Formerly they were called “tidal waves”, “tsunami” or “seismic sea waves,” but these terms have become obsolete since they do not adequately describe the phenomenon. The first two involve movements of tide, which is a different phenomenon and is related to oceanic imbalance caused by the gravitational pull exerted by the planets, the sun and particularly the moon. Seismic waves, on the other hand, involve an earthquake and we saw that there are several other causes of a tsunami.

         A tsunami is usually not felt by ships at sea (the waves at sea are small) or can be viewed from the height of a plane flying over the sea.
  
         As might be expected, tsunamis caused by earthquakes can be local or distant earthquakes. In both, the former are those that produce more devastating damage because not reached a sufficient time to evacuate the area (usually occur between 10 and 20 minutes after the earthquake) and the earthquake itself generates terror and chaos that makes it very difficult to organize an orderly evacuation.

As mentioned in the previous section, the Earthquakes are the great cause of tsunamis. For an earthquake triggering a tsunami the sea floor abruptly should be moved vertically so that the ocean is pushed outside its normal balance. When this vast body of water attempts to regain its equilibrium, waves are generated. The size of the tsunami will be determined by the magnitude of vertical deformation of seafloor. Not all earthquakes generate tsunamis, but only those of considerable magnitude, which occur under the seabed and are capable of stretching.
           While any ocean can experience a tsunami, more often occurring in the Pacific Ocean, whose shores are more commonly the seat of considerable magnitude earthquakes (particularly the coasts of Chile and Peru and Japan). Moreover, the type of fault that occurs between the Nazca and South American plates, called subduction, is that one plate is slipping under the other, make it more conducive to deformity of the seabed and therefore tsunamis.

           Despite the above, devastating tsunamis have been reported in the Atlantic and Indian Oceans and the Mediterranean Sea. A large tsunami accompanied the earthquake of Lisbon in 1755, the Mona Passage to Puerto Rico in 1918 and ee Grand Banks of Canada in 1929.

           The avalanches, volcanic eruptions and underwater explosions can cause tsunamis that often dissipate rapidly, without achieving a result in damage to its continental margins.

           For meteorites, no reliable records about its occurrence, but the shock wave that would cause to enter the ocean or the impact on the seabed in the event of falling into the shallow zone are sustainable enough factors to think about them as a possible cause of tsunami, especially if it is a large meteorite. The waves generally occur by the action of wind on the water surface and waves have a rhythmicity which is usually 20 seconds and at most often spread about 150 meters inland, as noted in the temporal or hurricanes. In fact the spread is limited by distance, so that it loses intensity with distance from the place where the wind is generating.
         A TSUNAMI, however, presents an opposite behavior, as the sudden movement of water from the depth creates a whiplash effect “to the surface that is capable of achieving unthinkable scale waves. The mathematical analysis indicate that the velocity equals the square root of the product between the force of gravity (9.8 m/s2) and depth. To get an idea take the usual depth of the Pacific Ocean that is 4,000 meters, would give us a wave that could move at 200 m / s, ie 700 km / h. And as the waves lose their strength in inverse proportion to its size, having 4,000 m can travel thousands of miles away without losing much strength.
         Only when they reach the coast begin to slow, decreasing the depth of the ocean. The height of the waves, however, can be increased to over 30 meters (the usual is a height of 6 or 7 m).

        The glitches in the Pacific Ocean coast where tectonic plates are introduced under the continental plate suddenly causes a phenomenon called “subduction”, which often generate tsunamis. Underwater landslides and volcanic eruptions can cause similar phenomena.

        The energy of the TSUNAMI remains more or less constant during the movement, so that on reaching shallower areas, having less water to move, the speed increases so formidable. An offshore tsunami that felt like a big wave can, upon reaching the coast, destroying even kilometers offshore. The turbulence that occurs in the sea rocks and sand drags causing damage beach erosion in reaching alter the geography for many years.

          Japan, for its geographical location, is the most beaten, by the tsunamis.