How do waves get their shape?

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I’m talking about waves in water. Oceans, lakes, pools, etc. How do they get their shape, and also why does that shape change when they come to shore?

In: Physics

Even though waves *look* like purely surface effects on oceans, lakes, etc., the interesting fact is that the wave actually affects the water all the way down from the surface to the solid seabed. *The total water depth* affects the surface wave’s height and speed.

Shallower water means slower (and taller) waves. Near land, this distorts the wave shape and makes it crash — a wave crest is literally speeding beyond its own base, in the shallows near shore.

Higher slower waves near shore are a particular problem for people dealing with tsunami waves: https://upload.wikimedia.org/wikipedia/commons/2/2d/Propagation_du_tsunami_en_profondeur_variable.gif