There are three main types of breakers: spilling, plunging, and surging. As is slows, the wavelength decreases and the wave height increases, until the wave breaks (Steven Earle “Physical Geology”). So the crest of the wave gets “ahead” of the rest of the wave, but has no water underneath it to support it (Figure 10.3.1).įigure 10.3.1 As waves approach shore they “touch bottom” when the depth equals half of the wavelength, and the wave begins to slow down.
This is because the bottom of the wave begins to slow down before the top of the wave, as it is the first part to encounter the seafloor. Often breakers will start to curl forwards as they break. Eventually the wave height exceeds 1/7 of the wavelength, and the wave becomes unstable and forms a breaker. However, the wave still contains the same amount of energy, so while the wavelength decreases, the wave height increases. As one wave slows down, the one behind it catches up to it, thus decreasing the wavelength. When the wave touches the bottom, friction causes the wave to slow down. At this point their behavior will begin to be influenced by the bottom. When waves approach the shore they will “touch bottom” at a depth equal to half of their wavelength in other words, when the water depth equals the depth of the wave base (Figure 10.3.1).
But what happens when these waves move towards shore and encounter shallow water? Remember that in deep water, a wave’s speed depends on its wavelength, but in shallow water wave speed depends on the depth ( section 10.1). Most of the waves discussed in the previous section referred to deep water waves in the open ocean.
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