UK Physical Landscapes: Overview and Weathering
The UK's Diverse Physical Landscape
The UK has a remarkably varied physical landscape for its small size, shaped by millions of years of geological processes, past glaciation, and ongoing erosion and deposition.
Upland and Lowland Areas
- Upland areas are found mainly in the north and west — Scottish Highlands, Lake District, Snowdonia, Pennines, Dartmoor
- Lowland areas dominate the south and east — East Anglia, the Midlands, London Basin, Hampshire Basin
- This pattern reflects the underlying geology — older, harder rocks (granite, slate, gneiss) in the north and west; younger, softer rocks (chalk, clay, sandstone) in the south and east
Major Rock Types
| Rock Type | Characteristics | Location Examples |
|---|---|---|
| Granite | Very hard igneous rock; resistant to erosion; forms tors and moorland | Dartmoor, Cairngorms, Land's End |
| Slate | Hard metamorphic rock; splits into thin layers; resistant | Snowdonia, Lake District |
| Limestone (Carboniferous) | Sedimentary; permeable (water passes through joints and bedding planes); forms caves, pavements, gorges | Yorkshire Dales, Peak District, Mendips |
| Chalk | Soft sedimentary; permeable; forms rolling hills (downs) and white cliffs | South Downs, North Downs, White Cliffs of Dover |
| Clay | Soft sedimentary; impermeable; forms flat lowlands; fertile but waterlogged | London Basin, Vale of York, Weald |
| Sandstone | Sedimentary; variable hardness; porous | New Red Sandstone (Midlands), Millstone Grit (Pennines) |
Weathering
Weathering is the breakdown of rocks in situ (in place) — the rock is weakened and broken down without being moved (unlike erosion, which involves movement).
Mechanical (Physical) Weathering
Freeze-thaw weathering:
1. Water enters cracks and joints in rock
2. Temperature drops below 0°C — water freezes and expands by approximately 9%
3. This expansion exerts pressure on the rock, widening the crack
4. When the temperature rises, the ice melts and water seeps deeper
5. Repeated cycles of freezing and thawing shatter the rock into angular fragments
6. Broken rock collects at the base of cliffs as scree
- Most effective where temperatures fluctuate around 0°C frequently (e.g. mountain environments, UK winters)
Onion-skin weathering (exfoliation):
- In hot environments, the outer layers of rock expand during the day and contract at night
- Repeated expansion and contraction causes the outer layers to peel off like the layers of an onion
- Common in desert environments (less relevant to UK but included in the specification)
Chemical Weathering
Carbonation:
1. Rainwater absorbs CO₂ from the atmosphere, forming a weak carbonic acid
2. This acid reacts with calcium carbonate in limestone and chalk
3. The calcium carbonate dissolves, forming calcium bicarbonate (which is soluble in water)
4. Over time, this creates features like limestone pavements (clints and grykes), caves, and swallow holes
- Chemical equation: CaCO₃ + H₂O + CO₂ → Ca(HCO₃)₂
- Carbonation is more effective in warm, wet climates (chemical reactions speed up with heat)
Oxidation:
- Iron in rocks reacts with oxygen and water, forming iron oxide (rust)
- Weakens the rock, making it crumble — often visible as orange/brown discolouration
Hydrolysis:
- Water reacts chemically with minerals in rock (especially feldspar in granite), decomposing them
- Particularly effective on granite — turns feldspar to clay (kaolin/china clay)
Biological Weathering
- Plant roots grow into cracks in rock, widening them as roots expand
- Burrowing animals (rabbits, earthworms) break up rock and soil
- Algae, lichens, and mosses produce weak acids that chemically weather rock surfaces
- Organic acids from decaying vegetation dissolve rock minerals
Mass Movement
Mass movement is the downhill movement of material under the influence of gravity. It is a key process in shaping landscapes, particularly along coastlines and in river valleys.
| Type | Description | Speed | Material |
|---|---|---|---|
| Rockfall | Fragments of rock break away from a cliff face (often due to freeze-thaw) and fall | Very fast | Rock fragments |
| Landslide | A block of rock slides downhill along a flat surface (e.g. a bedding plane) | Fast | Rock |
| Mudflow | Saturated soil and rock flows downhill as a liquid mass | Moderate to fast | Saturated soil/clay |
| Slumping (rotational slip) | Saturated material slides downhill along a curved slip plane; common in clay cliffs | Slow to moderate | Clay, soil |
| Soil creep | Very slow movement of soil particles downhill; causes terracettes (small step-like ridges) on hillsides | Very slow | Soil |
Factors Affecting Mass Movement
- Slope angle — steeper slopes increase gravitational force
- Water content — saturated soil is heavier and acts as a lubricant; reduces friction
- Rock/soil type — clay becomes slippery when wet; loose sediments are less stable
- Vegetation — roots bind soil and absorb water; deforested slopes are more vulnerable
- Undercutting — wave erosion at the base of a cliff or river erosion at the base of a valley removes support
- Human activity — construction, quarrying, deforestation increase instability
Exam tip: Weathering and mass movement are often confused. Remember: weathering breaks down rock in place (no movement); mass movement moves material downhill under gravity; erosion involves movement by a specific agent (water, wind, ice). Use these terms precisely in exam answers — examiners reward accurate use of terminology.