PETROLOGY

Shell Structure of the Earth

The crust, which is the outermost solid part of our earth is made up of different kind of rocks. The thickness of the crust is approximately 35 (thirty-five) km. Below this is separated from the mantle by the Moho discontinuity.

The rock crust is approximately called lithosphere, litho which means rock, and sphere which means zone or shell. The surface of this crust is uneven with many depression and elevations. These depressions are filled with water and are variously called lakes, seas, and oceans.

The discontinuous body of water in association with lithosphere is called hydrosphere. On land masses of the lithosphere and in water bodies of the hydrosphere, all living creatures exist. This is described as the biosphere. All these, in turn, are enveloped by a layer of ait which called atmosphere.