What’s a tsunami?


My eldest nephew is fascinated by natural disasters, in particular tsunami.

The Japanese word tsunami means ‘harbour wave’. This is because these kinds of waves are not very noticeable out at sea but are very dangerous when they reach land.

A tsunami is a special kind of wave. It has a small wave height (amplitude) but a very long wavelength, which can be up to hundreds of kilometres long! When the wave gets close to the shore, it is forced to slow down and its wave height gets bigger.

But, the trouble is that a tsunami doesn’t break like a normal wave. As this video shows, when it reaches land, a tsunami can cause a huge amount of damage – breaking and washing away anything in its path.

Tsunami are started by huge movements of the earth under the sea bed. These movements are often caused by natural disasters such as earthquakes, landslides or volcanic eruptions. But they can also be man-made by things like nuclear bomb test explosions.

For more information about tsunami, check out this National Geographic webpage.

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