Shaping of the Earth’s SurfaceClass 9 Social Science NCERT Solutions
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Q1Questions and activities
What are the sources of energy that are required to cause movements associated with the internal forces of the Earth?
Solution
The primary source of energy for the movements associated with the internal forces of the Earth is the intense heat originating from the planet's core. This heat warms the molten material in the mantle, causing it to rise. As this material moves towards the crust, it cools and sinks back down. This continuous circular movement creates powerful convection currents within the mantle. These currents push and pull the tectonic plates on the surface, causing them to move and resulting in internal forces like earthquakes and volcanic activity.
Q2Questions and activities
Relate various physiographic divisions you have studied in the earlier grades with various endogenic forces responsible for their origin.
Solution
Endogenic forces, which originate from within the Earth, are responsible for creating major physiographic divisions. Based on the chapter, we can understand the formation of large mountain ranges and volcanic regions.
- Fold Mountains: These are formed by the endogenic force of plate collision. When two continental plates move towards each other at a convergent boundary, the immense pressure causes the Earth's crust to buckle and fold, pushing up vast mountain ranges. The formation of the Himalayas is a prime example of this process, resulting from the collision of the Indo-Australian Plate with the Eurasian Plate.
- Volcanic Landforms: Volcanic activity, another result of endogenic forces, creates mountains and plateaus. This occurs at convergent boundaries where an oceanic plate sinks beneath a continental plate, melting and creating magma that rises to the surface. It also happens at divergent boundaries where plates pull apart, allowing magma to form new crust.
Q3Questions and activities
Why and where do earthquakes occur frequently? Is it possible to predict earthquakes?
Solution
Earthquakes occur frequently along plate boundaries, which are the edges where tectonic plates meet. The movement of these massive plates is not smooth. At convergent boundaries, plates collide; at divergent boundaries, they pull apart; and at transform boundaries, they slide past each other. These movements build up immense stress in the Earth's crust. When this stress is suddenly released, it causes the ground to shake, resulting in an earthquake. Consequently, regions located on or near these active boundaries, such as the area around the Pacific Ocean known as the 'Ring of Fire', experience frequent earthquakes.
The chapter does not state that it is possible to predict earthquakes with certainty. While ancient Indian texts noted how changes in animal behaviour or weather could signal them, modern science focuses on identifying earthquake-prone regions based on the theory of plate tectonics. This allows for better preparation and disaster management rather than predicting the exact time and location of a future earthquake.
Q4Questions and activities
"Plate movements are responsible for the distribution of earthquakes and volcanoes." Explain.
Solution
The statement is correct because the vast majority of earthquakes and volcanoes are concentrated along the boundaries where tectonic plates interact. The distribution of these geological events is not random; it directly corresponds to the map of the world's major tectonic plates.
- Convergent Boundaries: Where an oceanic plate collides with and sinks beneath a continental plate, the process leads to both intense earthquakes and the formation of volcanoes as the subducting plate melts.
- Divergent Boundaries: Where plates move away from each other, magma rises from the mantle to fill the gap, creating new crust. This process is associated with volcanic activity, such as the formation of mid-ocean ridges.
- Transform Boundaries: Where plates slide horizontally past one another, the friction builds up stress that is released as earthquakes. The San Andreas Fault is a key example.
The 'Ring of Fire' around the Pacific Ocean is the clearest evidence of this relationship. It is a long chain of volcanoes and a site of frequent earthquakes, and it perfectly outlines the boundaries where the massive Pacific Plate interacts with several other plates.
Q5Questions and activities
Draw and label a diagram of a meander and a delta.
Solution
This is a drawing activity. The diagrams should be based on Figures 2.11 and 2.12 in the textbook.
Description for a Meander Diagram:
- Draw a river with a large, winding S-shaped curve. This curve is the meander.
- On the outer bank of the bend, where the water flows faster, label it as the 'Zone of Erosion' or 'Cut Bank'. The bank should appear steep or undercut.
- On the inner bank of the bend, where the water flows slower, label it as the 'Zone of Deposition' or 'Point Bar'. This area should be shown with sediment deposits and a gentler slope.
- Use arrows to show the direction of the river's flow.
Description for a Delta Diagram:
- Draw a river flowing towards a larger body of water, like a sea or an ocean.
- At the point where the river meets the sea (the river mouth), show the river breaking up into many smaller channels. These are called 'distributaries'.
- Draw a fan-shaped or triangular area of land built up between these distributaries. This landmass is the delta.
- Label the main 'River', the 'Sea/Ocean', the 'Distributaries', and the 'Sediment Deposits' that form the delta.
