What is the impact of UK climate and sub-aerial processes on coastal landscapes?

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Edexcel B GCSE Geography > The UK’s Evolving Physical Landscape > What is the impact of UK climate and sub-aerial processes on coastal landscapes?

The shape of the UK’s coastline is not only affected by wave action and geology, but climate, weathering, and mass movement also play a significant role. These physical factors all interact to speed up or slow down coastal erosion and cliff retreat.

️Climate and Seasonality

The UK experiences seasonal variations in temperature and rainfall, which affect rates of weathering and erosion:

In winter, stronger winds, heavier rainfall, and cold temperatures increase the risk of cliff collapse.
During cold nights and milder days, freeze–thaw weathering is a common phenomenon. Water enters cracks, freezes and expands, then thaws and contracts – eventually breaking rock apart.
In summer, chemical weathering speeds up as temperatures rise, especially on cliffs made of rock like limestone.

These seasonal changes mean erosion and mass movement are more intense in winter, leading to faster coastal retreat during stormier months.

Prevailing Winds and Storm Frequency

The UK’s prevailing wind direction is from the southwest. These winds blow across the Atlantic Ocean, often bringing moisture and storms:

Strong, frequent winds create high-energy waves that batter the coast.
These winds are especially powerful in winter, which explains why cliff erosion is usually faster in colder months.
Storm surges and high tides increase the height and power of waves, putting even more stress on cliffs.

This combination of weather conditions means the UK’s coast is often exposed to rapid erosion.

Marine Processes: Destructive Waves

Winds are seasonal, and the strongest are in winter. Friction from wind blowing over the surface of the sea causes waves. Wave size depends on:

The strength of the wind.
How long the wind blows for.
The length of water the wind blows over (known as the fetch).

Winds are strongest in autumn and winter, leading to the formation of destructive waves. Destructive waves are the main cause of coastal erosion:

They have a high frequency, short wavelength, and steep gradient.
Their strong backwash scours the beach and drags material away.
They erode cliffs through hydraulic action, abrasion, and solution.

The characteristics of a destructive wave

Destructive waves are common in stormy conditions and are more powerful during the winter, speeding up the rate of cliff collapse and coastal retreat.

️Sub-aerial Processes: Weathering

Sub-aerial processes happen above the influence of the sea, but they still contribute to coastal erosion by weakening the rock:

Mechanical Weathering

Freeze-thaw: Water freezes and expands in cracks, splitting the rock apart.
Common in winter, especially in upland coastal areas.

Chemical Weathering

Rainwater is naturally slightly acidic.
It reacts with rocks like limestone and chalk, causing them to dissolve.
More effective in warm, wet climates.

Biological Weathering

Tree roots grow into cracks in the rock and force them wider.
Burrowing animals like rabbits can loosen soil, triggering small collapses.

All types of weathering make cliffs unstable, increasing the risk of erosion and mass movement.

Sub-aerial Processes: Mass Movement

Processes of mass movement

Mass movement is the downhill movement of material due to gravity. It’s often triggered by heavy rainfall, undercutting by waves, and unstable geology:

Mass movement	Characteristics
Slumping	Saturated clay slides down in a curved motion (common on coastal cliffs).
Rockfall	Loose rocks break off and fall quickly, often caused by freeze–thaw weathering.
Landslide	Large blocks of material move downhill in one piece.
Soil creep	Slow movement of soil downhill due to freeze/thaw or wet/dry cycles.
Flow	Saturated soil and debris flow rapidly downhill during heavy rain.

These processes don’t directly involve the sea, but they contribute to the retreat of the coastline by causing large sections of cliffs to collapse.

The Combined Effect: Why Coastal Retreat Happens Faster

The rate of coastal retreat depends on the interaction of all these factors:

In winter, destructive waves, heavy rainfall, freeze–thaw weathering, and mass movement combine to cause rapid cliff erosion.
In summer, erosion slows down, but chemical weathering may still occur.

The UK’s climate and geology mean that coastal retreat is an ongoing, natural process, but its rate of progression can vary depending on weather conditions, storm events, and wave energy.

Summary

UK Climate and Seasonality
The UK’s coastal erosion is seasonal. In winter, cold temperatures increase freeze–thaw weathering, and stronger winds generate more destructive waves, thereby accelerating erosion.
Prevailing Winds and Storms
The south-west prevailing winds bring frequent storms, heavy rain, and high tides. These lead to powerful waves that batter the coastline and increase cliff retreat.
Destructive Waves
Destructive waves have a steep profile and a strong backwash. They erode coastlines using processes like hydraulic action, abrasion, and solution, especially during stormy weather.
Mechanical Weathering
Freeze–thaw weathering occurs when water enters cracks in rocks, freezes and expands, splitting the rock apart. It’s common in winter in upland coastal areas.
Chemical and Biological Weathering
Chemical weathering dissolves rocks like limestone using slightly acidic rainwater. Biological weathering happens when plant roots widen cracks and animals loosen soil.
Mass Movement and Cliff Collapse
Heavy rainfall and undercutting by waves can trigger mass movements like slumping, rockfalls and landslides. These processes accelerate coastal retreat.