When an earthquake occurs under the sea, it can trigger a tsunami. A tsunami is a huge tidal wave that moves very quickly towards the shore.
How a tsunami happens:
- An undersea earthquake disturbs the sea bed and causes powerful waves to move out very quickly in all directions.
- The sea waves become much higher as they approach shallow waters near the coast. They can be up to 30 metres high or more.
- A tsunami can devastate low lying coastal areas.
Example: On St Stephans day 2004, a giant tsunami struck and devastated part of the coast of Indonesia.