What Is the Effect of Waves on Erosion?

The Coast

• Around the world coastlines vary dramatically, but the effects of erosion can almost always be seen. A sandy beach is caused by waves which have battered the rocks so long they have disintegrated into tiny sand particles. Similarly, a rocky beach has been going through this process for slightly less time. Cliff faces are also battered by waves, which eat away at the base of the cliff until the top is so heavy it falls off into the water.

Hydraulic Action

• To explain how erosion works, imagine getting hit in the chest by a powerful wave. It would knock you off your feet. While a cliff might look strong, getting continually hit by a wave will eventually take its toll. Cliffs are covered in cracks and fissures, which are filled with air. When waves hit them, the air is compressed into the fissure and exerts a pressure on the surrounding rock. Just like chipping away with a hammer, this eventually causes the fissure to grow. If it grows big enough, parts of the rock can fall away from the cliff. This is referred to as the ̶0;hydraulic action̶1; of waves. During a storm this force is even greater.

Attrition

• Even the weakest waves can wear a land mass away. Loose gravel, or sand, is carried by the waves as they strike the land. These tiny particles cause a special kind of erosion known as ̶0;attrition̶1;. The tiny rocks get rubbed against the coast, wearing down the surface and releasing yet more tiny particles into the water. These in turn get caught by the waves and also wear down the coastline. Over hundreds of thousands of years, this seemingly gentle process can change the shape of land masses.

Chemical Erosion

• Some cliff faces are made up of rocks such as limestone, which are easily dissolved by acid. Since most seawater contains carbonic acid, these cliff faces do not last very long. Instead of being worn down or broken off, they are literally melted by the continual arrival of the waves.

Loss of Energy

• Ultimately the waves will reach equilibrium with the land when they have eroded the coast so much that a beach has formed. Loose rocks are ground down into sand, and the resultant beach will slope down into the sea. As the waves reach the beach they gradually lose energy as they climb the sand and will dissipate before reaching the top of the beach. In this way, the process of erosion by waves is complete.