Question

Page No
7)
Write two characterstics of each of
the following (a) Crust (b) Mankle.
​

Answer 1

Crust

• It is the outermost solid part of the earth, normally about 8-40 kms thick.

• It is brittle in nature.

• Nearly 1% of the earth’s volume and 0.5% of earth’s mass are made of the crust.

• The thickness of the crust under the oceanic and continental areas are different. Oceanic crust is thinner (about 5kms) as compared to the continental crust (about 30kms).

• Major constituent elements of crust are Silica (Si) and Aluminium (Al) and thus, it is often termed as SIAL (Sometimes SIAL is used to refer Lithosphere, which is the region comprising the crust and uppermost solid mantle, also).

Mantle

• The portion of the interior beyond the crust is called as the mantle.

• The discontinuity between the crust and mantle is called as the Mohorovich Discontinuity or Moho discontinuity.

• The mantle is about 2900kms in thickness.

• Nearly 84% of the earth’s volume and 67% of the earth’s mass is occupied by the mantle.

• The major constituent elements of the mantle are Silicon and Magnesium and hence it is also termed as SIMA