NCERT Solutions Class 7 Social Science Our Environment Chapter 3

Earth's motions are classified according to the factors that cause them. Endogenic forces operate within the earth's interior, whereas exogenic forces operate on its surface. Earthquakes and volcanic eruptions wreak havoc on the earth’s surface. Weathering and erosion are two processes that continually erode the terrain. Chapter 3 sheds light on all these important topics. There is a set of questions given at the end of each chapter in the NCERT textbook, and students must solve these questions to understand the concepts in a better way. 

Students can access NCERT Solutions for Class 7 Geography Chapter 3 on Extramarks to get answers to all the textbook questions. The solutions will help students in improving their conceptual understanding and will be able to answer any question asked in the examination no matter how tweaked they are. 

NCERT Solutions for Class 7 Social Science Chapter 3 - Our Changing Earth - Download

Access NCERT Solutions for Class 7 Social Science (Geography) Chapter 3 - Our Changing Earth

NCERT Solutions for Class 7 Social Science Download

The NCERT Solutions are prepared in simple and easy-to-understand language to help students grasp the concepts effectively. The solutions are accessible on the website and app of Extramarks.

An Overview of the NCERT Class 7 Geography Chapter 3 Notes

The notes for Class 7 Geography Chapter 3 cover several areas of Geography. Let’s look at some important topics:

  • Lithospheric Plates: The lithosphere is broken into a number of plates called the Lithospheric plates. Because of the movement of molten magma inside the earth, the lithospheric plate gets broken into different plates and continues to move around slowly. 
  • The molten magma inside the earth continues to move in a circular motion. These movements are further divided on the basis of endogenic and exogenic factors. Endogenic forces, which occur in the interior, cause unexpected activities that result in earthquakes and volcanic eruptions. Exogenic forces, also known as exogamic forces, work on the surface of the earth. 
  • Volcano: A volcano is a vent in the crust of the earth. Molten material comes out of the volcano. 
  • Earthquake: When lithospheric plates move, the vibration of the earth travels across, causing earthquakes.
  • Epicentre: The epicentre is the point at which the actual movement of lithospheric plates occurs. Waves travel from the epicentre to other locations.

Major Landforms:

The chapter provides detailed information about how the landscape wears out through two different processes: weathering and erosion.The breaking up of rocks on the earth's surface is referred to as weathering.

  • Erosion is the process of the terrain getting eroded by various factors such as water, wind, and ice. Water and wind carry away the eroded material. Different landforms are formed due to the processes of erosion and deposition.

Work of Sea Waves

Changes in sea waves also contribute to a changing ecosystem. Here are some ways  sea waves change:

  • Sea Caves: Coastal landforms are formed due to erosion and deposition, which also keep rocks from striking each other and lead to cracks. These cracks keep on growing over time, creating caves.
  • Sea Arches: When cavities in the rock get larger, arches form.
  • Sea Cliff: Seacliff is a steep rocky coast that rises vertically and in different shapes.

Work of Wind

Aside from the water and the land, the wind also plays a major role in modifying landforms. The wind blowing in the desert is an active agent of erosion and deposition. On the other hand, sand dunes are formed when the wind carries sand from one location to another. When the wind stops blowing, the sand settles down. This area is called sand dunes.

Class 7 Geography Chapter 3 Notes

NCERT Class 7 Geography Chapter 3 notes are now available on Extramarks, which makes learning simple and more effective.. The solutions provide accurate information about a specific topic ,which allows students to gain in-depth knowledge.

NCERT Class 7 Social Science Our Environment Chapterwise Solutions

Extramarks provides the following NCERT Class 7 Social Science Chapter wise Solutions:

  • Chapter 1 - Environment
  • Chapter 2 - Inside Our Earth
  • Chapter 3 - Our Changing Earth
  • Chapter 4 - Air
  • Chapter 5 - Water
  • Chapter 6 - Natural Vegetation and Wildlife
  • Chapter 7 - Human Environment-Settlement, Transport and Communication
  • Chapter 8 - Human Environment Interactions - The Tropical and the Subtropical Region
  • Chapter 9 -  Life in the Deserts

NCERT Solutions for Class 7 Social Science

NCERT Solutions for Class 7 Social Science have the most appropriate answers to all of the questions from the Social Science textbook. The study materials include clear explanations and comprehensive discussions. Academic experts with years of experience have prepared these solutions as per the  NCERT books while adhering to the recent CBSE syllabus. 

