Samacheer Kalvi 9th Social Science Disaster Management — Responding to Disasters Exercise Solutions | KalviGavani

Disaster Management — Responding to Disasters — Exercise Solutions Guide

Solve every exercise on your own first, then cross-check your answers here. Understanding why an answer is correct matters more than memorising it.

I. Multiple Choice Questions (MCQs)

Q1. A sudden shaking of the earth's surface caused by the movement of tectonic plates is called

(a) Flood (b) Cyclone (c) Earthquake (d) Tsunami

Q2. The scale used to measure the intensity of an earthquake is called

(a) Beaufort scale (b) Richter scale (c) Saffir-Simpson scale (d) Fujita scale

Q3. Tsunami waves are caused by

(a) Heavy rainfall (b) Underwater earthquakes or volcanic eruptions (c) Strong winds (d) Drought

Q4. The National Disaster Management Authority (NDMA) is chaired by the

(a) President of India (b) Prime Minister of India (c) Home Minister (d) Chief Justice of India

Q5. Which of the following is a man-made disaster?

(a) Earthquake (b) Cyclone (c) Industrial accident (d) Drought

Q6. The point on the earth's surface directly above the origin of an earthquake is called the

(a) Focus (b) Epicentre (c) Seismic zone (d) Fault line

Q7. The Disaster Management Act was enacted in the year

(a) 2002 (b) 2005 (c) 2009 (d) 2013

Q8. A prolonged period of deficient rainfall leading to water shortage and crop failure is called

(a) Flood (b) Cyclone (c) Drought (d) Landslide

Q9. Which organisation in Tamil Nadu is responsible for disaster management at the state level?

(a) NDMA (b) NDRF (c) TNSDMA (d) IMD

Q10. The Indian Ocean Tsunami of 2004 occurred on

(a) 26 January (b) 26 December (c) 15 August (d) 26 November

Q11. Cyclones in the Bay of Bengal are monitored and warned by

(a) NDMA (b) Indian Meteorological Department (IMD) (c) ISRO (d) NDRF

Q12. The National Disaster Response Force (NDRF) was established in the year

(a) 2001 (b) 2006 (c) 2009 (d) 2014

II. True or False

1. Disasters can be both natural and man-made.

2. The Richter scale measures the intensity of cyclones.

3. Drought is a sudden-onset disaster.

4. The NDMA is a constitutional body.

5. Tamil Nadu is vulnerable to both cyclones and tsunamis.

6. Earthquakes can be accurately predicted in advance.

7. Disaster management includes only relief work after a disaster.

8. The NDRF is a specialised force for disaster response and rescue.

9. Deforestation increases the risk of floods.

10. The focus of an earthquake is the point on the surface where maximum damage occurs.

III. Fill in the Blanks

1. The point inside the earth where an earthquake originates is called the ___.

The focus (hypocentre) is the underground point where seismic energy is released, causing the earthquake.

2. The scale used to measure earthquake magnitude is the ___ scale.

The Richter scale measures earthquake magnitude on a logarithmic scale from 1 to 10.

3. The NDMA is chaired by the ___ of India.

The Prime Minister chairs the NDMA, ensuring the highest level of authority and coordination.

4. The Disaster Management Act was enacted in the year ___.

The Disaster Management Act, 2005, was enacted in the wake of the 2004 tsunami.

5. A large ocean wave caused by an underwater earthquake is called a ___.

Tsunamis can travel across oceans at speeds up to 800 km/h and grow to devastating heights near coastlines.

6. The State Disaster Management Authority is chaired by the ___.

Each state's SDMA is chaired by the respective Chief Minister, ensuring state-level coordination.

7. The Indian Meteorological Department issues ___ warnings for cyclones and floods.

The IMD monitors weather conditions and issues warnings to alert the public and authorities about impending disasters.

8. A prolonged period of deficient rainfall causing water shortage is called ___.

Drought is a slow-onset disaster that affects agriculture, water supply, and livelihoods over an extended period.

9. The full form of NDRF is National ___ Response Force.

The NDRF is a specialised force for disaster rescue and relief operations across India.

10. The four phases of disaster management are mitigation, preparedness, response, and ___.

Recovery (also called rehabilitation and reconstruction) is the phase where normalcy is restored after a disaster.

