Coastal Erosion Test

The sea shapes the coastal landscape. Coastal erosion is the wearing away and breaking up of rock along the coast. Destructive waves erode the coastline in a number of ways:

• Hydraulic action. Air may become trapped in joints and cracks on a cliffface. When a wave breaks, the trapped air is compressed which weakens the cliff and causes erosion.
• Abrasion. Bits ofrockand sand in waves grind down cliff surfaces like sandpaper.
• Attrition. Waves smash rocks and pebbles on the shore into each other, and they break and become smoother.
• Solution. Acids contained in sea water will dissolve some types of rock such as chalk or limestone.

There are various sources of the material in the sea. The material has been:

• eroded from cliffs
• transported by longshore drift along the coastline
• brought inland from offshore by constructive waves
• carried to the coastline by rivers

Waves can approach the coast at an angle because of the direction of the prevailing wind. The swash of the waves carries material up the beach at an angle. The backwash then flows back to the sea in a straight line at 90°. This movement of material is calledtransportation.

Continual swash and backwash transports material sideways along the coast. This movement of material is called longshore drift and occurs in a zigzag.

Coastal transport

There are four ways that waves and tidal currents transport sediment. These can then contribute to the movement of sediment by longshore drift.

ProcessDescription Solution Minerals are dissolved in sea water and carried in solution. The load is not visible. Load can come from cliffs made from chalk or limestone, and calcium carbonate is carried along in solution. Suspension Small particles are carried in water, eg silts and clays, which can make the water look cloudy. Currents pick up large amounts of…