🌍 Class 7 Geography – Chapter 3
Our Changing Earth
NCERT Notes | Easy Explanation

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🌋 Introduction

The Earth’s surface is constantly changing due to natural processes. These changes may occur slowly or suddenly.

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⏳ Lithospheric Plates

The Earth’s crust is made up of large pieces called lithospheric plates.

• These plates move slowly
• Their movement causes changes on Earth’s surface

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⚡ Endogenic Forces

Endogenic forces are forces that originate inside the Earth.

• Cause earthquakes
• Cause volcanic eruptions
• Cause formation of mountains

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🌋 Volcanoes

A volcano is an opening in the Earth’s crust through which magma comes out.

• Magma inside Earth → Lava on surface
• Volcanic eruptions can be destructive

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🌊 Earthquakes

An earthquake is the sudden shaking of the Earth’s surface.

• Caused by movement of plates
• The point of origin is called the focus
• The point above it on the surface is the epicentre

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🌪️ Exogenic Forces

Exogenic forces act on the Earth’s surface.

• Weathering
• Erosion
• Deposition

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💨 Erosion and Deposition

Erosion is the wearing away of land by agents like:

• Running water
• Wind
• Glaciers
• Sea waves

Deposition is the laying down of eroded material.

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🏞️ Landforms Created by Running Water

• Waterfalls
• Meanders
• Floodplains
• Deltas

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🏜️ Landforms Created by Wind

• Sand dunes
• Mushroom rocks
• Loess deposits

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❄️ Landforms Created by Glaciers

• U-shaped valleys
• Moraines
• Glacial lakes

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🌊 Landforms Created by Sea Waves

• Sea cliffs
• Sea caves
• Beaches

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📌 Key Exam Points:
• Endogenic = internal forces
• Exogenic = external forces
• Focus & Epicentre are very important terms

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