General Science Notes Chapter 9 Disaster Management Class 8 Maharashtra Board

Notes For All Chapters – General Science Class 8

1. Introduction

• Disaster is a sudden event that causes harm to life, property, and the environment.
• Disasters can be natural (earthquakes, floods, landslides) or man-made (fires, gas leaks).
• Disaster management involves preparing, responding, and recovering from disasters.

2. Earthquake

What is an Earthquake?

• Earthquake is the sudden shaking of the Earth’s surface due to movements inside the Earth.
• It creates seismic waves that cause tremors, cracks, and destruction.

Causes of Earthquake:

1. Volcanic Eruptions – Lava pressure shakes the ground.
2. Big Dams – Heavy water storage adds stress to the land.
3. Mining – Digging deep weakens the ground.
4. Underground Atomic Tests – Nuclear explosions disturb Earth’s crust.
5. Water in Cracks – Water turns into steam and expands, causing cracks.

Effects of Earthquake:

1. Loss of Lives – People, animals, and birds may die.
2. Destruction of Property – Houses, roads, bridges, and railways collapse.
3. Environmental Damage – Trees and biodiversity are lost.
4. River Flow Changes – Earthquakes can block or redirect rivers.
5. Fires and Explosions – Gas leaks and broken wires cause fires.
6. Tsunamis – Underwater earthquakes create giant sea waves.

Earthquake Measurement

• Seismograph (Seismometer) – A machine that records earthquake intensity.
• Richter Scale – A scale that measures earthquake strength.

3. Precautions During an Earthquake

Do’s:

1. If inside, take cover under a table or bed.
2. If outside, move to an open area away from buildings and trees.
3. Switch off gas and electricity to prevent fires.
4. Use a torch instead of candles after an earthquake.

Don’ts:

1. Do not use elevators; use stairs instead.
2. Do not stand near glass windows or walls.
3. Avoid waiting near buildings, trees, or electric poles.

4. Earthquake-Proof Buildings

• Buildings are constructed using earthquake-resistant designs to prevent damage.
• Important building codes:
  • IS 456 – For safe construction.
  • IS 1893 – Earthquake-resistant design.
  • IS 13920 – Strengthening of concrete structures.
• Shock-absorbing foundations and flexible materials are used.

5. Fire – A Natural or Man-made Disaster

Types of Fire:

1. Class A (Solid Materials) – Wood, paper, cloth (Use water to extinguish).
2. Class B (Liquid Fuels) – Petrol, oil, paint (Use fire extinguishers, not water).
3. Class C (Gas Fuels) – LPG, acetylene (Cut off gas supply, use foam).
4. Class D (Chemical Fires) – Sodium, potassium (Use dry sand, not water).
5. Class E (Electrical Fires) – Short circuits (Use carbon dioxide extinguishers).

Methods to Stop Fire:

1. Cool Down (Water Spray) – Lowers temperature to stop fire.
2. Suppress Fire (Foam or Sand) – Cuts off oxygen supply.
3. Remove Flammable Materials – Keeps fire from spreading.

Fire Safety Precautions:

1. Turn off gas and electrical appliances when not in use.
2. Keep fire extinguishers at home and workplaces.
3. Call the fire brigade immediately in case of fire.

6. Landslides – Causes and Effects

What is a Landslide?

• A landslide is when rocks, soil, and debris slide down a slope due to rain or earthquakes.

Causes of Landslides:

1. Heavy Rainfall – Water loosens soil, making it slide.
2. Deforestation – Cutting trees weakens the soil.
3. Construction on Hills – Roads and buildings weaken slopes.
4. Earthquakes – Tremors shake the ground, causing landslides.

Effects of Landslides:

1. Rivers Overflow – Landslides block rivers, causing floods.
2. Loss of Lives and Property – Houses and farms are destroyed.
3. Traffic Disruptions – Roads and railways get blocked.
4. Destruction of Plants and Animals – Trees and wildlife are lost.

Preventive Measures for Landslides:

1. Plant More Trees – Roots hold the soil together.
2. Avoid Unnecessary Construction on hills.
3. Create Retaining Walls – Stops soil from sliding down.

7. Disaster Management Plan

Government Agencies for Disaster Management:

1. NDRF (National Disaster Response Force) – Provides rescue and relief.
2. IMD (Indian Meteorological Department) – Issues weather and earthquake warnings.
3. Red Cross Society – Helps with medical aid and relief work.
4. Local Fire Brigade and Police – Provide emergency help during disasters.

Disaster Management in Schools:

• Schools should have a disaster plan including:
  1. Emergency exits and fire extinguishers.
  2. First aid kits and contact numbers of hospitals.
  3. Mock drills for fire and earthquake safety.
  4. Instructions on how to evacuate safely.