Exercise Solutions Available
Step-by-step answers for all textbook questions in this chapter
Understanding Disaster — Exercise Solutions
Use this guide alongside the Samacheer Kalvi textbook. Solve every question on your own first, then check below.
I. Fill in the Blanks
1. Stampede is a man-made disaster.
2. Avalanches are natural disasters.
3. The point where an earthquake originates is called its focus.
4. Volcanoes are openings/vents in the Earth's crust where lava erupts.
5. Waves generated by earthquakes and volcanic eruptions are called Tsunami.
6. A low-pressure area encircled by high-pressure wind is called a Cyclone.
7. Tsunami Early Warning System was established at Hyderabad in 2007.
8. Floods that occur within six hours during heavy rainfall are known as flash floods.
9. The lessening of adverse impacts of hazards and related disasters is called Mitigation.
10. Rain-fed areas are primarily supported with rainwater.
II. Choose the Correct Answer (MCQs)
Q1. A sudden event causing great damage to life and property is called \_\_\_\_\_\_. (a) Festival (b) Disaster (c) Celebration (d) Season
A disaster is defined as a serious disruption of the functioning of a society, involving widespread human and material loss.
Q2. Which of the following is a natural disaster? (a) Industrial accident (b) Stampede (c) Earthquake (d) Terrorism
Earthquakes are caused by natural tectonic plate movements. Industrial accidents, stampedes, and terrorism are man-made disasters.
Q3. Which of the following is a man-made disaster? (a) Volcano (b) Cyclone (c) Landslide (d) Fire
Fire (in buildings/forests due to human negligence) is classified as a man-made disaster. Volcanoes, cyclones, and landslides are natural disasters.
Q4. The point on the Earth's surface directly above the focus of an earthquake is called \_\_\_\_\_\_. (a) Focus (b) Epicentre (c) Crater (d) Vent
The epicentre is the point on the surface directly above the focus (the underground point of origin). Maximum damage usually occurs at the epicentre.
Q5. Tsunami Early Warning System was established at \_\_\_\_\_\_. (a) Mumbai (b) Chennai (c) Hyderabad (d) Kolkata
The Indian Tsunami Early Warning System was established at INCOIS (Indian National Centre for Ocean Information Services), Hyderabad, in 2007 after the 2004 Indian Ocean tsunami.
III. Match the Following
| A | B | Answer |
|---|---|---|
| Social media | Updated information | Updated information ✓ |
| DRR (Disaster Risk Reduction) | Reducing disaster | Reducing disaster ✓ |
| Floods | Sandbags | Sandbags ✓ |
| Tsunami | Massive waves | Massive waves ✓ |
| India | Disaster prone | Disaster prone ✓ |
IV. Short Answer Questions
Q1. Define disaster.
A disaster is a serious disruption of the functioning of a society, involving widespread human, material, economic, or environmental losses that exceed the ability of the affected community to cope using its own resources. Disasters are broadly classified into natural disasters and man-made disasters.
Q2. What are the two types of disasters? Give examples.
| Type | Examples |
|---|---|
| Natural Disasters | Earthquakes, Volcanoes, Tsunami, Cyclones, Floods, Landslides, Avalanches, Thunder and Lightning |
| Man-made Disasters | Fire, Destruction of buildings, Industrial accidents, Transport accidents, Terrorism, Stampede |
Q3. Write a short note on thunder and lightning.
Thunder and lightning are natural phenomena caused by atmospheric conditions. When warm, moist air rises and collides with cold air, electrical charges build up in the clouds. This discharge results in:
- Lightning — sudden flashes of light caused by electrical discharge
- Thunder — trembling sound waves produced by the rapid expansion and contraction of air heated by lightning
Lightning strikes can be dangerous — they can cause fires, damage buildings, and harm people and animals.
Q4. Chennai, Cuddalore, and the Cauvery delta are frequently affected by floods. Give reason.
During the Northeast Monsoon season (October to December), low-pressure depressions form in the Bay of Bengal. These depressions transform into cyclones and hit the coastal districts of Tamil Nadu. The heavy rainfall that follows these depressions and cyclones causes frequent flooding in Chennai, Cuddalore, and the Cauvery delta region. Additionally, these areas are low-lying and have inadequate drainage systems, making them more flood-prone.
