page_title: Abyssal plain
section_title: Cold seeps
hierarchical_section_title: Abyssal plain / Terrain features / Cold seeps
caption_attribution_description: English: Tubeworms, soft corals and chemosynthetic mussels at a seep located 3,000 metres down on the Florida Escarpment. Eelpouts, a Galatheid crab and an alvinocarid shrimp feed on mussels damaged during a sampling exercise. Image from NOAA Ocean Explorer. Français&#160;: Des Vers tubicoles, des coraux mous et des moules chimiosynthétiques vivent autour d'un suintement hydrothermal, à 3000 m aux pieds de l'escarpement du plateau continental de la Floride. Un poisson de la famille des lycodes, un crustacé décapode de la famille des Galatheidae|Galatheidae (sorte de crabe) et une crevette de la famille des Alvinocarididae s'alimentent sur des moules endommagées au cours d'un exercice d'échantillonnage.http://oceanexplorer.noaa.gov/explorations/deepeast01/background/complexity/media/complexity2.html Source de l'image&#160;:[NOAA Ocean Explorer].
context_page_description: An abyssal plain is an underwater plain on the deep ocean floor, usually found at depths between 3,000 metres and 6,000 metres. Lying generally between the foot of a continental rise and a mid-ocean ridge, abyssal plains cover more than 50% of the Earth's surface. They are among the flattest, smoothest, and least explored regions on Earth. Abyssal plains are key geologic elements of oceanic basins.
  The creation of the abyssal plain is the result of the spreading of the seafloor and the melting of the lower oceanic crust. Magma rises from above the asthenosphere, and as this basaltic 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 sediments, mainly clay and silt. Much of this sediment is deposited by turbidity currents that have been channelled from the continental margins along submarine canyons into deeper water. The rest is composed chiefly of pelagic sediments.
context_section_description: Another unusual feature found in the abyssal and hadal zones is the cold seep, sometimes called a cold vent. This is an area of the seabed where seepage of hydrogen sulfide, methane and other hydrocarbon-rich fluid occurs, often in the form of a deep-sea brine pool. The first cold seeps were discovered in 1983, at a depth of 3200 meters in the Gulf of Mexico. Since then, cold seeps have been discovered in many other areas of the World Ocean, including the Monterey Submarine Canyon just off Monterey Bay, California, the Sea of Japan, off the Pacific coast of Costa Rica, off the Atlantic coast of Africa, off the coast of Alaska, and under an ice shelf in Antarctica.
caption: Tubeworms and soft corals at a cold seep 3000 meters deep on the Florida Escarpment. Eelpouts, a galatheid crab, and an alvinocarid shrimp are feeding on chemosynthetic mytilid mussels.
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