Tsunami is a Japanese word which means 'harbour wave'. A tsunami is a large sea wave caused by the displacement of a large volume of water. They can be caused by earthquakes triggered by moving sections of the Earth's crust under the ocean.
In the last decade there have been a number of devastating tsunamis. Two large ones caused particularly extensive devastation: the Indian Ocean tsunami (26 December 2004) and the Japanese tsunami (11 March 2011).
The Indian Ocean tsunami of 2004 was caused by plates moving and slipping under the ocean.
Earthquake occurs and a tsunami forms