Tsunami

Sometimes reaching heights of 40 meters (120 ft.) or more, tsunamis are the most dramatic and destructive of waves.

Underwater disturbances, such as volcanoes, earthquakes and landslides, are the cause of these monster waves. The larger the disturbance, the larger the tsunami will be.



In the open ocean, tsunamis may be hard to spot. Long wavelengths can hide the size of the wave, but just like other kinds of waves, changes occur when the wave enters shallow water.

The wavelength shortens, and the height increases. The strength of the disturbance, the distance the wave travels and the shape of the coastline combined determine the tsunami's height, and ultimately, its destructiveness.

From http://www.onr.navy.mil/focus/ocean/motion/waves3.htm

An animation of the earthquake waves in 1833 similar to the Indonesia tsunami of 2004