All World Ocean, water of the rivers and other reservoirs, and also underground waters and eternal ices are united in the uniform hydrosphere of Earth. The water cover of the earth is in continuous interaction with earth crust and the atmosphere. The hydrosphere became the place of origin of life on our planet.
The hydrosphere (from ""hydra"" - water and ""sphere"" - a sphere) - a faltering water cover of Earth which is located a boundary the atmosphere and solid earth crust (lithosphere). It is set of oceans, seas, rivers and all surface water of sushi. It includes also underground waters, snow and ice of the Arctic and Antarctic. Even atmospheric water and water of living organisms, joins in this concept. Surface and atmospheric water makes only percent shares from all volume of the hydrosphere. The bulk of water is concentrated in the seas and oceans. The second place on volume belongs to underground waters. The third is occupied by water of glaciers and snow of Antarctica.
Despite insignificant percent from lump, a surface water plays an important role in life of people. They are a source of drinking and service water which people use for the needs.
Waters of the hydrosphere are in continuous continuous interaction with the atmosphere and a lithosphere. Passing from one phase into another, they take part in water cycle in the nature. All forms of water cycle make a uniform hydrological cycle in the course of which there is a resumption of all types of waters. The most long period is the share of updating of glaciers and deeply lying underground waters. Atmospheric waters and biological waters which are a part of plants and animals are most quicker updated. The hydrosphere - the system which is not closed. Between its waters there is a close interrelation which causes unity of a water cover of Earth as a natural system and its interaction with other geospheres. Besides, water is a life cradle on our planet. Only in the beginning the Palaeozoic Era living organisms came out of the water. Up to this point they grew and developed in the water environment. The modern hydrosphere - result of long evolution of Earth and differentiation of its substances.