Class 7 NCERT TIdes | Definition | What cause tides

                    TIDES

Definition - Periodic rise and fall of ocean water at regular interval, twice a day is called Tide. 

➡️  Tides are experienced in the ocean and seas. 

➡️ When the level of sea water  rises, it is high tide and when the level falls it is low tide. 

Causes - Tides are caused by the gravitational pull  of the moon and the sun on the earth. 

ii) The attraction of the moon is stronger because the moon is much closer to earth than the sun is. 

         The Opposite side of Gravitational force is known as centrifugal force. 

      

iii)  The height of tides depends upon the relative position of the moon and the sun with respect to the earth. 

iv) During full moon and new moon days, the sun, the moon and the earth are in the same line resulting in extra high tides. These are called Spring tides. 

  

When the moon is in the first and third quarter, the sun and moon are at right angles and the water gets drawn in  diagonally opposite directions. This results in low tides which are called neap tides. 

How tides are useful                                                   •     The rise in water level during high tides allows big ships   to enter or leave harbours safely. The port of Kandla in Gujarat and Diamond Harbour in West Bengal depend on such tides. 

•      During high tide, water rushes up the mouth of rivers. This helps large ships to move in and out of river ports like Kolkata, London, Hamburg, Rotterdam and Network. 

•   Tides helps in Fishing . During high tides more fish come near shore helping the fishermen to get plentiful catch

•  Tides also help to generate electricity. As the sea water gushes in during a high tide, it's energy can be tapped and used to generate electricity. India is yet to start utilising tidal energy. 

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