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This guide explains tsunami/Sunami definition. How do tsunamis occur? Where do tsunamis occur? and what causes tsunamis?. All these questions which often popup in human minds are dealt with below.
Tsunami, also written Sunami by people in Japan, is a massive flood which is caused by substantial offset of an ocean floor. It, as a result, displaces huge amount of sea water at the impacted site. The offset can be caused by an earth quake, volcanic eruption under the sea, landslides or meteorites shower.
The ocean water as a result rips through to the adjacent coastal locations in the form of mighty waves and consequently damages the human settlements.
The term sunami, in Japanese, means harbor waves, which, in deep/opoen sea, are characteristics of non destructive, low amplitude moving sea waves. Later on, as these approaches the coast, the waves strengthen enough to damage the surroundings coastal areas.
This phenomenon is in no way a tidal wave. High and low tides exclusively depend on the moon’s gravitational force.So this tidal phenomenon is experienced by all coast lines, even those who have never ever experienced tsunamis.
Yes, had the tsunami impacted area experiencing a high tide, the hazard would worsen than in the case of low tides.
Two things to remember here for non-technical persons or kids searching for tsunami facts i.e
Speed of a wave near a shore is directly proportional to floor depth but, if the wave is in deep sea, its speed rather depends on its wavelength. Speed in the deep sea is around 10 times the wavelength!
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What happens in general is that a tsunami wave, while moving through deep ocean, has a smaller amplitude and larger wavelength around 100 km in magnitude than the normal sea wave of 50 km.
So if you are on a ship in open sea and there is a tsunami threat nearby , it would be unnoticeable to you. Such a long wavelength disturbance is unobservable with a naked eye.
As mentioned before, the speed of a tsunami wave in open sea depends on its wavelength, therefore owing to 100 km in length, it is tremendously around 1000 km/h. The very same magnitude at which a passenger air plane flies!.
As the wave approaches the coast, its wavelength deceases due to shallow sea. This squashing of ocean water results in taller and taller waves . Upon reaching the shore line, the amplitude has risen to hundreds of meter, which as high as a 5 storey building, destructs everything coming its way. Thus, killing thousands of people!
It is a scientifically proven fact, that if the amplitude of a wave is 1/7 times its wavelength, the waves break on the shore and do not inundate the land, but such a scenario is rare in tsunamis as the wave amplitude, though surging in magnitude near the shore line, is still much less than the wavelength.