Class 7 Geography Chapter 2 Notes

Class 7 Geography Chapter 2 Notes provide you with a basic understanding of what is Inside Our Earth. Inside Our Earth class 7 notes pdf help student in their revision. In Notes of Class 7 Geography Chapter 2, we discuss the Interior of the Earth, Types of Rocks, and the Rock Cycle. Students can also download class 7 geography chapter 2 notes pdf for offline study.

Class 7 Geography Chapter 2 Notes
Class 7 Geography Chapter 2 Notes

Inside Our Earth Class 7 Notes

The earth is a dynamic planet. It is constantly undergoing changes inside and outside. In this chapter, we learn interior of the earth.

Interior of the Earth

Interior of the Earth

The earth’s interior is like an onion, the earth is made up of several concentric layers with one inside another. The radius of the earth is 6371 km.

The three Concentric layers are

  1. 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. It is thus called sial (si-silica and al-alumina).
    • The oceanic crust mainly consists of silica and magnesium; it is called sima (si-silica and ma-magnesium).
  2. Mantle- It is the second layer of the Earth.
    • It is just below the Crust and extends up to a depth of 2900 km.
    • The mantle can be divided into two layers, the upper mantle, and the lower mantle. 
    • The mantle is made of Silicate rocks that include 44.8% oxygen, 21.5% silicon, and 22.8% magnesium.
  3. Core- The innermost layer is the core.
    • the radius of the core is about 3500 km.
    • It is mainly made up of nickel and iron and is called nife (ni – nickel and fe – ferrous i.e. iron).
    • Pressure and temperature are very high at the core.

The crust forms only 1 per cent of the volume of the earth, 84 per cent consists of the mantle and
15 per cent makes the core.

Rocks and Minerals

Any natural mass of mineral matter that makes up the earth’s crust is called a rock. Rocks can be of different colours, sizes and textures.

Types of Rocks

There are three major types of rocks: igneous rocks, sedimentary rocks and metamorphic rocks.

Igneous Rocks

When the molten magma cools, it becomes solid. Rocks thus formed are called igneous rocks. They are also called primary rocks. There are two types of igneous rocks: intrusive rocks and extrusive rocks.

  • Extrusive Igneous Rocks – When the molten lava comes to 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. eg- basalt
  • Intrusive Igneous Rocks- Sometimes the molten magma cools down deep inside the earth’s crust. Solid rocks so formed are called intrusive igneous rocks. eg- Granite

Sedimentary Rocks

Rocks roll down, crack, and hit each other and are broken down into small fragments. These smaller particles are called sediments.

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. eg- Sandstone

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.

Rock Cycle

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.

Rock Cycle

Understand Rock Cycle- when the molten magma cools; it solidifies to become igneous rock. These igneous rocks are broken down into small particles that are transported and deposited to
form sedimentary rocks. When the igneous and sedimentary rocks are subjected to heat and pressure they change into metamorphic rocks. The metamorphic rocks which are still under great heat and pressure melt down to form molten magma. This molten magma again can cool down and solidify into igneous rocks

Minerals

Minerals are naturally occurring substances which have certain physical properties and definite chemical compositions. Minerals are very important/useful for us. Some minerals are used as fuels. For example, coal, natural gas and petroleum. minerals are also used in industries as raw materials like – iron, aluminium, gold, uranium, etc, in medicine, and in fertilisers, etc.

You may also like to read-

Key points of Class 7 Geography Chapter 2 Notes

key points of Inside Our Earth class 7 notes pdf helps you to understand the topic in a simple way.

Crust– The crust is the uppermost layer of the earth’s surface. It is the thinnest of all the layers.

Mantle– This layer is just beneath the crust. It extends up to a depth of 2900 km.

Core– The innermost layer is the core. The radius of the core is about 3500 km

Sial- The continental mass of the earth’s crust consist of silica and alumina. It is thus called sial (si-silica and al-alumina).

Sima-The oceanic crust mainly consists of silica and magnesium; it is called sima (si-silica and ma-magnesium).

Nife- The core is mainly made up of nickel and iron and is called nife (ni – nickel and fe – ferrous i.e. iron).

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

Igneous Rock- The rock formed after the cooling of magma are called igneous rocks.

Extrusive igneous rock– When the molten lava comes to the earth’s surface and is cold then the rock formed is called Extrusive igneous rock.

Intrusive igneous rock– When the molten lava comes to the earth’s surface and is cold then the rock formed is called Extrusive igneous rock.

Sediments– Rocks roll down, crack, and hit each other and are broken down into small fragments. These smaller particles are called sediments.

Sedimentary rock– Those rocks which are made by deposition of sediments are called sedimentary rocks.

Rock cycle– The process of transformation of the rock from one to another is known as the rock cycle.

Lava– Lava is actually fiery red molten magma coming out from the interior of the earth on its surface.

Basalt Rock– Basalt rocks are the aphanitic extrusive igneous rocks formed from the rapid cooling of low viscosity lava. The Deccan plateau is made up of basalt rocks.

Deccan Plateau– It is situated in the south-central region of the Indian subcontinent. It is located between western ghat and eastern ghat.

Mineral– Minerals are naturally occurring substances which have certain physical properties and definite chemical compositions.

We hope this post-class 7th geography chapter 2 notes help in your study.