Oceanic basin

In hydrology, an oceanic basin may be anywhere on Earth that is covered by seawater but geologically ocean basins are large geologic basins that are below sea level. Geologically, there are other undersea geomorphological features such as the continental shelves, the deep ocean trenches, and the undersea mountain ranges (for example, the mid-Atlantic ridge and the Emperor Seamounts) which are not considered to be part of the ocean basins; while hydrologically, oceanic basins include the flanking continental shelves and shallow, epeiric seas.

Oceanic basin
Diagrammatic cross-section of an ocean basin, showing the various geographic features

History

Older references (e.g., Littlehales 1930)[1] consider the oceanic basins to be the complement to the continents, with erosion dominating the latter, and the sediments so derived ending up in the ocean basins. More modern sources (e.g., Floyd 1991)[2] regard the ocean basins more as basaltic plains, than as sedimentary depositories, since most sedimentation occurs on the continental shelves and not in the geologically-defined ocean basins.[3]

Hydrologically some geologic basins are both above and below sea level, such as the Maracaibo Basin in Venezuela, although geologically it is not considered an oceanic basin because it is on the continental shelf and underlain by continental crust.

Earth is the only known planet in the solar system where hypsography is characterized by different kinds of crust, oceanic crust and continental crust.[4] Oceans cover 70% of the Earth's surface. Because oceans lie lower than continents, the former serve as sedimentary basins that collect sediment eroded from the continents, known as clastic sediments, as well as precipitation sediments. Ocean basins also serve as repositories for the skeletons of carbonate- and silica-secreting organisms such as coral reefs, diatoms, radiolarians, and foraminifera.

Geologically, an oceanic basin may be actively changing size or may be relatively, tectonically inactive, depending on whether there is a moving plate tectonic boundary associated with it. The elements of an active - and growing - oceanic basin include an elevated mid-ocean ridge, flanking abyssal hills leading down to abyssal plains. The elements of an active oceanic basin often include the oceanic trench associated with a subduction zone.

The Atlantic ocean and the Arctic ocean are good examples of active, growing oceanic basins, whereas the Mediterranean Sea is shrinking. The Pacific Ocean is also an active, shrinking oceanic basin, even though it has both spreading ridge and oceanic trenches. Perhaps the best example of an inactive oceanic basin is the Gulf of Mexico, which formed in Jurassic times and has been doing nothing but collecting sediments since then.[5] The Aleutian Basin[6] is another example of a relatively inactive oceanic basin. The Japan Basin in the Sea of Japan which formed in the Miocene, is still tectonically active although recent changes have been relatively mild.[7]

See also

Notes

  1. ^ Littlehales, G. W. (1930) The configuration of the oceanic basins Graficas Reunidas, Madrid, Spain, OCLC 8506548
  2. ^ Floyd, P. A. (1991) Oceanic basalts Blackie, Glasgow, Scotland, ISBN 978-0-216-92697-4
  3. ^ Biju-Duval, Bernard (2002) Sedimentary geology: sedimentary basins, depositional environments, petroleum formation Editions Technip, Paris, ISBN 978-2-7108-0802-2
  4. ^ Ebeling, Werner and Feistel, Rainer (2002) Physics of Self-Organization and Evolution Wiley-VCH, Weinheim, Germany, page 141, ISBN 978-3-527-40963-1
  5. ^ Huerta, Audrey D. and Harry, Dennis L. (2012) "Wilson cycles, tectonic inheritance, and rifting of the North American Gulf of Mexico continental margin" Geosphere 8(2): pp. 374–385, first published on March 6, 2012, doi:10.1130/GES00725.1
  6. ^ Verzhbitsky, E. V.; M. V. Kononov; V. D. Kotelkin (5 February 2007). "Plate Tectonics of the Northern Part of the Pacific Ocean". Oceanology (in translation from Okeanologiya ). 47 (5): 705–717. Bibcode:2007Ocgy...47..705V. doi:10.1134/S000143700705013X.
  7. ^ Clift, Peter D. (2004) Continent-Ocean Interactions Within East Asian Marginal Seas American Geophysical Union, Washington, D.C., pages 102–103, ISBN 978-0-87590-414-6

Further reading

External links

Adriatic Basin

The Adriatic Abyssal Plain, more commonly referred to as the Adriatic Basin, is an oceanic basin under the Adriatic Sea. The Adriatic Sea's average depth is 252.5 metres (828 ft), and its maximum depth is 1,233 metres (4,045 ft); however, the North Adriatic basin rarely exceeds a depth of 100 metres (330 ft).

