Samacheer Class 7 Social Science - Natural Hazards

1. A hazard is a disaster event that can cause harm or damage to humans and their property. Hazards are potential sources of danger that, if realized, can lead to significant negative consequences. 2. Activities taken during a disaster are called Response. Disaster response involves immediate actions taken during and immediately after a disaster to save lives, reduce health impacts, ensure public safety, and meet the basic subsistence needs of those affected. 3. Displacement of water can produce one or more huge destructive waves known as Tsunami. Tsunamis are typically caused by underwater earthquakes, volcanic eruptions, or landslides, which displace large volumes of water, generating powerful and fast-moving waves that can devastate coastal areas. 4. In case of fire accidents, call the nearby police station or the number 101 for the fire service. The fire service is a critical emergency service responsible for extinguishing fires, rescuing people from dangerous situations, and providing first aid. 5. Disaster management refers to conservation of lives and property during a natural or man-made disaster. It encompasses a comprehensive approach including preparedness, mitigation, response, and recovery efforts to minimize the impact of disasters and build resilience in communities.

dangerous phenomenon
2. A ………………….. (or) trembling of the earth crust is called as earthquake.
sudden movement
3. Due to a strong earthquake, loss of lives, buildings, roads, bridges, and dams are damaged are called …………………..
Hazards
4. ………………….. is a natural hazard. It develops at sea.
Hurricane
5. ………………….. means harbor waves.
Tsunami6. The term………….. is a sudden rush of a crowd of people.
stampede
7. ………………….. is a disaster.
Fire
8. ………………….. refers to the “real-time event of a hazard occurrence and affecting elements at risk.
Disaster Impact
9. ………………….. embraces all measures taken to reduce both the effects of the hazard itself and the vulnerable conditions.
Mitigation
10. If any ………………….. occur dial, 101 for Fire service and 108 for the Ambulance.
emergency medical help

Generally, 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, social and economic disruption, or environmental damage. Hazards are potential threats that have the capacity to cause harm. They can be natural, such as earthquakes, floods, and droughts, or human-induced, like industrial accidents, pollution, and conflicts. Understanding and identifying hazards is the first step in disaster risk reduction, as it allows for the implementation of measures to prevent or mitigate their potential impacts. The severity of a hazard's impact often depends on the vulnerability of the community exposed to it.

Two important agencies involved in the warning and response system in Tamil Nadu are the Tamil Nadu State Disaster Response Force (SDRF) and the National Disaster Response Force (NDRF). The Tamil Nadu State Disaster Response Force has been constituted with a strength of 80 Police Personnel who have been specially trained in disaster management and rescue operations. This training is conducted in consultation with the National Disaster Response Force, which is a specialized central agency that provides expertise and support for disaster response across the country. These agencies work together to ensure rapid and effective response to disasters, coordinate rescue and relief operations, and provide technical assistance during emergencies to protect lives and property in Tamil Nadu.

Flood and cyclone are both major natural disasters with distinct characteristics and impacts. A flood is caused by heavy rainfall, cyclones, melting of snow, tsunamis, or dam bursts, resulting in a large amount of water overflowing into populated areas. The effects of floods include displacement of people from their homes, loss of life and property, and the spread of contagious diseases such as cholera and malaria due to contaminated water. A cyclone is a severe tropical storm characterized by heavy rainfall and strong winds that form over warm ocean waters. When a cyclone reaches land, it destroys buildings, kills people, and can be described as a disaster. Cyclones disrupt transportation networks, damage power infrastructure, and interrupt communication systems, causing widespread chaos and economic losses. Both disasters require comprehensive disaster management strategies including early warning systems, evacuation plans, and relief operations to minimize human suffering and property damage.

The six disaster management phases that have been used in the concept of disaster cycle are as follows;
Pre-Disaster phase:
Prevention and Mitigation:
The term prevention is often used to embrace the wide diversity of measures to protect persons and property.
Mitigation embraces all measures taken to reduce both the effects of the hazard itself and the vulnerable conditions to it in order to reduce the scale of a future disaster.
Therefore, mitigation may incorporate addressing issues such as land ownership, tenancy rights, wealth distribution, implementation of earthquake-resistant building codes, etc.
Preparedness:
The process includes various measures that enable governments, communities and individuals to respond rapidly to disaster situations to cope with them effectively.
Preparedness includes for example, the formulation of viable emergency plans, the development of warning systems, the maintenance of inventories, public awareness and education and the training of personnel.
Early Warning:
This is the process of monitoring the situation in communities or areas known to be vulnerable to slow onset hazards, and passing the knowledge of the pending hazard to people harmless way.
To be effective, warnings must be related to mass education and training of the population who know what actions they must take when warned.
The Disaster Impact:
This refers to the “real-time event of a hazard occurrence and affecting elements at risk.
The duration of the event will depend on the type of threat; ground shaking may only occur in a matter of seconds during an earthquake while flooding may take place over a longer sustained period.
During Disaster Phase:
Response: This refers to the first stage of response to any calamity, which includes examples such as setting up control rooms, putting the contingency plan in action, issue warning, action for evacuation, taking people to safer areas, rendering medical aid to the needy, etc., simultaneously rendering relief to the homeless, food, drinking water, clothing, etc. to the needy, restoration of communication, disbursement of assistance in cash or kind.
The Post- Disaster Phase:
Recovery: Recovery is used to describe the activities that encompass the three overlapping phases of emergency relief, rehabilitation, and reconstruction.
Rehabilitation: Rehabilitation includes the provision of temporary public utilities and housing as interim measures to assist long-term recovery.
Reconstruction: Reconstruction attempts to return communities with improved pre-disaster functioning. It includes the replacement of buildings; infrastructure and lifeline facilities so that long-term development prospects are enhanced rather than reproducing the same conditions, which made an area or population vulnerable in the first place.
Development: In an evolving economy, the development process is an ongoing activity. Long-term prevention/disaster reduction measures. For example like the construction of embankments against flooding, irrigation facilities as drought-proofing measures, increasing plant cover to reduce the occurrences of landslides, etc.

