DEFINITION
A TSUNAMI (from the Japanese TSU: Port or bay, NAMI: Wave) is a wave or series of waves produced in a mass of water that is pushed violently by a force that moves it vertically. This term was adopted in a congress in 1963.
Earthquakes, volcanoes, meteorites, coastal or underground landslides and even large scale explosions may generate a TSUNAMI.
They were formerly called “surges”, “seaquakes” or “marine seismic waves”, but these terms are obsolete, since they do not describe the phenomenon appropriately. The first two imply tide movements, which is a different phenomenon and is related to an oceanic imbalance caused by the gravitational attraction exerted by the planets, the sun and especially the moon. The seismic waves, on the other hand, imply an earthquake and we have already mentioned several other causes for a TSUNAMI.
A tsunami is usually not felt by vessels at the sea (waves at open sea are small) or can be seen from the height of a plane flying over the sea.
A tsunami or seaquake, sometimes mistaken for a surge, is a series of huge waves created by a disturbance undersea similar to an earthquake. A tsunami can move hundreds of miles per hour in open seas and hit the coast with waves as high as 100 feet or more, although most waves are under 18 feet high.
From the area where the tsunami is originated, waves travel outwards in every direction as waves on the water when a rock is thrown in a pond. In deep waters, the tsunami wave is not noticeable. Once the wave approaches the coast, its height increases. All tsunamis are potentially dangerous, even when do not damage every coast when they hit. A tsunami can strike any place along most coasts of the United States. The most destructive tsunamis have happened along the coasts of California, Oregon, Washington, Alaska and Hawaii.
Shifting in the ocean floor induced by earthquakes often generate tsunamis. Landslides, volcanic eruptions and even meteorites may generate tsunamis. If a major earthquake or landslide happens near the coast, the first wave of a series may reach the beach in a matter of minutes, even before a warning is issued. The areas at most risk are those below 25 feet of sea level and at less than a mile from the coast. Drowning is the most common cause of death related to a tsunami. Tsunami waves and receding water are very destructive to structures in the area. Other dangers include flooding, drinking water pollution and fires due to gas pipelines or burst tanks.