Afar Triple Junction

The Afar Triple Junction (also called the Afro-Arabian Rift System) is located along a divergent plate boundary dividing the Nubian, Somali, and Arabian plates. This area is considered a present-day example of continental rifting leading to seafloor spreading and producing an oceanic basin. Here, the Red Sea Rift meets the Aden Ridge and the East African Rift. It extends a total of 6,500 kilometers (4,000 mi) in three arms from the Afar Triangle to Mozambique.The connecting three arms form a triple junction. The northern most branching arm extends North through the Red Sea and into the Dead Sea, while the eastern arm extends through the Gulf of Aden and connects to the Mid-Indian Ocean ridge further to the east. Both of these rifting arms are below sea level and are similar to a mid-ocean ridge.The third rifting arm runs south extending around 4000 km through the countries of Kenya, Uganda, the Democratic Republic of Congo, Rwanda, Burundi, Tanzania, Zambia, Malawi and, finally, Mozambique. This southern rifting arm is better known as the East African Rift or the East African Rift System (EARS), when it includes the Afar Triangle.

Agulhas Basin

The Agulhas Basin is an oceanic basin located south of South Africa where the South Atlantic Ocean and south-western Indian Ocean meet. Part of the African Plate, it is bounded by the Agulhas Ridge (part of the Agulhas-Falkland Fracture Zone) to the north and the Southwest Indian Ridge to the south; by the Meteor Rise to the west and the Agulhas Plateau to the east. Numerous bathymetric anomalies hint at the basin's dynamic tectonic history.

Alaska Plain

The Alaska Plain, also referred to as the Alaskan Plain or Alaskan Abyssal Plain, is an oceanic basin under the Gulf of Alaska. The plain is bordered to the northwest by the Alaskan portion of the Aleutian Trench, to the north and east by the continental shelf off the coast of Alaska and British Columbia, and to the south by two separate lines of seamounts, from Patton seamount in the northwest, located just south of Kodiak Island, to Bowie seamount in the southeast, located just west of Queen Charlotte Islands, running from 54°40′N 150°30′W and 53°18′N 135°38′W.

Aleutian Basin

The Aleutian Basin is an oceanic basin under the southwestern Bering Sea. While the northeastern half of the Bering Sea overlies the North American Plate in relatively shallow water, the Aleutian Basin consists of oceanic plate—the remnant of the Kula Plate that was mostly subducted under the North American Plate.Subduction of the Kula Plate ceased after the creation of the Aleutian Trench to its south. What remained of the Kula Plate attached to the North American Plate. This former subduction zone is now the Beringian Margin, which now hosts sixteen submarine canyons, including Zhemchug Canyon, the world's largest.The deep-water part of the Bering Sea is separated into the Commander and Bowers basins by the submarine Shirshov Ridge and Bowers Ridge. The Commander Basin occupies the western part of the Bering Sea, with the Shirshov Ridge on its eastern border. The Shirshov Ridge extends 750 km southward from the Russian Olyutorskii Peninsula to connect with Bowers Ridge. The Bowers Ridge extends in the form of an arc over approximately 900 km from the Aleutian Islands Arc to the northwestern termination, where it meets Shirshov Ridge. This former island arc, Bowers Ridge, is a prominent semi-circular-shaped geological that meets the Aleutian arc and, together with the Aleutians, bounds Bowers Basin.

The northern part of the Shirshov Ridge formed 95 My before the present. The ridge grows younger as it goes south, with the southern part of the Shirshov Ridge formed 33 My ago (Early Oligocene). Bowers Ridge was formed 30 My before the present (Late Oligocene).

Arabian Basin

The Arabian Basin is an oceanic basin located in the

southern part of the Arabian Sea between the Arabian Peninsula and India. It is centered at 10° N, 65° E. The basin depth ranges from 3,400 m in the north to 4,400 m in the south, with a maximum depth of 4,652 m. The floor is covered by sediments from the Indus submarine fan and is relatively smooth.The southern enclosure of this basin is formed by the Central Indian Ridge, the Carlsberg Ridge and the Chagos-Laccadive Ridge. Bottom water enters the basin through the Owen Fracture Zone to the west. The Carlsberg Ridge, at a depth of 3,800 m, separates this basin from the Somali Basin to the southwest. The Arabian Basin is separated from the shallow Oman Basin by the Murray Ridge. Most of the northern and eastern limits are formed by the Laxmi Ridge and the Laccadive Plateau.

