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 tides 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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