NCERT Solutions class 7 Geography Chapter 2. Inside Our Earth NCERT Exercise

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Q1. Answer the following questions.
(i) What are the three layers of the earth?
(ii) What is a rock?
(iii) Name three types of rocks.
(iv) How are extrusive and intrusive rocks formed?
(v) What do you mean by a rock cycle?
(vi) What are the uses of rocks?
(vii) What are metamorphic rocks?

Answer:

(i) Crust, mantle and core are the three layers of the earth.

(ii) The natural mass of minerals matter that makes up the earth's crust is called rock.

(iii) (a) Igneous rocks,                                                            (b) Sedimantery rocks,                                                            (c) Metamorphic rocks.

(iv) Excrutive rocks are formed due to the rapid colling and solidifaction of molten magma on the earth's surface.                                                    Intrustive rocks are formaed when molten magma cools down deep inside the earth's crust.

(v) The change of one type of rocks into another under certain condition in a cyclic manner is called a rock cycle.

(vi) (a) Used as fuel.                                                            (b) used in industries.                                                            (c) used in medicens.                                                              (d) used in fertilizers.

(vii) The type of rocks formed when igneous and sedimentary rocks undergo heat and pressure are called metamorphic rocks.            

Q2. Tick the correct answer.
(i) The rock which is made up of molten magma is
(a) Igneous (b) Sedimentary (c) Metamorphic
(ii) The innermost layer of the earth is
(a) Crust (b) Core (c) Mantle
(iii) Gold, petroleum and coal are examples of
(a) Rocks (b) Minerals (c) Fossils
(iv) Rocks which contain fossils are
(a) Sedimentary rocks
(b) Metamorphic rocks
(c) Igneous rocks
(v) The thinnest layer of the earth is
(a) Crust (b) Mantle (c) Core

Answer:

(i) (a) Igneous                                                                    (ii) (b) Core                                                                      (iii) (b) Minerals                                                                (vi) (a) Sedimantry rocks                                                          (v) (a) Crust.                                                                                                  
Q3. 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

Answer:

Q4. Give reasons.
(i) We cannot go to the centre of the earth.
(ii) Sedimentary rocks are formed from sediments.
(iii) Limestone is changed into marble.

Answer:

(i) The radius of the earth is more than 6000 Km. To reach the centre of the earth, we have to dig a hole to this depth, which is impossible.

(ii) Rocks breakdown into small fragments under various conditions. These fragments called sediments are transported by wind and water. Layers of sediments are comprresed and hardened. These layers of sediments thus form sedimentary rocks.

(iii) Igneous and sedimentary rocks change their form under great pressure and temperature conditions to form metamorphic rocks. The same thing happens with limestone, which under effect of heat and pressure changes into marble, which is an example of metamorphic rock.                 
Q5. For fun.
(i) What are the minerals most commonly used in the following objects?
(ii) Identify some more objects made up of different minerals.