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This sequence of images shows the effects of the tide on the coastline.

  • Location : Bretagne - Côte d'Armor (France)
  • Tidal coefficient : 87 (on a scale with a maximum of 120)
  • Low tide : 3:02 - 15:18
  • High tide : 9:04 - 21:18
  • Tidal range : 9 m

A tide is the variation of the height of the water level of a sea or an ocean. The combined gravitational force of the Moon and Sun is the main cause. The amplitude of the tide can be measured with the "tidal range" which is the difference in height between the high tide and the low tide.

The amplitude of the phenomenon is only 1 m in the open ocean and it does not exceed 20 cm in a closed sea like the Mediterranean Sea, but it reaches 10 m and more in some places of the Earth. Indeed the shape of the coastline can amplify this phenomenon. This is the case in the Bay of Fundy (Canada), the Bay of Mont Saint Michel Bay (France) and Puerto Gallegos (Argentina), which show tidal ranges of 15 m and more during high tides.

The tidal phenomenon animation illustrates the influence of the Sun and the Moon on the tides phenomenon.

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