How to Use This Page
This page provides complete exercise solutions for Samacheer Kalvi 7th Social Science — Geography Term 3, Chapter 3: Natural Hazases – Understanding of Disaster Management in Practice. Work through each section in order:
1. Read the Key Concepts for a quick recap of the chapter. 2. Attempt each exercise question on your own first. 3. Compare your answers with the detailed solutions below. 4. Review the Common Mistakes section to avoid losing marks. 5. Use the Exam Checklist before your test.
Key Concepts (Quick Recap)
- A hazard is a dangerous phenomenon that may cause harm or damage to humans and property.
- A disaster is a serious disruption causing widespread material, economic, social, or environmental losses.
- Disaster management refers to the conservation of lives and property during natural or man-made disasters.
- The disaster management cycle has six phases: Prevention, Mitigation, Preparedness, Response, Recovery, Rehabilitation/Reconstruction.
- Earthquake — sudden movement or trembling of the Earth's crust caused by tectonic plate movement.
- Tsunami — huge destructive waves produced by displacement of water, often triggered by undersea earthquakes.
- Cyclone — a low-pressure area encircled by high-pressure wind.
- Flood — sudden overflow of water caused by heavy rainfall, cyclone, melting of snow, tsunami, or dam burst.
- Drought — condition of insufficient rainfall leading to water scarcity.
- Mitigation — activities that reduce the effects of disasters.
- Response — activities taken during a disaster.
- Recovery — activities encompassing emergency relief, rehabilitation, and reconstruction.
Exercise Solutions
I. Choose the Correct Answer (MCQs)
1. \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ is an event which causes enormous physical damage to property, loss of life, and change in the environment.
Answer
- a) Hazard
- b) Disaster ✓
- c) Recovery
- d) Mitigation
ExplanationA disaster causes enormous physical damage, loss of life, and environmental change. A hazard is a potential threat, while a disaster is the actual occurrence that causes significant damage.
2. Activities that reduce the effects of disaster
Answer
- a) Preparation
- b) Response
- c) Mitigation ✓
- d) Recovery
ExplanationMitigation refers to all measures taken to reduce both the effects of the hazard and the vulnerable conditions in order to reduce the scale of a future disaster.
3. A sudden movement (or) trembling of the Earth's crust is called \_\_\_\_\_\_\_\_\_\_\_\_\_.
Answer
- a) Tsunami
- b) Earthquake ✓
- c) Fire
- d) Cyclone
ExplanationAn earthquake is a sudden movement or trembling of the Earth's crust caused by the movement of tectonic plates, mass wasting, landslides, or surface faults.
4. A sudden overflow of water in a large amount caused due to heavy rainfall is called \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_.
Answer
- a) Flood
- b) Cyclone ✓
- c) Drought
- d) Seasons
ExplanationNote: The textbook answer lists Cyclone (option b). A cyclone is a low-pressure area encircled by high-pressure wind that brings heavy rainfall. While floods are caused by heavy rainfall, a cyclone is specifically a weather phenomenon with strong winds and rain.
5. Road accidents can be avoided by permitting the persons who have \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ to drive vehicles.
Answer
- a) Ration card
- b) License ✓
- c) Permission
- d) Documents
ExplanationA driving license ensures that only trained and tested individuals operate vehicles, reducing the risk of road accidents.
II. Fill in the Blanks
1. A hazard is a disaster event that can cause harm or damage to humans and their property.
2. Activities taken during a disaster are called Response.
3. Displacement of water can produce one or more huge destructive waves known as Tsunami.
4. In case of fire accidents, call the nearby police station or the number 101 for the fire service.
5. Disaster management refers to conservation of lives and property during a natural or man-made disaster.
III. Match the Following
| Column A | | Column B |
|---|
| 1. Earthquake | → | b) Creak/Fault |
| 2. Cyclone | → | d) Eye of the storm |
| 3. Tsunami | → | a) Gigantic waves |
| 4. Industrial accident | → | e) Carelessness |
| 5. Drought | → | c) Uneven rainfall |
Explanation
- Earthquakes are caused by movement along faults/creaks in the Earth's crust.
