Coastal landforms

One of the most common features of a coastline is a cliff. Cliffs are shaped through a combination of erosion and weathering - the breakdown of rocks caused by weather conditions.

Soft rock, e.g. sand and clay, erodes easily to create gently sloping cliffs. Hard rock, e.g. chalk, is more resistant and erodes slowly to create steep cliffs.

• The sea attacks the base of the cliff between the high and low tide marks.
• Erosion processes of hydraulic action and abrasion, create a wave-cut notch .
• Over time the notch increases in size and the upper cliff is unsupported, while weathering weakens the upper cliff.
• These processes cause the cliff to collapse.
• A wave-cut platform is the gently sloping area of bedrock that is left behind as the cliff retreats.
• Breaking waves move the collapsed cliff sediment smoothing the wave-cut platform through abrasion.
• The erosion and cliff collapse sequence is repeated and the cliff continues to retreat.

Headlands are formed when the sea attacks a section of coast with alternating horizontal bands of hard and soft rock.

The bands of soft rock, such as sand and clay, erode more quickly than those of more resistant rock, such as chalk. This leaves a section of land jutting out into the sea called a headland.

The areas where the soft rock has eroded away, next to the headland, are called bays.

Erosion can create caves, arches, stacks and stumps along a headland.

1. Cracks in the rock erode through abrasion.
2. Caves occur when waves force their way into cracks in the cliff face. The water contains sand and other materials that grind away at the rock until the cracks become a cave. Hydraulic action and abrasion are the predominant erosion processes.
3. If the cave is formed in a headland, it may eventually break through to the other side forming an arch.
4. The arch will continue to be eroded by abrasion and hydraulic action. It will gradually become higher and wider until the roof can no longer be supported. When the arch collapses, it leaves an isolated column of rock or stack standing in the sea.
5. The stack will be attacked at the base in the same way that a wave-cut notch is formed. This weakens the structure and it will eventually collapse to form a stump.

Beaches are a common feature of a coastline. Beaches are made up of eroded material that has been transported from elsewhere and deposited by the sea.

Constructive waves help to build up beaches. The material found on a beach (i.e. sand or shingle ) depends on the geology of the area and wave energy.

A cross-section of a beach is called a beach profile.

The material found on a beach varies in size and type as you move further away from the shoreline. The smallest material is deposited near the water and larger material is found nearer to the cliffs at the back of the beach.

Large material is deposited at the back of the beach in times of high energy, for example during a storm. Most waves break on the shore between the high and low tidelines. Sediment here is effectively broken down and smoothed by attrition.

This is a beach where strong swash waves will be assisted by windy and stormy conditions to throw larger pieces of shingle further up the beach. Shingle beaches will usually contain many different ridges across their profile.

The smallest material will be found on the beach face and larger pieces of shingle/ pebble will be thrown to the back of the beach. Shingle beaches usually have much steeper profiles. This is because the wave will percolate through the shingle, making the backwash too weak to remove the material.

This is a beach where strong swash waves move sandy material up the beach with a spilling wave. Backwash will be weaker. The coarsest/ biggest pieces of sand will be found at the wave limit – further up the beach. Sandy beaches usually have a gently sloping profile. This is because there is less percolation of water and with sand being a lighter material, the backwash can remove it more easily.

Spits are also created by deposition. A spit is an extended stretch of beach material that projects out to sea and is joined to the mainland at one end.

Spits are formed where the prevailing wind blows at an angle to the coastline, resulting in longshore drift . An example of a spit is Spurn Head, found along the Holderness coast in Humberside.

1. Longshore drift moves material along the coastline in the direction of the prevailing wind. The angled swash brings material onshore, while the backwash removes the material in a straight line, perpendicular to the coastline.
2. This continues in a zig zag movement along the coast.
3. If the coast changes direction, material will continue to be deposited in the original direction in a shallow sea.
4. This build up of material is called a spit
5. A spit needs a constant supply of material, or it can be eroded by storm waves.
6. Over time, the spit grows further out and changes in wind direction may form a hook at its tip.
7. A spit will create a sheltered area between it and the land, here fine silt is deposited and mud flats or salt marshes form.