Class 7 Geography

Inside Our Earth

The earth is a dynamic planet i.e. it continuously undergoes changes. These changes are:

Interior of the earth

The earth is made up of several concentric layers. Concentric means having a common centre. The arrangement is like a ball inside another ball which is inside a third ball.

interiors of earth

Broadly, there are three layers of the earth:

  1. Crust
  2. Mantle
  3. Core

The Crust

It is the outermost layer over the earth's surface. It is

The main minerals constituting the continental mass are:

The continental mass is also called sial. The name sial is derived from letters si of silicon and al of alumina.

The main mineral constituents of the oceanic crust are:

The oceanic crust is called sima. The root of the word sima is si from silica and ma from magnesium.


It is the layer just beneath the crust and extends up to a depth of 2900 km below the crust.


It is the innermost layer i.e. it is below the mantle. Its radius is about 3500 km. The core consists of outer core and inner core. It is mainly made up of:

The innermost layer is also called nife. The name nife is derived from the word ni from nickel and fe from ferrous meaning iron. The temperature and pressure of the central core is very high.