G22: Coastal Landforms
Erosional landforms including headlands and bays, cliffs, wave-cut platforms, caves, arches and stacks, and depositional landforms including beaches, spits and bars.
⛏️ Erosional Coastal Landforms
Key Principle: Erosional landforms are created where the coastline is being worn back by wave action. The type of landform depends on the geology (hard vs soft rock), the wave energy, and the existing shape of the coastline.
Headlands and Bays
Headlands and bays form on discordant coastlines where bands of hard and soft rock run at right angles to the sea:
- Soft rock (clay, sandstone) erodes faster, retreating inland to form bays
- Hard rock (limestone, chalk, basalt) erodes more slowly, sticking out as headlands
- Bays have gentle, sandy beaches where deposited sediment collects in the sheltered water
- Headlands experience concentrated wave energy due to wave refraction
Example: Swanage Bay and Ballard Point
The Dorset coastline near Swanage shows classic headland and bay formation. Swanage Bay has formed in soft clay and sands, while the hard chalk of Ballard Point and the Purbeck limestone of Peveril Point project as headlands on either side. The bay provides a sheltered area where sediment accumulates to form a sandy beach.
Discordant vs Concordant: A discordant coastline has rock bands at right angles to the sea (headlands and bays). A concordant coastline has rock bands running parallel to the sea (like the Dorset coast with Lulworth Cove).
Cliffs and Wave-Cut Platforms
Cliff and Wave-Cut Platform Formation:
1. Waves erode the base of the cliff through hydraulic power and abrasion
2. A wave-cut notch develops at the cliff base, undercutting the rock above
3. The overhanging cliff becomes unstable and collapses (mass movement)
4. The collapsed material is washed away, exposing the cliff base to further erosion
5. As the cliff retreats inland, a flat, rocky wave-cut platform is left exposed at low tide
1. Waves erode the base of the cliff through hydraulic power and abrasion
2. A wave-cut notch develops at the cliff base, undercutting the rock above
3. The overhanging cliff becomes unstable and collapses (mass movement)
4. The collapsed material is washed away, exposing the cliff base to further erosion
5. As the cliff retreats inland, a flat, rocky wave-cut platform is left exposed at low tide
- Cliffs are steep or vertical rock faces formed by the continuous retreat of the coastline
- Wave-cut platforms are flat, rocky surfaces exposed at low tide, marking the former position of the cliff
- Platforms are typically 30-500 metres wide depending on the rate of cliff retreat and tidal range
- The process is most active during storms when wave energy is highest
Caves, Arches, Stacks and Stumps
These landforms form on headlands where wave energy is concentrated by wave refraction:
Formation Sequence:
Cave → Waves exploit weakness (crack/joint) in headland by hydraulic power and abrasion, enlarging it into a cave
Arch → Cave erodes right through the headland, creating a tunnel/bridge of rock above
Stack → Roof of the arch collapses due to weathering and gravity, leaving an isolated pillar of rock
Stump → Stack is further eroded and reduced in size, eventually becoming a small stump visible at low tide
Cave → Waves exploit weakness (crack/joint) in headland by hydraulic power and abrasion, enlarging it into a cave
Arch → Cave erodes right through the headland, creating a tunnel/bridge of rock above
Stack → Roof of the arch collapses due to weathering and gravity, leaving an isolated pillar of rock
Stump → Stack is further eroded and reduced in size, eventually becoming a small stump visible at low tide
| Landform | Formation | Example |
|---|---|---|
| Cave | Waves erode weakness in headland cliff face | Fingal's Cave, Staffa (Scotland) |
| Arch | Cave erodes through headland creating an opening | Durdle Door, Dorset |
| Stack | Arch roof collapses, leaving isolated rock pillar | Old Harry Rocks, Dorset |
| Stump | Stack is eroded down to a small rocky stump | Old Harry's wife (collapsed in 2023 area) |
Case Study: Old Harry Rocks, Dorset
Old Harry Rocks are chalk stacks at the eastern end of the Jurassic Coast, near Studland Bay. The chalk headland has been eroded to form a series of stacks. Old Harry is the main stack, standing approximately 20 metres tall. The original arch collapsed, leaving the stack separated from the cliff. The chalk is gradually being further eroded - another stack nearby (known as Old Harry's Wife) collapsed in the 19th century. The stacks demonstrate the cave → arch → stack → stump sequence in action.
🏖️ Depositional Coastal Landforms
Key Principle: Depositional landforms form where wave energy decreases and sediment is deposited. They are made from sand, shingle and other sediment transported by longshore drift and currents.
