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Tides can range in size from small to great, and certain areas of the world are prone to specifically-sized tides.
Some parts of the world, such as Tahiti, a Polynesian island in the South Pacific, have no lunar tides at all. There, a single daily tide caused by the Sun raises the seas just 1 foot. In other places, such as the famed Bay of Fundy in Nova Scotia, tides routinely rise and fall by 40 feet and can get much higher during extreme conditions that produce proxigean tides.
The tide rises, the tide falls,
The twilight darkens, the curlew calls;
Along the sea-sands damp and brown
The traveller hastens toward the town,
And the tide rises, the tide falls. –Henry Wadsworth Longfellow, American poet (1807-1882) |
Throughout the world, extreme tidal variations are largely due to the shape of the ocean bottom and a bay’s orientation and outline. High tides can be either exaggerated in height or reduced by the shape of the bay and the way the undersea surface rises at that location.
Tahiti (and all of Polynesia), however, experiences an entirely different effect. Think of it this way: Just as carrying a shallow pan of water sets up a swishing back-and-forth motion that soon makes the water spill over the pan’s sides, there is a middle, or fulcrum, point where the water hardly moves at all. The islands of Polynesia are located right at the fulcrum point for the Pacific basin (this fulcrum point has nothing to do with the equator), resulting in almost no tidal movement.
These and many other local physical variations, some still poorly understood, produce the fascinating range of tides found around the world.
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