Tidal cycles

A tidal cycle is one high tide plus a successive low tide. Due to land masses, the movement of water moving around on the Earths' surface due to tides is impeded. The resulting tidal cycle or pattern therefore depends on geographic location. There are three basic types of tidal cycles (Figure 2.15) that are globally distributed.

Semi-diurnal Tides

This is the most common tidal pattern, featuring two highs and two lows each day, with minimal variation in the height of successive high or low waters and is very common along much of the east coast of North America (Figure 2.17).

Diurnal Tides

Only a single high and a single low during each tidal day; successive high and low waters do not vary by a great deal. Such tides occur, for example, in the Gulf of Mexico, Java Sea and in the Tonkin Gulf (Figure 2.17).

Mixed Tides

Characterized by wide variation in heights of successive high and low waters, and by longer tide cycles than those of the semidiurnal cycle. Such tides occur, for example, along the U.S. Pacific coast and many Pacific islands (Figure 2.17).

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Figure 2.17: Plots showing the variation in tidal curves for diurnal, semidiurnal, and mixed semidiurnal tidal cycles during a tidal period and tidal day.
Credit: NOAA: Tides and Currents

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Figure 2.18: Global map showing the distribution of semidiurnal, diurnal, and mixed tides.
Credit: Wikipedia: Tide (public domain)