Beaches
Beaches are the most common depositional landform, found in sheltered bays and along low-energy coastlines:
- Sandy beaches: Form where fine sediment is deposited by constructive waves in sheltered bays; gentle gradient
- Shingle beaches: Form where larger pebbles and gravel are deposited by powerful waves; steeper gradient
- Sand dunes: Wind blows sand from the beach inland, forming dune systems behind the beach
- Beach profile changes seasonally - constructive waves build beaches in summer, destructive waves remove material in winter
Spits
Definition: A spit is a long, narrow ridge of sand and shingle that extends from the coast into the sea, formed by longshore drift depositing sediment where the coastline changes direction or where wave energy decreases.
- Longshore drift transports sediment along the coast
- When the coastline changes direction (e.g., at a river mouth or bay), sediment continues to be deposited in the same direction
- The spit grows out into the sea, extending across the bay or estuary
- The end of the spit curves round (a recurved spit) due to wave refraction or changes in wind direction
- Sheltered water behind the spit accumulates fine sediment, forming salt marshes
- Storm waves may create a temporary breach or overwash
Example: Spurn Head, Yorkshire
Spurn Head is a 5.5 km long spit at the mouth of the Humber Estuary. It is formed by longshore drift transporting approximately 500,000 tonnes of boulder clay sediment southwards each year from the Holderness Coast. The spit curves at its tip due to wave refraction from the North Sea. Salt marshes have developed in the sheltered water behind the spit. In 2013, a storm surge breached the spit, demonstrating how dynamic these landforms are.
Bars and Tombolos
| Landform | Formation | Example |
|---|---|---|
| Bar | A spit grows right across a bay, joining two headlands and cutting off a lagoon behind | Chesil Beach, Dorset (29 km shingle bar with the Fleet lagoon behind) |
| Tombolo | A spit or bar connects the mainland to an offshore island | Chesil Beach also connects Portland to the mainland |
| Offshore bar | Sediment is deposited parallel to the coast in shallow water, exposed at low tide | Common along sandy coastlines with gentle offshore gradients |
Sand Dunes
- Wind blows sand from the dry beach up and inland
- Obstacles (driftwood, plants) trap sand, forming small mounds
- Marram grass colonises the dunes; its deep root system stabilises the sand
- Dunes grow as more sand is trapped by vegetation
- The youngest dunes (embryo dunes) are nearest the sea; the oldest (grey dunes) are furthest inland
- Dune systems act as a natural coastal defence, absorbing wave energy
📊 Factors Affecting Landform Type
| Factor | Effect on Landforms |
|---|---|
| Geology | Hard rocks → headlands, cliffs, stacks; Soft rocks → bays, beaches |
| Wave energy | High energy → erosional landforms; Low energy → depositional landforms |
| Coastline shape | Irregular → differential erosion; Straight → uniform retreat |
| Sediment supply | Abundant → beaches, spits, bars; Scarce → rocky cliffs and platforms |
| Human activity | Sea walls, groynes and dredging modify natural processes |
❓ Practice Questions
Q1: Describe the formation of a wave-cut platform. (4 marks)
Q2: Explain the sequence from cave to stump on a headland. (4 marks)
Q3: Using a named example, explain how a spit forms. (4 marks)
Q4: Compare erosional and depositional coastal landforms. (6 marks)
Q5: "Geology is the most important factor in determining coastal landforms." To what extent do you agree? (9 marks)
✅ Answers
- Waves erode the base of the cliff through hydraulic power and abrasion, creating a wave-cut notch (1 mark). The notch undercuts the cliff above, making it unstable (1 mark). The overhanging cliff collapses through mass movement, and the debris is washed away (1 mark). As the cliff retreats inland, a flat rocky platform is left exposed at low tide, marking the former position of the cliff (1 mark).
- Waves exploit a weakness (crack or joint) in the headland through hydraulic power, enlarging it into a cave (1 mark). The cave is eroded right through the headland by wave action, creating an arch of rock above a tunnel (1 mark). Weathering and erosion weaken the roof of the arch until it collapses, leaving an isolated pillar of rock called a stack (1 mark). The stack is further eroded by waves and weathering, reducing it to a small stump visible at low tide (1 mark).
- Spurn Head in Yorkshire is a 5.5 km long spit formed by longshore drift. Prevailing north-easterly waves transport sediment southwards along the Holderness Coast (1 mark). When the coastline changes direction at the Humber Estuary, longshore drift continues to deposit sediment in the same direction, extending the spit out into the estuary (1 mark). The end of the spit curves round (recurved) due to wave refraction changing the direction of wave approach (1 mark). Behind the spit, sheltered water allows fine sediment to accumulate, forming salt marshes (1 mark).
