The rise and fall of the tides is due to the gravitational pull of the moon on the earth and to a lesser degree of the sun. The pull causes the ocean’s water to pile up in a bulge. Depending on the alignment of sun, earth and moon, the amplitude of the tides vary. There are two high tides and two low tides every day, each lasting about six hours. The highest and lowest tides occur twice a month at the times of new moon and full moon day.
The highest tide called spring tide occurs when the sun and moon are on a straight line with the earth. Tidal ranges are greatest because of the combined gravitational pulls of moon and sun.
The lowest tide called neap tide occurs when the sun and moon are at right angles to the earth. Now the gravitational pull counteracts each other.
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