Abyssal
Abyssal (from the Greek ἄβυσσος abyssos - bottomless depth, the bottomless; according to early ideas the ocean had no bottom) is, according to the majority view in research, the part of the seabed (marine benthal ) between 2,000 m and 6,000 m water depth, but sometimes it is also the This includes the entire deep sea area .
geology
The Abyssal includes the deepest parts of the continental shelf (continental rise) and to seaward subsequent, relatively powerful sediments covered deep sea levels , also known as the Abyssal Plains, and the basaltic , barely covered by sediments mid-ocean ridges . These areas make up almost 60% (58.3%) of the surface of the earth's body. On the continental rise and in the landward area of deep-sea sediments from the levels can turbiditic and sand containing sequences exist because at the shelf edge accumulating clasticSediment masses in some places regularly move down the continental slope in the form of huge submarine landslides ( turbidity currents ) . Otherwise, mainly purely pelagic sediments are deposited in the abyssal, i.e. sediments that consist almost exclusively of microscopically fine particles that slowly sink into the water column. Here, carbonatic sludge is restricted to sea depths above the calcite compensation depth (CCD), which is around 4,000 to 5,000 m . Below the CCD, the sea floor is covered extensively by red to brown deep-sea clay or otherwise non-carbonatic mud.
biology
The abyssal is lightless and therefore without plant life. This habitat ( biotope ), which is characterized by cold and constant conditions, is inhabited by benthic sponges , coelenterates , worms , crabs and echinoderms .
At the edge of the mid-ocean ridges there are hydrothermal springs with so-called black smokers , white smokers and hot vents with a highly specialized fauna that draws its energy from the rising sulfur compounds.
literature
- Robert J. Menzies et al .: Abyssal environment and ecology of the world oceans. Wiley, New York, 1973
- Richard Ellis: Deep Atlantic - Life, Death, and Exploration in the Abyss. Knopf, New York 1998, ISBN 0-679-43324-4
