NCERT Solutions for class 7 Geography Inside our earth

Exercise

1. Answer the following questions.

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

Ans: The three layers of earth are crust, mantle and core.

(ii) What is a rock?

Ans: Rocks are the naturally occurring substance, which are formed of fixed chemical composition.

(iii) Name three types of rocks.

Ans: The three types of rocks are

1. Igneous rock
2. Sedimentary rock
3. Metamorphic rock

(iv) How are extrusive and intrusive rocks formed?

Ans:

1. Intrusive igneous rocks: When molten magma cools down inside the earth’s surface and become solid is called intrusive igneous rocks.
2. Extrusive igneous rocks: When the molten magma coos down on the surface of the earth and become solid is called extrusive igneous rock.

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

Ans: The process of conversion of one rock to another is known as Rock cycle.

(vi) What are the uses of rocks?

Ans: Rocks are used in our daily life for various purposes:

1. Making cement
2. Roofing material
3. Writing chalks
4. Building material

(vii) What are metamorphic rocks?

Ans: Metamorphic rocks are formed when igneous and sedimentary rocks go under high pressure and temperature.

2. Tick the correct answer.

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

(a) Igneous (b) Sedimentary (c) Metamorphic

Ans: (a) Igneous

(ii) The innermost layer of the earth is

(a) Crust (b) Core (c) Mantle

Ans: (b) core

(iii) Gold, petroleum and coal are examples of

(a) Rocks (b) Minerals (c) Fossils

Ans: (b) Minerals

(iv) Rocks which contain fossils are

(a) Sedimentary rocks (b) Metamorphic rocks (c) Igneous rocks

Ans: (a) Sedimentary rocks

(v) The thinnest layer of the earth is

(a) Crust (b) Mantle (c) Core

Ans: (a) Crust

3. Match the following.

(i) Core	(a) Earth’s surface
(ii) Minerals	(b) Used for roads and buildings
(iii) Rocks	(c) Made of silicon and alumina
(iv) Clay	(d) Has definite chemical composition
(v) Sial	(e) Innermost layer
	(f) Changes into slate
	(g) Process of transformation of the rock

Ans:

(i) Core	(a) Innermost layer
(ii) Minerals	(b) Has definite chemical composition
(iii) Rocks	(c) Used for roads and buildings
(iv) Clay	(d) Changes into slate
(v) Sial	(e) Made of silicon and alumina

 

4. Give reasons.

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

Ans: There is high pressure and temperature at the centre of the earth where we cannot survive. Hence, it not possible to go to the centre of the earth.

(ii) Sedimentary rocks are formed from sediments.

Ans: Sediments are broken piece of igneous rock. When sediments are compressed together they form sedimentary rock.

(iii) Limestone is changed into marble

Ans: Due to high pressure and temperature limestone changes into marble.

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