Exercise Question Answers-Chapter 2- Shaping of the Earth's Surface- Class 9-Social Science

 Important Question Answers for the Class 9-Social Science Chapter 2- Shaping of the Earth's Surface

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The Big Questions: (These questions are as per new textbook)

Q1. What shapes the Earth’s surface?

Answer:-

The Earth’s surface is shaped by two main kinds of forces:

1. Internal forces originate inside the Earth. They are caused by heat and movements within the Earth. 

2. They produce: Earthquakes, Volcanic eruptions, Folding, Faulting. These forces build mountains, valleys, plateaus and ocean basins.

3. External forces work on the Earth’s surface. They include: Weathering, Erosion, Transportation, Deposition

4. Running water, sea waves, glaciers, wind and underground water act as agents of change.

5. They wear down high areas and deposit material in low areas.

Q2. What is plate tectonics? What are the effects of plate movement?

Answer:-

1. Plate tectonics is the theory that the Earth’s outer layer is divided into large and small tectonic plates.

2. These plates move slowly over the semi-molten layer below them.

3. Their movement is caused by convection currents in the mantle.

4. Plate collision may form fold mountains and cause strong earthquakes.

5. Plates moving apart may form rift valleys, ocean basins and mid-ocean ridges.

6. Plate movement also causes volcanic eruptions, faults, fractures and the movement of continents.

Q3. How are landforms formed and how are they classified?

Answer:-

1. Landforms are formed by internal processes such as folding, faulting, volcanic activity and plate movement.

2. They are also shaped by external processes such as weathering, erosion and deposition.

3. Running water forms valleys, waterfalls, meanders, floodplains and deltas.

4. Sea waves form cliffs, caves, arches, stacks and beaches.

5. Glaciers form U-shaped valleys, cirques, hanging valleys, fjords and moraines.

6. Wind and underground water form dunes, yardangs, caves, stalactites, stalagmites and sinkholes.

Q4. How are humans and other living beings connected to landforms?

Answer:-

1. River valleys and plains provide fertile soil, water and suitable land for farming and settlements.

2. Mountains are sources of rivers, forests, minerals and freshwater.

3. Mountain passes support travel, trade and cultural exchange.

4. Coastal areas support fishing, ports, international trade and tourism.

5. Deserts, oases and plateaus influence settlement patterns, occupations and ways of life.

6. Landforms also provide habitats for plants and animals and may have religious and cultural importance.

Q5. How do disasters associated with different landforms impact human lives?

Answer:-

1. Landslides on steep slopes may destroy houses, roads, bridges and farmland.

2. Avalanches in mountain regions may bury people, animals and transport routes.

3. Glacial Lake Outburst Floods may cause sudden flooding and damage settlements and hydropower projects.

4. Dust storms reduce visibility, damage crops and cause respiratory problems.

5. Earthquakes and volcanic eruptions may cause loss of life, property and infrastructure.

6. Their impact can be reduced through early-warning systems, safe construction, hazard mapping and evacuation planning.

Questions and activities 

1. What are the sources of energy required to cause movements associated with the internal forces of the Earth?

1. The main source of energy for internal movements is the intense heat present in the Earth’s core.
2. This heat warms the material in the mantle and makes it move slowly.
3. The hotter and lighter mantle material rises, while the cooler and heavier material sinks.
4. This continuous circulation produces convection currents in the mantle.
5. These currents push and pull the tectonic plates, causing folding, faulting, earthquakes, volcanic eruptions and the formation of major landforms.

2. Relate various physiographic divisions with the endogenic forces responsible for their origin. 

1. The Himalayan Mountains: They were formed by folding when the Indo-Australian Plate collided with the Eurasian Plate at a convergent boundary.
2. The Northern Plains: A large tectonic depression developed between the rising Himalayas and the Peninsular Plateau; it was later filled with river deposits.
3. The Peninsular Plateau: It is an ancient and stable part of the Earth’s crust shaped by uplift, faulting and volcanic activity.
4. The Coastal Plains: They developed partly through the uplift and subsidence of coastal margins and were later modified by river and marine deposition.
5. The Islands: The Andaman and Nicobar Islands are connected with tectonic and volcanic activity at a plate boundary, while Lakshadweep Islands are mainly of coral origin. 

