Chapter 15: Winds, Storms, and Cyclones

1. Natural Disasters

A natural disaster is an event caused by natural forces that results in damage to life and property. Some common natural disasters are:

  • Earthquakes – Sudden shaking of the Earth’s surface
  • Floods – Overflow of water due to heavy rain
  • Droughts – Long period of no rain
  • Cyclones – Strong circular wind storms
  • Tornadoes – Violently rotating columns of air

Table: Common Natural Disasters and Their Causes

DisasterCause
EarthquakeMovement of tectonic plates
FloodsHeavy rainfall, dam failure
DroughtsLack of rainfall for a long time
CyclonesFormation of low-pressure areas over warm seas
TornadoesStrong rotating winds formed over land

2. Air Pressure

What is air pressure?

  • Air has weight, and it pushes in all directions.
  • The force exerted by air on a surface is called air pressure.

Key Points About Air Pressure

✔ Air pressure decreases as we go higher from the Earth’s surface.
✔ The movement of air from high-pressure areas to low-pressure areas causes winds.

Example

  • When we drink juice with a straw, we reduce air pressure inside the straw, and the juice moves up due to the surrounding high pressure.

3. High-Speed Wind Causes Reduced Pressure

  • Fast-moving air creates low pressure.
  • This principle explains why cyclones and storms form.

Example

  • When a strong wind blows over the roof of a house, the pressure above the roof decreases, and the higher pressure inside the house can push the roof upward, sometimes blowing it away.

Experiment

  • Hold a paper strip close to your lips and blow over it.
  • The paper lifts up instead of going down.
  • This happens because fast-moving air above the paper creates lower pressure.

4. Air Expands on Heating

  • When air is heated, it expands and becomes lighter.
  • This causes warm air to rise and cool air to sink.

Example

  • Hot air balloons rise because the air inside them is heated and becomes lighter than the surrounding air.

Diagram: Expansion of Air on Heating

📌 (Insert a diagram showing warm air rising and cold air sinking.)

5. Wind Currents

  • Wind currents are created due to the uneven heating of the Earth.
  • Main causes of wind currents:
    1. Uneven heating of land and water: Land heats up faster than water, causing air movement.
    2. Uneven heating between the equator and poles: Warm air at the equator rises, and cold air from the poles moves in.

Diagram: Wind Currents on Earth

📌 (Insert a world map showing wind movement due to temperature differences.)

6. Thunderstorms, Cyclones, and Tornadoes

Thunderstorms

  • A thunderstorm is a violent weather condition with lightning, thunder, heavy rain, and strong winds.
  • It is caused by the rapid upward movement of warm, moist air.

Cyclones

  • A cyclone is a large, swirling storm that forms over warm ocean waters.
  • Cyclones have low-pressure centers and strong winds.

Formation of a Cyclone:

  1. Warm ocean water heats the air above it.
  2. Air rises, creating low pressure.
  3. More air rushes in, forming circular wind patterns.
  4. Clouds form, and strong winds start rotating.

📌 (Insert a labeled diagram of a cyclone structure.)

Tornadoes

  • A tornado is a narrow, fast-spinning column of air.
  • It has extremely high wind speeds.
  • Tornadoes are smaller but more destructive than cyclones.

Table: Comparison of Thunderstorms, Cyclones, and Tornadoes

FeatureThunderstormCycloneTornado
FormationUpward movement of warm, moist airWarm ocean waters create low-pressure zonesStrong rotating winds over land
SizeSmallVery largeSmall but intense
Wind SpeedModerate120-250 km/hOver 300 km/h
DamageLightning, heavy rainFloods, uprooted treesDestroys buildings, vehicles

7. Cyclone Forecasting and Warnings

  • Scientists monitor wind patterns to predict cyclones.
  • Cyclone warnings are issued before the cyclone reaches land.

Measures to Stay Safe During a Cyclone

✔ Before a Cyclone:

  1. Stay updated with weather forecasts.
  2. Keep emergency supplies ready.
  3. Move to safe shelters if advised.

✔ During a Cyclone:

  1. Stay indoors and away from windows.
  2. Store drinking water and food.
  3. Listen to emergency broadcasts.

✔ After a Cyclone:

  1. Stay away from broken power lines.
  2. Help injured people if possible.
  3. Follow government safety instructions.

📌 (Insert an image of a cyclone warning system or satellite monitoring.)

Key Takeaways

📌 Air pressure plays an important role in the movement of wind.
📌 Fast-moving air creates low pressure, leading to strong winds.
📌 Warm air rises, and cool air sinks, causing wind currents.
📌 Thunderstorms, cyclones, and tornadoes are different types of violent weather conditions.
📌 Scientists use advanced technology to predict cyclones and issue warnings.

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