A tsunami, meaning ‘harbour wave in Japanese, is a a huge wave that is caused by earthquakes, volcanic eruptions or landslides that occur under the sea.
When an undersea volcano erupts or an earthquake shakes the ocean floor, water becomes displaced and begins to form a tsunami.
Tsunamis can approach the shore suddenly as water draws back from the shoreline – this is the trough of the huge wave following behind.
A tsunami is not just one huge wave, a series of large waves will follow behind.
Tsunamis can cause mass flooding as the wave crashes onto the shoreline and the momentum and force pushes it well onto land.
Erosion can also occur because of a tsunami as water erodes the foundations of coastal structures.
Tsunamis are often caused by earthquakes and these occur when the tectonic plates that make up the Earth’s surface move against each other and collide causing seismic waves.
The 2004 Indian Ocean tsunami was triggered by a 9.3 magnitude earthquake with the initial surge wave of the tsunami measuring 33 metres.
It was the largest earthquake-generated tsunami in history.
Certain places in the world are subject to earthquakes and tsunamis more than others as there are only seven tectonic plates covering the earth and the borders of these plates lie in certain areas.
The cause of the most powerful earthquake in 230 years in Mexico which sparked a tsunami this week was due the possible collision of the Cocos plate which runs along the west of Mexico and the Caribbean plate or the Nazca Plate which contains Mexico and borders the west of Guatemela, El Salvador, and Nicaragua.
When the waves of a tsunami reach shallower water the height of the surging wave can increase by several metres but the shallow water slows the wave down.
Waves get closer together when they near the shore in shallow water, increasing their impact as they have also grown in size.
The speed of the tsunami waves depend on the depth of the ocean rather than the distance from the source of the tsunami.
A tsunami is not to be confused with a tidal wave which is caused by the gravitational pull of the sun and moon rather than movement below sea level.
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