The word tsunami (pronounced soo-NAH-mee) is Japanese, and it means ‘harbour wave’.

Tsunami - What is it?

A tsunami is a huge volume of moving seawater.  These giant waves can travel for thousands of miles across the sea and still have enough energy and force to destroy buildings, trees, wildlife and people.

If you throw a stone in a pond it will create a series of ripples.  A tsunami is just like those ripples but the disturbance that sets them moving is much greater than a small stone.  It can be triggered by an undersea earthquake, landslide or volcanic eruption.

In deep water tsunami waves can extend thousands of feet into the sea, and reach speeds of 500mph, almost fast enough to keep up with a jet airplane.  There can be up to a hundred miles between each wave, which may be just a few feet above the sea.

This image shows sediment (light brown & green colour) left after the tsunami along the northeast coast of Sri Lanka. (Image courtesy of ESA, Envisat MERIS image dated 28 December 2004)

Most Tsunamis are caused by undersea earthquakes.  These underwater earthquakes cause disruption to the seafloor and, in turn, the overlying water.  A tsunami and has nothing to do with tides although it is sometimes mistakenly called a tidal wave.
 

Read More: How and where do these undersea earthquakes occur?

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