RBSE Class 7 Social Science Notes Geography Chapter 2 Inside Our Earth

These comprehensive RBSE Class 7 Social Science Notes Geography Chapter 2 Inside Our Earth will give a brief overview of all the concepts.

RBSE Class 7 Social Science Notes Geography Chapter 2 Inside Our Earth

→ The earth is a dynamic planet. It is constantly undergoing changes inside and outside.

→ Interior of the Earth:
The earth is made up of several concentric layers with one inside another. They are :

→ Crust:

• The uppermost layer over the earth’s surface is called the crust,
• It is the thinnest of all the layers. It is about 35 km. on the continental masses and only 5 km. on the ocean floors. The main mineral constituents of the continental mass are silica and alumina.

→ Mantle:
Just beneath the crust is the mantle which extends up to a depth of 2900 km. below the crust. The innermost layer is the core.

→ Rocks

• The earth’s crust is made up of various types of rocks.
• Any natural mass of mineral matter that makes up the earth’s crust is called a rock.
• There are three major types of rocks :
  • igneous rocks,
  • sedimentary rocks and
  • metamorphic rocks.

(i) Igneous rocks: When the molten magma cools, it becomes solid. Rocks thus formed are called, igneous rocks. There are two types of igneous rocks :
(a) intrusive rocks and
(b) extrusive rocks.

(ii) Sedimentary rocks: Rocks roll down, crack, and hit each other and are broken down into small fragments. These smaller particles are called sediments. These sediments are transported and deposited by wind, water, .etc. These loose sediments are compressed and hardened to form layers of rocks. These types of rocks are called sedimentary rocks. For example, sandstone.

(iii) Metamorphic rocks: Igneous and sedimentary rocks can change into metamorphic rocks under great heat and pressure. For example, clay changes into slate and limestone into marble.
Minerals: Rocks are made up of different minerals. Minerals are naturally occurring substances which have certain physical properties and definite chemical composition.