NCERT 7th Class (CBSE) Science: Winds, Storms and Cyclones

Question: Explain how a cyclone is formed?

Answer: Cyclones are caused by warm moisture-bearing air over the oceans. Cyclones are usually formed in low-pressure regions where air gets easily heated by sun. Warm air rises up carrying the water vapour. As this moisture-laden air rises and reaches the cooler regions of the atmosphere, the water vapour gets condensed into small water droplets, which from high thunderclouds. When water vapour condenses into droplets, a lot of heat is released into the air, which heats this air further. Hot air further rises and creates a low-pressure region. When the hot air rises up, the cold air rushes into the low-pressure region created by the rising hot air. The wind thus flows in spiral manner due to the effect of rotation of the Earth about its own axis. This process continues and produces a very law-pressure region, causing winds to move still taster. This rotating wind forms a huge spiral of diameter ranging from a few kilometres to a few hundred kilometres.

Question: Explain the disastrous effects of a cyclone.

Answer:

1. Huge  waves, produced by the strong winds, accompanied by rains hit the shores and cause heavy floods in the nearby areas.
2. The strong winds can damage buildings, uproot trees and disrupt electrical and communication lines, etc.
3. In the month of October 2013, a severe tropical cyclone named Phailin made landfall in the north-east region of India. It was the second strongest tropical cyclone ever to have landfall in India.

Question: Write the precautions to be taken during thunderstorms.

Answer: A thunderstorm can cause a lot of damage to living beings and property. Some precautions that need to be taken during thunderstorms are as follows:

1. If you are inside your house or any building, stay inside till the thunderstorm stops.
2. If you are outside, do not hold an umbrella and walk during thunderstorm.
3. Do not take shelter under a tree as it creates an easy path for the discharge of electricity during lighting.
4. If you are sitting inside a vehicle, do not come out of the vehicle.