Why are there waves in the sea?

When you stand at the seaside, the water never stops moving. Wave after wave rolls in and tumbles onto the sand. But where do all these waves come from? The answer is something you cannot even see — the wind!

Wind gives the water a push

The air is always moving over the top of the sea. When wind blows across the water, it gives the smooth surface a gentle push. This makes little wrinkles called ripples.

If the wind keeps blowing, it pushes the ripples again and again, and they grow taller and taller into rolling waves. A strong wind far out at sea can make big waves that travel for many days before they reach a beach.

The water stays, the wave travels

Here is the clever part. When a wave passes by, the water itself does not really rush forward. Most of it just bobs up and down, like a duck rising and dipping on the sea.

It is the shape of the wave that moves along, not the water. Think of shaking a long rope — the wiggle travels to the end, but the rope stays in your hand!

Crashing on the shore

When a wave reaches shallow water near the beach, the bottom of the wave drags on the sand and slows down. The top keeps going, tips over, and crashes in a frothy splash. That is the foamy wave you love to jump in!

Wonder fact: The biggest ocean waves of all are made by undersea earthquakes. They are called tsunamis and can race as fast as a jet plane!