Q.1 Observe the photographs given below. These are various features made by a river. Identify them and also tell whether they are erosional or depositional or landforms formed by both.

Ans-

Q.2 Answer the following questions.
(i) Why do the plates move?
(ii) What are exogenic and endogenic forces?
(iii) What is erosion?
(iv) How are flood plains formed?
(v) What are sand dunes?
(vi) How are beaches formed?
(vii) What are ox bow lakes?

Ans-

(i) Plates move because of the movement of molten magma inside the earth. The molten magma moves inside the earth in a circular manner.

(ii)The forces which act on the surface of the earth are known as exogenic forces, whereas the forces which act in the interior of the earth are known as endogenic forces.

(iii)The wearing away of landscape by different agent of nature like wind, water, and ice is known as erosion.

(iv) Layers of fine soil and other materials known as sediments are deposited along the banks of river, whenever a river floods. This leads to the formation of a fertile floodplain.

(v) When the wind blows in a desert, it transports sand from one place to another. When it stops blowing, the sand falls and gets deposited in low hill-like structures, which are known as sand dunes.

(vi) Beaches are formed when sediments carried by the sea waves are deposited along the shores. The finer sediments are deposited near the sea, while the coarser ones are deposited further inland.

(vii) Rivers start meandering when they enter the plains. In due course of time, the meander loop cuts off from the river and forms a cut-off lake, which is also known as an ox bow lake.

Q.3 Tick the correct answer.

(i) Which is not an erosional feature of sea waves?
(a) Cliff (b) Beach (c) Sea cave

(ii) The depositional feature of a glacier is:
(a) Flood plain (b) Beach (c) Moraine

(iii) Which is caused by the sudden movements of the earth?
(a) Volcano (b) Folding (c) Flood plain

(iv) Mushroom rocks are found in:
(a) Deserts (b) River valleys (c) Glaciers

(v) Ox bow lakes are found in:
(a) Glaciers (b) River valleys (c) Deserts

Ans-

(i) (b) Beach ✓
(ii) (c) Moraine ✓
(iii) (a) Volcano ✓
(iv) (a) Deserts ✓
(v) (b) River valleys ✓

Q.4 Match the following.

(i) Glacier (a) Sea shore
(ii) Meanders (b) Mushroom rock
(iii) Beach (c) River of ice
(iv) Sand dunes (d) Rivers
(v) Waterfall (e) Vibrations of earth
(vi) Earthquake (f) Sea cliff
(g) Hard bed rock
(h) Deserts

Ans-

(i) Glacier (c) River of ice
(ii) Meanders (d) Rivers
(iii) Beach (a) Sea shore
(iv) Sand dunes (h) Deserts
(v) Waterfall (g) Hard bed rock
(vi) Earthquake (e) Vibrations of earth
Q.5 Give reasons.
(i) Some rocks have a shape of a mushroom.
(ii) Flood plains are very fertile.
(iii) Sea caves are turned into stacks.
(iv) Buildings collapse due to earthquakes.

Ans-

(i) Erosion of rocks in a desert by wind progresses at a different rate at its bottom to that at its top. Winds erode lower section of rocks more than the upper section. Thus, rocks take the shape of a mushroom, i.e., narrower at the base and wider at the top.
(ii) Flood plains are formed due to depositional activity of rivers. Sometimes, the rivers flood and layers of fine sediments and other materials are deposited along its banks. This causes floodplains to be formed. The deposited sediments and other materials make the land fertile.
(iii) Continuous striking of sea waves against the rocks causes the rocks to develop hollow like caves on them. These hollows are known as sea caves. They become larger and larger due to continuous erosion, leaving the cave with only a roof, thus forming sea arches. Further erosion breaks the roof and only walls are left. These wall like structures are known as stacks.
(iv) An earthquake is a sudden release of energy from the earth’s crust that travels in waves. When the intensity of earthquake is high, it can cause damage to many man-made and natural things on the surface of the earth. Buildings can collapse when they cannot stand the intensity of earthquake.

