Abyssal plain

Abyssal plain

Abyssal plains are flat or very gently sloping areas of the deep ocean basin floor. They are among the Earth's flattest and smoothest regions and the least explored. Abyssal plains cover approximately 40% of the ocean floor and reach depths between 2,200 and 5,500 m (7,200 and 18,000 ft). They generally lie between the foot of a continental rise and a mid-oceanic ridge.

The abyssal plain is formed when the lower crust (sima), is melted and pushed up by the up-welling mantle, reaches the surface at mid-ocean ridges and forms new oceanic crust. This new oceanic crust is mostly basalt and has a rugged topography. The roughness of this topography is a function of the rate at which the mid-ocean ridge is spreading (the spreading rate). Magnitudes of spreading rates vary quite significantly, and are generally broken down into 3 rates (fast, medium and slow). Typical values for fast-spreading ridges are >100 mm/yr, whilst medium-spreading rates are ~60 mm/yr, and slow-spreading ridges are typically <20 mm/yr. Studies have shown that the slower the spreading rate, the rougher the new oceanic crust will be, and vice versa. It is thought this is due to faulting at the mid-ocean ridge when the new oceanic crust was formed. This oceanic crust eventually becomes overlain with sediments, producing the flat appearance.

Abyssal plains result from the blanketing of an originally uneven surface of oceanic crust by fine-grained sediments, mainly clay and silt. Much of this sediment is deposited from turbidity currents that have been channeled from the continental margins along submarine canyons down into deeper water. The remainder of the sediment comprises chiefly dust (clay particles) blown out to sea from land, and the remains of small marine plants and animals (the plankton), which sink from the upper layer of the ocean, known as Pelagic sediments. The sediment deposition rate in remote areas is estimated at two to three centimetres per thousand years. In some areas of the plains manganese nodules are common with significant varying concentrations of metals, including iron, nickel, cobalt, and copper. These nodules may provide a significant resource for future mining ventures.

Sediment-covered abyssal plains are less common in the Pacific than in other major ocean basins because sediments from turbidity currents are trapped in submarine trenches that border the Pacific Ocean.

List of Abyssal Plains

Atlantic Ocean

*Labrador Plain
*Irminger Plain
*Iceland Plain
*Norwegian Plain
*Cape Verde Plain
*Sierra Leone Plain
*Guinea Plain
*Angola Plain
*Cape Plain
*Argentine Plain
*Brasil Plain
*Guayana Plain
*Mexico Plain
*Sohm Plain

Indian Ocean

*Agulhas Plain
*Natal Plain
*Madagaskar Plain
*Somalian Plain

*Middle-Indian Plain
*Andamanian Plain
*Wharton Plain
*Perth's Plain
*Crozet's Plain
*Atlantic-Indian Plain
*North Australian Plain
*South Australian Plain

Pacific Ocean

*Celebes' Plain
*South Chinese Plain
*West Carolinian Plain
*East Carolinian Plain
*Coral sea Plain
*Tasmani Plain
*Southern Fiji Plain
*Northern Fiji Plain
*Melanesian Plain
*East Mariana Plain
*Northwestern Pacific Plain
*Japanese Plain
*Kurillian Plain
*Middle Pacific Plain
*Southwestern Pacific Plain
*Southeastern Pacific Plain
*Chile Plain
*Peru Plain
*Guatemala Plain

See also

*List of Oceanic Landforms

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Look at other dictionaries:

  • abyssal plain — Flat seafloor area at a depth of 10,000–20,000 ft (3,000–6,000 m), generally adjacent to a continent. The larger plains are hundreds of miles wide and thousands of miles long. The plains are largest and most common in the Atlantic Ocean, less… …   Universalium

  • abyssal plain — noun : any of the great flat sediment covered areas of ocean floor * * * abyssal plain, a deep, extremely level undersea plain, such as the plain lying about 750 miles to 1,000 miles off the eastern coast of North America, with deposits of clay,… …   Useful english dictionary

  • abyssal plain —   large, relatively flat areas of ocean floor found at 5,000 6,000m below sea level. If sediments are discharged from a river and deposit relatively quickly onto the plain they may form an abyssal fan …   Geography glossary

  • abyssal plain — noun Date: 1954 any of the great flat sediment covered areas of ocean floor see continental shelf illustration …   New Collegiate Dictionary

  • abyssal plain — the area of the generally flat ocean floor excluding ocean trenches below 2000 fathoms (3660 metres, presumably an older version based on fathoms) or 4000 metres …   Dictionary of ichthyology

  • abyssal plain — noun a large expanse of very flat and smooth ocean floor, usually found at depths of 4,600 to 5,500 meters (15,000 to 18,000 feet) …   Wiktionary

  • abyssal plain — /əbɪsəl ˈpleɪn/ (say uhbisuhl playn) noun a flat or very gently sloping area on the bottom of the abyssopelagic zone which is covered in sediment accumulated over millions of years …   Australian English dictionary

  • Colombian Abyssal Plain — ▪ plain, Caribbean Sea       submarine plain forming part of the floor of the south central Caribbean Sea, and the deepest and flattest portion of the Colombian Basin. It rises to the southeast to form the Caribbean coast of Colombia, joins the… …   Universalium

  • Hatteras Abyssal Plain — ▪ submarine plain, Atlantic Ocean       submarine plain forming the floor of the northwestern Atlantic Ocean. It lies east of the North American continental shelf between the southern United States and Bermuda, extending about 900 mi (1,450 km)… …   Universalium

  • abyssal floor — abyssal plain …   Dictionary of ichthyology

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