Tides You walk along a beach, seashells, driftwood and seaweed left by the retreating tides at your feet. These bulges create high tides.
The low points are where low tides occur. Download animation It might seem strange that the ocean would bulge on the side farthest from the Moon as well as the side closest to it.
Download animation As Earth rotates within this layer of water, its landmasses pass through the two bulges. Our observer sees the tides rise when passing through the bulges, and fall when passing through the low points. The timing and heights of the tide near you will be affected by those additional elements.
Download animation Did You Know? Thousands of young, lobate scarps have been revealed in Reconnaissance Orbiter Camera images. The shape of our planet has a lot to do with differences in gravitational pull at various locations. If Earth was a true sphere covered by an ocean of constant depth, then it would be true that a high tide event would occur at the location with the moon overhead.
The tidal "bulge" would move around the Earth with the moon, but this is not the case with our planet. The Earth is not a true sphere, but bulges slightly at the Equator. It is also dotted with large land masses continents. At the same time, the depth of the world ocean varies greatly. All of these factors play into the height of the tides. Another thing to consider when thinking about tides is the dimension of time.
There are lags in time when an observer experiences high or low tide, and the lag varies from one location to another. Every six hours the tide goes from high to low and high to low again. Over 24 hours you typically see two high tides and two low tides. The sun, if it happens to be aligned with the moon, also exerts a gravitational force and can work together with the moon to make the tides even stronger.
If the sun is unaligned with the moon, then it works against the moon, reducing the high tide and raising the low tide a little bit so the peak and valley are not as large. The process is more complicated the oceans have a shape, different depths and coastlines, so the water sloshes around in ways that causes the sea level to rise and lower by different amounts depending on where you are. Some locations, like the Bay of Fundy in Canada, see a sea level variation from low to high by as much as 50 feet.
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