- A cyclone has a calm centre called the "eye of the storm."
- Tsunamis produce gigantic waves that can devastate coastal areas.
- Industrial accidents often result from carelessness or negligence.
- Droughts are caused by uneven or insufficient rainfall.
IV. Consider the Following — Tick the Appropriate Answer (Assertion-Reason)
1. Assertion (A): In the modern world we can't live happily every day. Reason (R): Due to pollution and environmental degradation we are undergoing natural hazard and disaster.
Answer
- a) A and R are correct and A explains R ✓
- b) A and R are correct but A does not explain R
- c) A is incorrect but R is correct
- d) Both A and R are incorrect
ExplanationBoth statements are correct and A is explained by R — pollution and environmental degradation cause natural hazards and disasters, making it difficult to live happily.
2. Assertion (A): Sudden movement (or) trembling of the Earth's crust is called an earthquake. Reason (R): Movement of the tectonic plates, mass wasting, surface fault all lead to earthquake.
Answer
- a) A and R are correct and A explains R ✓
- b) A and R are correct but A does not explain R
- c) A is incorrect but R is correct
- d) Both A and R are incorrect
ExplanationBoth statements are correct. The definition of an earthquake (A) is directly explained by the causes mentioned in (R) — movement of tectonic plates, mass wasting, and surface faults all lead to earthquakes.
V. Very Short Answers (1–2 sentences)
1. Define Hazard.
Answer
A hazard is a dangerous phenomenon, substance, human activity, or condition that may cause loss of life, injury, health impacts, property damage, loss of livelihoods, services, and social or economic disruption or environmental damage.
2. What is a disaster?
Answer
A disaster is a serious disruption in society causing widespread material, economic, social, or environmental losses that exceeds the ability of the affected community to cope using its own resources.
3. What are the concepts of the disaster management cycle?
Answer
The six concepts of the disaster management cycle are: Prevention, Mitigation, Preparedness, Response, Recovery, and Rehabilitation.
4. Name any two agencies involved in the warning system in Tamil Nadu.
Answer
The Tamil Nadu State Disaster Response Force (SDRF) with 80 Police Personnel, and the National Disaster Response Force (NDRF) which trains the SDRF in disaster management and rescue operations.
5. Write about any three effects of floods.
Answer
Three effects of floods are: (1) Loss of life and property, (2) Displacement of people from their homes, and (3) Spread of contagious diseases such as cholera and malaria.
6. Give any four rail safety tips.
Answer
Four rail safety tips are: (1) Stay alert as trains can come from either direction at any time, (2) Never sit on the edge of the station platform, (3) Cross the tracks only at designated areas, and (4) Do not use mobile phones while crossing railway tracks.
7. Name any four different industries which undergo industrial disasters frequently.
Answer
Four industries prone to frequent disasters are: (1) Nuclear industries, (2) Chemical industries, (3) Match and crackers factories, and (4) Cotton and paper industries.
VI. Distinguish Between
1. Earthquake and Tsunami.
Answer
| Feature | Earthquake | Tsunami |
|---|
| Definition | Sudden movement or trembling of the Earth's crust | Huge destructive waves produced by displacement of water |
| Causes | Movement of tectonic plates, mass wasting, landslides, surface faults | Undersea earthquakes, volcanic eruptions, or landslides that displace water |
| Location | Occurs on land or under the sea | Originates in the ocean and affects coastal areas |
| Duration | Lasts seconds to minutes | Waves can travel across oceans and last hours |
2. Flood and Cyclone.
Answer
| Feature | Flood | Cyclone |
|---|
| Definition | Sudden overflow of water in large amounts | Low-pressure area encircled by high-pressure wind |
| Causes | Heavy rainfall, melting snow, dam burst, tsunami | Atmospheric disturbance with strong winds and heavy rain |
| Effects | Displacement, diseases like cholera and malaria | Destruction of buildings, disruption of transport and communication |
| Area affected | Plains and river basins | Coastal and inland areas along the cyclone's path |
3. Hazard and Disaster.
Answer
| Feature | Hazard | Disaster |
|---|
| Definition | A dangerous phenomenon or condition that may cause harm | A serious disruption causing widespread losses |
| Nature | Potential threat | Actual occurrence |
| Example | A fault line near a city (potential earthquake) | An earthquake that destroys buildings and kills people |
| Impact | May or may not cause damage | Causes significant damage exceeding community's coping capacity |
VII. Detailed Answers (Paragraph-length)
1. Write about the disaster management cycle.
Answer
The disaster management cycle consists of several phases that help communities prepare for, respond to, and recover from disasters.
