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The tidal range is the vertical difference between the high tide and the succeeding low tide. Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon and the Sun and the rotation of the Earth.
Neap tides occur during the first and last quarters of the moon's phases. The largest annual tidal range can be expected around the time of the equinox, if coincidental with a spring tide. Tidal data for coastal areas is published by the national hydrographic service of the country concerned.