Quote:
Originally Posted by PR_Glen
it's odd how you can be 30 minutes out at sea and a tsunami, which is endlessly destructive to the land, is nothing more than a ripple when you are in a boat. In contrast a rogue wave can knock over a huge boat but cause no harm on the land...
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They are two completely different kinds of wave.
In the case of a rogue wave at sea, which is created by the random combining of several large, wind-created waves, you end up with a wave that has a very high amplitude, (wave height), but a very short wave-length. In the ocean it will smash a boat or roll it over, since the extreme height combined with the short length makes it have a very steep front and back. When it hits land, the short wavelength means that it simply collapses on the shore and draws back
In the case of a Tsunami, the wave has a more moderate amplitude, compared to it's VERY long wave length, sometimes hundreds of meters. In effect, the wave becomes almost a "step up" in the water. In front of the wave the water is X deep, and after it the water is X + the amplitude deep.
In deep water the long wave length means that the wave front is relatively gradual, so ships can ride over it easily, but when it reaches land, the shoaling water makes the wave pile up, steepening the front, and when it hits the shoreline itself, the long wave length means that it doesn't really collapse, it simply keeps on rolling further and further inland.
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