Q5. Differentiate landslide and avalanche.
| Feature | Landslide | Avalanche |
|---|---|---|
| Material | Mass of rocks, debris, soil | Mass of ice, snow, and rock |
| Location | Down a mountain slope or hillside | Down the side of a snow-covered mountain |
| Cause | Heavy rain, earthquake, deforestation | Snow accumulation, wind, temperature change |
| Speed | Moderate to fast | Very fast |
| Occurrence | Hilly and mountainous terrain with loose soil | Snow-covered mountain regions |
Q6. What are volcanoes?
Volcanoes are openings or vents in the Earth's crust through which molten rock (lava), ash, gases, and small rocks are ejected onto the surface. When pressure from magma (molten rock beneath the surface) builds up, it forces its way to the surface through these vents, causing a volcanic eruption.
Q7. What is a cyclone?
A cyclone is a low-pressure area encircled by high-pressure wind. In a cyclone, air rotates inward toward the centre of the low-pressure zone. Cyclones bring heavy rainfall and strong winds, causing damage to life and property in coastal areas.
V. Detailed Answer Questions
Q1. What is a flood? Explain the do's and don'ts during floods.
A flood is an overflow of a large amount of water beyond its normal limits, especially over what is normally dry land. Floods are common in rain-fed areas during heavy rainfall.
Do's during floods: 1. Find out if the settlement area is likely to be affected by floods. 2. Keep a radio, torch, extra batteries, drinking water, dry food, salt, and sugar. 3. Safeguard kerosene, candles, match boxes, clothes, and valuables. 4. Keep umbrellas and bamboo poles. 5. Keep a first aid box and strong ropes. 6. Dig canals from farmland to drain excess water; keep sandbags.
Don'ts during floods: 1. Don't reconnect electricity once it is cut. 2. Don't operate vehicles in floodwater. 3. Don't swim against floodwaters. 4. Avoid going on excursions during flood warnings. 5. Don't neglect flood warning messages.
Q2. Explain the different types of floods.
| Type | Description |
|---|---|
| Flash Floods | Occur within six hours of heavy rainfall. Very sudden and dangerous. |
| River Floods | Caused by precipitation over large catchment areas or melting of snow and ice. Gradual but widespread. |
| Coastal Floods | Associated with cyclones, high tides, and tsunami. Affect coastal regions. |
Q3. Explain focus and epicentre of an earthquake.
Focus (Hypocentre): The point inside the Earth's crust where an earthquake originates is called the focus. This is where the seismic energy is first released.
Epicentre: The point on the Earth's surface directly above the focus is called the epicentre. The maximum damage from an earthquake is usually experienced at the epicentre.
Seismic waves radiate outward from the focus in all directions. The closer a place is to the epicentre, the stronger the shaking and damage experienced.
Q4. What does the World Disaster Report say about India?
According to the World Disaster Report:
- Disasters have increased in frequency and intensity over the years.
- India is one of the most disaster-prone countries in the world.
- India is vulnerable to multiple types of disasters — earthquakes, floods, cyclones, droughts, tsunamis, and landslides.
- Climate change and environmental degradation are increasing the risk of disasters.
- Preparedness and mitigation measures are essential to reduce the impact of disasters.
Q5. Explain Disaster Risk Reduction (DRR).
Disaster Risk Reduction (DRR) is the concept and practice of reducing disaster risks through systematic efforts. It involves:
1. Prevention — Reducing the severity or likelihood of a disaster. 2. Mitigation — Lessening the adverse impacts of hazards. 3. Preparedness — Knowledge and capacities to anticipate, respond to, and recover from disasters. 4. Response — Providing emergency services and rescue operations during and immediately after a disaster. 5. Recovery — Restoring and improving facilities and livelihoods after a disaster.
DRR aims to save lives, reduce injuries, protect property, and minimise economic losses through planning, awareness, and community participation.
Additional Practice Questions
MCQs (Additional)
Q1. Earthquakes are caused by \_\_\_\_\_\_. (a) Heavy rainfall (b) Tectonic plate movements (c) Deforestation (d) Volcanic eruption only
Earthquakes occur when tectonic plates move, collide, or slide past each other, releasing seismic energy.
