Geography Notes: Coastal Landscapes
- Isle of Wight Case Study
Overview: The Isle of Wight as a Coastal Microcosm
The Isle of Wight serves as an excellent case study for coastal processes,
representing a microcosm of Southeast England’s geology. The island’s geology
is identical to Surrey and Sussex but in miniature, making it ideal for studying diverse
coastal landforms and processes.
1. GEOLOGICAL STRUCTURE & ROCK TYPES
Rock Types and Ages
Cretaceous Chalk (65 million years old)
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Most resistant rock on the island
Forms headlands at The Needles and St. Catherine’s Point
Laid down during the mass extinction of dinosaurs
Contains calcium carbonate that dissolves in seawater
Wealden Rocks (120 million years old)
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Older but less resistant than chalk
Include clays, sandstones, and green sand
Contain dinosaur fossils due to their Jurassic period origin
Green sand contains glauconite mineral that turns green when exposed to
atmosphere
Geological Structure
Upper Greensand Series
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Chalk (top layer) - permeable
Chert - permeable
Clay - impermeable (crucial for mass movement)
Green Sand - permeable
Angle of Dip: Rocks dip down towards the English Channel, creating instability
2. COASTAL PROCESSES
Wave Energy and Fetch
Prevailing Winds: Southwest direction
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Maximum fetch from the Caribbean/Atlantic
Destructive waves dominate the southwest coast
Processes: Hydraulic action, abrasion, attrition, corrasion
Longshore Drift
Northern Coast: West to East movement
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Southern Coast: Complex bidirectional patterns
Material transported by solution, suspension, saltation, traction
3. SOUTHWEST COAST - EROSION DOMINATED
Rate of Erosion
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2 meters per year at Compton Bay - fastest rate on the island
Caused by: maximum fetch + prevailing winds + weak rocks
Erosional Features
Headlands and Bays
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The Needles (chalk headland)
St. Catherine’s Point (chalk headland)
Freshwater Bay and Compton Bay (less resistant rock areas: Clay &
Sandstone)
Discordant coastline created by differential erosion
Scientific Importance
SSSI Status (Site of Special Scientific Interest)
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No coastal defenses allowed
Continuous erosion reveals dinosaur fossils
Natural laboratory for studying coastal processes
4. SOUTHEAST COAST - MASS MOVEMENT
The Undercliff
Largest area of mass movement in Europe
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Extends 10 miles from St. Catherine’s to Monks Bay
Rotational slip is the dominant process
Causes of Mass Movement
Geological Factors:
1. Permeable rocks above impermeable clay layer
2. Angle of dip towards the sea
3. Water saturation during wet periods
Process Explanation:
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Rain percolates through chalk, chert, and green sand
Water meets impermeable clay layer
Creates slip plane along bedding planes
Rocks slide towards sea due to gravity + angle of dip
Historical Context
Pluvial Period (4,500 years ago)
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Wetter climate than today
Major rotational slips occurred during this period
Continues today but at smaller scale
Human Impact: Ventnor
Victorian Development
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Town built on unstable undercliff area
1950s: Buildings developed cracks and structural damage
Now sparsely populated with “bohemian” character
Example of poor land-use planning
5. NORTHERN COAST – DEPOSITIONAL COAST
Yarmouth - Multi-Feature Depositional Site
Features Present:
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Beach (20-30 meters wide, sandy with stones)
Norton Spit (trying to seal harbor entrance)
Salt marsh (halosere succession)
Sand dunes (psammosere succession) - aeolian features
Groynes (Victorian coastal management to maintain ferry port)
Newtown Nature Reserve
Historical Context:
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Former Roman capital (2,000 years ago)
Now salt marsh due to sea level rise
Estuary formation: drowned river valley
Demonstrates long-term coastal change
Medina Estuary
Formation: Drowned river valley due to post-glacial sea level rise
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Sheltered harbour for yachting industry
East and West Cowes - major ports
Site of Cowes Week international regatta
Ride Sands - Cuspate Foreland
Formation Process:
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Two longshore drift systems meet
Bidirectional deposition creates shark fin-shaped feature
Extends 3-4 miles into sea
Railway pier built to reach deep water for ferry access
6. SUBAERIAL PROCESSES
Weathering Types
Physical Weathering: Freeze-thaw, salt crystallization Chemical Weathering:
Solution of limestone, oxidation Biological Weathering: Root action, organic acids
Mass Movement Types
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Rotational slip (primary type on Isle of Wight)
Landslides and landslips
Rock falls
Soil creep (smallest scale)
Succession
Psammosere (sand dune succession):
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Pioneer species → grasses → shrubs → climax vegetation
Halosere (salt marsh succession):
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Pioneer halophytes → salt-tolerant grasses → scrubland
7. COASTAL MANAGEMENT IMPLICATIONS
Feedback Systems
Positive Feedback loop:
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Erosion → undercutting → more mass movement → more material for erosion
Negative Feedback loop:
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Mass movement → debris barrier → reduced wave energy → slower erosion
Denudation Concept
Definition: General wearing away of coastline through:
1. Marine erosion (waves)
2. Subaerial weathering
3. Mass movement
All three processes working together cause overall landscape retreat.
8. TEMPORAL CHANGES
Geological Time
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120 million years: Wealden rocks formation
65 million years: Chalk formation (Cretaceous period)
15,000 years: Post-glacial sea level rise
4,500 years: Major mass movement (pluvial period)
2,000 years: Human settlement (Roman period)
Modern Rates
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Erosion: 2m/year (Compton Bay)
Mass movement: Continues but smaller scale than prehistoric
Deposition: Ongoing longshore drift processes
Key Examination Points
Process Understanding: Link geological structure to coastal processes Human
Interaction: Ventnor case study shows planning challenges
Temporal Scale: Different processes operate over different timescales Systems
Approach: Feedback mechanisms between processes Management: SSSI
designation vs. human development needs Comparative Analysis: Contrasting
north (deposition) vs. southwest (erosion) coasts
This case study exemplifies how geological structure fundamentally controls
coastal morphology and processes, making it an ideal example for demonstrating
the relationship between rock type, structure, and coastal landscape evolution.