Q6Questions and activities
How are deforestation and erosion associated with each other? Explain.
Solution
Deforestation and erosion are closely associated because the removal of trees and vegetation directly accelerates the process of erosion. Forests and plant cover play a critical role in protecting the land in several ways:
- Binding the Soil: The roots of trees and plants form a dense network that holds soil particles together, making the soil compact and resistant to being carried away.
- Reducing Water Impact: The canopy of trees intercepts heavy rainfall, slowing it down and reducing its force before it hits the ground. This prevents rainwater from dislodging and washing away topsoil.
- Slowing Wind Speed: Trees act as natural windbreaks, reducing the speed of wind at the ground level.
When deforestation occurs, this protective cover is lost. The bare soil is left exposed to the full force of wind and rain. As a result, fertile topsoil is easily eroded by water (water erosion) or blown away by strong winds (wind erosion). This not only degrades the land but also increases the risk of related disasters like landslides, as the unstable soil on slopes can no longer hold its position.
Q7Questions and activities
Develop a plan to protect the land in your local area from erosion.
Solution
A plan to protect land from erosion in a local area can be developed by combining natural methods and community action, based on principles mentioned in the chapter.
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Afforestation and Revegetation: The most important step is to plant more trees, shrubs, and grasses, especially on slopes and along riverbanks. As mentioned in the landslide poster, trees help 'hold the Soil Together'. This will create a natural barrier against wind and water erosion.
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Proper Water Management:
- Clean Drainage Systems: Ensure that drains and natural water channels are kept clean and open to allow water to flow freely, preventing waterlogging that can weaken soil.
- Construction of Check Dams: Build small dams across streams to reduce the velocity of water flow, which helps prevent soil erosion and allows sediment to deposit.
- Contouring and Terracing: On sloped land used for farming, create terraces or practice contour ploughing. These methods, mentioned as ancient Indian techniques, slow down the flow of water down the hill, reducing erosion.
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Sustainable Land Use Practices:
- Avoid unplanned construction, especially on steep slopes or near natural drainage paths, as this disturbs the stability of the land.
- Promote farming practices that do not leave the soil bare for long periods, such as planting cover crops.
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Community Awareness: Educate local residents about the causes and dangers of soil erosion and involve them in tree plantation drives and maintenance of community water channels.
Q8Questions and activities
Which disasters do you think you might experience in your region? Discuss a mitigation plan in your classroom.
Solution
The specific disaster depends on the geographical location of the region. For example, if the region is a hilly or mountainous area like Uttarakhand or the Himalayas, a likely disaster is a landslide.
A mitigation plan for landslides, based on the information in the chapter, can be discussed in the classroom and should include measures to be taken before, during, and after the event.
Mitigation Plan for Landslides:
Before a Landslide (Preparedness):
- Prevention: The most effective measure is to grow more trees and vegetation on slopes to bind the soil and increase stability.
- Planning: Avoid constructing buildings near steep slopes, on loose soil, or in natural drainage paths.
- Early Warning: Listen to radio, watch TV, and read newspapers for any alerts or warnings, especially during heavy rainfall. Be vigilant for warning signs like cracks appearing on the ground, subsidence of buildings, or unusually muddy river water.
- Infrastructure: Keep drains and culverts clean to prevent water from accumulating and saturating the soil.
During a Landslide:
- Evacuation: Move away from the landslide path or downstream valley as quickly as possible. Do not take shelter in buildings within the path of the slide.
After a Landslide (Response):
- Safety First: Stay away from the slide area. Do not touch or walk over loose material, and be cautious of downed electrical wires or poles.
- Rescue: Check for injured and trapped persons. Inform rescue teams immediately.
- First Aid: Do not move an injured person unless they are in immediate danger, and provide first aid if trained.
- Health: Do not drink water from rivers or springs near the landslide area as it may be contaminated. Wait for authorities to declare water sources safe.
Q9Questions and activities
Prepare a model of landforms created by underground water.
Solution
This is a practical activity to create a model of Karst topography.
Materials Needed:
- A large cardboard box or a tray with high sides.
- Clay or play-doh in different colors (brown, grey).
- Small twigs or toothpicks.
- Plaster of Paris (optional).
- Blue paint or blue cellophane.
Steps to Prepare the Model:
- Create the Base: Use the cardboard box as the base. Build up a thick layer of brown or grey clay inside it to represent the Earth's surface and the limestone rock layer beneath it.
- Carve a Cave: Carefully scoop out a hollow space inside the clay layer to represent a cave. Make the entrance visible from one side of the box.
- Form Stalactites and Stalagmites:
- Stalactites: Roll small, thin, cone-shaped pieces of clay and hang them from the ceiling of the cave. These are stalactites.
