Coastal Erosion Landforms

Destructive waves

Within destructive waves, there are three main types of erosional processes that take place along our coastlines. These are abrasion, attrition and hydraulic action, and these all create different coastal erosion landforms. Below is a table explaining these.

Rock type and structure

The type of rock is another factor that can affect how coastal erosion landforms are formed. Soft rock is easier to wear down; therefore, erosion often takes place at a faster rate. On the other hand, hard rock is harder to wear down and will require more force and pressure to erode. This means that it typically takes longer for the hard rock to be eroded. As a result, a coastline containing both hard and soft rock will create different erosional landforms since erosion usually occurs at different rates depending on how resistant the rock is. This also means that the structure of the rock can influence how coastal erosion landforms are formed. For example, if a rock face has different layers of both hard and soft rock, the rate of erosion will vary within the rock face, depending on the rock's resistance to erosion.

Coastal erosion landform revision

Diagrams are great for geography revision! Below is a diagram that shows how each of the three main coastal erosional processes (abrasion, attrition, and hydraulic power) take place within a destructive wave.

Coastal erosion landform features

Coastal erosional landforms come in many shapes and sizes, some of which you may have seen before. This is due to the combination of the rock type and erosional processes, such as abrasion, attrition and hydraulic action that take place within destructive waves. Along a coastline, all three main types of erosional processes will take place, and this means you can often find multiple different erosional landforms on the same coastline. These landforms are cliffs, wave cut platforms, headlands, bays, caves, arches, and stacks.

Coastal erosion landforms types

OK, time to actually examine the different coastal erosion landforms.

Cliffs

Now, I'm sure when you think of the coast, you'll typically picture giant cliffs. But how do these iconic coastal landforms actually form?

Fig. 2 - Cliffs along a coastline.

Well, cliffs are eroded at the cliff base by abrasion. The rocks within the ocean waves carve out a curve at the base of the cliff, called a wave cut notch. This eventually causes the cliff to collapse above the wave cut notch as it becomes unstable due to a lack of support at the base, leaving behind a steep cliff face. Over time, this leads to something called cliff retreat, which is a process where the cliff face slowly erodes further and further inland, parallel to the coast.

Wave cut platforms

Unlike cliffs, wave cut platforms are probably not a feature you will notice and point out during a trip to the coast. They actually occur as a consequence of cliffs forming. Wave cut platforms are wide areas of rock at the base of the cliff that slope towards the sea. As the cliff is eroded, retreating further inland, a wave cut platform forms below the cliff. Material breaks off the cliff because of erosion, and this material builds up at the base of the cliff, forming the wave cut platform. This wide area of rock is often quite rough because of abrasion that takes place. Wave cut platforms can also frequently be covered by the sea as rising sea levels occur.

Headlands and bays

When searching for the perfect spot to sit when visiting the coast, you'll more than likely choose a bay, rather than a headland. This is because headlands have sea on three of their sides, whereas bays have land on three of their sides, making them more sheltered. You can see this in the image below.

Fig. 3 - Coastline, showing headlands (rock jutting out to sea) and bays (curved sandy formations).

Headlands and bays form next to one another. Headlands are tall areas of coast that stick out into the sea, this is because they are made of harder rock that is more resistant to erosion. As erosion takes place, the more resistant rock remains, to form a headland and the less resistant rock erodes, to create a bay. Bays are inlets within the rocky coastline that curve inland, found either side of headlands, they are composed of weaker, less resistant rock. This means that headlands and bays can form due to the rock type and structure within a coastline.

Caves

Something you might love to explore when you visit the coast, are caves. Caves actually form at headlands. Over time, through abrasion, waves erode into the sides of these headlands, carving out a cave. This can happen on either side of the headland, or even on both sides at the same time!

Arches

Arches are an extension of caves. After continual erosion of the cave, eventually, the water will erode entirely through the headland so that that water can flow completely through the arch from one side of the headland to the other.

Stacks

Ultimately, arches are weakened through continued erosion and eventually the top of the arch collapses. This creates stacks, which are pillars of rock stood out at sea, away from the headland.

Coastal erosion landforms diagram

This is a diagram showing the various coastal erosion landforms along a coastline.

Notice how many different formations that can occur in one area! Have you ever seen any of them before?