IV. Match the Following

1. Earthquake → b. Release of energy from tectonic plates — Earthquakes occur when stress built up along fault lines is suddenly released, causing the ground to shake. 2. Tsunami → d. Large ocean wave from underwater quake — Tsunamis are generated by sudden displacement of ocean water, most commonly by underwater earthquakes, volcanic eruptions, or landslides. 3. Drought → a. Deficient rainfall over long period — Drought develops slowly as rainfall remains below normal for months or years, causing water shortage and crop failure. 4. Cyclone → c. Strong rotating winds over ocean — Cyclones are intense low-pressure systems with sustained winds of 62 km/h or more, forming over warm ocean waters. 5. Flood → e. Overflow of water submerging land — Floods occur when water overflows rivers, lakes, or coastal areas, submerging normally dry land. 6. Landslide → f. Mass movement of rock/soil down a slope — Landslides involve the downward movement of earth, rock, or debris on slopes, often triggered by heavy rain or earthquakes.

V. Short Answer Questions (2-3 marks)

Q1. What is a disaster? Differentiate between natural and man-made disasters.

A disaster is a sudden, calamitous event that causes significant damage, loss of life, destruction of property, and disruption of normal life, exceeding the affected community's ability to cope using its own resources. Natural disasters are caused by natural processes beyond human control. Examples: earthquakes (caused by tectonic plate movement), floods (caused by heavy rainfall or river overflow), cyclones (caused by atmospheric conditions over warm oceans), droughts (caused by prolonged deficient rainfall), tsunamis (caused by underwater earthquakes), and volcanic eruptions. Man-made disasters result from human actions, negligence, or technological failures. Examples: industrial accidents (Bhopal gas tragedy), nuclear disasters (Chernobyl, Fukushima), terrorist attacks, oil spills, forest fires caused by human negligence, and building collapses due to poor construction. Some disasters have both natural and man-made elements — for example, floods are natural but are worsened by deforestation and unplanned urbanisation.

Q2. Explain the disaster management cycle with its four phases.

The disaster management cycle is a continuous process with four interconnected phases: (1) Mitigation — Long-term measures taken before a disaster to reduce its impact. Examples: building earthquake-resistant structures, constructing embankments to prevent floods, afforestation, enforcing building codes, and land-use zoning. Mitigation reduces the risk and potential damage. (2) Preparedness — Planning and readiness actions taken before a disaster strikes. Examples: early warning systems, evacuation plans, emergency kits, stockpiling food and medicine, training volunteers, conducting mock drills, and public awareness campaigns. Preparedness ensures a quick and effective response. (3) Response — Immediate actions taken during and right after a disaster to save lives and protect property. Examples: rescue operations, first aid, emergency shelter, food and water distribution, medical care, and deployment of NDRF teams. Response focuses on saving lives and minimising suffering. (4) Recovery — Long-term actions to restore normalcy after a disaster. Examples: rebuilding houses and infrastructure, restoring livelihoods, counselling for trauma, and implementing better building standards. Recovery aims to build back better and reduce future vulnerability.

Q3. What is an earthquake? How are earthquakes measured?

An earthquake is a sudden shaking or trembling of the earth's surface caused by the release of energy stored in the earth's crust. This energy is released when tectonic plates move along fault lines, creating seismic waves that cause the ground to shake. The point inside the earth where the earthquake originates is called the focus (hypocentre), and the point on the surface directly above is called the epicentre. Measurement: Earthquakes are measured using instruments called seismographs (or seismometers), which detect and record seismic waves. The magnitude (energy released) is measured on the Richter scale (1-10, logarithmic). Each increase of 1 represents a tenfold increase in amplitude. Earthquakes below 3.0 are usually not felt, 3.0-4.9 are minor to light, 5.0-5.9 are moderate, 6.0-6.9 are strong, 7.0-7.9 are major, and 8.0+ are great earthquakes causing massive destruction. The intensity (observed effects) is measured on the Modified Mercalli scale (I-XII).

Q4. Describe the causes and effects of floods.

Causes of floods: (1) Heavy and prolonged rainfall that exceeds the capacity of rivers and drainage systems. (2) Cyclones and storms causing coastal flooding and storm surges. (3) Melting of snow and glaciers in upstream areas. (4) Overflow of rivers and dams due to excess water. (5) Man-made causes: deforestation (reducing water absorption), unplanned urbanisation (blocking natural drainage), encroachment on floodplains, and poor dam management. Effects of floods: (1) Loss of life and injury to humans and animals. (2) Destruction of houses, roads, bridges, and infrastructure. (3) Damage to crops and agricultural land. (4) Contamination of drinking water leading to water-borne diseases like cholera and dysentery. (5) Displacement of populations and loss of livelihoods. (6) Economic losses running into thousands of crores. Mitigation measures: Construction of embankments and levees, afforestation in catchment areas, improving drainage systems, early warning systems, flood zoning, and regulated dam releases.

Q5. What is a cyclone? How does it form?

