Most waves are caused by the wind blowing across the water. A wave occurs when the wind causes the surface of the water to rise as the wind pulls it and then gravity pulls it down. This causes the down and up movement of the waves that most people are familiar with. The size of the wave is generally influenced by the distance the wave travels and the strength and direction of the wind. The top of the wave is called the crest and the bottom is called the trough. When the crests break on the surface of the water they are called whitecaps. But, why do waves break when they reach the shore? Read on to find out.
Why do waves break?
Waves that break on, or close to, the shore are common on many beaches throughout the world. The reason that waves break is because the base of the wave is no longer able to support the top of the wave. This happens for a variety of reasons, but the most common is when a wave enters shallow water, such as the shore, reef or sandbar. When this happens the water is forced forwards onto the beach or against the rocks.
The different types of waves
There are four basic types of breaking waves, which are identified by their different characteristics. Spilling waves occur when the shoreline has a gradual slope and these are generally the safest type of wave. Plunging waves occur when there is a sharper rise in the ocean floor, such as a reef or sandbar. These waves are popular with experienced surfers, but can be dangerous for people swimming. Surging waves occur on steeper beaches, where the wave may not actually break. These are considered very dangerous for swimmers. A collapsing wave is a mix between plunging and surging waves.