3. Why and where do earthquakes occur frequently? Is it possible to predict earthquakes?

Why and where do earthquakes occur?

1. Earthquakes occur when stress created by moving tectonic plates is suddenly released along plate boundaries or faults.
2. They occur frequently at convergent and transform boundaries, especially around the Pacific Ocean in the Ring of Fire.

Is it possible to predict earthquakes?

1. The exact time, place and magnitude of an earthquake cannot be predicted accurately.
2. Scientists can identify earthquake-prone regions by studying plate boundaries, faults, past earthquakes and seismic activity.
3. Such identification helps in disaster preparedness, safer construction and reducing the loss of life and property. 

4. “Plate movements are responsible for the distribution of earthquakes and volcanoes.” Explain. 

1. Tectonic plates move slowly over the semi-molten asthenosphere because of convection currents in the mantle.
2. At convergent boundaries, plates collide, and an oceanic plate may sink beneath another plate, causing earthquakes and volcanic eruptions.
3. At divergent boundaries, plates move apart and magma rises to form new crust, producing volcanic activity and earthquakes.
4. At transform boundaries, plates slide past one another, creating friction and frequent earthquakes.
5. Therefore, most earthquakes and volcanoes are concentrated along plate boundaries, particularly around the Pacific Ocean’s Ring of Fire.

Q5. Draw and label a diagram of a meander and a delta.

               

6. How are deforestation and erosion associated with each other? Explain. 

1. Trees and plants protect the soil from the direct impact of rainfall and strong winds.
2. Their roots bind soil particles together and prevent the fertile topsoil from being carried away.
3. Deforestation removes this protective vegetation cover and leaves the land bare.
4. Rainwater then flows rapidly over the exposed surface, while wind easily blows away loose soil particles.
5. Therefore, deforestation increases soil erosion, reduces soil fertility and may also make slopes unstable, leading to landslides.

7. Develop a plan to protect the land in your local area from erosion. 

1. Plant trees, grasses and shelter belts on open land and along roads, fields and water channels to hold the soil firmly.
2. Construct field bunds and contour trenches to slow surface run-off and allow rainwater to enter the soil.
3. Build small check dams across drains and streams to reduce the speed of water and encourage sediment deposition.
4. Prevent unnecessary tree cutting, overgrazing and unplanned construction, and organize regular community monitoring of erosion-prone places.

8. Which disasters might occur in your region? Give a mitigation plan.

For the Hussainpur–Punjab region, the following disasters may occur:

1. Floods and waterlogging: Drains should be cleaned before the monsoon, flood-prone places should be identified and safe evacuation routes should be marked.
2. Earthquakes: Buildings should follow earthquake-resistant designs, heavy furniture should be secured and students should practice “Drop, Cover and Hold.”
3. Dust storms and strong winds: People should remain indoors, close windows, protect their faces and plant shelter belts around fields and settlements.
4. Classroom mitigation plan: Prepare an emergency contact list, first-aid kit, assembly point and student disaster-management teams, and conduct regular evacuation drills.

 9. Prepare a model of landforms created by underground water.          

             

10. What precautionary measures will you take if you are staying in an earthquake-prone region? 

1. I will ensure that the house is constructed according to earthquake-resistant building standards and avoid weak or damaged structures.
2. I will firmly secure cupboards, shelves, gas cylinders and other heavy objects so that they do not fall during an earthquake.
3. I will keep an emergency kit ready with drinking water, dry food, medicines, a torch, a first-aid box and important contact numbers.
4. During an earthquake, I will follow “Drop, Cover and Hold”, stay away from windows and lifts, and take shelter under a strong table.
5. After the shaking stops, I will switch off electricity and gas, move carefully to an open area, help injured persons and follow official safety instructions.

