Ocean Tides | Types Of Tides | Difference Between High and Low Tides - Dear India

Ocean Tides | Types Of Tides | Difference Between High and Low Tides


Ocean Tides | Types Of Tides | Difference Between High and Low Tides

What Is Tide?

The rise and fall of  seawater due to gravitational forces (centripetal) of the sun and the moon are called tides. The sea waves generated by tides are called tidal waves. The rise of seawater and its movement towards the coast is called tide and the resultant high water level is known as high tidewater. The fall of seawater and its movement towards the sea is called ebb and the resultant low water level is known as low tidewater.



Origin of Tide

The tides in the ocean primarily occurs due to gravitational forces of the sun and the moon. It may be pointed out that the earth rotates from west to east and revolves around the sun following elliptical orbit. Similarly, the moon rotates from west to east and revolves around the earth along with an elliptical orbit so that the distance between the moon and the earth changes during different times in every month. Consequently, the water of the earth’s surface facing the moon is attracted and pulled and high tide occurs.
               When the sun, the earth, and the moon are in the same line (at the time of full or new moon) their gravitational forces work together and high tides are formed. On the other hand, when the sun and the moon are at the position of a right angle with reference to earth, the gravitational forces of the sun and the moon work against each other and hence low tides are formed. This situation occurs during the 8th day of each fortnight of a month.

Types Of tides

 Spring  Tide 

 Very high tide is caused when the sun, the moon, and the earth are almost in the same line. Such high tides are called spring tides. The Position of the sun, the moon, and the earth in a straight line is called Syzygy.
 When the sun, the earth and the moon is in the position of right angle, this position is called quadrature.

 Neap Tide

 The sun, the earth and the moon come in the position of  quadrature (i.e forming right angle)  on the seventh or eighth day of every fortnight of a month and thus the tide producing forces of the sun and the moon works in the opposite direction, as a result low tide is formed. Such tide, which is lower in height than the normal tide is called neap tide. The height of neap tide is generally 20 percent lower than the normal tide.

Tropical and equatorial tides 

 Like the sun there is also the northward and southward position of the moon in relation to the equator of the earth. If the sun completes its northward and southward position in one year i.e., in roughly 365 days, the moon completes it in 27.5 days or say in one synodic month. When there is maximum declination of the moon to the north of equator, the moon’s rays fall vertically on the tide centres (near the Tropic of Cancer) and hence spring tides are caused. Such tropical tides move westward along the Tropic of Cancer.
Spring tides are also caused along the Tropic of Capricorn which is opposite to the Tropic of Cancer. Thus, successive high and low water occurring along the tropics of Cancer and Cap­ricorn are of unequal heights. Such tides and ebbs are of higher and lower heights than the normal tides and ebbs respectively. Such tides recur twice every month when the moon’s rays fall vertically on the tropics of Cancer (during the northward position of the moon) and Capricorn (during southward position of the moon).
Thus, the tides occurring along the tropics of Cancer and Capricorn are called tropical tides. There is no diurnal inequality of tides in terms of heights of two neap tides and two spring tides because the moon is vertical on the equator every month. Such tides are called equatorial tides.
 Apogean and Perigean Tides

The nearest position of the moon with the earth is called perigee when the distance between them is 3,56,000 km. The tidal force of the moon is most powerful during this position and hence high tides are caused. Such tides, called as perigean tides, are 15 to 20 per cent higher than the normal tides. On the other hand, the tidal force of the moon is minimum during the position of apogee when the moon is at the farthest distance (4,07,000 km) from the earth and hence low tides are caused.
Such low tides, called as apogean tides, are 20 per cent lower than the normal tides. When the spring tide and perigean high tide occur at the same time, the resultant tide becomes abnormal. Similarly, when neap tide and apogean tide occur at the same time, the water level becomes significantly low.
Daily and Semi-diurnal Tides

The tides re­curring at the interval of 24 hours, 52 minutes daily are called diurnal or daily tides while the tides recurring at the interval of 12 hours 26 minutes are called semi­diurnal tides.
Equinoctial Spring Tides:
The tides recur­ring at an interval of 6 months due to the revolution of the earth around the sun and sun’s varying declinations are called equinoctial tides.

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Ocean Tides | Types Of Tides | Difference Between High and Low Tides Ocean Tides | Types Of Tides | Difference Between High and Low Tides Reviewed by Pawan Prakassh on August 21, 2019 Rating: 5

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