However water is found elsewhere in the solar system. Clarke has pointed out it would be more appropriate to refer to planet Earth as planet Ocean. By volume, the ocean provides about 90 percent of the living space on the planet. Jupiter's moon Europa may have an underground ocean which supports life.Īltogether the ocean occupies 71 percent of the world surface, averaging nearly 3.7 kilometres (2.3 mi) in depth. Shifts in the oceanic temperature distribution can cause significant weather shifts, such as the El Niño-Southern Oscillation. Sea water has an important influence on the world's climate, with the oceans acting as a large heat reservoir. The oceans are also a reservoir of dissolved atmospheric gases, which are essential for the survival of many aquatic life forms. Some salts are released from volcanic activity or extracted from cool igneous rocks. Most of the salt in the ocean comes from the weathering and erosion of rocks on land. The average salinity of Earth's oceans is about 35 grams (1.2 oz) of salt per kilogram of seawater (3.5% salt). Most fresh water – about 69% – is present as ice in ice caps and glaciers.
The Earth's water cycleĪbout 97.5% of the water on Earth is saline the remaining 2.5% is fresh water. If all of Earth's crustal surface was at the same elevation as a smooth sphere, the depth of the resulting world ocean would be about 2.7 kilometres (1.7 mi). The world ocean covers an area of 3.618 ×10 8 km 2 with a mean depth of 3682 m, resulting in an estimated volume of 1.332 ×10 9 km 3. The mass of this world ocean is 1.35 ×10 18 metric tons, or about 1/4400 of Earth's total mass. Ĭonventionally the planet is divided into five separate oceans, but these oceans all connect into a single world ocean.
Earth's hydrosphere consists chiefly of the oceans, but technically includes all water surfaces in the world, including inland seas, lakes, rivers, and underground waters down to a depth of 2,000 metres (6,600 ft) The deepest underwater location is Challenger Deep of the Mariana Trench in the Pacific Ocean, having a depth of 10,900 metres (6.8 mi). The abundance of surface water on Earth is a unique feature in the Solar System. Quantities in relation to 1 kg or 1 litre of sea water. The Nobel Prize winner Albert Szent-Györgyi referred to water as the mater und matrix: the mother and womb of life. Water is the only common substance to exist as a solid, liquid, and gas under conditions normal to life on Earth. It has been described as the universal solvent for its ability to dissolve many substances, and as the solvent of life. The term marine comes from the Latin mare, meaning "sea" or "ocean". Marine life is studied scientifically in both marine biology and in biological oceanography. Marine microorganisms, including protists and bacteria and their associated viruses, have been variously estimated as constituting about 70% or about 90% of the total marine biomass. Marine species range in size from the microscopic like phytoplankton, which can be as small as 0.02 micrometres, to huge cetaceans like the blue whale – the largest known animal, reaching 33 m (108 ft) in length. An average of 2,332 new species per year are being described. dolphins, whales, otters, and seals) need to surface periodically to breathe air.Īs of 2023, more than 242,000 marine species have been documented, and perhaps two million marine species are yet to be documented. Fish have gills instead of lungs, although some species of fish, such as the lungfish, have both. Marine invertebrates exhibit a wide range of modifications to survive in poorly oxygenated waters, including breathing tubes as in mollusc siphons. Plankton forms the general foundation of the ocean food chain, particularly phytoplankton which are key primary producers. Plant forms such as kelp and other algae grow in the water and are the basis for some underwater ecosystems. One group of amphibians evolved into reptiles and mammals and a few subsets of each returned to the ocean as sea snakes, sea turtles, seals, manatees, and whales. Some of these evolved into amphibians, which spend portions of their lives in water and portions on land. The earliest vertebrates appeared in the form of fish, which live exclusively in water. By volume, oceans provide about 90% of the living space on the planet. Most life forms evolved initially in marine habitats. Marine life in part shape and protect shorelines, and some marine organisms even help create new land (e.g. Marine organisms, mostly microorganisms, produce oxygen and sequester carbon.
At a fundamental level, marine life affects the nature of the planet. Marine life, sea life, or ocean life is the plants, animals, and other organisms that live in the salt water of seas or oceans, or the brackish water of coastal estuaries.
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