Q) List and explain the different types of tides and theories of origin of tides.
STRUCTURE
Introduction – What are tides ( 15 words)
Body –
1) Explain the different types of tides (60 words)
2) Explain the theories of origin of tides (60 words)
Conclusion – Mention a short conclusion (15 words)
ANSWER :
The periodic short term rise and fall in the sea level is known as Tide.
DIFFERENT TYPES OF TIDES
Tides based on Frequency
Semi-diurnal tide
· Two high tides and two low tides each day
· Occur at regular intervals of 12 hours and 25 minutes
Diurnal tide
One high tide and one low tide during each day
Mixed tide
· Two unequal high and low tides lead to the formation of the mixed tidal cycle
· Widely observed in the Gulf of Mexico , Caribbean Sea, Southeastern Brazilian coast
Tides based on the Position of Earth, Sun, and the Moon
Spring Tides
· Tides formed when the sun, the moon, and the earth are in a straight line(a configuration known as a syzygy)
· In this position the height of the tide will be higher
Neap Tides
· When the Moon is at first quarter or third quarter, the Sun and Moon are separated by 90° when viewed from the Earth, and the solar tidal force partially cancels the Moon’s. (a configuration known as a Quadranture)
· At these points in the lunar cycle, the tide’s range is at its minimum; this is called the neap tide
THEORIES OF THE ORIGIN OF TIDES
Factors responsible for formation of tides -
Gravitational forces exerted by the Moon and the Sun
Rotation of Earth (Centrifugal force)
A tide is formed under the action of above forces
When the two forces are not in balance, it gives rise to the tide-generating force. The ‘tide-generating’ force is the difference between gravity and centrifugal force
Under the influence of these forces, the ocean waters are pulled towards the direction of forces leading to creation of tides
These points are explained in various theories like Issac Newton (1687), dynamical theory by Laplace (1755), progressive was theory by William Whewell (1833), canal theory by G.B. Airy (1842), stationary wave theory by R.A. Harris etc.
Thus , the connection between gravity & tides could be understood
