- Home
- > Geography
- > Natural hazards
- > Tsunamis
A tsunami is a huge wave, usually caused by volcanic or earthquake activity under the ocean, which can eventually crash onto the shoreline. The effects on a community can be devastating.
What causes a tsunami?
When an earthquake, volcano or landslide happens on the ocean floor, water is displaced. This water forms the start of the tsunami.
When the waves reach shallower water:
- their height can increase by several metres
- the shallow water slows the wave
- the waves get closer together
It is hard to see that a tsunami is approaching. The most obvious sign is the coastal water retreats just before the waves reach the shore. This is actually the trough of the wave following behind.
What effects does a tsunami have?
The main impact a tsunami has is flooding. The waters are also able to erode the foundations of coastal structures.
Listen
Links
bbc.co.uk navigation
BBC links
BBC © 2012 The BBC is not responsible for the content of external sites. Read more.
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.