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Chapter – 8, Winds Stroms and Cyclones, •, , Air: The invisible gaseous substance surrounding the earth, a mixture mainly of oxygen and, nitrogen., , •, , Properties of Air:, (i), , Air around us exerts pressure., , (ii), , Air expands on heating and contracts on cooling., , (iii), , Warm air rises up, whereas comparatively cooler air tends to sink towards the earth’s, surface., , (iv), , As warm air rises, air pressure at that place is reduced and the cooler air moves to, that place., , •, , Wind: The moving air is called wind. Air moves from region of high air pressure to region of, low air pressure., , •, , Types of Wind:, (i), , Wind Currents: Wind currents are generated due to uneven heating on earth., Uneven heating on the earth is the main cause of wind movements., , (ii), , Thunderstorms: Storm with thunder and lighting along with rain., , •, , Winds carrying water vapour bring rain., , •, , High-speed winds and air pressure difference can cause cyclones., , •, , It has become easier to monitor cyclones with the help of advance technology like satellites, and radars., , •, , Self-help is the best help. Therefore it is better to plan in advance and be ready with defence, against any approaching cyclone., , •, , The following flow chart will help you to understand the phenomena that lead to the, formation of clouds and falling of rain and creation of storms and cyclones.