TIDE

The rise and fall of the sea is called the tide. Tides are caused by the earth’s spin and by gravitational force, the mysterious force that makes things tug at each other. High tides take place on the part of the earth facing the moon as it circles round the earth. Each part of the sea has two high tides each day- one when it is beneath the moon and one when the moon is on the opposite side of the earth. And of course each day has two low tides also. Usually a estuary is flooded with high tide.