Why the waves go to the beach

The wind blows in all directions. But the movement of the sea goes only to one side. Why do the waves go towards the beach? There is a mathematical explanation.

It is born from a transfer of energy between the wind and the seas. When the bodies of water are limited by land, the path is interrupted by the coast. Luz María García García holds a PhD in Applied Mathematics. She is director and researcher at the Oceanographic Center of A Coruña (IEO-CSIC). She explains that wave motion is not limited to the sea. On the contrary, it is also seen in other bodies of water, such as lakes and rivers.

Why do the waves go towards the beach, if the wind blows in all directions?
Why do the waves go towards the beach, if the wind blows in all directions?

Approach to the coast

These are waves of energy that are dispersed on the surface of the water when they come into contact with the wind. “To generate them, the wind transfers energy to the seawater. First, small disturbances are formed on the surface that grow into larger waves.”

But first, there is the Sun, says Iván Darío Correa, PhD in Marine Geology. When its light heats the Earth’s atmosphere, it generates the wind that, in turn, creates the movement of the waves. What does their size depend on? On the intensity of the wind, the time it blows and a long, uninterrupted path.

These waves of kinetic energy over the sea meet some fragment of island or landmass. And they generate the gentle sound of waves crashing on the beach. This does not happen, for example, in the open sea. Waves have no restrictions on direction or travel.

As waves approach the beach, they appear to get higher. This phenomenon is known as shore approach. Two different energies that make up wave motion are united: kinetic and potential.

The wave becomes high as the energy changes from kinetic to potential.
The swell becomes high by changing the energy from kinetic to potential.

Kinetic and potential

“In deeper water, most of the energy is in the form of kinetic energy. As waves approach the shore, they lose speed as they feel the bottom. The kinetic energy is transferred to potential energy, which causes the height of the waves to increase. They break on the beach, where they release their energy.”

You know why the waves go onto the beach. Think about that the next time you see the sea. Or maybe not, just enjoy the show it puts on for you.

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