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sea-floor topography
cular system that runs with radial branches all through the umbrella. At the
end of the season, the medusae produce eggs; the ciliated planula larvae settie on the seabed to form new polyps while the medusae die and often wash
ashore in great masses. Many species have symbiontic (-tsymbiosis) algae
(e.g., the upside down jellyfish, Cassiopeia), or are luminescent (Pelagia).
Common species of the northern hemisphere are Aurelia, Cyanea,
Chrysaora (sea nettle). In the order Stauromedusea the animal is sessile.
sea interconnected saline waters of the world ocean with a volume of 1.4 10 9
km3• In the special context of wave studies and wave observations the term
"sea" is used for waves generated by or in equilibrium with the wind. If the
wind changes or the waves travel out of their generation area, the waves are
indicated by the term swell. As the higher wave frequencies disappear rapidly outside the wind field, the crests in swell are less steep and the periods are
longer and more regular.
sea anemones -tActiniaria.
sea cucumbers -tHolothuroidea.
sea farming the man-controlled mass production of marine organisms in a sea
area. A distinction can be made between intensive and extensive farming. In
intensive sea farming, organisms (fish, shrimps, etc.) are kept in high densities in cages, enclosed ponds or bays with extra fertilizer or food supply. In
extensive sea farming, animals are kept in the natural system (estuaries,
lagoons, on rafts in the open sea) by stocking the cultured population artificially with brood collected elsewhere in the sea (as in the cultures of, e.g.,
mussels, oysters and clams), or reared in special hatcheries (as, e.g., the
Baltic or Pacific salmon). -taquaculture.
sea-floor spreading -tplate tectonics.
sea-floor topography (syn. bottom topography) the general configuration of the sea
floor, including its relief and man-made features. The largest-scale features
are the continental shelves, reaching down to ca. 100-200 m depth, and the
submarine ridges that divide the ocean floor into deep-sea basins with an
average depth of ca. 4300 m. The shelf grades down towards the deep ocean
along the continental slope; at the slope basis a continental rise and submarine
fans (-tdeep-sea fan) can be found. Other large-scale features are oceanic
trenches [the deepest being the Mariana Trench (11 030 m)], which can extend
for several thousand kilometers. Smaller features are abyssal hills, which cover
most of the abyssal plains, and seamounts, extinct volcanoes, which are isolated elevations rising up to 1000 m above the surrounding sea floor. Along the
shelf edge and the continental slope, submarine canyons are often conspicuous.
sea-floor topography
cular system that runs with radial branches all through the umbrella. At the
end of the season, the medusae produce eggs; the ciliated planula larvae settie on the seabed to form new polyps while the medusae die and often wash
ashore in great masses. Many species have symbiontic (-tsymbiosis) algae
(e.g., the upside down jellyfish, Cassiopeia), or are luminescent (Pelagia).
Common species of the northern hemisphere are Aurelia, Cyanea,
Chrysaora (sea nettle). In the order Stauromedusea the animal is sessile.
sea interconnected saline waters of the world ocean with a volume of 1.4 10 9
km3• In the special context of wave studies and wave observations the term
"sea" is used for waves generated by or in equilibrium with the wind. If the
wind changes or the waves travel out of their generation area, the waves are
indicated by the term swell. As the higher wave frequencies disappear rapidly outside the wind field, the crests in swell are less steep and the periods are
longer and more regular.
sea anemones -tActiniaria.
sea cucumbers -tHolothuroidea.
sea farming the man-controlled mass production of marine organisms in a sea
area. A distinction can be made between intensive and extensive farming. In
intensive sea farming, organisms (fish, shrimps, etc.) are kept in high densities in cages, enclosed ponds or bays with extra fertilizer or food supply. In
extensive sea farming, animals are kept in the natural system (estuaries,
lagoons, on rafts in the open sea) by stocking the cultured population artificially with brood collected elsewhere in the sea (as in the cultures of, e.g.,
mussels, oysters and clams), or reared in special hatcheries (as, e.g., the
Baltic or Pacific salmon). -taquaculture.
sea-floor spreading -tplate tectonics.
sea-floor topography (syn. bottom topography) the general configuration of the sea
floor, including its relief and man-made features. The largest-scale features
are the continental shelves, reaching down to ca. 100-200 m depth, and the
submarine ridges that divide the ocean floor into deep-sea basins with an
average depth of ca. 4300 m. The shelf grades down towards the deep ocean
along the continental slope; at the slope basis a continental rise and submarine
fans (-tdeep-sea fan) can be found. Other large-scale features are oceanic
trenches [the deepest being the Mariana Trench (11 030 m)], which can extend
for several thousand kilometers. Smaller features are abyssal hills, which cover
most of the abyssal plains, and seamounts, extinct volcanoes, which are isolated elevations rising up to 1000 m above the surrounding sea floor. Along the
shelf edge and the continental slope, submarine canyons are often conspicuous.