Waves are caused by the transfer of energy from the wind to the sea due to the friction of wind on the water’s surface. In deep water, water molecules within a wave move in a circular movement. It is only in shallow water that the water itself is moving forward. This occurs along the coastline.
Why are some waves stronger than others?
The size of a wave depends on its fetch. The fetch is the distance a wave travels. The greater the fetch, the larger the wave. Wind speed also has a significant effect on the size of waves. The stronger the wind the larger the wave. This is because energy is transferred from the wave. Finally, wind duration also affects the size of a wave. The longer wind blows over the sea or ocean the larger the wave.
As waves move into shallow water, they begin to stack up as frictional drag with the seabed increases, the base of the wave is slowed down so the top part is travelling faster. This causes the wave to tilt, break and move towards the shore in the surf zone. Waves can be constructive or destructive.