Water on Earth  The Science of Tides

b. The effect of the earth's ocean basins and land masses

The real earth contains land masses (continents) and has oceans of variable depth. These combine to make the actual patterns of tides very complex.

As the earth rotates under the tidal bulge, the bulge acts as if it were a wave sweeping around the earth. As you learned in Lesson 10, the speed of a wave is affected by the depth of the water. So as this wave sweeps around the earth, its speed varies, depending on the depth of the ocean at each point.