If you stand on a beach during a winter storm, you can literally feel the ground shake as waves smash into the cliffs. The power behind these waves is determined by wind strength, the time the wind has been blowing, and the fetch (the distance over open water). The UK's prevailing wind blows from the South-West across the Atlantic Ocean, generating incredibly powerful waves.
There are two main types of waves that shape the coast:
As destructive waves hit the coast, they erode the land through four key processes:
Eroded material is then transported along the coast. Longshore drift moves sediment in a zig-zag pattern: the prevailing wind pushes the swash up the beach at an angle, and gravity pulls the backwash straight down at a 90-degree angle. Sediment in the water is moved by traction (rolling boulders), saltation (bouncing pebbles), suspension (floating fine particles), or solution (dissolved minerals). When the sea loses energy, it drops this material through .
The sea is not the only force destroying cliffs; processes happening high above the waves are just as destructive. Sub-aerial processes alter the cliff face above the high-tide mark through weathering and mass movement.
Weathering is the breakdown of rock in situ (in its original place).
Once weathering weakens the rock, mass movement takes over. This is the gravity-driven downward movement of material. Slumping (or rotational slip) is common on soft, unconsolidated cliffs like boulder clay. Heavy rainfall saturates the clay, increasing its weight and lubricating a curved slip plane, causing whole sections to slide down. On steep, solid cliffs, rockfall occurs when loose fragments drop rapidly, while landslides involve material moving down a straight slip plane.
The UK has a Temperate Maritime climate with cool, wet winters and warm, wet summers. During winter, frequent low-pressure systems (depressions) create storm surges—a temporary rise in sea level where a 1 millibar pressure drop causes a 1 cm rise in the sea. Winter storms severely accelerate coastal retreat by providing high-energy waves and heavy rainfall.
To fully analyse coastal retreat, you must explain how climate, sub-aerial, and marine processes interact to change specific landforms:
1. The Retreat Cycle (Wave-cut Platform Formation)
2. Arch and Stack Collapse
A stretch of coastline erodes by 85 metres over a period of 17 years. Calculate the average annual rate of coastal retreat.
Step 1: State the formula.
Step 2: Substitute the values.
Step 3: Calculate the final answer with units.
Students frequently confuse abrasion with attrition. Remember the 'sandpaper' analogy for abrasion (which erodes the cliff face) and 'clashing rocks' for attrition (which only breaks down the sediment).
In exam questions about hydraulic action, always use the specific phrase 'compresses air into cracks' to secure maximum marks.
If asked to draw or annotate longshore drift, you must clearly label the swash moving at an angle (matching the prevailing wind) and the backwash moving straight down the beach at a 90-degree angle.
When tackling 'Analyse' questions about landform change, you MUST link sub-aerial and marine processes. For example, explain that an arch collapses because sub-aerial weathering thins the roof while marine erosion widens the base.
To explain the formation of a wave-cut platform, ensure you mention the 'wave-cut notch' as the starting point of undercutting.
When discussing mass movement, link geology to the process: 'Slumping' is specific to unconsolidated material like boulder clay, whereas 'Rockfall' happens on consolidated hard rock like limestone.
Fetch
The maximum distance of open water over which the wind has blown to create waves.
Prevailing wind
The most frequent wind direction (in the UK, this is from the South-West).
Hydraulic action
The force of waves smashing against cliffs, compressing trapped air into cracks and explosively shattering the rock.
Longshore drift
The zig-zag movement of sediment along a coastline caused by waves approaching at an angle and returning at right angles due to gravity.
Traction
Large boulders and rocks are rolled along the seabed by the force of moving water.
Saltation
Small pebbles and stones are 'hopped' or bounced along the seabed.
Suspension
Fine light material (like silt or clay) is carried along within the water column.
Solution
A chemical reaction where mildly acidic seawater dissolves certain alkaline rock types like chalk or limestone.
Deposition
The process where the sea loses energy and drops the sediment it is carrying.
Weathering
The breakdown or disintegration of rock in situ (in its original place) by the atmosphere, plants, or animals.
Sub-aerial processes
Land-based processes, such as weathering and mass movement, that alter the cliff face above the high-tide mark.
Mechanical weathering
The physical breakdown of rock without changing its chemical composition (e.g., freeze-thaw).
Chemical weathering
The breakdown of rock through chemical changes, often involving acidic rain reacting with minerals.
Biological weathering
The breakdown of rocks by living things, such as plant roots growing into cracks or animals burrowing.
