Inside Our Earth

NCERT Solution

Give Reasons:

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.

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.

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
CoreEarth's surface
MineralsUsed for roads and buildings
RocksMade of silicon and alumina
ClayHas definite chemical composition
SialInnermost layer
Changes into slate
Process of transformation of rocks

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

Multiple Choice Questions:

The rock which is made up of molten magma is

  1. Igneous
  2. Sedimentary
  3. Metamorphic

    Answer: (a) Igneous

The innermost layer of the earth is

  1. Crust
  2. Core
  3. Mantle

    Answer: (b) Core

Gold, petroleum and coal are examples of

  1. Rocks
  2. Minerals
  3. Fossils

    Answer: (b) Minerals

Rocks which contain fossils are

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

    Answer: (a) Sedimentary rocks

The thinnest layer of the earth is

  1. Crust
  2. Mantle
  3. Core

    Answer: (a) Crust

Answer the following questions:

What are the three layers of the earth?

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

What is a rock?

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

Name three types of rocks.

Answer: Igneous rocks, sedimentary rocks and metamorphic rocks.

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.

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.

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).

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.

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