Arctic Basin

The Arctic Basin (also North Polar Basin) is an oceanic basin in the Arctic Ocean, consisting of two main parts separated by the Lomonosov Ridge, a mid-ocean ridge running between north Greenland and the New Siberian Islands. The basin is bordered by the continental shelves of Eurasia and North America.

The Eurasian Basin (also Norwegian Basin) consists of the Nansen Basin (formerly: Fram Basin) and the Amundsen Basin

The Amerasian Basin consists of the Canada Basin and the Makarov Basin

Baffin Basin

The Baffin Basin is an oceanic basin located in the middle of Baffin Bay between Baffin Island and Greenland. With a maximum depth of over 2,700 m (8,900 ft), the basin represents the deepest point of Baffin Bay. The basin formed as a result of seafloor spreading at the time of the opening of Baffin Bay around 56 million years ago.

Bathymetric chart

A bathymetric chart is the submerged equivalent of an above-water topographic map. Bathymetric charts are designed to present accurate, measurable description and visual presentation of the submerged terrain.

Bathymetric surveys and charts are more closely tied to the science of oceanography, particularly marine geology, and underwater engineering or other specialized purposes.

Bathymetric charts can also be converted to bathymetric profiles.

Canada Basin

The Canada Basin is a deep oceanic basin within the Arctic Ocean. It is part of the Amerasian Basin.

Eustatic sea level

The eustatic sea level is the distance from the center of the earth to the sea surface. An increase of the eustatic sea level can be generated by decreasing glaciation, increasing spreading rates of the mid-ocean ridges or more mid-oceanic ridges. Conversely, increasing glaciation, decreasing spreading rates or fewer mid-ocean ridges lead to a fall of the eustatic sea level.

Changes in the eustatic sea level lead to changes in accommodation and therefore affect the deposition of sediments in marine environments.

Eustatic (global) sea level refers to the sea level change of the volume of Earth’s oceans. This is not a physical level but instead represents the sea level if all of the water in the oceans were contained in a single basin. Eustatic sea level is not relative to local surfaces, because relative sea level is dependent on many factors including tectonics, continental rise and subsidence. Eustatic sea level follows the ‘bathtub approach’ which describes the ocean as a single bathtub. One can add or remove water and Earth’s oceans will gain or lose water globally. Differences of eustatic sea level are caused by three main factors:

Changes in total ocean water mass, for instance, by ice sheet runoff. When an ice sheet such as Greenland begins to lose its ice mass due to melt, the liquid water is transported to the ocean. According to the ‘bathtub approach’, ice sheet runoff from Greenland will affect eustatic sea level in all areas of the world, whether nearby or distant. Ocean water mass may also shrink in size if the continental ice sheets grow in size, thereby removing liquid water from oceans and converting them to grow ice sheets

Changes in the size of the ocean basin, for instance, by tectonic seafloor spreading or by sedimentation. These slow processes can cause the total volume of the oceanic basin to change.

Density changes of the water, for instance, by thermal expansion. One driver of thermal expansion is a rise in greenhouse gases such as carbon dioxide, methane, and ozone. These gases cause surface temperatures to increase, which in turn increases ocean temperatures. This warming will cause water to experience greater molecular motion, thus increasing the volume a molecule will occupy. A decrease in atmospheric greenhouse gases will cause surface temperatures to drop. Expansion of water may also be caused by changes in ocean salinity. As continental ice accumulates, the ocean water freezes onto land but the salt it carried will mostly remain in the ocean. Thus, as ice sheets increase, ocean salinity also increases (and vice versa). An increase in salinity will increase the density of the ocean basin. Melting of ice sheets and a decrease of ocean salinity will effectively decrease the density of the water. These two effects together are called the steric sea level. The thermal part is called the thermosteric sea level, whereas the salinity part is called the halosteric sea level.

