Page 129 - Ripples SCIENCE 7 - TEJPUR Edition 2024 Answer Key

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14 Winds, Storms and Cyclones

Chapter in a Nutshell

v The moving air is called wind.
v Sometimes, when winds blow at high speeds, they give rise to storms. These storms may

sometimes cause natural calamities like cyclones, thunderstorms and tornadoes.
v The Earth is surrounded by a blanket of air known as the atmosphere.

v The air has weight and air exerts pressure on everything on the Earth. This air pressure is
called atmospheric pressure.

v Downward or upward movement of air caused due to the differences in air pressure creates

cloudy sky and brings rain.
v The changes in air pressure give important clues for weather forecasting.

v Wind blows from high pressure region to low pressure region.
v The speed of the wind depends upon the pressure difference between the two regions. If

the pressure difference increases, the wind speed also increases.
v Air expands on heating and it becomes lighter. This lighter air always tends to rise up and

the cooler air, being heavier, moves down.

v The movement of air depends on the difference in air pressure between two regions. The
difference in air pressure is created by uneven heating or unequal heating on the Earth’s

surface.
v During the day, land heats up faster than water and so does air above the land. This warm

air over the land expands and rises up creating a low pressure area. The cold air from the
sea moves towards the land to fill this low pressure area thereby generating sea breeze.

v However, during the night, the land cools faster than the sea and hence the air above the

sea gets warmer than the air above land. The air above the sea, therefore, expands and rises
and the cool air from the land rushes towards the sea to fill in the space thereby resulting

in land breeze.
v In the summer season, the land near the equator gets warmer and its temperature generally

remains higher than that of the ocean waters. The air above the land rises up and the cool
air from the oceans moves towards the land. Thus, winds blow from the oceans to the land.

These winds are called monsoon winds.
v A thunderstorm is characterized by the presence of lightning and thunder. It is also known

as lightning storm.

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