STRUCTURE OF THE EARTH

             STRUCTURE OF THE EARTH 

The study of the structure of the earth focusses on it's layered structure and the variations in the density and temperature, at various depths. The shape of the earth is that of a spheroid with mean equatorial radius of 6378 km. And polar radius of 6357km.

Broadly, the earth's interior has been divided into three major parts : 

              1.The Crust,

              2.The Mantle,

              3.The Core.



1. The Crust :

                       It is the top most layer of the earth. It's thickness over the oceanic area is generally 5 to 10 kms. Whereas on the continental area, it is 35kms and the thickness ranges from 55 to 70kms in Orogenic belts.

Sub-divisions of the crust :

                       The crust of the earth is sub-divided into sub layers as follows.

                        1. Sial,

                        2. Sima.

2. The Mantle : 

                         It is separated from the over-lying crust by the Mohorovicic - Discontinuity which is a first order discontinuity. It's thickness is about 2865kms. It forms 83% of the earth by volume and 68% by mass.

3. The Core : 

                      It is separated from the mantle by the Guttenberg Weichert Discontinuity and extends up to the center of the earth. It consists of three parts :

                         1. Outer Core,

                         2. Middle Core,

                         3. Inner Core.