NCERT Solutions For Class 7 Geography Social Science Chapter 2 Inside Our Earth

Q 1- Answer the following questions.

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

Ans :-  The three layers of the earth are :-

i)  Crust – the uppermost layer.

ii) Mental – the middle layer.

iii) Core – the inner most layer.

(ii)   What is a rock?

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

(iii)  Name three types of rocks.

Ans :-    Three types of rocks are :-

i) Igneous rocks

ii) Sedimentary rocks                     

iii) Metamorphic rocks

(iv) How are extrusive and intrusive rocks formed?

Ans-

Intrusive rocks – When the molten magma coming out of the earth, cools down deep inside the earth’s crust. It forms intrusive igneous rocks.

Extrusive rocks – When the molten magma comes out of the earth, it cools down rapidly on the surface of the earth to form extrusive igneous rocks.

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

Ans:-     The process of transformation of rocks from one form to another due to extreme heat and pressure is called rock cycle.

(vi)  What are the uses of rocks?

Ans :-    Rocks  can be used for :-

                (i) Construction of roads and buildings.

                (ii) Obtaining minerals like coal, iron etc.

                (iii) Grinding of spices and grains.

(vii)  What are metamorphic rocks?

Ans :-   Rocks arising from the transformation of existing rocks into new types of rocks through the process of metamorphism, is called metamorphic rock.

                Example : Slate, Marble etc.

Q 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 :-    (b) Metamorphic rocks

                (v) The thinnest layer of the earth is

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

Ans :-    (a) Crust

Q 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)           (e)

                (ii)           (d)

                (iii)          (b)

                (iv)         (f)

                (v)          (c)

Q 4- Give reasons.

                (i)            We can not go to the center of the earth.

                Reasons – We can not go to the center of the earth because the center lies in the 3rd layer i.e. core which has very high temperature and pressure.

                  This layers remains in molten state due to high temperature.

                (ii)           Sedimentary rocks are formed from sediments.

                Reasons – Sediments of igneous rocks are transported by water and wind and deposited at some place.

                These depositions when undergo high temperature and pressure, sedimentary rocks are formed.

                (iii)          Limestone is changed into marble.

Ans-       Limestone when subjected to high temperature and pressure, it changes its form to become marble.

Q 5– For fun.

                (i) What are the minerals most commonly used in the following objects?

Ans-