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From shallow waters to the deep sea, the open ocean to rivers and lakes, numerous terrestrial and marine species depend on the surface ecosystem and the organisms found there. [28] The ocean's surface acts like a skin between the atmosphere above and the water below, and harbours an ecosystem unique to this environment.
The submerged surface has mountainous features, including a globe-spanning mid-ocean ridge system, as well as undersea volcanoes, [20] oceanic trenches, submarine canyons, oceanic plateaus and abyssal plains. The mass of the oceans is approximately 1.35 × 10 18 metric tons, or about 1/4400 of the total mass of the Earth.
The pelagic zone can be thought of as an imaginary cylinder or water column between the surface of the sea and the bottom. Conditions in the water column change with depth: pressure increases; temperature and light decrease; salinity, oxygen, micronutrients (such as iron, magnesium and calcium) all change.
The ocean's surface is an important reference point for oceanography and geography, particularly as mean sea level. The ocean surface has globally little, but measurable topography, depending on the ocean's volumes. The ocean surface is a crucial interface for oceanic and atmospheric processes.
Salt surface structures are extensions of salt tectonics that form at the Earth's surface when either diapirs or salt sheets pierce through the overlying strata. They can occur in any location where there are salt deposits, namely in cratonic basins, synrift basins, passive margins and collisional margins .
The World Ocean. For example, the Law of the Sea states that all of the World Ocean is "sea", [8] [9] [10] [b] and this is also common usage for "the sea". Any large body of water with "Sea" in the name, including lakes. River – a narrow strip of water that flows over land from a higher elevation to a lower one
The biomass of the abyssal zone actually increases near the seafloor as most of the decomposing material and decomposers rest on the seabed. [9] The composition of the abyssal plain depends on the depth of the sea floor. Above 4000 meters the seafloor usually consists of calcareous shells of foraminifera, zooplankton, and phytoplankton.
In the tropics, with the sun nearly overhead, the temperature of the surface layers can rise to over 30 °C (86 °F) while near the poles the temperature in equilibrium with the sea ice is about −2 °C (28 °F). There is a continuous circulation of water in the oceans.