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How are cyclones formed?

Class 8 ScienceNCERT chapter: Pressure, Winds, Storms, and Cyclonesइसे हिंदी में पढ़ें

Exam-ready answer

A cyclone forms over a warm ocean. Warm, moist air rises, creating a region of low pressure. As the rising water vapour condenses into clouds, it releases heat, which warms the air further and makes it rise faster. Surrounding air rushes in and starts spinning. This repeating cycle builds a very low-pressure centre with high-speed winds revolving around it.

Explanation

Cyclones begin over warm ocean water near the equator. The Sun heats the sea surface, and the air above it becomes warm and full of water vapour. This warm, moist air rises, leaving a region of low pressure near the sea surface. Air from surrounding areas, at higher pressure, moves in towards this low-pressure region.

As the moist air rises and cools, its water vapour condenses into droplets, forming tall clouds and heavy rain. Condensation releases heat into the air. This heat warms the air even more, so it rises faster and the pressure at the centre drops further. More air rushes in, and because the Earth is rotating, the inflowing air does not move straight but spirals around the centre.

This cycle repeats again and again, so the system grows stronger. The result is a very low-pressure centre with very fast winds revolving around it, along with heavy rain and storm surges along the coast. The calm, nearly cloudless centre is called the eye. In India, cyclones usually form over the Bay of Bengal and the Arabian Sea, and weather departments issue warnings so people can move to safety.

Points to remember

  1. A cyclone is a large storm with a very low-pressure centre and high-speed winds spiralling around it.
  2. It forms over warm seas, where warm, moist air rises and creates low pressure.
  3. Condensation of water vapour releases heat, which makes the air rise faster and lowers the pressure further.
  4. The Earth's rotation makes the inflowing winds spin around the centre.
  5. The calm centre of a cyclone is called the eye; strong winds, heavy rain and storm surges cause the damage.

Exam tip

Write the formation as a cycle: warm sea → moist air rises → low pressure → condensation releases heat → air rises faster → more air rushes in and spins. Draw a simple labelled diagram showing the eye and the spiralling winds.

Questions students also ask

What is the eye of a cyclone?
The eye is the calm central region of a cyclone. It has light winds, very low pressure and few clouds. It is surrounded by a ring of tall clouds where the strongest winds and heaviest rain occur, so the danger returns after the eye passes.
Why do cyclones weaken after reaching land?
A cyclone gets its energy from warm, moist air over the sea. Over land, this supply of moisture is cut off, so less water vapour condenses and less heat is released. Friction with the land also slows the winds, so the cyclone gradually weakens.
What should people do when a cyclone warning is issued?
People should follow official weather warnings, move to safer shelters away from the coast if told to, keep drinking water and essential items ready, and stay indoors during the storm. Fishermen should not go out to sea.

Chapter labels help you find the topic in your textbook. Check your own edition: chapter names and order can change. These are Know.it explanations, not official NCERT solutions.