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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 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. As the continental shelf and the slope are part of the continental margin, both are covered in this article. This article or section does not cite its references or sources. ... 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). ... Sunset at sea Look up Sea in Wiktionary, the free dictionary Look up maritime in Wiktionary, the free dictionary. ... A gulf or bay is a part of a lake or ocean that extends so that it is surrounded by land on three sides. ... Abyssal plains are flat or very gently sloping areas of the deep ocean basin floor. ...

Structure

The width of the continental shelf varies significantly. It is common for an area to have virtually no shelf at all, especially where the forward edge of an advancing oceanic plate dives beneath continental crust in an offshore subduction zone such as off the coasts of Chile or the west coast of Sumatra. The largest shelf—the Siberian shelf in the Arctic Ocean—stretches to 1500 kilometers 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 kilometers. The depth of the shelf also varies, but is generally limited to water shallower than 150 m.(Pinet 37) 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.(Pinet 36-37) Age of oceanic crust Oceanic crust is the part of Earths lithosphere which underlies the ocean basins. ... The continental crust is the layer of granitic, sedimentary and metamorphic rocks which form the continents and the areas of shallow seabed close to their shores, known as continental shelves. ... Categories: Geology stubs | Plate tectonics ... Sumatra (also spelled Sumatara and Sumatera) is the sixth largest island of the world (approximately 470,000 km²) and is the 3rd largest island of Indonesia after Kalimantan and New Guinea. ... 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). ... The South China Sea, showing surrounding countries and neighbouring seas and oceans The South China Sea is a marginal sea, part of the Pacific Ocean, encompassing an area from Singapore to the Strait of Taiwan of around 3,500,000 km². It is the largest sea body after the five... Geologically, the Sunda Shelf is an extension of the continental shelf of Southeast Asia, covered during interglacials by the South China Sea, which isolates as islands Borneo, Sumatra Java and smaller islands. ... Borneo and Sulawesi. ... 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. ... 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). ... The metre, or meter, is a measure 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.(Pinet 35-36) 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.(Pinet 90-93) 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. ... [[Image:http://www. ... The Atlantic Ocean is the second-largest ocean, covering approximately one-fifth of the earths surface. ... Global earthquake epicenters, 1963–1998. ...

Shelf break

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 130 m; this is likely a hallmark of past ice ages, when sea level was lower than it is now.(Gross 43)

Continental Slope and Rise

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°.(Pinet 36, Gross 43) The slope is often cut with submarine canyons, features whose origin was mysterious for many years.(Pinet 98, Gross 44) 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°.(Pinet 37) Extending as far as 500 km from the slope, it consists of thick sediments deposited by turbidity currents from the shelf and slope.(Pinet 39, Gross 45) 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. ...

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.(Pinet 84-86, Gross 43) The Murray River in Australia. ...

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.(Gross 121-22) These shelf sediments accumulate at an average rate of 30 cm/1000 years, with a range from 15-40 cm.(Gross 127) 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.(Pinet 316-17, 418-19) 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. ... Sublittoral comes from the latin words Sub (Under) and Littora (Beach), referring to that part of the Earths surface which are immediately below the inter-tidal zone and thus permanently covered with seawater. ...

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. ... Coal rail cars in Ashtabula, Ohio Fossil fuels, also known as mineral fuels, are hydrocarbon-containing natural resources such as coal, oil and natural gas. ...

Economic Significance

██ The global continental shelf, hilighted in cyan 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. ...

The relatively accessible continental shelf is by far the best understood part of the ocean floor. Most commercial exploitation, such as oil and gas extraction, from the sea 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,[1] partly superseded by the 1982 United Nations Convention on the Law of the Sea. It has been suggested that black gold (oil) be merged into this article or section. ... A gas is one of the four main phases of matter (after solid and liquid, and followed by plasma), that subsequently appear as a solid material is subjected to increasingly higher temperatures. ... International Law Comission The International Law Comission was established by the General Assembly of the United Nations in 1947 with the purpose of codifying and promoting international law. ... 1982 (MCMLXXXII) was a common year starting on Friday of the Gregorian calendar. ... United Nations Convention on the Law of the Sea Opened for signature ??? at ??? Entered into force November 16, 1994[1] Conditions for entry into force 60 ratifications Parties 149[2] The term United Nations Convention on Law of the Sea (UNCLOS, also called simply the Law of the Sea or...

External links

• Office of Naval Research: Ocean Regions: Continental Margin & Rise

References

• Gross, Grant M. Oceanography: A View of the Earth. Englewood Cliffs: Prentice-Hall, Inc., 1972. ISBN 0136296599

• Pinet, Paul R. (1996) Invitation to Oceanography. St. Paul, MN: West Publishing Co., 1996. ISBN 0763721360 (3rd ed.)