CBSE Class 7 Social Science: Our Changing Earth NCERT Solutions

Reviewed by NCERT Help Editorial Team · Updated on 29 Jul 2026

NCERT Solutions PDF Class 7 PDF

This chapter, "Our Changing Earth," delves into the dynamic processes that shape our planet's surface. The NCERT Solutions for Class 7 Social Science provide clear explanations for complex concepts. Students will understand why tectonic plates move, driven by the molten magma within the Earth's core. The solutions differentiate between endogenic forces, which act from within the Earth and cause phenomena like earthquakes and volcanoes, and exogenic forces, which operate on the surface, leading to erosion and deposition. Key landforms like floodplains, sand dunes, and beaches are explained through their formation processes, involving agents like rivers, wind, and sea waves. These solutions are designed to simplify these geological concepts, making them accessible for students and aiding in effective exam preparation by clarifying the mechanisms behind Earth's ever-changing landscape.

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Quick info

Board	CBSE
Class	Class 7
Subject	Social Science Our Environment
Session	2026
Language	English
Type	NCERT Solutions
Chapter	Chapter 3

Chapter summary

Chapter 3, "Our Changing Earth," focuses on the geological forces that continuously modify the planet's surface. The NCERT Solutions cover the reasons behind the movement of lithospheric plates, the distinction between internal (endogenic) and external (exogenic) forces, and the processes of erosion and deposition. Specific landforms like floodplains, sand dunes, and beaches are explained in detail, highlighting the roles of rivers, wind, and sea waves. This chapter's solutions aim to build a foundational understanding of Earth's dynamic nature.

Learning outcomes

Understand the reasons behind the movement of tectonic plates.
Differentiate between endogenic and exogenic forces acting on the Earth.
Explain the process of erosion and its agents.
Describe the formation of landforms such as floodplains, sand dunes, and beaches.
Identify the role of natural forces in shaping the Earth's surface.

Topics covered

Paper topics

Movement of Earth's Plates
Endogenic Forces
Exogenic Forces
Erosion
Deposition
Floodplains
Sand Dunes
Beaches
Agents of Erosion (Wind, Water, Ice, Sea Waves)

Important topics

Endogenic vs. Exogenic Forces
Process of Erosion
Formation of Floodplains
Formation of Sand Dunes
Formation of Beaches
Plate Tectonics

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Questions and Solutions

Question 1 (a)

Why do the plates move?

Solution: The Earth's core is composed of molten magma. This magma is in constant motion deep beneath the Earth's surface. The movement of this molten magma creates convection currents, which in turn cause the lithospheric plates floating above to move. These plate movements are a fundamental cause of geological events like earthquakes.

Question 1 (b)

What are exogenic and endogenic forces?

Solution: Forces that act on or within the Earth are categorized based on their origin:

Endogenic forces: These are the forces that operate from the interior of the Earth. They are responsible for sudden movements that can lead to natural disasters like earthquakes, volcanic eruptions, and landslides. They also play a role in the formation of major landforms like mountains.

Exogenic forces: These are the forces that act on the exterior or surface of the Earth. They are primarily involved in processes of erosion and deposition. Agents like rivers, glaciers, wind, and sea waves are examples of exogenic forces that continuously shape the Earth's surface.

Question 1 (c)

What is erosion?

Solution: Erosion is the process by which the Earth's surface is worn away. This happens when natural agents like wind, rivers, sea waves, and ice gradually remove soil and rock from one location. These agents are known as the agents of erosion, and they play a crucial role in shaping landscapes over time.

Question 1 (d)

How are flood plains formed?

Solution: Floodplains are formed when a river overflows its banks, typically due to heavy rainfall or increased water levels. During such floods, the river carries fine soil and other materials, known as sediments. As the floodwaters recede, these sediments are deposited in layers along the river banks. This process of deposition creates a flat, fertile area adjacent to the river, which is called a floodplain. The raised banks formed by deposition are called levees.

Question 1 (e)

What are sand dunes?

Solution: Sand dunes are mounds or ridges of sand formed by the action of wind. When wind blows across sandy areas, it picks up and transports sand particles. As the wind encounters an obstacle or its speed decreases, it drops the sand particles. These deposited particles accumulate over time, forming characteristic hill-like structures known as sand dunes. They are commonly found in desert regions where sand is abundant and wind is a significant erosional agent.

Question 1 (f)

How are beaches formed?

Solution: Beaches are formed by the combined erosional and depositional activities of sea waves. Waves constantly move towards the shore, carrying sand, pebbles, and other sediments. Over time, these sediments are deposited along the coastline. As this process continues, layers of these deposited materials build up, creating the sandy or pebbly shorelines we recognize as beaches.

Common mistakes

Confusing endogenic and exogenic forces.
Not clearly defining erosion and its agents.
Incomplete explanation of landform formation processes.

Revision tips

Draw diagrams to illustrate the formation of floodplains, sand dunes, and beaches.
Create a table comparing endogenic and exogenic forces.
Focus on understanding the 'why' behind plate movement and erosion.
Review the definitions of key terms like erosion, deposition, and sediments.

Practice MCQs

Q1. What is the primary reason for the movement of lithospheric plates?

Q2. Which of the following are examples of endogenic forces?

Q3. What is the process by which landscapes wear away?

Q4. Floodplains are formed by the deposition of:

Q5. Sand dunes are primarily formed by the action of:

Frequently asked questions

What causes the plates of the Earth's lithosphere to move?

The plates move due to the continuous movement of molten magma deep within the Earth's core. This convection current in the magma causes the overlying lithospheric plates to shift.

What is the difference between endogenic and exogenic forces?

Endogenic forces originate from the interior of the Earth and cause events like earthquakes and volcanoes. Exogenic forces act on the Earth's surface and are responsible for erosion and deposition by agents like wind, water, and ice.

How are floodplains formed?

Floodplains are formed when a river overflows its banks due to heavy rainfall or increased water levels. The floodwaters deposit layers of fine soil and sediments along the river banks, creating a flat, fertile plain.

What are sand dunes and how do they form?

Sand dunes are hills of sand formed by the action of wind. As wind blows, it carries sand particles, and when the wind's speed decreases, these particles are deposited, creating dune-like structures, especially in desert areas.

What role do sea waves play in shaping the coast?

Sea waves are agents of erosion and deposition. Their continuous action along the coast can wear away the land (erosion) and deposit sediments, leading to the formation of beaches.

Why is understanding 'Our Changing Earth' important for Class 7 students?

Understanding 'Our Changing Earth' helps students grasp the dynamic geological processes that shape our planet. It explains natural phenomena like earthquakes and the formation of various landforms, fostering scientific curiosity and awareness of environmental changes.

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