3rd Class Science Our Environment Rocks and Minerals

Rocks and Minerals

Category : 3rd Class

*     Rocks and Minerals

 

Small grains lump together to form rock. Hard surface of the earth constitutes the rock. Rocks are also formed inside the earth from mud and sand under high pressure and heat.

 

*           Types of Rocks

There are three types of rocks, namely, igneous rock, sedimentary rock and metamorphic rock. All the rocks are formed in different ways.

 

Look at the following picture of different types of rocks:

 

 

 

*         Igneous Rocks

With volcanic eruptions, melted magma comes out on the surface of the earth. When these melted magma cool to solidify, igneous rocks are formed.

 

*       Sedimentary Rocks

This rock is formed by sedimentation of material at the surface of the earth and within the bodies of water.   

 

*       Metamorphic Rocks

Igneous and sedimentary rocks changes to metamorphic rock under heat and high pressure.

 

*       Marbles and Slate

Rock is made up of grains or crystals called minerals.

Diamond is a mineral, which is the hardest substance in the world. Other minerals are rubies, emeralds, sapphires, gold, silver etc. which are used in making jewelry and ornaments. Taj Mahal, a beautiful monument in India is made up of marble which is a rock.  

*       Uses of Rocks

Rocks are used in building and construction work. For example : Marble, slate, limestone granite etc. It is used for the making of ornaments and jewelry. For example : Gold silver, diamond. Rubies (minerals).

 

 

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     Which one of the following types of rock is formed when melted magma cool to solidify?

(a) Igneous rock

(b) Metamorphic rock

(c) Sedimentary rock  

(d) All of these

(e) None of these

 

Answer: (a)

Explanation

When melted magma cool to solidify. Igneous rock is formed. Therefore, option (a) is correct and rest of the options is incorrect.

 

 

    Which one of the following rocks changes into soil?

(a) Igneous rocks

(b) Metamorphic rocks

(c) Sedimentary rocks

(d) All of these

(e) None of these

 

Answer: (d)

Explanation

All rocks are changed into soil by natural means. Therefore, option (d) is correct and rest of the options is incorrect.

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