A place of Extreme: Tides in the upper gulf of california

A Place of Extreme:
Tides in the Upper Gulf of California

Anyone who has spent a day on the beach at Puerto Peñasco during a new or full moon, can appreciate the remarkable tides that rise and fall twice daily on the shores. The upper Gulf of California (from Puerto Peñasco and San Felipe to the Colorado River Delta) has one of world’s most extreme tidal ranges, with a sea level change of almost 9 meters( 27 feet ) vertically from the highest to lowest levels. The distance the tide drops varies tremendously and depends on the slope of the beach or the body of water. Compared to other places in the Gulf of California, the upper Gulf has the most extreme tidal range of all. When the tidal wave enters the shallow and narrow northern Gulf, it pushes the water level up really high, and as the tidal wave recedes, the water slosh down low, somewhat like water in a bathtub. Great tidal range like this occur in many places in the world with similar shallow, enclosed bays, such as the Bay of Fundy in Canada. In the northern Gulf of California, two low tides and two high tides occur each day producing a semidiurnal pattern.
There are many forces at work to create the tides. The most important are the gravitational pull of the sun and the moon on the earth, and the centrifugal force of the rotating earth. The combined effect of these two forces creates two bulges of water, one on the side of the earth that faces the moon and the other on the opposite side of the earth. These two water bulges represent high tide and the corresponding lack of bulges, are the low tides.
About every two weeks, during the new and full moon phases, when the sun, moon and earth are aligned, the tidal range is the greatest. These are called spring tides. In between new and full moons, during quarter and three quarter phases, the sun and moon are not aligned; their gravitational pulls are working at 90 degrees to each other, and the tidal fluctuations are at a minimum. These are called neap tides. During spring tides in the upper Gulf, low tides tend to occur early in the morning and late in the afternoon.
In the upper Gulf of California, the extreme tides create strong currents and dictate the overall circulation pattern for the entire region, as well as the nearshore water movements. They affect the distribution of sediments and nutrients, the movements of larvae and many living creatures. In the open sea, migration and feeding habits of mammals, fish and birds are influenced by the tides. Fishermen’s activities also follow the flow of tides, determining how, when and where they fish. On the shore, a myriad of spineless creatures and seaweeds are alternately covered and exposed to the surrounding desert by the rhythmical rise and fall of the tide. Essentially, any visitors to the seashore in the upper Gulf must adjust to the ebb and flow of tides.

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