The earth not a monolitna, and consists of several covers. The soft and liquid cloak is covered by earth's plates on which the seas and oceans – the so-called hydrosphere were formed. All layers of the planet inhabited by living beings are called the biosphere.
Lithosphere
Lithosphere call an outer sheath of Earth from rather solid material: it is earth crust and the top layer of a cloak. The term "lithosphere" was put into practice by the American scientist Burrell in 1916, but at that time meant only solid rocks of which earth crust consists by this concept – softer cloak was not considered as a part of this cover. Included the top sites of this layer of the planet (up to several dozen kilometers wide) in a lithosphere later: they border on a so-called asthenosphere which differs in the lowered viscosity, high temperature at which substances already begin to melt.
Thickness of a lithosphere is various in different parts of Earth: under oceans its layer can make from five kilometers in thickness – under the deepest places, and at the coast already raises up to 100 kilometers. Under continents the lithosphere stretches to two hundred kilometers in depth.
In the past was considered that the lithosphere has monolithic structure and is not segmented. But this assumption is disproved long ago – this cover of the earth consists of several plates which move on a plastic cloak and interact among themselves.
Hydrosphere
As follows from the name, the hydrosphere is the cover of Earth consisting of water, to be exact, all this waters on the surface of our planet and underground: oceans, seas, rivers and lakes and also underground waters. Ices and water in gaseous state or steam are a part of a water cover too. The hydrosphere consists more than of one and a half billion cubic kilometers of water. Water covers 70% of the Earth's surface, its most part is the share of the World Ocean – nearly 98%. Only one and a half percent are allocated for ices on poles, and the rest – the rivers, lakes, reservoirs, underground waters. Fresh water makes only 0.3% of all hydrosphere. The hydrosphere is obliged by the emergence to a lithosphere: from its plates at an early stage of development of Earth water vapor and underground waters was emitted. And we, in turn, are obliged by the emergence to a water cover of the planet: in the ocean the life arose, and without water it is impossible.
Biosphere
The biosphere is not a separate cover of Earth, but a part of other "spheres" inhabited by living beings. Organisms live on the surface of the planet – in a lithosphere, in oceans, the seas and other waters – the hydrosphere and also in the atmosphere which surrounds Earth. All areas where life and waste products of live meets, are called the biosphere. The biosphere initially arose in the hydrosphere – in water, but over time extended to other territories. It is one of the most unstable and unstable covers of Earth: human activity, natural cataclysms and space influences can seriously damage the biosphere.