The continental shelf and the slope are part of the continental margin. Abyssal plains are flat or very gently sloping areas of the deep ocean basin floor. ...  Sediment  Rock  Mantle The continental shelf is the extended perimeter of each continent, which is covered during interglacial periods such as the current epoch by relatively shallow seas (known as shelf seas) and gulfs. ...


The shelf area is commonly subdivided into the inner continental shelf, mid continental shelf, and outer continental shelf, each with their specific geomorphology and marine biology. Surface of the Earth Geomorphology is the study of landforms, including their origin and evolution, and the processes that shape them. ... Various species of reef fish in the Hawaiian Islands. ...


The character of the shelf changes dramatically at the shelf break, where the continental slope begins. With a few exceptions, the shelf break is located at a remarkably uniform depth of roughly 140 m (460 ft); this is likely a hallmark of past ice ages, when sea level was lower than it is now.[1]


The continental slope is much steeper than the shelf; the average angle is 3°, but it can be as low as 1° or as high as 10°.[2] The slope is often cut with submarine canyons, features whose origin was mysterious for many years.[3] A Submarine canyon is a steep-sided valley on the seafloor of the continental slope. ...


The continental rise is below the slope, but landward of the abyssal plains. Its gradient is intermediate between the slope and the shelf, on the order of 0.5-1°.[4] Extending as far as 500 km from the slope, it consists of thick sediments deposited by turbidity currents from the shelf and slope. Sediment cascades down the slope and accumulates as a pile of sediment at the base of the slope, called the continental rise.[5] A turbidity current or density current is a current of of rapidly moving, sediment-laden water moving down a slope through air, water, or another fluid. ...


Geographical distribution

The width of the continental shelf varies considerably – it is not uncommon for an area to have virtually no shelf at all, particularly where the forward edge of an advancing oceanic plate dives beneath continental crust in an offshore subduction zone such as off the coast of Chile or the west coast of Sumatra. The largest shelf – the Siberian Shelf in the Arctic Ocean – stretches to 1500 kilometers (930 miles) in width. The South China Sea lies over another extensive area of continental shelf, the Sunda Shelf, which joins Borneo, Sumatra, and Java to the Asian mainland. Other familiar bodies of water that overlie continental shelves are the North Sea and the Persian Gulf. The average width of continental shelves is about 80 km (50 mi). The depth of the shelf also varies, but is generally limited to water shallower than 150 m (490 ft).[6] The slope of the shelf is usually quite low, on the order of 0.5°; vertical relief is also minimal, at less than 20 m (65 ft).[7] Age of oceanic crust Oceanic crust is the part of Earths lithosphere that surfaces in the ocean basins. ... The thickness of the Earths crust (km). ... Categories: Geology stubs | Plate tectonics ... For other uses, see Sumatra (disambiguation). ... The Siberian Shelf, one of the Arctic shelves, is the largest continental shelf of the Earth, a part of the continental shelf of Russia. ... A kilometer (Commonwealth spelling: kilometre), symbol: km is a unit of length in the metric system equal to 1,000 metres (from the Greek words χίλια (khilia) = thousand and μέτρο (metro) = count/measure). ... “Miles” redirects here. ... Filipino name Tagalog: Luzon Sea Portuguese name Portuguese: Mar da China Meridional Vietnamese name Vietnamese: The South China Sea is a marginal sea south of China. ... The Sahul Shelf and the Sunda Shelf during the last glacial maximum about 18,000 years ago. ... Borneo is the third largest island in the world and is located at the centre of Maritime Southeast Asia. ... Java (Indonesian, Javanese, and Sundanese: Jawa) is an island of Indonesia, and the site of its capital city, Jakarta. ... The North Sea is a sea of the Atlantic Ocean, located between the coasts of Norway and Denmark in the east, the coast of the British Isles in the west, and the German, Dutch, Belgian and French coasts in the south. ... Map of the Persian Gulf. ... This article is about the unit of length. ...


Though the continental shelf is treated as a physiographic province of the ocean, it is not part of the deep ocean basin proper, but the flooded margins of the continent.[8] Passive continental margins such as most of the Atlantic coasts have wide and shallow shelves, comprised of thick sedimentary wedges derived from long erosion of a neighboring continent. Active continental margins have narrow, relatively steep shelves, due to frequent earthquakes that move sediment to the deep sea.[9] Physical geography or physiogeography is a subfield of geography that focuses on the systematic study of patterns and processes within the hydrosphere, biosphere, atmosphere, and lithosphere. ... Animated map exhibiting the worlds oceanic waters. ...  Sediment  Rock  Mantle The continental margin is the zone of the ocean floor that separates the thin oceanic crust from thick continental crust. ... The Atlantic Ocean, not including Arctic and Antarctic regions. ...  Sediment  Rock  Mantle The continental margin is the zone of the ocean floor that separates the thin oceanic crust from thick continental crust. ... Global earthquake epicenters, 1963–1998. ...


Sediments

The continental shelves are covered by terrigenous sediments; that is, those derived from erosion of the continents. However, little of the sediment is from current rivers; some 60-70% of the sediment on the world's shelves is relict sediment, deposited during the last ice age, when sea level was 100-120 m lower than it is now.[10] In oceanography, terrigenous sediments are those derived from the erosion of rocks on land; that is, that are derived from terrestrial environments. ... For other uses, see River (disambiguation). ...


Sediments usually become increasingly fine with distance from the coast; sand is limited to shallow, wave-agitated waters, while silt and clays are deposited in quieter, deep water far offshore.[11] These shelf sediments accumulate at an average rate of 30 cm/1000 years, with a range from 15-40 cm.[12] Though slow by human standards, this rate is much faster than that for deep-sea pelagic sediments. This article is being considered for deletion in accordance with Wikipedias deletion policy. ... Pelagic sediments, also known as marine sediments, are those that accumulate in the abyssal plain of the deep ocean, far away from terrestrial sources that provide terrigenous sediments; the latter are primarily limited to the continental shelf, and deposited by rivers. ...