Pre-Disaster Phase:
- Prevention and Mitigation: Prevention includes measures to protect persons and property. Mitigation embraces all measures taken to reduce both the effects of the hazard and the vulnerable conditions. This includes addressing issues like land ownership, tenancy rights, wealth distribution, and implementing earthquake-resistant building codes.
- Preparedness: This includes formulating viable emergency plans, developing warning systems, maintaining inventories, creating public awareness and education, and training personnel.
- Early Warning: This involves monitoring communities or areas known to be vulnerable to slow-onset hazards and passing knowledge of the pending hazard to people in a harmless way. Effective warnings require mass education so people know what actions to take when warned.
Disaster Impact Phase: This refers to the real-time event of a hazard occurrence affecting elements at risk. The duration depends on the type of threat — ground shaking may last seconds during an earthquake, while flooding may persist over a longer period.
During Disaster Phase:
- Response: This includes setting up control rooms, putting contingency plans into action, issuing warnings, evacuating people to safer areas, providing medical aid, and distributing relief materials like food, drinking water, clothing, and shelter.
Post-Disaster Phase:
- Recovery: Encompasses emergency relief, rehabilitation, and reconstruction.
- Rehabilitation: Provision of temporary public utilities and housing as interim measures.
- Reconstruction: Replacing buildings, infrastructure, and lifeline facilities with improved pre-disaster functioning.
- Development: Long-term prevention measures like constructing embankments, irrigation facilities, and increasing plant cover to reduce landslide occurrences.
2. Write about floods, their effects, and mitigation.
Answer
A flood is a sudden overflow of water in a large amount caused by heavy rainfall, cyclones, melting of snow, tsunamis, or dam bursts. When floodwaters inundate an area, they cause significant destruction.
Effects of floods:
- Loss of life and property — homes, crops, and infrastructure are destroyed.
- Displacement of people from their homes and communities.
- Spread of contagious diseases such as cholera, malaria, and other water-borne illnesses due to contaminated water and stagnant pools.
- Damage to agricultural land and loss of crops.
- Disruption of transportation and communication networks.
Mitigation for floods: Structural measures include constructing flood walls, sea walls, flood gates, levees, and embankments to prevent floodwaters from reaching inhabited areas. Building dams and reservoirs helps regulate water flow. Non-structural measures reduce damage by removing people and property from risk areas. These include elevated structures, property buyouts, permanent relocation of vulnerable communities, zoning regulations, subdivision controls, and building codes that require flood-resistant construction. Early warning systems and community preparedness programmes are also essential components of flood mitigation.
3. Write about any five general survival techniques.
Answer
Five general survival techniques during different disasters are:
1. During an earthquake: Get under a sturdy table or chair, kneel on the floor, and hold on firmly. Go near a strong wall, sit on the floor, and protect yourself. Use only torch lights — never candles or matches.
2. During floods: Store necessary supplies like first aid kits, food, and clean water. Listen to local Radio/TV for instructions and warnings. Cut off all electrical supplies to prevent electrocution.
3. During fire accidents: Call the fire service immediately (No. 101). If your clothes catch fire, remember "Stop, Drop, and Roll" — do not run, as running fans the flames.
4. Rail safety: Stay alert at all times because trains can come from either direction. Never sit on the edge of the station platform. Cross tracks only at designated safe areas.
5. During cyclones: Stay indoors, away from windows. Keep emergency supplies ready including food, water, torch, and first aid. Listen to weather warnings and follow official evacuation orders.
