NCERT Class 7 Geography Chapter 2 Notes Inside Our Earth

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NCERT Class 7 Geography Chapter 2 Notes Inside Our Earth

CBSE Class 7 Geography Chapter 2 Notes Understanding The Lesson

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

2. The uppermost layer over the earth’s surface is called the crust. It is the thinnest layer and its depth is about 40 km its range is about 35 km on the continental masses and only 5 km. on the ocean floors.

3. 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. Rocks can be of different colour, size and texture.

4. The main mineral constituents of the continental mass are silica and alumina. It is called ‘sial’. The oceanic crust mainly consists of silica and magnesium. It is therefore called ‘sima’.

5. Below the crust is the mantle which extends up to a depth of 2900 km.

6. In the earth, the innermost layer is the core with a radius of about 3500 km. It is mainly made up of nickel and iron and is called ‘nife’. The core has very high temperature and pressure.

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

8. Igneous rocks further can be classified as Intrusive rocks and Extrusive rocks.

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

10. Rocks are very useful to us. The hard rocks are used for making roads, houses and buildings.

11. Under certain conditions, one type of rock changes to another type in a cyclic manner. This process of transformation of the rock from one to another is known as the rock cycle.

Notes of Geography Class 7 Chapter 2 Important Terms

Fossils: The remains of the dead plants and animals trapped in the layers of rocks are called fossils.

Core: Innermost layer of the earth.

Rocks: Natural masses of mineral matter.

Sediments: These are small fragments of rocks.

Rock cycle: The process of transformation of rock from one to another.

Igneous: This is a Latin word which meant fire.

Metamorphic: Change of form.

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