Tides,whirlpools+and+oceans

Hi this is Diwei here. Do you know what causes tides. They are caused by the gravity of the moon. As the Earth spins round, the water in the oceans is 'pulled' towards the Moon slightly,making a bulge.There is a corresponding bulge on the other side of the Earth. Wherever the bulges are positioned it is high tide. In between the water is shallower and so it is low tide. High tides occur every 25 hours, because at the same time that the earth is spinning on its axis, the Moon is travelling around the Earth once every 27 1/2 days.This means that high tide is about one hour later every day.

For centuries sailors have been in terror of being sucked into a whirlpool that would swallow them and thier ships. Whirlpools happen when opposing currents meet,causing the water to spin round very rapidly. Huge whirlpools in the sea are usually caused by powerful tides.The most famous is thbe Maelstrom ,which appears between two islands off the coast of Norway. At times this whirlpool is strong enough to destroy small ships. Another dangerous whirlpool is Charybdis in the Medditerranean, which was a hazard to the ancient Greek and Roman sailors.The ancient greeks believed that a monster caused this whirlpool.