NCERT Class 7 Geography Chapter 2 inside our earth notes.

Chapter-2: Inside our Earth

These NCERT Class 7 Geography Chapter 2 notes explain the internal structure of the Earth and the materials that form its surface. The chapter helps students understand that the Earth is made up of different layers and is not solid from inside.

Inside Our Earth introduces the three main layers of the Earth – crust, mantle and core – and explains their composition and importance. The chapter also explains different types of rocks, their formation and the continuous rock cycle.

This chapter builds a strong base for understanding physical geography and natural processes of the Earth.

1. Introduction

  • The Earth is not solid from the inside and has a layered structure.
  • It is made up of three concentric layers, similar to the layers of an onion.
  • Each layer has different composition and characteristics.
  • This chapter explains the internal structure of the Earth.
  • It also introduces different types of rocks and the rock cycle.

2. Structure of the Earth

  • The Earth is divided into three main layers: crust, mantle and core.
  • These layers differ in thickness, composition and temperature.
  • The outer layers are cooler compared to the inner layers.
  • Pressure and temperature increase as we move towards the centre.
  • Understanding these layers helps us know about volcanic and seismic activities.

3. Crust

  • The crust is the outermost and thinnest layer of the Earth.
  • Its thickness is about 35 km on continents and 5 km under oceans.
  • Continental crust is made of SIAL (silica and alumina).
  • Oceanic crust is made of SIMA (silica and magnesium).
  • Humans live on the crust where agriculture, settlements and industries develop.

4. Mantle

  • The mantle lies just below the crust.
  • It extends up to a depth of about 2900 km.
  • The mantle is made of very dense rocks.
  • It is the main source of magma.
  • Magma comes out during volcanic eruptions from this layer.

5. Core

  • The core is the innermost layer of the Earth.
  • It is extremely hot and heavy.
  • The core is mainly made of nickel and iron, called NIFE.
  • The outer core is semi-molten in nature.
  • The inner core is solid due to very high pressure.

6. Rocks

  • A rock is a natural mass of mineral matter forming the Earth’s crust.
  • Rocks are found in different shapes, sizes and colours.
  • They form the basic material of the Earth’s surface.
  • Rocks help in understanding Earth’s history.
  • Examples of rocks include granite, basalt and limestone.

7. Igneous rocks

  • Igneous rocks are formed from magma or lava.
  • They are known as primary rocks.
  • Intrusive igneous rocks form inside the Earth and cool slowly.
  • Extrusive igneous rocks form on the surface and cool quickly.
  • Granite and basalt are common examples.

8. Sedimentary rocks

  • Sedimentary rocks are formed from sediments.
  • Sediments are small pieces of broken rocks.
  • These rocks are formed through deposition, compaction and cementation.
  • They are usually found in layers.
  • Sedimentary rocks often contain fossils.

9. Metamorphic rocks

  • Metamorphic rocks are formed when existing rocks change.
  • The change occurs due to heat and pressure.
  • The original form of the rock is altered.
  • Limestone changes into marble.
  • Coal changes into diamond under extreme conditions.

10. Rock cycle

  • The rock cycle explains the continuous transformation of rocks.
  • One type of rock can change into another over time.
  • Igneous rocks can become sedimentary rocks.
  • Sedimentary rocks can change into metamorphic rocks.
  • This cycle continues endlessly and no rock is permanent.

11. Uses of rocks

  • Hard rocks are used in buildings and roads.
  • Soft rocks are used in making cement.
  • Minerals obtained from rocks are used in industries.
  • Rocks provide fossil fuels like coal and petroleum.
  • Rocks are essential for economic development.

12. Important keywords

  • Crust is the outermost layer of the Earth.
  • Mantle lies below the crust.
  • Core is the central part rich in nickel and iron.
  • SIAL, SIMA and NIFE describe Earth’s composition.
  • Igneous, sedimentary and metamorphic rocks are main rock types.
  • Rock cycle shows continuous change of rocks.

Understanding NCERT Class 7 Geography Chapter 2 is important to learn about the Earth’s internal structure and the role of rocks in shaping the surface of the planet. The chapter clearly explains how rocks are formed, transformed and used by humans.

The concepts discussed in Inside Our Earth are essential for developing basic geological understanding and are highly useful for school examinations and foundation-level preparation.

Continue reading NCERT Class 7 Geography Chapter 3 – Our Changing Earth to understand the forces that continuously shape the Earth’s surface.

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FAQs

Q1. What are the main layers of the Earth?
The Earth has three main layers: crust, mantle and core.

Q2. What is the crust?
The crust is the outermost and thinnest layer of the Earth where humans live.

Q3. What are igneous rocks?
Igneous rocks are formed from magma or lava and are called primary rocks.

Q4. What is the rock cycle?
The rock cycle shows how one type of rock changes into another over time.

Q5. Why is this chapter important for exams?
It explains Earth’s structure and rock formation, making it important for school exams and foundation-level preparation.

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