Chapter 2 – Shaping of the Earth’s Surface - Class 9 Social Science

2 MARKS

Q1. A region experiences frequent earthquakes and volcanic eruptions. On examining a map, most of these events are found near the boundaries of tectonic plates. Why?

Answer: Tectonic plates interact at their boundaries. Their movement can cause earthquakes and volcanic activity. Most earthquakes and volcanoes therefore occur along plate boundaries.

Q2. A student says that the Earth's crust is a single solid piece that does not move. Is this correct? Give a reason.

Answer: No. The lithosphere is broken into several tectonic plates that move slowly over the semi-molten asthenosphere.

Q3. Two continental plates move towards each other. What major landform can be formed?

Answer: The collision of two continental plates can form fold mountains, such as the Himalayas.

Q4. A rock breaks into smaller pieces because of repeated heating and cooling, but the pieces remain at the same place. Is this weathering or erosion? Why?

Answer: It is weathering because the rock is being broken down without movement of the material.

Q5. A river carries soil from one place and deposits it somewhere else. Which process is involved?

Answer: This involves erosion and transportation, followed by deposition where the river loses energy and deposits the material.

Q6. Plant roots enter cracks in rocks and gradually split them apart. Identify the type of weathering.

Answer: It is biological weathering because plants are responsible for breaking the rocks.

Q7. Why are deltas generally suitable for agriculture?

Answer: Rivers deposit rich alluvial soil at their mouths, making deltas highly fertile and suitable for agriculture.

Q8. A glacier moves through a valley and widens and deepens it. What type of valley is likely to result?

Answer: A U-shaped valley is formed by glacial erosion.

Q9. Why can deforestation increase soil erosion?

Answer: Trees and vegetation help hold soil in place. When vegetation is removed, soil becomes exposed to water and wind erosion.

Q10. A glacial lake suddenly releases a huge amount of water and causes flooding downstream. Identify the disaster and give one major cause.

Answer:
It is a Glacial Lake Outburst Flood (GLOF). Rapid glacier melting can enlarge a glacial lake and put pressure on its natural ice or moraine dam, which may suddenly collapse.

3 MARKS

Q1. A mountain range is located where two continental plates meet. Explain how plate movement could have produced it.

Answer:

1. The two continental plates move towards each other at a convergent boundary.
2. The crust is compressed and folded.
3. This produces fold mountains, such as the Himalayas.

Q2. Explain how convection currents contribute to the movement of tectonic plates.

Answer:

• Heat from the Earth's core causes hot material in the mantle to rise.
• Cooler material sinks.
• This continuous movement creates convection currents that push and pull tectonic plates.

Q3. Differentiate between weathering and erosion with three points.

Answer:

Weathering	Erosion
Breaks rocks into smaller pieces	Wears away and carries materials
Does not involve movement	Involves movement
May be physical, chemical or biological	Mainly caused by water, wind, ice and waves

Q4. A farmer notices that fertile topsoil is being removed from his field every year. Explain two possible effects and one way of reducing the problem.

Answer:

• Removal of topsoil can reduce soil fertility and crop yields.
• Continued erosion can damage agricultural land.
• Measures such as contouring, bunding or terracing can reduce erosion.

Q5. A river changes its landforms from its upper course to its lower course. Explain the major changes.

Answer:

• In the upper course, strong erosion forms V-shaped valleys, waterfalls and rapids.
• In the middle course, meanders and floodplains develop as the river loses energy.
• In the lower course, deposition forms deltas, levees and alluvial features.

Q6. Why are deltas important to human beings despite being vulnerable to floods?

Answer:

• Deltas have fertile alluvial soil suitable for agriculture.
• They support fishing and aquatic ecosystems.
• Rivers provide routes for transport and trade, encouraging settlements.

Q7. Explain how waves can both create and destroy coastal landforms.

Answer:

• Waves deposit sediments to form beaches and sand bars.
• Waves erode coastlines to form cliffs and caves.
• Continued erosion can transform caves into arches and eventually stacks.

Q8. How do glaciers benefit human beings apart from creating landforms?

Answer:

• Glaciers are important sources of fresh water.
• They feed rivers that support downstream populations.
• Glacial landscapes support tourism, trekking, skiing and mountaineering.

Q9. A hillside settlement experiences a landslide after prolonged heavy rainfall. Explain three factors that could have contributed to it.

Answer:

1. Heavy rainfall increases the water content and weight of soil and reduces friction.
2. Steep slopes and loose or weathered rocks make slopes unstable.
3. Human activities such as deforestation, road construction or unplanned construction can further disturb slopes.

Q10. Why are dust storms more common in dry and semi-arid regions?

Answer:

• Low rainfall and drought make soil dry and loose.
• Sparse vegetation leaves the ground exposed.
• Strong winds can then lift and transport loose soil and sand.

5 MARKS

Q1. A country located near a plate boundary experiences frequent earthquakes and volcanic eruptions. Using the concept of plate tectonics, explain why this happens.

Answer: Plate tectonics explains the movement of the Earth's crust.

1. The lithosphere is divided into several tectonic plates.
2. These plates move slowly over the asthenosphere.
3. Their movement is driven by convection currents in the mantle.
4. At convergent boundaries, plates move towards each other and can cause earthquakes, mountain formation and volcanic activity.
5. At transform boundaries, plates slide past one another and mainly cause earthquakes.

Therefore, areas near plate boundaries are generally more prone to earthquakes and volcanic activity.