11. Prepare a map showing landform-associated disasters that happened in the current calendar year.

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Very Short Answer Questions:

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1. Define plate tectonics.

Answer:-  Plate tectonics is the theory that the Earth's lithosphere is divided into plates that move slowly over time.

2. Name the 3 main layers of the earth.

Answer:-  The 3 main layers are

        *  Crust

        * Mental 

        * Core

3. What is weathering?

Answer:- Weathering is the breaking of rocks into smaller pieces at the same place.

4. What is erosion?  

Answer:- Erosion is the removal and transportation of weathered material from one place to another.

5. Name two agents of erosion.

Answer:-  * Rivers

                   *  Wind

6. What is a glacier? 

Answer:- A glacier is a large mass of moving ice formed from compacted snow. 

7. What is an earthquake? 

Answer:- An earthquake is the sudden shaking of the Earth surface caused by movements inside the Earth. 

8. What is a landslide? 

Answer:- A landslide is the downward movement of rocks, soil and debris on a slope  due to gravity.

9. What does GLOF stands for?

Answer:- GLOF stands for Glacial Lake Outburst Flood.

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Short Answer Type Questions

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1. Explain the theory of plate tectonics.

Answer:-

• Plate tectonics explains that the Earth's lithosphere is divided into large plates.
• These plates move slowly over the semi-fluid mantle.
• Their movement causes earthquakes, volcanoes, and mountain formation.

2. Describe the structure of the Earth.

Answer:-

• The Earth has three layers: crust, mantle, and core.
• The crust is the outermost layer, while the mantle lies beneath it.
• The core is the innermost layer and is mainly made of iron and nickel.

3. Differentiate between weathering and erosion.

Answer:-

Weathering	Erosion
Breaking of rocks at the same place.	Removal and transport of weathered materials.
No movement of material occurs.	Material is carried away.
Caused by temperature, water, plants, etc.	Caused by rivers, wind, glaciers, and waves.

4. Explain the work of rivers as agents of gradation.

Answer:-

• Rivers erode, transport, and deposit materials.
• In the upper course they form valleys, gorges, and waterfalls.
• In the lower course they deposit sediments and form floodplains and deltas.

5. How do waves shape coastal landforms?

Answer:-

• Sea waves continuously strike the coast and cause erosion.
• They remove materials from some places and deposit them in others.
• This process changes the shape of coastlines.

6. Describe the action of wind in deserts.

Answer:-

• Wind picks up sand and dust and transports them.
• It erodes rocks by rubbing sand particles against them.
• Wind also deposits sand to form dunes.

7. Explain the formation of U-shaped valleys.

Answer:-

• Glaciers move slowly over land carrying rocks and debris.
• They erode the sides and bottom of valleys.
• This erosion creates broad U-shaped valleys.

8. What are the causes of earthquakes?

Answer:-

• Movement of tectonic plates.
• Sudden release of energy inside the Earth.
• Activity along faults and plate boundaries.

9. Write short notes on landslides.

Answer:-

• Landslides involve the movement of rocks, soil, and debris down slopes.
• They are caused by heavy rainfall, earthquakes, and human activities.
• They can damage roads, houses, and agricultural land.

10. What is GLOF? Explain its impact.

Answer:-

• GLOF stands for Glacial Lake Outburst Flood.
• It occurs when water from a glacial lake is suddenly released.
• It can cause severe flooding, destruction of property, and loss of life.

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Long Answer Type Question:

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1. Explain the theory of plate tectonics with suitable examples.

Answer:-

Plate tectonics is the theory that the Earth's lithosphere is divided into large plates that move slowly over the semi-fluid mantle. These movements are caused by convection currents inside the Earth. The theory explains continental drift, earthquakes, volcanic activity, and mountain formation. For example, the Indian Plate colliding with the Eurasian Plate formed the Himalayas. Plate movements also create ocean trenches and volcanoes.

2. Describe the interior of the Earth with a neat labelled diagram.

Answer:-

The Earth is made up of three main layers:

Crust: The outermost and thinnest layer of the Earth.

