Tsunami.

A Tsunami is a giant and powerful sea wave caused by a submarine Earthquake. The submarine ground rises, pushing the water away. At the begining the wave isn't very tall: in fact, if you are in a boat at the sea, you don't feel anything; only a small movement under your feet. But when the wave arrives to the sea shore, it quickly grows, reaching meters in height.

There have been very high tsunamis along the History: Lisbon and Cádiz (1755), Malasia (2004) or more reciently, New Zealand (Last weekend, November the 12th) A Tsunami wave can reach more than 20 meters, destroying and killing everything. The most destructive one was in Malasia: more than 230.000 people died in that natural disaster.

Actually there are Tsunami alarms in many parts of the world (including Spain) Some hours before the impact of the wave the police advises people in order to evacuate the coast.

Malasia Tsunami, 2004.