Class 7 NCERT Solutions for Social Science (Geography) Chapter – 2 Inside Our Earth

Inside Our Earth

Text Book Page No. 9

Question 1.
Collect pictures of some monuments and find out which are the rocks used to build them. Two pictures have been collected for you.

Answer:

  1. Qutub Minar – Red sandstone.
  2. Ashokan Pillar – Iron.
  3. Jama Masjid – Red sandstone.

Text Book Page No. 10

Question 1.
What are the minerals found in your state?

Answer:
Students do themselves. For the convenience of students one example is given below :

  • Students of Chhattisgarh – Iron ore.
  • Students of Orissa – Bauxite, mica.

Exercise Questions and Answers

Question 1.
Answer the following questions :

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

Answer:
Crust, mantle and core are the three layers of the earth.

(2) What is a rock?

Answer:
The natural mass of mineral matter that makes up the earth’s crust is called rock.

(3) Name three types of rocks.

Answer:
The three types of rocks are :
(a) Igneous rocks
(b) Sedimentary rocks
(c) Metamorphic rocks

(4) How are extrusive and intrusive rocks formed?

Answer:
Extrusive rocks are formed due to ‘ the rapid cooling and solidification of molten magma on the earth’s surface. Intrusive rocks are formed when molten magma cools down deep inside the earth’s crust.

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

Answer:
The change of one type of rocks into another under certain conditions in a cyclic ” manner is called a rock cycle.

(6) What are the uses of rocks?

Answer:
Following are some uses of rocks :
(a) They are used as fuels
(b) They are used in industries
(c) They are used in medicines
(d) They are used in fertilizers

(7) What are metamorphic rocks?

Answer:
The type of rocks formed when igneous and sedimentary rocks undergo heat and pressure are called metamorphic rocks.

Question 2.
Tick the correct answer :

(1) The rock which is made up of molten magma is
(a) Igneous
(b) Sedimentary
(c) Metamorphic
Answer:
(a) Igneous

(2) The innermost layer of the earth is
(a) Crust
(b) Core
(c) Mantle
Answer:
(b) Core

(3) Gold, petroleum and coal are examples of
(a) Rocks
(b) Minerals
(c) Fossils
Answer:
(b) Minerals

(4) Rocks which contain fossils are
(a) Sedimentary rocks
(b) Metamorphic rocks
(c) Igneous rocks
Answer:
(a) Sedimentary rocks

(5) The thinnest layer of the earth is
(a) Crust
(b) Mantle
(c) Core
Answer:
(a) Crust

Question 3.
Match the following :

CoreChanges into slate
MineralsUsed, for building roads and buildings
RocksMade of silica and alumina
ClayHas definite chemical composition
SialInnermost layer

Answer:

CoreInnermost layer
MineralsHas definite chemical composition
RocksUsed, for building roads and buildings
ClayChanges into slate
SialMade of silica and alumina

Question 4.
Give reasons :

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

Answer:
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.

(2) Sedimentary rocks are formed from sediments.

Answer:
Rocks breakdown into small fragments tinder various conditions. These fragments, called sediments, are transported by wind and water. Layers of sediments are formed when loose sediments are compressed and hardened. These layers of sediments thus form sedimentary rocks.

(3) Limestone is changed into marble.

Answer:
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 the effect of heat and pressure changes into marble, which is an example of metamorphic rock.

FOR FUN

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

Answer:

KarhaiIron
OrnamentsGold, silver,
Pan/Tawairon
Bellcopper, zinc, iron
HammerIron
Lampcopper, zinc

(2) Identify some more objects made up of different minerals.

Answer:

Ringsilver, gold
Bucketiron, aluminium
Electric wireAluminium , copper