- Stalagmites: Form slightly thicker cone shapes and place them on the floor of the cave, directly beneath the stalactites. These are stalagmites.
- Create Sinkholes: On the top surface of the clay, press your thumb down to create a few shallow depressions. These represent sinkholes, where the ground has collapsed into a cavity below.
- Add an Underground River: Carve a small channel flowing through the cave system. You can paint this channel blue or line it with blue cellophane to represent an underground river.
- Label the Landforms: Use small paper flags attached to toothpicks to label the different parts of your model: 'Cave', 'Stalactite', 'Stalagmite', 'Sinkhole', and 'Underground River'.
Q10Questions and activities
What precautionary measures will you take if you are staying in an earthquake-prone region?
Solution
If staying in an earthquake-prone region, it is crucial to be prepared. The precautionary measures can be divided into actions to take before, during, and after an earthquake.
Before an Earthquake (Preparation):
- Secure Your Home: Fasten heavy furniture like cupboards and shelves to the walls. Place heavy objects on lower shelves.
- Identify Safe Spots: Identify safe spots in each room, such as under a sturdy table or against an interior wall, away from windows, mirrors, and heavy objects.
- Prepare an Emergency Kit: Keep an emergency kit ready with essential items like a first-aid kit, non-perishable food, water, a flashlight, batteries, and important documents.
- Have a Plan: Create a family emergency plan, deciding on a meeting point in case you get separated.
During an Earthquake (Response):
- Drop, Cover, and Hold On: If you are indoors, drop to the ground, take cover under a sturdy piece of furniture, and hold on until the shaking stops.
- Stay Away from Hazards: Stay away from windows, glass, and anything that could fall.
- If Outdoors: Move to an open area away from buildings, trees, and power lines.
After an Earthquake (Recovery):
- Check for Injuries: Check yourself and others for injuries and provide first aid where necessary.
- Be Cautious: Be prepared for aftershocks. Check for gas leaks, electrical damage, and structural damage to your home before re-entering.
- Stay Informed: Listen to the radio or official news channels for instructions and information from authorities.
Q11Questions and activities
Prepare a map showing landform-associated disasters that happened in the current calendar year.
Solution
This is a research-based mapping activity. To complete it, you should follow these steps:
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Research: Use reliable sources like newspapers, government disaster management websites, and international news agencies to find information about major landform-associated disasters that have occurred in the current calendar year. The disasters to look for include:
- Landslides
- Avalanches
- Glacial Lake Outburst Floods (GLOFs)
- Dust Storms
- Earthquakes
- Volcanic Eruptions
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Obtain a Map: Get an outline map of the world, or a map of a specific continent or country like India, depending on the scope of your research.
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Locate and Mark: For each disaster you have researched, find its location on the map and mark it using a specific symbol. For example:
- A triangle (▲) for a volcano
- A star (★) for an earthquake
- A wavy line (~) for a flood/GLOF
- A downward arrow (↓) for a landslide
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Create a Legend: In a corner of the map, create a legend or key that explains what each symbol represents. You can also use different colors for different types of disasters.
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Add Details: For each marked disaster, you can add a small note with the date and name of the event (e.g., "Chamoli Flood, February 2021").
Q12Questions and activities
Create a poster showing landforms that are considered to be sacred or important in your region, and add the folk stories associated with them.
Solution
This is a creative and region-specific activity. Here is a template for how to structure the poster:
Poster Title: Sacred Landforms of Our Region
Section 1: The Sacred Mountain
- Image: A drawing or picture of a prominent mountain in your region.
- Name: Write the name of the mountain.
- Importance: Explain why it is important (e.g., "Believed to be the abode of a local deity").
- Folk Story: Briefly narrate the folk story associated with it. (e.g., "Legend says that a great sage meditated here for a thousand years, and the mountain protects our villages from harm.")
Section 2: The Holy River
- Image: A drawing or picture of a local river.
- Name: Write the name of the river.
- Importance: As the chapter mentions, waterfalls can have religious significance. Similarly, rivers are often considered sacred. (e.g., "Its water is believed to have healing properties.")
- Folk Story: Share a local legend about the river. (e.g., "It is said that the river is a goddess who descended from the heavens to nourish the land.")
Section 3: The Mysterious Cave
- Image: A drawing or picture of a cave.
- Name: Write the name of the cave.
- Importance: Explain its cultural significance (e.g., "Ancient rituals were performed here; it is a site of pilgrimage.")
- Folk Story: Tell the story linked to the cave. (e.g., "A mythical hero is said to have taken refuge in this cave during a great war.")
