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Tides

A rocky islet, one of the "flower-pot rocks", at low tide in the Bay of Fundy, between Nova Scotia and New Brunswick, Canada. The...Read More >>A rocky islet, one of the "flower-pot rocks", at low tide in the Bay of Fundy, between Nova Scotia and New Brunswick, Canada. The base of the rock is being eroded away by the sea waters at high tide. Sea levels rise and fall twice a day. This pattern is known as the tides. The tidal range is the difference between high and low tide. Seas that are almost surrounded by land, such as the Mediterranean Sea, have a very small tidal range. Tides are caused by the the combined gravitational pull of the Moon and the Sun and the rotation of the Earth. Most coastlines have two low tides and two high tides each day, while others have only one of each or as many as four.



The gravitational pull by the Sun and Moon on the Earth

How are tides caused?

Tides are caused by the pull of gravity by the Sun and Moon on the Earth. As the Earth spins, the ocean waters on the side of the Earth closest to the Moon (and the opposite side) bulge outwards, causing a high tide. At the same time, the rest of the Earth has a low tide.

The highest tidal range is found in the Bay of Fundy, between Nova Scotia and New Brunswick, Canada. The greatest average spring tide range is 14.5 m (48 ft).

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