Interior of the Earth:What is the earth made up of? - gk lokam

3 February 2020

Interior of the Earth:What is the earth made up of?

 Interior of the Earth:What is the earth made up of?

The earth, our homeland is a dynamic planet. It is constantly undergoing changes inside and outside. 

what lies in the interior of the earth?

The earth, our homeland is a dynamic planet. It is constantly undergoing changes inside and outside.

Just like an onion, the earth is made up of several concentric layers with one inside another .

 Earth's outer Layer : The Crust

The uppermost layer over the earth’s surface is called the crust. It is the thinnest of all the layers.

It is about 35 km. on the continental masses and only 5 km. on the ocean floors.

The main mineral constituents of the continental mass are silica and alumina. It is thus called sial (si-silica and al-alumina).

The oceanic crust mainly consists of silica and magnesium; it is therefore called sima (si-silica and ma-magnesium)


Just beneath the crust is the mantle which extends up to a depth of 2900 km. below  the crust


The innermost layer is the core with a radius of about 3500 km. It is mainly made up of nickel and iron and is called nife (ni – nickel and fe – ferrous i.e. iron).

The central core has very high temperature and pressure.

 The crust forms only 1 per cent of the volume of the earth,84 per cent consists of the mantle and 15 per cent makes the core.


The earth’s crust is made up of various types of rocks

 What is a Rock?

Any natural mass of mineral matter that makes up the earth’s crust is called a rock.

Rocks can be of different colour, size and texture.

There are three major types of rocks: 

igneous rocks, sedimentary rocks and metamorphic rocks.

Origin of name of rocks:

Igneous: Latin word Ignis meaning fire.

Sedimentary: Latin word sedimentum meaning settle down.

Metamorphic: Greek word metamorphose meaning change.

 Lava is actually fiery red molten magma coming out from the interior of the earth on its surface. When this molten lava comes on the earth’s surface, it rapidly cools down and becomes solid.

 extrusive igneous rocks

Rocks formed in such a way on the crust are called extrusive igneous rocks. They have a very fine grained structure.

For example, basalt. 

The Deccan plateau is made up of basalt rocks. 

intrusive igneous rocks:

Sometimes the molten magma cools down deep inside the earth’s crust. Solid rocks so formed are called intrusive igneous rocks.

Since they cool down slowly they form large grains.
Granite is an example of such a rock.

Grinding stones used to prepare paste/powder of spices and grains are made of granite.

sedimentary rocks:


Rocks roll down, crack, and hit each other and are broken down into small fragments. These smaller particles are called sediments.

These sediments are transported and deposited by wind, water, etc.
These loose sediments are compressed and hardened to form layers of rocks. These types of rocks are called sedimentary rocks.

For example, sandstone is made from grains of sand.

These rocks may also contain fossils of plants, animals and other microorganisms that once lived on them.

metamorphic rocks:


Igneous and sedimentary rocks can change into metamorphic rocks under great heat and pressure.

For example, clay changes into slate and limestone into marble.

Uses of Rocks:

Rocks are very useful to us. The hard rocks are used for making roads, houses and buildings.

We use stones in many games. For example, seven stones (pitthoo), hopscotch (stapu/kit kit), five stones (gitti).

The Red Fort is made of red sandstone .

The Taj Mahal is made of white marble

What is a Rock Cycle?

One type of rock changes to another type under certain conditions in a cyclic manner. This process of transformation of the rock from one to another is known as the rock cycle.

when the molten magma cools; it solidifies to become igneous rock.

These igneous rocks are broken down into small particles that are transported and deposited to form sedimentary rocks.

When the igneous and sedimentary rocks are subjected to heat and pressure they change into metamorphic rocks. 

The metamorphic rocks which are still under great heat and pressure melt down to form molten magma.

This molten magma again can cool down and solidify into igneous rocks Rocks are made up of different minerals.


Minerals are naturally occurring substances which have certain physical properties and definite chemical composition.

Minerals are very important to humankind. Some are used as fuels. For example, coal, natural gas and petroleum.

They are also used in industries – iron, aluminium, gold, uranium, etc, in medicine, in fertilisers, etc.

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