Conclusion: Add a concluding line like "Our landforms shape our culture and history."
Q13Questions and activities
Document a case of a disaster that hit your region in the past, highlighting its effects on various human activities.
Solution
This is a case study activity. Using the example of the Gujarat earthquake mentioned in the textbook, a case study can be documented as follows:
Case Study: The Gujarat Earthquake, 2001
1. The Disaster: A major earthquake with its epicenter near Bhuj in the Kutch district of Gujarat struck on January 26, 2001. As the text states, India has experienced major earthquakes in the past, and this was one of the most devastating.
2. Cause: The earthquake was caused by the movement of the Indian tectonic plate. As a densely populated country, the impact was severe.
3. Effects on Human Activities:
- Loss of Life and Injury: The disaster resulted in thousands of deaths and left many more injured, as noted in the chapter's general discussion on earthquakes in India.
- Damage to Infrastructure and Property: As shown in Figure 2.5, there was extensive damage to buildings, roads, bridges, and communication lines. Many people lost their homes and were displaced.
- Economic Disruption: Businesses, industries, and agricultural activities came to a standstill. The destruction of infrastructure severely hampered economic activity and livelihoods in the region.
- Social and Psychological Impact: The disaster caused immense psychological trauma for the survivors who lost family members and their homes. Community life was severely disrupted for a long period.
- Environmental Impact: The shaking ground caused changes in the land, and the destruction of infrastructure led to environmental contamination risks.
Q14Questions and activities
Translate the given poster on landslide into your native language and display it in your home.
Solution
This is a practical translation activity. The goal is to translate the key safety messages from the landslide poster into your native language. The phrases to be translated are:
Heading:
- LANDSLIDE
- Ready Now to stay secure
Before:
- Grow More trees that can hold the Soil Together
- Listen to Radio/ Watch T.V and Newspaper for any alerts
- Keep drains clean, Keep holes open
- Watch out for any warning signs such as subsidence of building, cracks on rocks, muddy river water
- DO NOT Construct near Steep slopes and near drainage path
After:
- DO NOT Touch / Walk over loose material and electrical Wires or Poles
- Move away from landslip path and downstream valley quickly
- Check for Injured and Trapped Person
- DO NOT move an Injured person without rendering first aid unless he/she is in immediate danger
- DO NOT drink contaminated water directly from rivers, springs, wells etc.
For example, if your native language is Hindi, "Grow More trees" would be translated to "अधिक पेड़ लगाएं".
Q15Questions and activities
Divide the class into three groups. Each group will work on one project (water, wind, and glacier). The project should highlight the causes, impact on human life and the environment, and mitigation measures.
Solution
This is a group project activity. Below is a structured outline for one of the projects, focusing on Glaciers, based on the chapter content.
Project: The Work of Glaciers
1. Causes (The Process of Glacial Action):
- Erosion: Explain that glaciers are slow-moving rivers of ice that shape the landscape. As they move, they scrape and pluck rocks and soil from the ground, carving out features like U-shaped valleys, cirques (bowl-shaped depressions), and arêtes (sharp ridges).
- Deposition: Describe how glaciers deposit the eroded material (called till) when they melt. This process forms landforms called moraines (lateral, medial, and terminal).
2. Impact on Human Life and Environment:
- Positive Impacts:
- Fresh Water Source: Glaciers are crucial sources of fresh water, feeding rivers that sustain millions of people downstream.
- Agriculture: The soil left behind by glaciers in moraines and valleys can be very fertile and suitable for agriculture.
- Tourism and Recreation: Glacial landscapes like U-shaped valleys and fjords are major tourist attractions for activities like trekking, skiing, and mountaineering.
- Hydroelectric Power: Lakes formed by moraines can be used for generating hydroelectric power.
- Negative Impacts (Hazards):
- GLOFs (Glacial Lake Outburst Floods): Rapid melting due to climate change can cause glacial lakes to burst their natural dams, leading to devastating floods downstream, as seen in the 2021 Chamoli disaster.
- Avalanches: Unstable snow on glaciated mountain slopes can cause deadly avalanches, posing a risk to settlements and trekkers.
3. Mitigation Measures:
- Monitoring: Regularly monitor glacial lakes using satellite imagery and ground sensors to detect rising water levels or instability in their dams.
- Early Warning Systems: Install early warning systems in downstream areas to alert communities in case of a GLOF or avalanche threat.
- Controlled Drainage: In some cases, engineers can carefully drain water from dangerous glacial lakes to reduce pressure on the natural dam.
- Climate Action: Address the root cause of rapid melting by taking measures to combat global warming and climate change.