Coast Erosion Essay

The coast is dynamic, meaning it is constantly changing. It does so as a result of erosion and deposition, forming various types of landforms in the process. The landforms of erosion are headlands, bays, cliffs, rock platforms, caves, arches, stacks and blowholes. The landforms of deposition are beaches, lagoons, bars, barriers, spits and tombolos.

LANDFORMS OF EROSION
Headlands and Bays
Along the coast where there are alternating patterns of hard and soft rock, headlands and bays may form as a result of hydraulic action. The harder more resistant rock erodes away slower, forming a headland that juts out into the ocean. When the softer rock between headlands erodes away and at a faster rate, it creates a curved inlet, or bay.

Cliffs and Rock Platforms
Now the headland is more exposed to the hydraulic action of the waves than the protected bay. As the waves near the shore, they refract and “mould” to the shape of the coastline,

concentrating their energy around the headland. Consequently, a wave-cut notch forms at the foot of the landform. This indent enlarges as more rock is eroded away. Eventually, the overhanging rock becomes too heavy and collapses. A cliff face is left behind. This process repeats itself and the cliff face retreats inland.

After the cliff collapses and the rubble is swept away, a rock platform is formed.

It is generally unaffected by erosion by hydraulic action, since waves strike forward rather than downwards. However the platform can be be continued to be shaped by corrasion, which is the abrasion by particles rolling back and forth with the waves.

Caves, Arches, Stacks and Blowholes
When erosion can carve out sea caves, arches, stacks and blowholes in a headland. Sea caves form when weak areas of headlands and cliffs are hollowed out. The cave could be worn away to reach the other side of the rock, or two sea caves might meet. In both cases, a sea arch results. The waves continue to corrode the rock until the arch collapses due to the weakening of the top portion. All that remains is a stack, which is eventually reduced to a stump by wave erosion.

If there is a weak section of rock in the roof of a sea cave, it can collapse from the pressure of compressed air and water when waves rush into the cave. A blowhole is produced.

LANDFORMS OF

DEPOSITION
Beaches
Constructive waves deposit eroded material along the shore, which eventually builds up over time to form a beach. The smallest particles are deposited nearest to the edge of water because the waves break more often along the shoreline and break down the particles through the process of attrition. Attrition is the process in which waves cause particles to crash into each other and wear each other down. On the other hand, the biggest pieces are left nearer to the back of the beach. This is because waves only have the power to cast out bigger objects during times of high energy, such as during a storm.