The word tsunami comes from the Japanese word for ‘harbour wave’.
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Tsunamis can be unpredictable and happen unexpectedly.
About four out of five tsunamis happen within the Ring Of Fire, a zone in the Pacific Ocean where earthquakes and volcanic eruptions frequently take place.
How to they start?
The most common way is by earthquakes.
These happen when giant slabs of the Earth’s crust, called tectonic plates, grind together. Sometimes, though, the plates get stuck, the pressure builds up and they suddenly slam into a new position. This causes an earthquake.
How big is a tsunami?
Out in the open ocean, tsunami waves are only about one-metre high because the water is deep. However, as the water becomes shallow, the waves slow down and begin to grow.
They can rise 35m or higher – that’s the same as a 10-floor block of flats! However, the scariest thing about a tsunami is its wavelength, as this determines how far inland it can travel.
Whereas a large wave caused by a storm might have a wavelength of up to 150m, a tsunami could reach up to a fearsome 1,000km!