A tsunami is a sudden invasion of the coastal strip by ocean waters due to a tsunami, a large sea wave caused by a tremor of underwater land, that is, an earthquake under the sea.
When this occurs, it usually causes serious damage to the affected area.
Tidal waves are more common on the coastlines of the Pacific and Indian oceans, in seismically active areas.
The terms tsunami and tsunami are considered synonyms. Of all the seismic movements, the tsunami can be the deadliest, since it can travel a long distance and affects the coasts, which are usually very densely populated areas.
Underwater earthquakes cause movements of seawater (tidal waves or tsunamis). Tsunamis are huge waves with wavelengths of up to 100 kilometers that travel at speeds of 700 to 1000 km / h. On the high seas the height of the wave is small, without exceeding the meter; but when they reach the coast, when rolling over the seabed they reach much higher heights, up to 30 meters and more.
The tsunami is formed by several waves that arrive separated from each other for 15 or 20 minutes. The first that arrives is not usually the highest, but is very similar to the normal ones. Then there is an impressive decline in sea level followed by the first gigantic wave and then several more.
The false security that is usually given by the drop in sea level has caused many victims among people who, recklessly, approach by curiosity or other reasons, to the coastline.
Spain can suffer catastrophic tsunamis, as was proven in the Lisbon earthquake in 1755. As a result of this earthquake several large waves swept the Gulf of Cádiz causing more than 2,000 deaths and many injured.
In 1946 the tsunami warning network was created after the tsunami that swept the city of Hilo (Hawaii) and several other Pacific ports. Hawaii is affected by a catastrophic tsunami every 25 years, approximately, and the US, along with other countries, have set up surveillance stations and detectors that warn of the occurrence of waves caused by earthquakes.