NCERT Class 7 Geography Chapter 2 - Inside Our Earth

Chapter 2 - Inside Our Earth

Question 1: Answer the following questions.
i) What are the three layers of Earth?
Answer: The three layers of Earth are crust, mantle and core.

ii) What is a rock?
Answer: Any natural mass of mineral matter that makes up the earth’s crust is called a rock. Rocks can be of different colour, size and texture.

iii) Name three types of rocks.
Answer: There are three types of rocks. They are:
• Igneous rocks
• Sedimentary rocks
• Metamorphic rocks

iv) How are extrusive and intrusive rocks formed?
Answer: When the molten lava comes on the earth’s surface, it rapidly cools down and becomes solid. Rocks formed in such a way on the crust are called extrusive igneous rocks. They have a very fine grained structure. Sometimes the molten magma cools down deep inside the earth’s crust. Solid rocks so formed are called intrusive igneous rocks. Since they cool down slowly they form large grains.

v) 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.

vi) What are the uses of rocks?
Answer: Some uses of rocks are:
• The hard rocks are used for making roads, houses etc.
• It is used for games like seven stones (pitthoo), hopscotch (stapu/kit kit), etc.

vii) What are metamorphic rocks?
Answer: The type of rocks which are formed by igneous and sedimentary rocks that change under great heat and pressure are called metamorphic rocks.

Question 2: Tick the correct answer.
i) The rock which is made up of molten magma is
a) Igneous
b) Sedimentary
c) Metamorphic
Answer: a) Igneous

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

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

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

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

Question 3: Match the following

Answer:

4. Give reasons.
i) We cannot go to the centre of the earth.
Answer: We cannot go to the centre of the earth because the temperature and pressure at the centre of the earth, i.e., core, is very high and not just we humans, but even rocks melt due to this intensity.

ii) Sedimentary rocks are formed from sediments.
Answer: Rocks roll down, crack and hit each other and break down into small fragments. These small fragments of rock are called sediments. These sediments are transported and deposited by wind, water, etc. and are compressed and hardened to form layer of rocks called the sedimentary rocks.

iii) Limestone is changed into marble.
Answer: Igneous and sedimentary rocks change into metamorphic rocks under great heat and pressure. This takes place in case of limestone. Under great heat and pressure limestone changes into marble.