Formation of Tides

  • More than 70% of the Earth’s surface is covered with oceans. Oceans are dynamic in nature. They move horizontally and vertically. The vertical movement of the oceans is known as tides.
  • The periodical rise and fall of the oceanic water is called tides. It is due to the attraction of Sun and Moon, once or twice in a day.
  • Average difference in the water level between the high tide and the low tide at any place is known as tidal range or amplitude.
  • Flow is a time between low tide and high tide. Ebb is a time between high tide and low tide.
  • The forces that cause tides are gravitational pull and centrifugal force.
  • Tidal current is the movement of water, inward and outward in a gulf, connected with sea through a narrow channel.
  • Tides occur at the interval of about 12 hours 26 minutes. It is because the Earth and the Moon are rotating in the same direction.
  • Tides may be grouped into various types on the basis of frequency, position and distance.
  • On the basis of the frequency, tides can be classified as semi-diurnal tide, diurnal tide, and mixed tide.
  • Semi-diurnal tide experiences two high and two low tides of approximately equal size, every lunar day.
  • Diurnal tide experiences one high and one low tide every lunar day.
  • Mixed tides experience two high and two low tides of different size in every lunar day.
  • On the basis of height, tides can be classified as spring tide and neap tide.
  • Spring tides occur, when the Sun, the Moon and the Earth are in a straight line.
  • Neap tides occur when the Sun, the Moon and the Earth form a right angle.
  • On the basis of distance of Earth from the Sun, tides can be classified as perihelion and aphelion.
  • Perihelion tides are formed when Earth is closest to the Sun. Aphelion tides are formed when Earth is farthest from the Sun.
  • On the basis of distance of Earth from the Moon, tides can be classified as Perigean and Apogean tides.
  • Perigean tides are formed when the Moon is closest to Earth, forming higher range of tides.
  • Apogean tides are formed when the Moon is farthest from Earth.
  • Tides are useful in navigation, generating electricity and controlling the activities of fishermen.

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