A flood is the sudden overflow of water in large amounts caused due to heavy rainfall, cyclones, melting of snow, tsunamis, or dam bursts. Floods occur when water bodies exceed their capacity and inundate surrounding areas, affecting both urban and rural communities. The effects of floods are severe and multifaceted, including loss of life and property as homes, crops, and infrastructure are destroyed. Floods cause displacement of people from their homes, forcing them to seek temporary shelter and creating humanitarian crises. Additionally, floods spread contagious diseases such as cholera and malaria because contaminated water mixes with drinking water sources and sanitation systems collapse. Mitigation measures for floods include both structural and non-structural approaches. Structural measures include flood walls and sea walls that act as barriers, flood gates that control water flow, levees that contain water within channels, and evacuation routes that provide safe passage for people. Non-structural measures reduce damage by removing people and property out of risk areas through various methods. These include elevated structures that are built above flood levels, property buyouts where governments purchase vulnerable properties, permanent relocation of communities to safer areas, zoning regulations that restrict development in flood-prone areas, subdivision controls, and building codes that ensure structures can withstand flooding.

General Survival Techniques:
During the earthquake be under the table, chair, kneel to the floor and protect yourself. Go near a sturdy wall, sit on the floor and hold the floor strongly and protect yourself. Use only torch lights,
During flood forecast, store up necessary things like first aid etc. Listen to the local Radio/TV for instructions. Cut off all the electrical supplies during flood and earthquake,
In case of fire accidents call fire service (No. 101)
If clothes are on fire, “Don’t Run; Stop, Drop and Roll,”
Stay alert. Trains can come from either direction at any time,
Never sit on the edge of the Station Platform,
Cross the tracks safely.

Earthquake:
A sudden movement (or) trembling of the earth’s crust is called an earthquake. The movement of the tectonic plates, mass wasting, landslides, surface fault, etc., causes earthquakes.
Effects:
Due to a strong earthquake, loss of lives, buildings, roads, bridges, and dams are damaged. Earthquakes cause floods, tsunamis, landslides, fires, breakdown of water supply, and electrical lines. It may change the course of a river too.
Mitigation steps:
Construct an Earthquake resistant building.
Seek shelter under stable tables.
Move to open areas.
Secure your belonging.
Put latches on cabinet doors and file cabinets.
Store hazardous materials in a sturdy place.
Keep fire extinguishers.

Understanding natural disasters is crucial for several important reasons that affect individual safety and community wellbeing. We should know about natural disasters to prevent loss of life by being aware of risks and taking appropriate precautions. Knowledge of disasters helps us protect our belongings and property by understanding which areas are vulnerable and how to safeguard valuable possessions. Learning about natural disasters creates awareness among youngsters, building a culture of disaster preparedness from an early age so future generations are better equipped to handle emergencies. Being informed allows us to be prepared with emergency phone numbers and contact information for rescue services, enabling quick response when disasters strike. We can stock essential supplies such as food, water, and medicine in advance, ensuring survival during periods when normal supply chains are disrupted. Special attention to disaster preparedness is necessary for children and elderly people who are more vulnerable and require additional support and care during emergencies. Overall, knowledge of natural disasters empowers individuals and communities to respond effectively, minimize casualties, and recover more quickly from disaster impacts.

Landslides occur in several regions of India due to geographical and climatic conditions. In the Western Ghats and Konkan hills region, states like Tamil Nadu, Kerala, and Maharashtra experience frequent landslides due to steep terrain and heavy monsoon rainfall. The North Eastern Himalayas, particularly in Darjeeling and Sikkim, are prone to landslides because of the high altitude, heavy precipitation, and unstable soil composition. The North West Himalayas, including Uttarakhand and Himachal Pradesh, also face significant landslide risks due to the mountainous terrain and geological instability. Additionally, Jammu and Kashmir in the northern region experience landslides triggered by heavy snowfall, rainfall, and seismic activity. These areas are vulnerable because of their topography, weather patterns, and the nature of the soil and rock formations present in these regions.

General survival techniques during disasters vary depending on the type of disaster. During an earthquake, it is crucial to take shelter immediately by getting under a sturdy table or desk and holding the floor strongly to protect yourself from falling debris and collapsing structures. Before floods occur, based on weather forecasts, people should store necessary items such as drinking water, food, first aid kits, and important documents in safe places. In case of fire accidents, one should immediately dial 101 to contact the fire service for professional help and evacuation assistance. Road accidents can be prevented by following road safety rules such as wearing seatbelts, obeying traffic signals, avoiding speeding, and not using mobile phones while driving. When traveling by air, it is important to read the safety briefing card available in the seat pocket carefully to understand emergency procedures and the location of emergency exits, which could be lifesaving in case of an aircraft emergency.