Inside Our Earth

Q1. Answer the following questions.

(i) What are the three layers of the earth?

Ans:

Three Layers of the Earth are crust, mantle & core.

(ii) What is a rock?

Ans:

A mass of mineral matter that makes up the crust of the earth is called rock.

(iii) Name three types of rocks.

  Ans:

Three types of rocks are igneous, sedimentary & metamorphic rocks. 

(iv)  How are extrusive and intrusive rocks formed?

Ans:

1. Lava is the hot red molten magma coming out from the interior of the earth.
2. When this molten lava comes on the surface of the earth, it cools down rapidly and becomes solid to form rocks on the crust are called extrusive rocks. Eg: basalt rock.
3. Sometimes, the molten magma cools down deep inside the earth's crust to form solid rocks called intrusive rocks. Eg: granite                            

(v) What do you mean by a rock cycle?   

Ans:

1. Molten magma cools & solidifies to form igneous rocks.
2. Igneous rocks are broken into small particles to form sedimentary rocks.
3. Igneous and sedimentary rocks are subjected to heat and pressure they change into metamorphic rocks,
4. The metamorphic rocks which are still under heat & pressure melt down to form molten magma which cools and solidifies to form igneous rocks.
5. This process of transformation of rocks from one form to another is called the rock cycle.       

(vi) What are the uses of rocks?

Ans:

The uses of rocks are:

1. Hard rocks like stones, slate, granite, marble, etc. are used in making roads, house, buildings, bridges and barrages.
2. To play numerous games like Seven stones (phitthoo), Hopscotch (stapu), five stone (gitti).

(vii) What are metamorphic rocks?

Ans:

Igneous and sedimentary rocks, under heat and pressure change their form to metamorphic rocks.
Examples: Clay changes to slate, limestone changes to marble.

Q2. Tick the correct answer.

(i) The rock which is made up of molten magma is

Ans: (a) Igneous

(ii) The innermost layer of the earth is  

Ans: (b) core

(iii) Gold, petroleum and coal are examples of  

Ans: (b) minerals

(iv) Rocks which contain fossils are 

Ans: (a) Sedimentary rocks

(v) The thinnest layer of the earth is  

Ans: (a) Crust

Q3. Match the following

Ans:

Q4. Give reasons.

(i) We cannot go to the center of the earth.

Ans:

We cannot go to the center of the earth because:

1. The radius of the earth is 6371 km which is the thickness of the earth from the crust to the core.
2. As we move from the crust to the core the temperature and pressure increases.
3. Due to this everything is in a molten state as we move towards the core.
4. There is no oxygen.
5. We cannot go to the center of the earth as we can't survive these conditions.

(ii) Sedimentary rocks are formed from sediments.

Ans:

1. Rocks crack, roll, hit each other and break into small pieces called sediments due to weathering.
2. These sediments are carried & deposited away by water, wind, glacier, etc. in low lying areas.
3. These sediments get compressed & hardened to form layers of rocks.
4. These are sedimentary rocks.

(iii) Limestone is changed into marble.  

Ans:

Limestone is changed into marble due to the following reasons:

1. Limestone is a type of sedimentary rock.
2. Due to high pressure of the overlying layers of rocks and high temperature limestone changes form.
3. It changes to marble.