Tides and its significance

1. Guided by:
Dr. B.Suresh
Reader, DOS in Earth
Sciences,
University of Mysore
Submitted by:
Zumchilo T. Ezung
1st
Semester
M.Sc ,Geology
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2. CONTENTS
1. Introduction
2. Forces producing tides
3. Types of tides
4. Origin of tides
5. Tide table prediction
6. Significance of tides
7. Misapplications
8. Conclusion
9. Reference
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3. Tides refer to the regular vertical rise and fall of
water level in the world’s ocean resulting from gravitational
attractions of the sun and the moon on the earth’s surface.
Tides are the longest waves known. And like any other
waves they have both crest and trough. Movement between
these crest s and troughs brings about the tidal phenomena.
Tides are universal and everyday phenomena. Generally
two high tides and two low tides are observed daily
corresponding to the time between successive phases of
moon over any point on earth.
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4. FORCES PRODUCING TIDES
Gravitational Force: This is the force of attraction between between
masses. This force is directly proportional to the masses being
considered and inversely proportional to the square of the distance
between them.
F= G*M1M2/r²
Centrifugal force: An apparent “centre-fleeing force” felt by objects
experiencing uniform circular motion. Result of inertial resistance to
centripetal acceleration. This force is equally felt on all points of the
earth ,directed away from the moon along a line that parallels a
hypothetical line joining the centre of the earth and the moon.
Coriolis Force: An apparent force caused by the rotation of the earth, 4

5. TYPES OF TIDES
Daily tides
Diurnal tides: The regular pattern of one high
tide and one low tide per day. The tidal period
is 24 hrs. 50 min.
Semi diurnal tides: Two high tides and two low
tides of equal amplitude. The tidal period is 12
hrs. 25 min.
Mixed tides: A semi diurnal tide in which the
high tides reach different levels and the low
water drops to different levels.
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6. CHARACTERISTICS
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7. Monthly cycles of tides
Spring tides and neap tides
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(QUATRATURE)
(SYZYGY)

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CHARACTERISTICS OF
SPRING AND NEAP TIDES
PICTORAL ILLUSTRATION
ON TIDAL RANGES
EXPERIENCED DURING
SPRING AND NEAP TIDES

9. AT HIGH TIDES AT LOW TIDES
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10. ORIGIN OF TIDES
 Origin of tides is explained by two theories.
 The Equilibrium Tidal Theory.
 The Dynamic Tidal Analysis.
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11. THE EQUILIBRIUM TIDAL THEORY
o This theory was proposed and explained by Newton.
o This theory is based on the assumption that the earth is covered by a uniform
layer of water having uniform depth and containing no continents.
o Modification of the theory.
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12. DYNAMIC THEORY OF TIDES
o The predicted equilibrium tides do not accurately correspond to observed
tides.(c²=gd)
o Tidal waves are refracted by change in water depths and defracted as it
passes through gaps between continents.
o Tidal range increases as the ocean become narrow.
o The rotation of the earth further modifies the scheme of oscillations. The
“coriolis force” gets the tidal waves deflected from their original path. The
gyratory motion produced makes the wave to rotate over a central point
known as amphidromic point. The tide crests radiate out from these
points and the tidal range increases away from the points
o The theory considers the configuration of ocean basins, frictional forces,
coriolis forces, convergence and resonance and many other variables.
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13. AMPHIDROMIC TIDAL SYSTEM OF THE OCEAN
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14. SIGNIFICANCE OF TIDES
o Tides are responsible for moving large amount of sediments perpendicular to
the coast.
o Tidal range governs the width of the littoral zone.
o The periodic rise and fall of tides varies the distribution of wave energy along
the beach profile.
o Tides influence the distribution and morphology of tidal flats, coastal deltas,
barrier islands, spits etc.
o Tides influence salt and fresh water mixing in estuaries.
o Tides may play an important role in the mixing of ocean water.
o In the world of commerce tides are important for fishing and navigation.
o The tidal force can be used as a source for generating electricity. For example,
France and Japan have power stations which convert tidal energy into
electricity.
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15. La Rance tidal power plant at St. Malo, France
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16. Cont….o The receding tides carry away most of the rubbish of the coastal towns thrown
on the sea coast.
o Tidal movement helps in studying intertidal ecology.
o Sea water keeps on moving to tides and does not freeze even in higher
latitudes. Most of the British ports remain ice free due to tides. 16

17. MISAPPLICATION
• Tsunamis caused by earthquakes are sometimes called tidal waves but they are not.
Their name is simply given by their resemblance to the tide.
• Other phenomena unrelated to tide but using the word tide are rip tide, storm tide,
hurricane tide and red tide.
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18. CONCLUSION
• The ocean surface rises and fall each day because of tides.
• Most places have two high tides and two low tides each day.
• Tides happen because of gravitational pull of the sun and the moon on ocean
water. The type of tide depends upon the position on the globe, water depth,
contour and shape of the ocean basin.
• The moon has greater impact on tides than the sun because it is much closer.
• The tidal range changes throughout the year as the location of the sun and
moon in relation to earth changes.
• The tidal range can be as little as few centimeters to as much as several meters
depending on the shape of the ocean floor.
• Tides are generally determined by using astronomical data as well as climatic
variations.
• Tides are powerful forces and their main application lies in the generation of
electricity.
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19. REFERENCE
1999, K. Siddhartha, Oceanography A brief
introduction. Published by: Kisalaya publications Pvt.
Ltd.( Page250 to 262.)
Dr. Shanti Swaroop, Physical Geography, published
by ©Harsha Rastogi propreitor, King’s books.
(page406 to 409).
 http//www.Wikipedia.com/Ocean tides.
en.wikipedia.org/wiki/tide
en.wikipedia.org/wiki/earth tide
en.wikipedia.org/wiki/tidal power
http//www. Google.com/Tides and significance.
www.google.co.in/images.tides 19

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