What Is a Tsunami and What Causes It

Tsunami Is Often Unpredictable

What is a tsunami and what causes it? A tsunami is a large ocean wave that moves at a very high speed and is generated by an impact in the earth’s surface such as an earthquake or a massive landslide. The word “tsunami” is from Japanese and means harbor (tsu) wave (nami), since many harbors in the history of Japan have been experiencing cataclysmic wave impacts. A tsunami is not a single wave, but a series of waves that move rapidly across oceans and have a length of around 200 kilometers (compared to 100 meters of a regular ocean wave). Tsunamis are popularly referred to as tidal waves although such a term is a misnomer since tsunamis have nothing to do with the tidal oscillations.

Before the impact the water along the shore retracts for as much as hundreds of meters depending on the slope of the coast. While still at a distance from the coastal area a tsunami does not show high amplitude and cannot be easily detected over deep waters. Upon reaching the shore, however, the wave slows down significantly – from a couple of hundred kilometers per hour to around 80 kilometers per hour; it gains abruptly in amplitude and theoretically may reach a height greater than 500 meters (these are often termed “mega tsunamis”).

How Destructive Is a Tsunami?

Tsunamis are potentially very destructive but not all incidents end up in a. For example, if the tsunami-stricken area is not populated, there are no chances for catastrophes. Since a huge amount of water and debris is released, structural damage is often imminent. In order to save lives, much has been done over the years to sophisticate the instruments for predicting the coming of the wave and alerting the population close to the shore. A tsunami is not at all easy to predict and prevention is virtually impossible. Efforts have been made, however, to alleviate the effects of the wave by creating carefully engineered walls and floodgates.

Perhaps one of the most destructive events of this kind occurred in 2004 in India, known as the 2004 Indian Ocean tsunami or Asian Tsunami, which killed over 200,000 people in fourteen different countries. There were series of huge waves and they reached the height of 30 meters. This particular movement of water was induced by a third largest earthquake ever recorded. The vast majority of tsunamis in the world were recorded in the Pacific Ocean. Still, any substantial body of water, a great lake for instance, may also produce a tsunami if preceded by a powerful movement of the earth’s surface.

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