Biota

Combined with the sunlight available in shallow waters, the continental shelves teem with life compared to the biotic desert of the oceans' abyssal plain. The pelagic (water column) environment of the continental shelf constitutes the neritic zone, and the benthic (sea floor) province of the shelf is the sublittoral zone.[13] Abyssal plains are flat or very gently sloping areas of the deep ocean basin floor. ... The pelagic zone is the part of the open sea or ocean comprising the water column, i. ... The neritic zone spans from the low-tide line to the edge of the continental shelf in oceans. ... In marine geology and biology, benthos are the organisms and habitats of the sea floor; in freshwater biology they are the organisms and habitats of the bottoms of lakes, rivers, and creeks. ... The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ...


Though the shelves are usually fertile, if anoxic conditions in the sedimentary deposits prevail, the shelves may in geologic time become sources of fossil fuels. Oceanic Anoxic Events occur when the Earths oceans become completely depleted of O2 below the surface levels. ... The table and timeline of geologic periods presented here is in accordance with the dates and nomenclature proposed by the International Commission on Stratigraphy. ... Fossil fuels or mineral fuels are fossil source fuels, this is, hydrocarbons found within the top layer of the earth’s crust. ...


Economic significance

The relatively accessible continental shelf is the best understood part of the ocean floor. Most commercial exploitation from the sea, such as oil and gas extraction, takes place on the continental shelf. Sovereign rights over their continental shelves were claimed by the marine nations that signed the Convention on the Continental Shelf drawn up by the UN's International Law Commission in 1958 partly superseded by the 1982 United Nations Convention on the Law of the Sea.[14] Petro redirects here. ... Gas phase particles (atoms, molecules, or ions) move around freely Gas is one of the four major states of matter, consisting of freely moving atoms or molecules without a definite shape and without a definite volume. ... The International Law Commission was established by the General Assembly of the United Nations in 1948 with the purpose of codifying and promoting international law. ... Year 1982 (MCMLXXXII) was a common year starting on Friday (link displays the 1982 Gregorian calendar). ... United Nations Convention on the Law of the Sea Opened for signature December 10, 1982 in Montego Bay (Jamaica) Entered into force November 16, 1994[1] Conditions for entry into force 60 ratifications Parties 149[2] For maritime law in general see Admiralty law. ...


See also

A baseline is the line from which the seaward limits of a States territorial sea and certain other maritime zones of jurisdiction are measured. ... In oceanic biogeochemistry, the continental shelf pump is proposed to operate in the shallow waters of the continental shelves, acting as a mechanism to transport carbon (as either dissolved or particulate material) from surface waters to the interior of the adjacent deep ocean. ... The terms continental shelf of Russia or Russian continental shelf have two related meanings. ... Sea areas in international rights Under the law of the sea, an Exclusive Economic Zone (EEZ) is a seazone over which a state has special rights over the exploration and use of marine resources. ... The terms international waters or trans-boundary waters apply where any of the following types of bodies of water (or their drainage basins) transcend international boundaries: oceans, large marine ecosystems, enclosed or semi-enclosed regional seas and estuaries, rivers, lakes, groundwater systems (aquifers), and wetlands [1]. Oceans and seas, waters... This article or section does not cite its references or sources. ... The Outer Continental Shelf (OCS) is a peculiarity of the political geography of the United States and is the part of the internationally recognized continental shelf of the United States which does not fall under the jurisdictions of the individual U.S. states. ... Map of Sealand and the United Kingdom, with territorial water claims of 3nm and 12nm shown. ...

Footnotes

  1. ^ Gross 43.
  2. ^ Pinet 36, Gross 43.
  3. ^ Pinet 98, Gross 44.
  4. ^ Pinet 37.
  5. ^ Pinet 39, Gross 45.
  6. ^ Pinet, 37.
  7. ^ Pinet 36-37.
  8. ^ Pinet 35-36.
  9. ^ Pinet 90-93.
  10. ^ Pinet 84-86, Gross 43.
  11. ^ Gross 121-22.
  12. ^ Gross 127.
  13. ^ Pinet 316-17, 418-19.
  14. ^ http://untreaty.un.org/ilc/texts/instruments/english/conventions/8_1_1958_continental_shelf.pdf

References

  • Gross, Grant M. Oceanography: A View of the Earth. Englewood Cliffs: Prentice-Hall, Inc., 1972. ISBN 0-13-629659-9
  • Pinet, Paul R. (1996) Invitation to Oceanography. St. Paul, MN: West Publishing Co., 1996. ISBN 0-7637-2136-0 (3rd ed.)

External links


  Results from FactBites:
 
Continental Shelf | World of Earth Science (528 words)
The continental shelf is a gently sloping and relatively flat extension of a continent that is covered by the oceans.
Seaward, the shelf ends abruptly at the shelf break, the boundary that separates the shelf from the continental slope.
The shelf's gentle slope and relatively flat terrain are the result of erosion and sediment deposition during the periodic fall and rise of the sea over the shelf in the last 1.6 million years.
Ocean Regions: Ocean Floor - Continental Margin & Rise (273 words)
This shelf is relatively shallow, tens of meters deep compared to the thousands of meters deep in the open ocean, and extends outward to the continental slope where the deep ocean truly begins.
The continental slope connects the continental shelf and the oceanic crust.
The continental slope, which is still considered part of the continent, together with the continental shelf is called the continental margin.
  More results at FactBites »

 
 

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