A cyclone is an intense low-pressure weather system with strong rotating winds (62 km/h or more) that forms over warm tropical ocean waters. Cyclones are called hurricanes in the Atlantic and typhoons in the Pacific. Formation: (1) Warm ocean water (above 26.5 degrees Celsius) heats the air above it, causing it to rise and creating a low-pressure area. (2) More warm air rushes in to fill the low-pressure area, picking up moisture from the ocean. (3) The rising moist air cools and condenses, forming clouds and releasing heat (latent heat) that further fuels the storm. (4) The Coriolis effect (due to the earth's rotation) causes the air to spin, creating a rotating system. (5) As more warm air rises and more heat is released, the system intensifies into a cyclone with a calm centre called the eye. Classification: Depression (wind speed 31-61 km/h), deep depression (62-88 km/h), cyclonic storm (89-117 km/h), severe cyclonic storm (118-165 km/h), very severe cyclonic storm (166-221 km/h), extremely severe cyclonic storm (222 km/h+). The Bay of Bengal is one of the most cyclone-prone areas in the world, and Tamil Nadu's coast is frequently affected.

Q6. Explain the role of NDMA and SDMA in disaster management.

NDMA (National Disaster Management Authority): The apex body for disaster management in India, chaired by the Prime Minister. Its roles include: (1) Formulating national disaster management policies and guidelines. (2) Approving the National Disaster Management Plan. (3) Coordinating disaster response across states and central ministries. (4) Promoting research, training, and awareness in disaster management. (5) Recommending financial assistance to states during disasters. (6) Working with state authorities and international organisations. SDMA (State Disaster Management Authority): The state-level body, chaired by the Chief Minister. Its roles include: (1) Formulating the state disaster management plan. (2) Coordinating disaster response within the state. (3) Ensuring implementation of NDMA guidelines at the state level. (4) Promoting awareness and capacity-building at the district and local levels. (5) Recommending relief and rehabilitation measures. (6) Working with District Disaster Management Authorities (DDMAs). The NDMA provides national-level coordination and policy, while SDMAs handle implementation and response at the state level. Together, they form a multi-tier disaster management framework.

Q7. What is drought? What are its types and effects?

Drought is a prolonged period of deficient rainfall that leads to water shortage, crop failure, and environmental degradation. It is a slow-onset disaster that develops over months or years. Types: (1) Meteorological drought — when rainfall is significantly below normal for an extended period. (2) Hydrological drought — when water bodies (rivers, lakes, reservoirs, groundwater) fall below normal levels due to prolonged dry conditions. (3) Agricultural drought — when soil moisture is insufficient to support crop growth, leading to crop failure. (4) Socio-economic drought — when drought conditions cause food shortages, price rises, and economic hardship. Effects: (1) Crop failure and loss of agricultural income. (2) Water shortage for drinking, irrigation, and industry. (3) Malnutrition and health problems due to food scarcity. (4) Migration from rural to urban areas in search of livelihood. (5) Degradation of land and desertification. (6) Loss of livestock and wildlife. (7) Economic losses and increased poverty. (8) Conflicts over water resources. Mitigation: Rainwater harvesting, watershed management, afforestation, drip irrigation, drought-resistant crops, and maintaining buffer food stocks.

Q8. What safety measures should be taken during an earthquake?

Before an earthquake (preparedness): (1) Identify safe spots in each room — under sturdy tables, against interior walls, away from windows. (2) Prepare an emergency kit with water, food, first aid, torch, radio, batteries, and important documents. (3) Secure heavy furniture and appliances to walls. (4) Know the location of gas, electricity, and water shutoffs. (5) Conduct family earthquake drills. During an earthquake (response): (1) Drop, Cover, and Hold On — drop to the ground, take cover under a sturdy table or desk, and hold on until the shaking stops. (2) Stay indoors if you are inside — do not run outside. (3) Stay away from windows, glass, heavy furniture, and exterior walls. (4) If outdoors, move to an open area away from buildings, trees, and power lines. (5) If in a vehicle, stop in an open area and stay inside. (6) Do not use elevators. After an earthquake (recovery): (1) Check for injuries and provide first aid. (2) Check for gas leaks, electrical damage, and fire hazards. (3) Be prepared for aftershocks. (4) Do not enter damaged buildings. (5) Use battery-powered radio for emergency information. (6) Help neighbours and vulnerable people.

VI. Detailed Answer Questions (5 marks)

Q1. Explain the causes, effects, and safety measures for tsunamis.

