I don't think this question has been asked on this forum before (at least I didn't find it).
In the case of a tsunami, an earthquake generates a wave which will travel with the sea/ocean as the medium. However, what I remember from high school is that mechanical waves transfer energy but energy only. On a sectional view we represented molecules of water going up and down as the wave travels but the molecules never moved horizontally.
Then why does a tsunami can flood half of a country? in that case the water does move horizontally. what am I missing?
I have read that for regular waves, the problem is different and their momentum comes from wind streams, but I don't think this is the case for tsunami.
I would appreciate some pieces of answer.