Abyssal plain

An abyssal plain is an underwater <a href="/facts/Plain/yM1ghtmc">plain</a> on the deep <a href="/facts/Ocean_floor/VvxuEWJu">ocean floor</a>, usually found at depths between 3,000 and 6,000 metres (9,800 and 19,700 ft). Lying generally between the foot of a <a href="/facts/Continental_rise/WgkU7zA3">continental rise</a> and a <a href="/facts/Mid-ocean_ridge/wYdgdSW3">mid-ocean ridge</a>, abyssal plains cover more than 50% of the <a href="/facts/Earth/HLLmDfj0">Earth</a>'s surface. They are among the flattest, smoothest, and least explored regions on Earth. Abyssal plains are key geologic elements of <a href="/facts/Oceanic_basin/TKKHflL6">oceanic basins</a>. (the other elements being an elevated mid-ocean ridge and flanking <a href="/facts/Abyssal_hill/U5gp04hn">abyssal hills</a>)
The creation of the abyssal plain is the result of the spreading of the seafloor (plate tectonics) and the melting of the lower <a href="/facts/Oceanic_crust/0lGjI7jN">oceanic crust</a>. Magma rises from above the <a href="/facts/Asthenosphere/lXpE97oP">asthenosphere</a> (a layer of the upper <a href="/facts/Mantle_(geology)/RpDdtjCr">mantle</a>), and as this <a href="/facts/Basalt/uhbwGPTb">basaltic</a> material reaches the surface at mid-ocean ridges, it forms new oceanic crust, which is constantly pulled sideways by spreading of the seafloor. Abyssal plains result from the blanketing of an originally uneven surface of oceanic crust by fine-grained <a href="/facts/Sediment/zsIH1A6U">sediments</a>, mainly <a href="/facts/Clay/xnwouEkB">clay</a> and <a href="/facts/Silt/HAxJkhDP">silt</a>. Much of this sediment is deposited by <a href="/facts/Turbidity_current/GkwnfNfa">turbidity currents</a> that have been channelled from the <a href="/facts/Continental_margin/Wgc47bX7">continental margins</a> along <a href="/facts/Submarine_canyon/GptxqPlX">submarine canyons</a> into deeper water. The rest is composed chiefly of <a href="/facts/Pelagic_sediments/D286yP33">pelagic sediments</a>. Metallic <a href="/facts/Manganese_nodule/e9RCgkFo">nodules</a> are common in some areas of the plains, with varying concentrations of metals, including <a href="/facts/Manganese/j9ELd1TL">manganese</a>, <a href="/facts/Iron/QK1JYy8E">iron</a>, <a href="/facts/Nickel/KwMCHYRP">nickel</a>, <a href="/facts/Cobalt/gqhScEw4">cobalt</a>, and <a href="/facts/Copper/I8PEE8oX">copper</a>. There are also amounts of carbon, nitrogen, phosphorus and silicon, due to material that comes down and decomposes.
Owing in part to their vast size, abyssal plains are believed to be major reservoirs of <a href="/facts/Biodiversity/GruakEzs">biodiversity</a>. They also exert significant influence upon ocean <a href="/facts/Carbon_cycle/gVusRaPF">carbon cycling</a>, dissolution of <a href="/facts/Calcium_carbonate/UQ1wLFna">calcium carbonate</a>, and <a href="/facts/Carbon_dioxide_in_Earth%27s_atmosphere/h6A4HSzy">atmospheric CO2 concentrations</a> over <a href="/facts/Geologic_time_scale/vBAm0D8Q">time scales</a> of a hundred to a thousand years. The structure of abyssal <a href="/facts/Ecosystem/kVE8mSmR">ecosystems</a> is strongly influenced by the rate of <a href="/facts/Marine_snow/mLM6Ea24">flux of food</a> to the seafloor and the composition of the material that settles. Factors such as <a href="/facts/Climate_change/rEN4BDE7">climate change</a>, <a href="/facts/Trawling/rpMEY9r7">fishing practices</a>, and <a href="/facts/Ocean_nourishment/slPNVRIf">ocean fertilization</a> have a substantial effect on patterns of <a href="/facts/Primary_production/14RzcF5E">primary production</a> in the <a href="/facts/Photic_zone/pTrzLGG5">euphotic zone</a>. Animals absorb dissolved oxygen from the oxygen-poor waters. Much dissolved oxygen in abyssal plains came from polar regions that had melted long ago. Due to scarcity of oxygen, abyssal plains are inhospitable for organisms that would flourish in the oxygen-enriched waters above. <a href="/facts/Deep-water_coral/xdSunpFw">Deep sea coral reefs</a> are mainly found in depths of 3,000 meters and deeper in the abyssal and <a href="/facts/Hadal_zone/QXaG9bH2">hadal zones</a>.
Abyssal plains were not recognized as distinct <a href="/facts/Physiographic/NByHKLCQ">physiographic</a> features of the <a href="/facts/Seabed/VvxuEWJu">sea floor</a> until the late 1940s and, until recently, none had been studied on a systematic basis. They are poorly preserved in the <a href="/facts/Geologic_record/37Y1dLN4">sedimentary record</a>, because they tend to be consumed by the subduction process. Due to darkness and a water pressure that can reach about 750 times atmospheric pressure (76 megapascal), abyssal plains are not well explored.

Abyssal plain open-in-new

Abyssal plain