Causes of tsunamis: Tsunamis are large ocean waves generated by the sudden displacement of a large volume of water. The primary causes are: (1) Underwater earthquakes — the most common cause, when a powerful earthquake (usually magnitude 7.5+) displaces the seafloor vertically. (2) Volcanic eruptions — underwater volcanic eruptions can displace massive volumes of water. (3) Landslides — underwater or coastal landslides can push water and generate tsunamis. (4) Meteor impacts — extremely rare but theoretically possible. In the open ocean, tsunami waves travel at speeds of up to 800 km/h with wavelengths of hundreds of kilometres but are only about 1 metre high. As they approach the coast, they slow down, grow in height (sometimes 30+ metres), and unleash devastating force. Effects of tsunamis: (1) Massive loss of life — the 2004 Indian Ocean tsunami killed over 2.3 lakh people across 14 countries. (2) Complete destruction of coastal infrastructure — houses, roads, bridges, ports, and power lines. (3) Contamination of freshwater sources with saltwater, making them undrinkable. (4) Loss of livelihoods for fishing and coastal communities. (5) Environmental damage — destruction of coral reefs, mangroves, and coastal ecosystems. (6) Psychological trauma for survivors. (7) Long-term economic damage to tourism and fisheries. Safety measures: (1) Early warning systems — the Indian Ocean Tsunami Warning System (IOTWS) and INCOIS (Indian National Centre for Ocean Information Services) monitor seismic activity and issue alerts. (2) If you feel a strong earthquake near the coast, move immediately to higher ground — do not wait for an official warning. (3) Never go to the beach to watch a tsunami — the waves are far more powerful than they appear. (4) If a tsunami warning is issued, evacuate coastal areas immediately and move at least 2 km inland or to ground at least 30 metres above sea level. (5) After a tsunami, do not return to the coast until authorities declare it safe — tsunamis often come in multiple waves. (6) Mangrove plantations along the coast act as natural barriers against tsunami waves. (7) Construction of sea walls and elevated shelters in vulnerable areas. (8) Community awareness programmes and regular tsunami drills in coastal areas.

Q2. Describe the disaster management framework in India — NDMA, SDMA, DDMA, and NDRF.

India's disaster management framework is a multi-tier system established under the Disaster Management Act, 2005, ensuring coordination from national to district level. NDMA (National Disaster Management Authority): The apex body chaired by the Prime Minister, with a Vice Chairperson (with cabinet minister status) and other members. Functions: formulate national disaster management policies and guidelines; approve the National Disaster Management Plan; coordinate disaster response across the country; promote research, training, and public awareness; recommend financial assistance to states; and liaise with international organisations. SDMA (State Disaster Management Authority): Chaired by the Chief Minister of each state, with a Vice Chairperson and members. Functions: formulate the state disaster management plan; ensure implementation of NDMA guidelines; coordinate disaster response within the state; promote capacity-building and awareness; and recommend relief measures. In Tamil Nadu, the TNSDMA coordinates cyclone, flood, and tsunami preparedness and response. DDMA (District Disaster Management Authority): Chaired by the District Collector/Deputy Commissioner, with the local MP as Co-Chairperson. Functions: prepare the district disaster management plan; coordinate disaster response at the district level; ensure training and awareness at the grassroots; and implement state and national plans at the district level. The DDMA is the operational unit that directly manages rescue and relief. NDRF (National Disaster Response Force): A specialised force constituted in 2006 with 16 battalions stationed across India. Functions: deploy quickly to disaster-affected areas; conduct search and rescue operations; provide medical first aid; clear debris; respond to chemical, biological, and nuclear emergencies; and train local communities in disaster preparedness. The NDRF has been deployed in major disasters including the 2004 tsunami, 2013 Uttarakhand floods, 2018 Kerala floods, and the 2020 COVID-19 pandemic. How they work together: The NDMA provides national policy and coordination, the SDMA implements at the state level, the DDMA manages operations at the district level, and the NDRF provides specialised rescue and relief capacity. Early warning comes from the IMD, INCOIS, and other agencies. This integrated framework ensures that disaster management is not ad hoc but systematic, from prevention to recovery.

Q3. Discuss the causes, effects, and mitigation measures for cyclones with special reference to Tamil Nadu.

