What happens to the wavelength and height of tsunami waves as they approach land from the open ocean?
They get taller in appearance, but that doesn’t mean they are becoming more powerful. What happens is, in the ocean when a tsunami starts, the water is usually very deep . The initial amount of energy of the tsunami begins to propagate thru the water. Often you cannot even see a ‘wave’. If you were to see one in open water it may only appear as a ripple no bigger than that made by the tiniest of stones thrown into, say a pool. The energy of the ‘wave’ travels, and it’s energy will change and dissipate some decreasing its overall intensity, but usually the energy is so large that the losses are fairly small in comparison to the overall energy of the initial wave. So, for the most part the energy of the wave remains the same (for the most part, depending on the water density thru which the wave passes, and what kinds of underwater structure the wave encounters along the way. Most open water structure is at the bottom, offering little or no opposition to the energy of the wave, so the wav
