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Name: Frank
Status: Educator
Age: 9-12
Location: MA 
Country: United States
Date: March 2006

I have a question regarding semi-diurnal and diurnal tides. My understanding is that some locations only have diurnal tides because of the of the angle of the moon's orbit with respect to the earth's equator. By looking at the "tidal force envelope" it makes sense to see diurnal tides at certain latitudes. What I cannot picture is why there are diurnal tides in the Gulf of Mexico.


I entered some information on tides previously in NEWTON, so you may want to look for that.

However, in many places in the Gulf of Mexico there are diurnal tides, for instance along much of the west coast of Florida and northern Gulf coast. The positions of the Moon and Sun and how their tides combine or detract from each other control whether tides are diurnal or semi-diurnal.

For a good reference to this go to or

By checking the tide tables for the various ports around the Gulf of Mexico, you can see where there are diurnal and semi-diurnal tides.

David R. Cook
Climate Research Section
Environmental Science Division
Argonne National Laboratory

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