Mantle: Located below the crust and extending to about 2900 km. It is made of hot semi-molten rocks.

Core: The innermost layer made mainly of iron and nickel. The outer core is liquid, while the inner core is solid.

Diagram Labels:

3. Explain different types of weathering with examples.

Answer:-

Weathering is of three types:

Physical Weathering: Rocks break into smaller pieces without changing their composition. Example: Rocks cracking due to heating and cooling.

Chemical Weathering: Minerals in rocks change due to chemical reactions. Example: Limestone dissolving in water.

Biological Weathering: Living organisms break rocks. Example: Tree roots growing into rock cracks.

These processes help in soil formation and landscape development.

4. Explain the role of rivers in erosion, transportation and deposition.

Answer:-

Rivers act as important agents of gradation.

Erosion: In the upper course, rivers cut deep valleys, gorges, rapids, and waterfalls.

Transportation: Rivers carry rocks, sand, and sediments downstream.

Deposition: In the lower course, rivers deposit sediments and form floodplains, distributaries, and deltas.

Thus, rivers continuously shape the Earth's surface.

5. Explain the work of glaciers as agents of gradation.

Answer:-

Glaciers are large moving masses of ice. As they move, they erode rocks and transport debris. They carve broad U-shaped valleys and carry sediments over long distances. When glaciers melt, they deposit materials in different places. Thus, glaciers modify landscapes through erosion, transportation, and deposition.

6. Describe the formation of coastal landforms by waves and currents.

Answer:-

Sea waves continuously strike the coast and erode rocks. They carry sediments from one place to another and deposit them along the shore. This process creates different coastal landforms and changes the coastline over time. Waves therefore act as important agents of erosion and deposition.

7. Explain the causes, effects and safety measures of earthquakes.

Answer:-

Causes:

• Movement of tectonic plates.
• Sudden release of energy inside the Earth.
• Activity along faults.

Effects:

• Collapse of buildings.
• Damage to roads and bridges.
• Loss of life and property.

Safety Measures:

• Construct earthquake-resistant buildings.
• Follow warning systems.
• Spread awareness and preparedness.

8. Describe landslides and avalanches with preventive measures.

Answer:-

Landslides:
Landslides are the downward movement of rocks, soil, and debris on slopes. They are caused by heavy rainfall, earthquakes, deforestation, and construction activities.

Avalanches:
Avalanches are rapid flows of snow, ice, and rocks down mountain slopes. They occur due to heavy snowfall, earthquakes, temperature changes, and human activities.

Preventive Measures:

• Afforestation.
• Retaining walls and protective barriers.
• Proper drainage systems.
• Early warning systems.
• Avoid construction in high-risk areas.

9. Explain Glacial Lake Outburst Flood (GLOF) and its impact on mountain regions.

Answer:-

A Glacial Lake Outburst Flood (GLOF) occurs when water stored in a glacial lake is suddenly released. This may happen due to glacier melting, weak moraine dams, earthquakes, or heavy rainfall.

Impacts:

• Severe flooding in mountain valleys.
• Damage to roads, bridges, and houses.
• Loss of agricultural land.
• Threat to human life and ecosystems.

Monitoring glacial lakes and early warning systems help reduce the risks.

10. Discuss dust storms and their effects in arid regions.

Answer:-

Dust storms occur when strong winds lift large amounts of dust and sand into the atmosphere. They are common in arid and semi-arid regions.

Effects:

• Reduced visibility.
• Respiratory and health problems.
• Damage to crops.
• Soil degradation.
• Disruption of transport and daily life.

Planting trees, conserving soil, and controlling land degradation help reduce the impact of dust storms.

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To Learn More NCERT Solutions Click Below:

Chapter 1- Social Science: Meaning, Scope and Importance- CLICK HERE

Chapter 2-Shaping of the Earth's Surface - CLICK HERE

Chapter 3- Atmosphere and Climate - CLICK HERE

Chapter 9-Democracy- CLICK HERE