4. Write about earthquakes, their effects, and mitigation steps.
Answer
An earthquake is a sudden movement or trembling of the Earth's crust. It is caused by the movement of tectonic plates, mass wasting, landslides, and surface faults. The intensity of an earthquake is measured on the Richter scale.
Effects of earthquakes:
- Loss of lives, destruction of buildings, roads, bridges, and dams.
- Can trigger secondary disasters like floods, tsunamis, landslides, and fires.
- Breakdown of water supply and electrical lines.
- May change the course of rivers.
Mitigation steps:
- Construct earthquake-resistant buildings using appropriate engineering techniques and materials.
- Seek shelter under sturdy tables during tremors.
- Move to open areas away from buildings and power lines.
- Secure heavy furniture and belongings to prevent them from falling.
- Put latches on cabinet doors and file cabinets to keep them closed during tremors.
- Store hazardous materials in sturdy, secure places.
- Keep fire extinguishers readily accessible.
- Prepare an emergency kit with food, water, first aid, and communication devices.
Additional Important Questions — MCQs
1. On 2nd-3rd May 2018, high-velocity dust storms swept across North India killing over 125 people (b).
2. After the 2004 tsunami, Cyclone Gaja was the worst natural disaster to hit Tamil Nadu (a).
3. The word "Tsunami" is derived from the Japanese word (d).
4. A low-pressure area encircled by high-pressure wind is called a Cyclone (b).
5. In the early hours of November 10, 2018, Gaja cyclone spread at 120 kmph (c).
6. Recovery is used to describe activities encompassing emergency relief, rehabilitation, and reconstruction (a).
7. Reconstruction attempts to return communities with improved pre-disaster functioning (b).
8. State Disaster Management Plan perspective plan: 2018-2030 (a).
9. During an earthquake, be under the table, kneel to the floor and protect yourself (a).
10. In case of fire accidents, dial 101 for fire service (c).
Additional Important Questions — Fill in the Blanks
1. Generally, a hazard is a dangerous phenomenon.
2. A sudden movement or trembling of the Earth's crust is called an earthquake.
3. Due to a strong earthquake, loss of lives, buildings, roads, bridges, and dams are damaged — these are called Hazards.
4. Hurricane is a natural hazard that develops at sea.
5. Tsunami means harbour waves.
6. The term stampede is a sudden rush of a crowd of people.
Common Mistakes
1. Confusing hazard and disaster: A hazard is a potential threat; a disaster is the actual event that causes damage. Every disaster was once a hazard, but not every hazard becomes a disaster. 2. Mixing up mitigation and response: Mitigation reduces effects BEFORE a disaster; response involves actions DURING a disaster. They are different phases. 3. Confusing earthquake and tsunami causes: Earthquakes are caused by tectonic plate movement; tsunamis are caused by water displacement (often triggered by undersea earthquakes). 4. Saying floods only come from rain: Floods can also be caused by cyclones, melting snow, tsunamis, or dam bursts. 5. Forgetting the fire service number: The correct emergency number for fire service is 101, not 100 (police) or 102 (ambulance). 6. Confusing recovery and rehabilitation: Recovery is the overall phase; rehabilitation is a specific part involving temporary housing and utilities. 7. Mixing up cyclone and flood effects: Cyclones primarily disrupt transport and communication with strong winds; floods primarily cause displacement and disease.
Exam Checklist
- [ ] Can you define hazard and disaster and distinguish between them?
- [ ] Can you list and explain all phases of the disaster management cycle?
- [ ] Do you know the difference between mitigation, preparedness, and response?
- [ ] Can you explain earthquake causes, effects, and mitigation steps?
- [ ] Can you explain tsunami formation and its effects?
- [ ] Can you describe flood causes, effects, and mitigation measures?
- [ ] Do you know the difference between cyclone and flood?
- [ ] Can you list at least five general survival techniques?
- [ ] Do you remember the emergency numbers — 101 (fire), 100 (police), 102 (ambulance)?
- [ ] Can you name the agencies involved in disaster warning in Tamil Nadu (SDRF, NDRF)?
- [ ] Can you distinguish between earthquake and tsunami?
- [ ] Can you explain the role of early warning systems in disaster preparedness?