Carbonation
A form of chemical weathering where weak carbonic acid in rainwater reacts with calcium carbonate in rocks like limestone.
Mass movement
The downward, gravity-driven movement of rock, soil, or mud down a slope.
Slumping
A type of mass movement where saturated, unconsolidated material moves down a slope with a rotational motion along a curved slip plane.
Rockfall
A type of mass movement where fragments of rock break away from a steep cliff face, often triggered by freeze-thaw weathering.
Landslides
The downward movement of a large block of material moving along a straight slip plane.
Boulder clay
Unconsolidated, soft glacial deposit (also known as till) that erodes rapidly.
Temperate Maritime
The UK's climate, characterized by cool, wet winters and warm, wet summers.
Storm surges
A temporary rise in local sea level caused by low atmospheric pressure and strong winds.
Destructive waves
High-energy waves with a strong backwash that remove sediment from a beach and erode the coast.
Constructive waves
Low-energy waves with a strong swash that deposit sediment and build up beaches.
Abrasion
The 'sandpaper' effect of waves hurling sediment against a cliff face, wearing it away.
Attrition
The process where rocks carried by the sea collide and break into smaller, smoother fragments.
Freeze-thaw
A type of mechanical weathering where water in cracks expands by 9% upon freezing, shattering the rock.
Wave-cut notch
An undercut at the base of a cliff created by marine erosion at the high-tide mark.
Wave-cut platform
A rocky, gently sloping area at the base of a cliff, left behind as the cliff retreats inland.
Stack
An isolated pillar of rock left standing in the sea after the roof of an arch has collapsed.
Put your knowledge into practice — try past paper questions for Geography B
Fetch
The maximum distance of open water over which the wind has blown to create waves.
Prevailing wind
The most frequent wind direction (in the UK, this is from the South-West).
Hydraulic action
The force of waves smashing against cliffs, compressing trapped air into cracks and explosively shattering the rock.
Longshore drift
The zig-zag movement of sediment along a coastline caused by waves approaching at an angle and returning at right angles due to gravity.
Traction
Large boulders and rocks are rolled along the seabed by the force of moving water.
Saltation
Small pebbles and stones are 'hopped' or bounced along the seabed.
Suspension
Fine light material (like silt or clay) is carried along within the water column.
Solution
A chemical reaction where mildly acidic seawater dissolves certain alkaline rock types like chalk or limestone.
Deposition
The process where the sea loses energy and drops the sediment it is carrying.
Weathering
The breakdown or disintegration of rock in situ (in its original place) by the atmosphere, plants, or animals.
Sub-aerial processes
Land-based processes, such as weathering and mass movement, that alter the cliff face above the high-tide mark.
Mechanical weathering
The physical breakdown of rock without changing its chemical composition (e.g., freeze-thaw).
Chemical weathering
The breakdown of rock through chemical changes, often involving acidic rain reacting with minerals.
Biological weathering
The breakdown of rocks by living things, such as plant roots growing into cracks or animals burrowing.
Carbonation
A form of chemical weathering where weak carbonic acid in rainwater reacts with calcium carbonate in rocks like limestone.
Mass movement
The downward, gravity-driven movement of rock, soil, or mud down a slope.
Slumping
A type of mass movement where saturated, unconsolidated material moves down a slope with a rotational motion along a curved slip plane.
Rockfall
A type of mass movement where fragments of rock break away from a steep cliff face, often triggered by freeze-thaw weathering.
Landslides
The downward movement of a large block of material moving along a straight slip plane.
Boulder clay
Unconsolidated, soft glacial deposit (also known as till) that erodes rapidly.
Temperate Maritime
The UK's climate, characterized by cool, wet winters and warm, wet summers.
Storm surges
A temporary rise in local sea level caused by low atmospheric pressure and strong winds.
Destructive waves
High-energy waves with a strong backwash that remove sediment from a beach and erode the coast.
Constructive waves
Low-energy waves with a strong swash that deposit sediment and build up beaches.
Abrasion
The 'sandpaper' effect of waves hurling sediment against a cliff face, wearing it away.
Attrition
The process where rocks carried by the sea collide and break into smaller, smoother fragments.
Freeze-thaw
A type of mechanical weathering where water in cracks expands by 9% upon freezing, shattering the rock.
Wave-cut notch
An undercut at the base of a cliff created by marine erosion at the high-tide mark.
Wave-cut platform
A rocky, gently sloping area at the base of a cliff, left behind as the cliff retreats inland.
Stack
An isolated pillar of rock left standing in the sea after the roof of an arch has collapsed.