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

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

Class 7 Geography Chapter 2 Inside Our Earth InText Questions and Answers

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.

Class 7 Geography Chapter 2 Inside Our Earth Exercise Questions and Answers

Question 1.
Answer the following questions :
(1) What are the three layers of the earth?
Answer:
The three layers of the earth are:

• Crust
• Mantle
• Core

(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:
Three types of rocks are:

• Igneous rocks also known as primary rocks.
• Sedimentary rocks.
• 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:
One type of rock changes to another type under certain conditions in a cyclic manner. This process of transformation of the rock from one to another is known as the rock cycle. Let’s understand it through example—Igneous rocks change into sedimentary rocks. When the igneous and sedimentary rocks are subjected to heat and pressure, they change into metamorphic rocks. The metamorphic rocks which are still under great heat and pressure meet down to form molten magma. This molten magma again can cool down and solidify into igneous rocks.

(6) What are the uses of rocks?
Answer:
Following are some uses of rocks:

• They are used as fuels
• They are used in industries
• They are used in medicines
• They are used in fertilizers

(7) What are metamorphic rocks?
Answer:
When the igneous and sedimentary rocks are subjected to heat and pressure they change into metamorphic rocks. For example, clay changes into slate and limestone into marble.

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:

Core	Changes into slate
Minerals	Used, for building roads and buildings
Rocks	Made of silica and alumina
Clay	Has the definite chemical composition
Sial	Innermost layer

Answer:

Core	Innermost layer
Minerals	Has the definite chemical composition
Rocks	Used, for building roads and buildings
Clay	Changes into slate
Sial	Made of silica and alumina

Question 4.
Give reasons :
(1) We cannot go to the centre of the earth.
Answer:
To reach the centre of the earth one will have to dig a hole 6000 km. deep on the ocean floor. This is quite impossible and therefore we cannot go to the centre of the earth.

(2) Sedimentary rocks are formed from sediments.
Answer:
Rocks break down into small fragments known as sediments. These sediments are transported and deposited by wind, water, etc. These loose sediments are compressed and hardened to form layers of rocks known as sedimentary rocks.

(3) Limestone is changed into marble.
Answer:
Limestone is changed into marble because igneous and sedimentary rocks change into metamorphic rocks under great heat and pressure.

FOR FUN

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

Karhai	Iron
Ornaments	Gold, silver,
Pan/Tawa	iron
Bell	copper, zinc, iron
Hammer	Iron
Lamp	copper, zinc

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

Ring	silver, gold
Bucket	iron, aluminium
Electric wire	Aluminium, copper