- Erosional landforms are created where wave energy wears back the coastline - headlands form where hard rock resists erosion, while bays form where soft rock retreats (1 mark). Cliffs and wave-cut platforms form through undercutting and cliff collapse (1 mark). Caves, arches and stacks develop on headlands where concentrated wave energy exploits weaknesses (1 mark). Depositional landforms form where wave energy decreases and sediment accumulates - beaches form in sheltered bays from constructive wave deposition (1 mark). Spits extend from the coast where longshore drift deposits sediment across bays or river mouths (1 mark). Bars and tombolos form when spits grow to connect headlands or islands (1 mark). Erosional landforms dominate on exposed, high-energy coastlines, while depositional landforms dominate in sheltered, low-energy areas.
- I agree that geology is very important because rock type determines whether a coastline features erosional or depositional landforms - hard resistant rocks like chalk and limestone form headlands, cliffs, caves and stacks, while soft rocks like clay form bays (1 mark). Discordant coastlines with alternating hard and soft rock produce the classic headland and bay pattern, while concordant coastlines produce more uniform features (1 mark). The geological structure (joints, faults, bedding planes) controls where caves and arches develop (1 mark). However, wave energy is also crucial - high-energy coasts experience more erosion regardless of geology, while low-energy coasts favour deposition (1 mark). Sediment supply is important for depositional landforms - without a supply of material, beaches, spits and bars cannot form (1 mark). The shape of the coastline affects wave refraction, concentrating energy on headlands (1 mark). Human activity can override natural processes through coastal defences that alter sediment transport (1 mark). Climate and sea level change are also significant factors over longer timescales (1 mark). On balance, geology provides the fundamental template, but the interaction of geology with wave energy, sediment supply and coastal shape determines the specific landforms that develop (1 mark).
🎯 Exam Tips
- Learn the formation sequence: cave → arch → stack → stump
- Always use named examples for each landform (Old Harry Rocks, Spurn Head, Chesil Beach)
- Use annotated diagrams in your answers where possible
- Distinguish clearly between discordant (headlands/bays) and concordant coastlines
- For spits, always mention longshore drift, the change in coastline direction, and the recurved end
- Link each landform to the processes that create it - don't just describe the shape
📝 Exam Technique
Geography Exam Tips — Coastal Landforms:
1. For Coastal Landforms questions, always name specific case studies with factual detail
2. Use geographical terminology precisely (e.g. specific processes, not vague descriptions)
3. Consider social, economic and environmental perspectives in your evaluations
4. Support your points about Coastal Landforms with data, statistics or named examples
5. For 'assess' or 'evaluate' questions, reach a clear judgement supported by evidence
1. For Coastal Landforms questions, always name specific case studies with factual detail
2. Use geographical terminology precisely (e.g. specific processes, not vague descriptions)
3. Consider social, economic and environmental perspectives in your evaluations
4. Support your points about Coastal Landforms with data, statistics or named examples
5. For 'assess' or 'evaluate' questions, reach a clear judgement supported by evidence
⚠️ Common Errors
Watch Out!
Students often write vague answers without specific geographical evidence. Wrong: Writing generalised statements like 'it causes problems' Correct: Using specific data and named examples, e.g. 'the 2010 Haiti earthquake killed over 200,000 people due to poor building quality'
Students often confuse causes and effects. Wrong: Mixing up what caused the event with what resulted from it Correct: Clearly separate causes (why it happened) from effects (what happened as a result)
Students often describe rather than evaluate. Wrong: Listing strategies without assessing their effectiveness Correct: Weighing up strengths and weaknesses of each approach and reaching a supported judgement
✍️ Model Answer
Full-Mark Response
6 marks: Explain the key factors affecting coastal landforms.
Coastal Landforms involves multiple interconnected factors that geographers must understand. The key concepts include the processes that create and change coastal landforms, the impacts on both people and environment, and the strategies used to manage associated challenges. For a comprehensive answer, specific case study evidence should be used throughout, with named examples and data to support each point. Geographical terminology should be used precisely, and the interrelationship between physical and human factors should be demonstrated. Top-level responses evaluate the relative importance of different factors and consider how the situation varies between locations.
Mark scheme: 2 marks for identifying key factors, 2 marks for explaining processes with detail, 2 marks for using specific evidence
📊 AO Deep Dive
Assessment Objective Analysis
AO1 requires knowledge of the key facts and processes related to coastal landforms. AO2 demands understanding of how and why these processes operate, and their implications. AO3 asks you to analyse, evaluate and make judgements — this is where grade 9 answers stand out by weighing up competing perspectives and reaching supported conclusions. AO4 may involve interpreting maps, graphs or data related to this topic. To move from grade 5 to grade 9: use precise geographical terminology, support every point with specific case study evidence, and always evaluate rather than just describe.
📝 Exam Questions by Topic
🎬 Video Resources
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