The ocean floor significantly impacts waves, primarily by influencing their speed, height, and direction as they approach the shore.
How the Ocean Floor Changes Waves
As waves travel from deep water towards the shore, they encounter shallower areas of the ocean floor. This interaction causes several key changes:
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Decreased Wave Speed: The base of the wave experiences friction against the sea bottom. This friction slows down the wave's base while the top continues at a faster speed. NOAA Ocean Explorer and University of British Columbia explain this process. This difference in speed causes the wave to become steeper.
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Increased Wave Height: The slowing of the wave's base, coupled with the continued forward momentum of the top, causes the wave to pile up, resulting in a dramatic increase in wave height. This is detailed in the NOAA Ocean Explorer resource.
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Wave Refraction: The uneven topography of the ocean floor causes waves to bend or refract. Waves slow down more in shallower areas, causing the wave crests to become parallel to the shoreline. University of Hawai'i describes how waves tend to break parallel to the coast because of this effect.
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Wave Breaking: As the wave becomes increasingly steep due to the friction and speed differential, it eventually breaks, transferring its energy to the shore. The NOAA Ocean Explorer website details this process as the wave crest leans forward until it collapses.
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Tsunami Impact: The shape and composition of the ocean floor play a crucial role in tsunami formation and propagation. Sudden movements in the seafloor, like underwater earthquakes, can generate powerful tsunami waves. The NOAA and National Centers for Environmental Information emphasize this connection.
Not all waves interact with the seafloor in the same way. Deep-water waves don't feel the bottom, while shallow-water waves are significantly impacted by it. University of Hawai'i explains this depth-dependent interaction.