Q.6 Solve the crossword puzzle with the help of given clues.

Across:

2. Loop like the bend of a river

4. Solid form of water

7. Moving mass of ice

9. Sudden descent of water in the bed of a river

11. Natural cavity on weak rocks formed by the action of waves

12. Embankment on a river that keeps it in its channel

13. Large body of water

14. Dry area where sand dunes are found

15. Small hill of sand caused by the action of wind

16. Flat plain formed by river deposits during time of flood

Down:

1. Rise and fall of water caused by friction of wind on water surface

3. Flow of water in a channel

5. Steep perpendicular face of a rock along a sea coast

6. Debris of boulder and coarse material carried by glacier

8. Crescent shaped lake formed by a meandering river

10. Fine sand deposited by the action of wind

13. Isolated mass of rising steep rock near a coastline

14. Alluvial tracts of land formed by the river deposits at the mouth of a river

Ans-

Across:

2. Loop like the bend of a river: Meander

4. Solid form of water: Ice

7. Moving mass of ice: Glacier

9. Sudden descent of water in the bed of a river: Waterfall

11. Natural cavity on weak rocks formed by the action of waves: Cave

12. Embankment on a river that keeps it in its channel: Levee

13. Large body of water: Sea

14. Dry area where sand dunes are found: Desert

15. Small hill of sand caused by the action of wind: Sand dune

16. Flat plain formed by river deposits during time of flood: Floodplain

Down:

1. Rise and fall of water caused by friction of wind on water surface: Wave

3. Flow of water in a channel: River

5. Steep perpendicular face of a rock along a sea coast: Cliff

6. Debris of boulder and coarse material carried by glacier: Moraine

8. Crescent shaped lake formed by a meandering river: Oxbow lake

10. Fine sand deposited by the action of wind: Loess

13. Isolated mass of rising steep rock near a coastline: Stack

14. Alluvial tracts of land formed by the river deposits at the mouth of a river: Delta

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FAQs (Frequently Asked Questions)

There are many types of forces on earth. Chapter 3 discusses how the movement of the earth is divided on the bases of the two forces – endogenic and exogenic. Endogenic forces work within the earth’s interior, while exogenic factors function on its surface. These endogenic pressures frequently cause abrupt movements, but they can also cause sluggish movements. Volcanoes form as a result of these rapid movements.

 

The coastal zone is a portion of the land surface heavily impacted by maritime processes. Coastal zones have an active role on the earth’s surface, producing coastal rocks, beaches, and dunes as well as marine and atmospheric processes. Mangroves, coral reefs, and salt marshes are all found along these beaches. The wind blows in the ocean, which causes waves to form. The longer the waves pick, the stronger the wind.

Lithospheric plates are formed when areas of the earth’s crust and upper mantle of the lithosphere are broken into multiple plates. These plates move slowly due to the flow of molten magma within the earth’s crust. The movement of these lithospheric plates is responsible for all of the changes on  Earth’s surface. Volcanoes, earthquakes, and other natural disasters are caused by the sudden movements of these lithospheric plates.

The heat is created in the earth’s core as convection currents in the mantle cause movement in the lithospheric plates. When the warmer material rises, the colder material descends. This process of rising and sinking keeps repeating itself, causing the lithospheric plates to rise and become the reason for their movement.

The flowing water of the river erodes the landscape. A waterfall is formed when a river rushes at a steep angle over hard rocks or down a deep valley side. Due to continual erosion and deposition along the meander’s sides, the ends of the meander loop get closer and closer.

The cut-off lake, also known as an ox-bow lake, is formed when the meander loop splits from the river. When the river overflows its banks, flooding occurs in the surrounding areas. As it floods, it dumps sediments, which are layers of fine dirt and other debris, along its banks.

An earthquake is a natural tragedy that we cannot avert. We may, however, decrease the impact if we are prepared ahead of time. During an earthquake, we should always evacuate to a safe spot. We should hide behind a kitchen counter, table, or desk against a door or a wall. Fireplaces, areas near chimneys, and windows with reflective surfaces, such as mirrors and picture frames, should all be avoided.Â