Causes of cyclones: Cyclones form over warm ocean waters (above 26.5 degrees Celsius) when moisture-laden air rises, creating a low-pressure zone. The Coriolis effect causes the air to rotate, intensifying the system into a cyclone. The Bay of Bengal is particularly prone to cyclone formation due to its warm waters and shallow continental shelf. Cyclones typically occur in India during the pre-monsoon (April-May) and post-monsoon (October-December) seasons. Effects of cyclones: (1) Extremely high winds (up to 250+ km/h in severe cyclones) destroying buildings, trees, and infrastructure. (2) Heavy rainfall causing flooding in coastal and inland areas. (3) Storm surges — walls of seawater pushed inland by cyclone winds, inundating coastal areas. (4) Loss of life, livestock, and livelihoods. (5) Damage to crops, fisheries, and coastal ecosystems. (6) Disruption of power, communication, and transport networks. (7) Saline water intrusion contaminating freshwater sources and agricultural land. Cyclones and Tamil Nadu: Tamil Nadu's 1,076 km coastline along the Bay of Bengal makes it highly vulnerable to cyclones. Major cyclones that hit Tamil Nadu include: the 1977 Diviseema cyclone, the 1999 Odisha cyclone (affected TN coast), Cyclone Vardah (2016, hit Chennai), Cyclone Gaja (2018, devastated delta districts), Cyclone Nivar (2020), and Cyclone Michaung (2023, caused severe flooding in Chennai). The post-monsoon season (October-December) is the most cyclone-prone period for Tamil Nadu. Mitigation and preparedness measures: (1) Early warning systems — IMD issues cyclone warnings through cyclone alert (48 hours before), cyclone warning (24 hours before), and post-landfall outlook. (2) Cyclone shelters — permanent shelters built along the coast for evacuation during cyclones. (3) Coastal embankments and sea walls to reduce storm surge impact. (4) Mangrove plantations — natural barriers that reduce cyclone damage and storm surge. (5) Community awareness programmes and regular drills. (6) Evacuation plans with identified routes and shelters. (7) Strengthening of buildings and infrastructure to withstand cyclone-force winds. (8) TNSDMA coordination with district authorities for pre-cyclone preparedness and post-cyclone relief. (9) Stockpiling of food, water, medicine, and emergency supplies. (10) Rapid deployment of NDRF teams to affected areas before and after cyclone landfall.

Common Mistakes

1. Confusing the focus and epicentre of an earthquake: The focus (hypocentre) is inside the earth where the earthquake originates. The epicentre is on the surface directly above the focus. Maximum damage occurs near the epicentre, not the focus.

2. Saying drought is a sudden disaster: Drought is a slow-onset disaster that develops over months or years. It is not sudden like an earthquake or cyclone. Understanding this distinction is important for mitigation strategies.

3. Confusing NDMA and NDRF: NDMA is the policy-making authority (chaired by the PM) that formulates guidelines and plans. NDRF is the specialised response force that conducts rescue and relief operations on the ground. They are different bodies with different functions.

4. Calling the NDMA a constitutional body: The NDMA is a statutory body created under the Disaster Management Act, 2005, not a constitutional body. Do not confuse it with constitutional bodies like the Election Commission.

5. Mixing up the Richter scale and the Saffir-Simpson scale: The Richter scale measures earthquake magnitude. The Saffir-Simpson scale measures cyclone intensity. They are different scales for different disasters.

6. Thinking disaster management is only about relief work: Disaster management includes four phases — mitigation, preparedness, response, and recovery. Relief work is only part of the response phase. Mitigation and preparedness (before the disaster) are equally important.

7. Forgetting that tsunamis come in multiple waves: The first wave of a tsunami is often not the largest. Multiple waves can arrive over hours, and people should not return to the coast until authorities declare it safe.

Exam Checklist

• [ ] Can define disaster and differentiate between natural and man-made disasters
• [ ] Know the four phases of the disaster management cycle (mitigation, preparedness, response, recovery)
• [ ] Can explain the causes, effects, and safety measures for earthquakes
• [ ] Can explain the causes, effects, and safety measures for tsunamis (especially the 2004 tsunami)
• [ ] Can explain the causes, effects, and mitigation measures for cyclones (with TN reference)
• [ ] Can explain the causes, effects, and mitigation measures for floods and droughts
• [ ] Know the Richter scale (earthquakes) and Saffir-Simpson scale (cyclones)
• [ ] Understand the disaster management framework: NDMA, SDMA, DDMA, NDRF
• [ ] Know the Disaster Management Act, 2005, and its provisions
• [ ] Can explain the role of the TNSDMA in Tamil Nadu
• [ ] Know earthquake safety measures (Drop, Cover, and Hold On)
• [ ] Understand tsunami warning systems and evacuation procedures

Internal Links

• [Class 9 Social Science — Disaster Management — Responding to Disasters Guide](/school/tamil-nadu-state-board/class/9/social/disaster-management-responding-to-disasters)
• [All Class 9 Social Solutions](/school/tamil-nadu-state-board/class/9/social/solutions)
• [Class 9 Social Science Subject Guide](/school/tamil-nadu-state-board/class/9/social)