Answer to Question 1
As a wave approaches the shoreline from deep water, the circular orbit of water molecules within the wave begins to interact with the bottom. The circular orbit flattens out and forms an ellipse. This means that the top portion of the wave is travelling faster than the bottom portion of the wave. Water piles up and when the height of the wave is 7 times the wavelength, then the water plunges forward creating breaking surf.
Answer to Question 2
Water particles in a wave travel in a circular (orbital) motion. A deep-water wave is a wave in which the water depth is greater than one-half of the wavelength. At this depth, the water is deep enough so that water travels in a circular motion without interacting with the ocean bottom. Deep-water waves travel faster than shallow-water waves because the orbital motion of deep-water waves is not affected by the seafloor. In comparison, shallow-water waves occur when the water depth is less than 1/20 of the wavelength. In shallow water, the lower wave orbitals interact with the shallow seafloor and are slowed as they their orbital paths are flattened. Thus, shallow-water waves move slower than their deep-water counterparts of the same wavelength.
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