Class 7 Geography

Inside Our Earth

NCERT Solution

Give Reasons:

Question 1: We cannot go to the centre of the earth.

Answer: Since the temperature and pressure increase enormously as we go deeper and deeper inside the earth, we cannot go to the centre of the earth.

Question 2: Sedimentary rocks are formed from sediments.

Answer: Because of extreme compression and hardening of the particles of sediment which are deposited by wind, water, etc.

Question 3: Limestone is changed into marble.

Answer: Because of extreme heat and pressure, limestone undergoes a change in its form and turns into marble.

Match the following:

Column IColumn II
(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
(g) Changes into slate
(h) Process of transformation of rocks

Answer: (i) e, (ii) d, (iii) b, (iv) f, (v) a

Multiple Choice Questions:

Question 1: The rock which is made up of molten magma is

  1. Igneous
  2. Sedimentary
  3. Metamorphic

Answer: (a) Igneous

Question 2: The innermost layer of the earth is

  1. Crust
  2. Core
  3. Mantle

Answer: (b) Core

Question 3: Gold, petroleum and coal are examples of

  1. Rocks
  2. Minerals
  3. Fossils

Answer: (b) Minerals

Question 4: Rocks which contain fossils are

  1. Sedimentary rocks
  2. Metamorphic rocks
  3. Igneous rocks

Answer: (a) Sedimentary rocks

Question 4: The thinnest layer of the earth is

  1. Crust
  2. Mantle
  3. Core

Answer: (a) Crust

Answer the following questions:

Question 1: What are the three layers of the earth?

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

Question 2: What is a rock?

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

Question 3: Name three types of rocks.

Answer: Igneous rocks, sedimentary rocks and metamorphic rocks.

Question 4: How are extrusive and intrusive rocks formed?

Answer: Extrusive rocks are formed by the cooling down and solidification of the molten lava on the earth's surface. Intrusive rocks are formed by the cooling down of the molten magma deep inside the earth’s crust.

Question 5: What do you mean by a rock cycle?

Answer: A cyclic manner is followed in transformation of one type of rock to another type under certain conditions. This process of transformation of the rock from one to another is called the rock cycle.

Question 6: What are the uses of rocks?

Answer: Hard rocks are used for making roads, houses, factories, buildings, etc. Stones are used in many games such as; seven stones (pitthoo), hop – scotch (stapu) and five stones (gitti).

Question 7: What are metamorphic rocks?

Answer: Metamorphic rocks are the rocks that are formed when the igneous and sedimentary rocks change their form under great heat and pressure.