Q2. Which type of flood occurs within six hours of heavy rainfall? (a) River flood (b) Coastal flood (c) Flash flood (d) Groundwater flood
Flash floods are sudden floods that occur within six hours of heavy rainfall, making them extremely dangerous.
Q3. INCOIS, which houses the Tsunami Early Warning System, is located at \_\_\_\_\_\_. (a) Chennai (b) Visakhapatnam (c) Hyderabad (d) Thiruvananthapuram
Fill in the Blanks (Additional)
1. The 2004 Indian Ocean tsunami was caused by an earthquake off the coast of Sumatra. 2. An avalanche is a mass of ice, snow, and rock falling rapidly down a mountain. 3. The Richter scale measures the magnitude of an earthquake. 4. Cyclones in the Bay of Bengal affect the eastern coast of India. 5. The full form of DRR is Disaster Risk Reduction. 6. The Indian Tsunami Early Warning Centre was established in the year 2007.
True or False (Additional)
Q1. All disasters can be prevented.
Natural disasters like earthquakes and tsunamis cannot be prevented, but their impact can be reduced through preparedness and mitigation.
Q2. Lightning is a man-made disaster.
Lightning is a natural phenomenon. However, fires caused by lightning can sometimes be classified under mixed causes.
Q3. Flash floods develop slowly over days.
Flash floods develop very quickly — within six hours of heavy rainfall. That is why they are called "flash" floods.
Q4. India is one of the most disaster-prone countries in the world.
According to the World Disaster Report, India is highly vulnerable to multiple types of disasters.
Q5. The epicentre experiences the least damage during an earthquake.
The epicentre experiences the maximum damage during an earthquake, as it is closest to the surface point above the focus.
Common Mistakes
1. Confusing natural and man-made disasters — Earthquakes, volcanoes, tsunamis, cyclones, floods, landslides, avalanches, and thunder/lightning are natural. Fire (due to negligence), industrial accidents, transport accidents, terrorism, and stampedes are man-made.
2. Mixing up focus and epicentre — Focus is the point inside the Earth where the earthquake originates. Epicentre is the point on the surface directly above the focus. Maximum damage occurs at the epicentre.
3. Saying all floods are the same — There are three types: flash floods (within 6 hours), river floods (gradual, from catchment areas), and coastal floods (from cyclones/tides).
4. Confusing landslide and avalanche — A landslide involves rocks, soil, and debris sliding down a slope. An avalanche involves ice, snow, and rock falling rapidly down a snow-covered mountain.
5. Thinking disasters cannot be prepared for — While natural disasters cannot be prevented, their impact can be reduced through mitigation, preparedness, early warning systems, and community awareness.
6. Confusing mitigation and prevention — Mitigation means reducing the adverse impacts of disasters. Prevention means stopping the disaster from happening altogether (possible only for some man-made disasters).
7. Forgetting that India is disaster-prone — India faces earthquakes, floods, cyclones, tsunamis, droughts, and landslides. The World Disaster Report specifically highlights India's vulnerability.
Exam Checklist
- [ ] Can define disaster and classify types (natural vs man-made)
- [ ] Can list examples of natural disasters (earthquake, volcano, tsunami, cyclone, flood, landslide, avalanche, thunder/lightning)
- [ ] Can list examples of man-made disasters (fire, stampede, industrial accident, transport accident, terrorism)
- [ ] Can explain focus and epicentre of an earthquake
- [ ] Can explain what volcanoes are and how they erupt
- [ ] Can define tsunami and explain its causes
- [ ] Can explain cyclones and their impact on coastal areas
- [ ] Can differentiate between flash floods, river floods, and coastal floods
- [ ] Can differentiate between landslide and avalanche
- [ ] Can list do's and don'ts during floods
- [ ] Can explain why Chennai, Cuddalore, and Cauvery delta are flood-prone
- [ ] Can explain Disaster Risk Reduction (DRR) and its components
- [ ] Can state what the World Disaster Report says about India
- [ ] Knows the year and location of the Indian Tsunami Early Warning System (2007, Hyderabad)