Foxe Basin

Foxe Basin is a shallow oceanic basin north of Hudson Bay, in Nunavut, Canada, located between Baffin Island and the Melville Peninsula. For most of the year, it is blocked by sea ice (fast ice) and drift ice made up of multiple ice floes.

The nutrient-rich cold waters found in the basin are known to be especially favourable to phytoplankton and the numerous islands within it are important bird habitats, including Sabine's gulls and many types of shorebirds. bowhead whales migrate to the northern part of the basin each summer.

The basin takes its name from the English explorer Luke Foxe who entered the lower part in 1631.

Itbay

Itbāy (Arabic: اطبيه‎) or ʿAtbāy is a region of southeastern Egypt and northeastern Sudan. It is characterised by a chain of mountains, the Red Sea Hills, running north–south and parallel with the Red Sea. The hills separate the narrow coastal plain from the Eastern Desert.

Porcupine Seabight

The Porcupine Seabight is a deep-water oceanic basin located on the continental margin in the northeastern portion of the Atlantic Ocean. It can be found in the southwestern offshore portion of Ireland and is part of a series of interconnected basins linked to a failed rift structure associated with the opening of the Northern Atlantic Ocean. The basin extends in a North-South direction and was formed during numerous subsidence and rifting periods between the Late Carboniferous and Late Cretaceous. It is bordered by the

Goban Spur to the south

Slyne Ridge to the north

Porcupine Bank to the west

Porcupine Abyssal Plain to the southwestDue to subsidence, water depths range from 3000 m in the south near its mouth to 400 m in the north. The Porcupine Basin lies on the Caledonian metamorphic basement and preserves up to 12 km of sedimentary strata from Late Palaeozoic to Quaternary which includes significant hydrocarbon reservoirs. Sediment was likely sourced from the uplifted Caledonian metamorphic rocks of the Porcupine Median Ridge.The basin lent its name to Operation Seabight, an Irish drug-bust of November 2008.

Tsushima Basin

The Tsushima Basin (対馬海盆, tsushima kaibon) or Ulleung Basin (울릉분지 ulleung bunji) is an oceanic basin located where the Sea of Japan meets the Korea Strait. It lies immediately south of Ulleung-do and Liancourt Rocks, in the eastern end of the South Korean EEZ and the western end of the Japanese EEZ.

In 1978, the Japanese government registered the name "Tsushima Basin" with the International Hydrographic Bureau. In April 2006, Japan's plans to survey the region and South Korea's plans to register the name "Ulleung Basin" with the International Hydrographic Bureau resulted in a diplomatic standoff between the two countries. The two countries later agreed to address the issue "at an appropriate time." The first exploratory drilling for gas was in 1972, but gas discoveries have drawn regional interest since the late 1980s. The first commercial gas discovery was reported in 1998. Nine of 15 exploratory wells have contained gas, a rate indicating high potential prospects.The East Korea Warm Current, Ulleung Warm Eddy, and Offshore Branch interact within this basin.A feature of the southwestern Sea of Japan is a deep, developing continental shelf. The eastern Oki Islands, a big ridge of three rows lines up in parallel to the Japanese archipelago, and it connects with a Yamato Basin which has expanded from Oki Islands and offshore of the Tōhoku region to the south in between those. The vast Tsushima Basin has extended on the tip of the Oki offshore that expands from Oki Islands on the north side.

Valais Ocean

The Valais Ocean is a subducted oceanic basin which was situated between the continent Europe and the microcontinent Iberia or so called Briançonnais microcontinent. Remnants of the Valais ocean are found in the western Alps and in tectonic windows of the eastern Alps and are mapped as the so-called "north Penninic" nappes.

West Caroline Basin

The West Caroline Basin is an oceanic basin in the south-west Pacific Ocean north of New Guinea.

West Philippine Basin

The West Philippine Basin, also known as the West Philippine Sea Basin, is the oceanic crust located underneath the western part of the Philippine Sea. It was formed during the early Oligocene epoch. To its southwest is the Philippine Trench, and to its east is the Kyushu-Palau Ridge. The West Philippine Basin is deeper and older than the eastern basins and has crustal heat-flow values approaching that of old oceanic crust. It is roughly bisected by the Central Basin Fault zone which comprises a band of high relief running from the northwest corner to the Kyushu-Palau Ridge near 14°N. Characterized by the presence of several submarine plateaus (Benham Rise and Anami and Oki-Daito Ridges).

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