Q2. A geographical region contains mountains, valleys, plains and coastal features. Explain how internal and external forces work together to create such varied landforms.

Answer:

Internal forces:

• Earthquakes and volcanic activity originate from forces within the Earth.
• Folding and faulting can create mountains, valleys and other large features.
• Plate movements contribute to the formation of major landforms.

External forces:

• Weathering breaks down rocks.
• Erosion removes and transports material.
• Deposition builds up material in other places.

Agents such as running water, glaciers, wind, waves and groundwater continuously reshape the surface.

Thus, Earth's landforms result from the combined action of internal and external forces.

Q3. A farmer in a hilly region is losing fertile soil from his fields. Suggest a suitable soil-conservation strategy and explain why it would work.

Answer: The farmer can use terracing, contouring and bunding.

• Terracing creates step-like surfaces on hillsides and reduces the speed of runoff.
• Contouring involves creating trenches along contour lines to slow, hold and infiltrate rainwater.
• Bunding uses earthen embankments to slow surface runoff and increase water infiltration.

These measures reduce the speed of water flow, prevent soil from being washed away and improve soil moisture.

Q4. A river supports farming, settlements, transport and fishing but also causes floods. Explain how different river landforms influence human life.

Answer:

• Waterfalls can attract tourists and can be used for hydroelectric power generation.
• Meanders create fertile areas and can support agriculture and settlements.
• Floodplains provide fertile land but may be vulnerable to flooding.
• Deltas are highly fertile and support agriculture and fishing.
• River systems also provide routes for navigation, irrigation and trade.

Thus, river landforms provide many benefits while also creating risks such as flooding.

Q5. A coastal village is facing increasing erosion. Explain the processes involved and the possible effects on human life.

Answer: Coastal erosion occurs when waves, tides and currents wear away coastal land.

The process can create:

• Sea cliffs
• Wave-cut platforms
• Sea caves
• Sea arches
• Sea stacks

Increasing erosion can:

• Destroy beaches and coastal land.
• Threaten houses and infrastructure.
• Force communities to take coastal-protection measures.
• Affect tourism and other coastal activities.

Therefore, coastal erosion is both a geomorphological process and a human hazard.

Q6. Compare the formation and human importance of glacial landforms and wind-created landforms.

Answer:

Glacial landforms

Glaciers erode and transport material as they move.

Examples:

• U-shaped valleys
• Cirques
• Aretes
• Hanging valleys
• Fjords
• Moraines

They support tourism, provide freshwater and can support agriculture in suitable areas.

Wind landforms

Wind erodes and deposits loose sand and soil.

Examples:

• Yardangs
• Ventifacts
• Deflation hollows
• Desert pavements
• Sand dunes

They influence settlement and agriculture and can attract tourism.

Thus, both glaciers and wind reshape the Earth's surface but operate differently according to environmental conditions.

Q7. A mountain region experiences heavy rainfall followed by a landslide. Roads, houses and bridges are damaged. Explain the causes and suggest measures to reduce the risk.

Answer:

Causes:

• Prolonged heavy rainfall increases the weight of soil and rocks.
• Water reduces friction and destabilises slopes.
• Steep slopes and loose rocks increase vulnerability.
• Deforestation and road construction can weaken slopes.
• Poor drainage can allow water to accumulate.

Measures:

• Improve drainage.
• Avoid unplanned construction on unstable slopes.
• Control deforestation.
• Use appropriate slope-stabilisation measures.
• Identify and monitor landslide-prone areas.

Q8. A glacial lake in a mountain region is rapidly increasing in size because of rising temperatures. Explain how this could lead to a GLOF and why it is dangerous.

Answer:

1. Rising temperatures can cause rapid glacier melting.
2. Meltwater increases the size and water level of the glacial lake.
3. Pressure increases on the natural dam made of ice or loose moraines.
4. Heavy rainfall, snowfall, earthquakes, avalanches or landslides may weaken the dam.
5. If the dam collapses, a huge volume of water can suddenly rush downstream, causing destructive flooding.

This is called a Glacial Lake Outburst Flood (GLOF).

Q9. A desert region has experienced prolonged drought and loss of vegetation. Strong winds are now frequently carrying sand and dust into nearby settlements. Explain the causes, effects and possible measures.

Answer:

Causes:

• Prolonged drought and low rainfall.
• Dry and loose soil.
• Sparse vegetation.
• Strong winds.
• Deforestation, overgrazing and poor farming practices can worsen the situation.

Effects:

• Loss of fertile soil.
• Reduced visibility.
• Problems for settlements and human activities.
• Increased wind erosion.

Measures:

• Protect and increase vegetation cover.
• Prevent overgrazing.
• Adopt suitable land-management practices.
• Reduce exposure of loose soil to strong winds.

Q10. “Human life is deeply connected with landforms.” Explain the statement with suitable examples from the chapter.

Answer: Landforms influence human life in many ways:

1. Plains and river valleys provide fertile land for agriculture and support settlements.
2. Mountains can act as barriers and protect regions, while mountain passes can encourage cultural exchange.
3. Deserts may restrict large settlements but can encourage trade routes.
4. Coasts and harbours support fishing, trade, travel and cultural contacts.
5. Glaciers and rivers provide freshwater, while landforms such as waterfalls, beaches and caves support tourism.

Thus, landforms influence settlement, agriculture, trade, occupations, culture and economic activities.