A wave is a disturbance on the surface of a large body of water which takes the form of an arch and breaks upon the shore.
They commonly happen on very large bodies of water, such as oceans, and are a result of wind blowing over the water surface.


Water particles within a wave move in a circular orbit. Each particle, or a floating object, tends to move vertically up and down. It is only the shape of the wave and its energy that is transferred horizontally towards the coast. However, when the wave reaches shallow water, the velocity at its base will be slowed due to friction with the sea-bed, and the circular orbit is changed to one that is more elliptical. The top of the wave, unaffected by friction, becomes higher and steeper until it breaks. Only at this point does the remnant of the wave, the swash, actually move forward.

Types of waves

  1. Constructive waves
  2. Destructive waves

Comparison table

Constructive Waves
Destructive Waves

  • Associated with calm weather.
  • Are less powerful waves.
  • Break on the shore and tend to deposit material.
  • Are responsible for transporting material.
  • Swash is stronger than the backwash.
  • Associated with storm conditions.
  • Are created when the wave energy is high and there is a large fetch.
  • Tend to remove material from the coast and are therefore associated with erosion.
  • Backwash is stronger than the swash.

Swash and Backwash

Waves can approach the coast at an angle because of the prevailing winds. The swash of the waves carries the material up the beach at an angle. The backwash then flows back to the sea in a straight line at 90 degrees. This movement of material is called transportation.
Continual swash and backwash transports material sideways along the coast. This movement of material is called longshore drift and occurs in a zigzag.

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A key thing to note is that not all waves are formed due to wind action. Tsunamis, for example, are formed due to seismic and geological reasons.
Tsunami that hit Japan