Most tsunamis are caused by earthquakes generated in a subduction zone, an area where an oceanic plate is being forced down into the mantle by plate tectonic forces. The friction between the subducting plate and the overriding plate is enormous. read more
Earthquake Causes Tsunami. Energy accumulates in the overriding plate until it exceeds the frictional forces between the two stuck plates. When this happens, the overriding plate snaps back into an unrestrained position. This sudden motion is the cause of the tsunami - because it gives an enormous shove to the overlying water. read more
When plate tectonics shift, it causes an earthquake, so, when plate tectonics shift underwater then there is an earthquake under water and because of those vibrations, waves keep growing bigger and bigger depending on how big or small the earthquake is, and that’s what causes a tsunami. read more