Hydrosphere

What distinguishes the Earth from the other planets is the presence of the seas and oceans. Satellite pictures show the Earth as a “blue” planet, because two thirds of its surface are covered by huge masses of water. The whole of the earth’s environments where water is present in its liquid, solid or gaseous state is called hydrosphere. Most water can be found in the oceans, underground waters and in its solid state as ice in polar hemispheres. Water contained in the atmosphere as water vapour is instead just a very small part of the total amount. But this small part is very important in order to maintain the climate and feed the underground layers. Generally speaking, the hydrosphere can be divided into two different environments: salty water basins (seas and oceans) and fresh water basins. The main feature that distinguishes salty water basins from fresh water basins is their high salt content (or salinity), which is generally 35 grams per litre. Fresh water basins (or continental waters) can be divided into surface waters (rivers, lakes, lagoons, marshes) and underground waters (deep layers, surface layers and springs).

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From the Multimedia section

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    Availability of water resources

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    The water cycle

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    Map of water scarcity

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    Annual availability of freshwater

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    Hydrosphere

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    Surface tension

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  • water

    Availability of water resources

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  • water

    The water cycle

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  • water

    Map of water scarcity

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