What is a tsunami?
A tsunami is a large ocean wave usually caused by an underwater earthquake or a volcanic explosion.
Tsunamis are not tidal waves, because tidal waves are caused by the forces of the moon, sun, and planets upon the tides, as well as the wind as it moves over the water.
With typical waves the water flows in circles, however with a tsunami the water flows straight.
This is why tsunamis cause so much damage!