Natural resource of Class 9

All the places on Earth are not equally heated up by the sun. When a place becomes heated, the surrounding air also becomes warm. The warm air, being lighter, rises up. A low pressure area is created there. The cold air from the cooler and high pressure regions then moves in to take its place. This movement of air takes place due to uneven heating of different places on the Earth. Due to the unequal heating of places, convection currents are produced in the air. When air moves horizontally, it is called wind. Water vapours are formed due to the heating of water bodies by solar radiations as well as the activities of living organisms. The phenomena like movement of air (whether the movement of air will be in the form of a gentle breeze, a strong wind or a terrible storm) and the rain are the result of changes that take place in our atmosphere due to the uneven heating of air and the formation of water vapours. However, couples of other factors like the rotation of Earth, the presence of mountain ranges in the path of the winds also influence.

Air in called wind. Speed of wind can be determined by:

  • Heating of air                                         
  • Formation of water vapour

Factors controlling movement of air

  • Rotation of earth.
  • In the path of wind, mountain ranges may come across. The general pattern of winds over earth is known as general circulation and specific winds are named for the direction from which they originate (e.g. wind blowing from west to east is westerly). Wind speeds are often classified according to Beaufort scale.

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