IGCSE Geography / Coastal environments

Headlands, bays, cliffs and wave-cut platforms revision notes

Edexcel International GCSE Geography (4GE1), chapter 2: Coastal environments, specification point 2.1c. Free lesson.

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Headlands and bays form because different rocks erode at different speeds. Waves also cut into the base of cliffs, causing them to retreat and leaving a flat wave-cut platform.

Why headlands and bays form

A discordant coast has bands of hard and soft rock meeting the sea at right angles. The same waves hit both types of rock, but they erode the less resistant soft rock faster. This is called differential erosion. The coast is cut back into a bay where the soft rock is, while the harder rock is left projecting into the sea as headlands. Chalk and limestone are resistant hard rocks, so they erode slowly. Clay is less resistant, so it erodes faster and forms a bay. Once a bay has formed, it is sheltered by the headlands. Waves lose energy there and deposit sand, forming a beach.…

Where erosion happens on a cliff

Waves reach the foot of a cliff between the high tide mark and the low tide mark. They erode this part of the cliff rather than wearing it back evenly from top to bottom. Hydraulic action and abrasion cut a hollow into the base, called a wave-cut notch. Hydraulic action is erosion caused by the force of water and trapped air in cracks. Abrasion is when rocks carried by waves scrape against the cliff.

How a cliff retreats

As the wave-cut notch deepens, it undercuts the cliff. The rock above the notch loses support and forms an overhang. Eventually, the overhang collapses. Waves clear away the fallen rock and begin cutting another notch, so the process repeats and the cliff retreats. The flat ledges of hard rock at Kimmeridge Bay in Dorset are an example of a wave-cut platform.

How a wave-cut platform is left behind

As the cliff retreats, it leaves a flat rock ledge at its foot. This ledge is called a wave-cut platform. A strong formation answer names the processes and puts the stages in order, using links such as “so” to show how each stage causes the next.

More lessons in Coastal environments

• Waves and coastal erosion
• Longshore drift and coastal deposition
• Weathering and mass movement on the coast
• Caves, arches, stacks and stumps
• Beaches, spits and bars
• Geology and the shape of the coast
• Vegetation, people and sea-level change
• Coastal ecosystems: coral reefs and mangroves
• Coastal ecosystems: sand dunes and salt marshes
• Inside one coastal ecosystem: the Sundarbans mangrove
• Coastal ecosystems under threat
• Case study: managing the mangrove
• Conflicts at the coast
• Why coasts flood
• Predicting and preventing coastal flooding
• Hard engineering at the coast
• Soft engineering and shoreline management plans
• Case study: coastal management in The Gambia
• Case study: coastal management in Sri Lanka
• Case study: coastal management in the UK
• Coastal fieldwork: collecting the data
• Coastal fieldwork: results, conclusions and evaluation