NCERT Solutions for Class 7 Geography Chapter 2 – Inside Our Earth

NCERT Solutions for Class 7 Geography Chapter 2 – Inside Our Earth

1. Answer the following questions.

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

The three layers of the earth are:

  • Crust
  • Mantle
  • Core

(ii) What is a rock?

The earth’s outermost layer or the crust is made up of the lithosphere, which consists of various types of rocks. Rocks are therefore mineral mater which maybe formed due to various reasons millions of years ago. Rocks can be divided into various classes depending on its size, colour, hardness, composition as well as texture.

(iii) Name three types of rocks.

Rock’s on the earth’s surface are classified based on their mode of origin. They are:

  • Igneous Rocks
  • Sedimentary Rocks
  • Metamorphic Rocks

(iv) How are extrusive and intrusive rocks formed?

Igneous rocks are formed primarily due to the solidification of lava when it comes out of the earth through a volcano. Igneous rocks are further divided into two categories based on their location.

  • Intrusive Igneous Rocks: These are found below the surface of the earth, as the volcano erupts some of the magma does not reach the surface and solidifies into cracks and fissures. For example: Granite.
  • Extrusive Igneous Rocks: This type of rocks are found on the surface. They are poured out from the volcanic craters during an eruption, crystallise and form extrusive rocks. Basalt is an example of extrusive igneous rocks.

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

Rock cycle is the transformation of one type of rock into another after millions of years. The igneous rocks are known as the primary rocks as they are formed primarily out of volcanic substance, this type of rock may after millions of years be eroded by river and transported over a layer of sandstone to form a sedimentary rock. This sedimentary rock which is also known as a secondary rock, may under intense pressure after another 100 million years be converted to metamorphic rock. This cycle goes on and is extremely important for geographers and geologists who study rocks.

(vi) What are the uses of rocks?

Rocks are very useful to us because :

◆ rocks are of great resource value, they have various minerals stored within it which may have precious stones.

◆ Soils are derived from weathering of rocks.

◆ Rocks are used for building walls of houses, for paving roads and other solid structures like bridges, wells dams.

(vii) What are metamorphic rocks?

The Greek word ‘metamorphose’ means a “change in structure or form”. These types of rocks are not formed naturally but are converted from either the igneous rocks or the sedimentary rocks under great pressure or intensive amounts of heat.

NCERT Solutions for Class 7 Geography Chapter 2 – Inside Our Earth

2. Tick the correct answer.

(i) The rock which is made up of molten magma is
(a) Igneous

(b) Sedimentary
(c) Metamorphic

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

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

(iv) Rocks which contain fossils are
(a) Sedimentary rocks

(b) Metamorphic rocks
(c) Igneous rocks

(v) The thinnest layer of the earth is
(a) Crust

(b) Mantle
(c) Core

NCERT Solutions for Class 7 Geography Chapter 2 – Inside Our Earth

3. Match the following.

NCERT Solutions for Class 7 Geography Chapter 2 Question 3

NCERT Solutions for Class 7 Geography Chapter 2 – Inside Our Earth

4. Give reasons.

(i) We cannot go to the centre of the earth: The centre of the earth or the core is composed of molten rocks mainly iron and nickel, it is extremely hot with temperatures above 4,400° Celsius.

(ii) Sedimentary rocks are formed from sediments: Sedimentary rocks are made of different layers od sediments brought by the rivers, winds, tides, glaciers etc. They get deposited on top of the other and harden to form sedimentary rocks.

(iii) Limestone is changed into marble:  Limestone is a sedimentary rock whivh is metamorphosed to marble due to extreme compression by the overlying layers. The particles are tightened and hardened to form marble which is an extremely hard rock.

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