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What causes tides and waves?

Stormy waves in the open ocean Sea levels rise and fall twice a day. This pattern is known as the tides. When the wind blows across the surface of the sea, it turns the water over and over in circles. These are waves. The stronger the wind and the greater the distance over which it blows, the larger the waves.


 

The gravitational pull by the Sun and Moon on the Earth

Tides

Tides are caused by gravity: the attraction that a large object (in this case, the Moon) has over another object. As the Earth spins, the ocean waters on the side of the Earth closest to the Moon bulge outwards. This results in a high tide. The rest of the Earth has a low tide.
A rocky islet, one of the "flower-pot rocks", at low tide in the Bay of Fundy, Nova Scotia, Canada. The base of the rock is being...Read More >>A rocky islet, one of the "flower-pot rocks", at low tide in the Bay of Fundy, Nova Scotia, Canada. The base of the rock is being eroded away by the sea waters at high tide. The Bay of Fundy has the highest tidal range in the world. The average spring tide range is 14.5 m (48 ft). When the Sun and Moon line up, the Sun’s gravity increases the pull. This results in very high and low tides, called spring tides. When the Sun and Moon are at right angles, the tidal range, the difference between high and low tide, is at its lowest. These are neap tides.
The tidal range during a spring tide (1), where the high tides are higher and low tides lower than during a neap tide (2).
The Arnside bore, a tidal bore on the estuary of the River Kent in northwest England

Tidal bore

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 feet).

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