Unit 8 Essays - Coastal Landforms UPDATED Flashcards
Assess the extent to which rock type and rock structure are important factors in explaining the characteristics of coastal cliffs.
Paragraph 1: How Rock Type (Lithology) Affects Coastal Cliffs
Point:
Different rock types erode at different rates, influencing the shape and stability of cliffs.
Soft rocks (e.g., clay, sand, glacial till) erode quickly, creating unstable, retreating coastlines.
Hard rocks (e.g., limestone, sandstone, chalk) erode slowly, leading to the formation of steep, rugged cliffs with distinct landforms.
Evidence (Case Studies):
Holderness Coast (East Yorkshire):
Soft glacial till (clay, sand, gravel) deposited during the Ice Age.
Erosion rate: 1.8m per year, making it one of the fastest eroding coastlines in Europe.
Cliffs are low, slumped, and prone to collapse due to weak material.
Jurassic Coast (Dorset):
Resistant limestone, sandstone, and chalk erode much slower.
Portland limestone erodes at only 1-2 mm per year, creating steep, dramatic cliffs.
Chalk cliffs (e.g., near Old Harry Rocks) form tall, vertical structures due to their hardness.
Development:
Spatial variation: Different coastlines experience different erosion rates based on their rock type.
Temporal variation: Over centuries to millennia, softer coasts retreat significantly while harder coasts form long-lasting features.
Paragraph 2: How Rock Structure Affects Cliff Stability and Shape
Point:
Rock structure (bedding planes, joints, faults) influences how cliffs break apart, their stability, and their overall form.
Evidence (Case Studies):
Holderness Coast:
Weakly consolidated glacial till lacks strong structure, leading to frequent slumping.
Waves easily erode loose material, leading to rapid cliff retreat.
Jurassic Coast:
Lulworth Cove:
Concordant coastline (hard rock outer layer, softer rock inside) allows erosion to create a circular bay.
Durdle Door:
Discordant coastline (alternating layers of hard and soft rock) leads to the formation of arches, stacks, and stumps.
Old Harry Rocks:
Chalk cliffs with joints and bedding planes allow differential erosion, leading to stacks and stumps.
Development:
Spatial variation: Different structural patterns create different landforms.
Temporal variation: Over thousands of years, faults and joints allow cliffs to erode into distinct shapes.
Paragraph 3: The Role of Marine Erosion in Cliff Development
Point:
While rock type and structure are important, wave energy and marine erosion can speed up or slow down cliff retreat.
Evidence (Case Studies):
Holderness Coast:
Powerful North Sea waves (long fetch) attack soft cliffs, rapidly eroding them.
Longshore drift removes sediment, preventing beaches from forming, leaving cliffs unprotected.
Jurassic Coast:
Old Harry Rocks: Waves erode softer sections, leaving behind harder rock as stacks.
Wave-cut platforms (e.g., Kimmeridge Bay) formed as waves wear away cliff bases.
Development:
Scale variation: Even hard rock coasts will erode over long timescales.
Human impact: Coastal defences can reduce erosion in some areas but cause increased erosion elsewhere.
Paragraph 4: The Impact of Weathering and Climate on Cliffs
Point:
Weathering weakens cliffs, making them more vulnerable to collapse.
Climate change is increasing the frequency of extreme weather events, accelerating cliff retreat.
Evidence (Case Studies):
Holderness Coast:
Heavy rainfall increases slumping by making clay-rich cliffs absorb water and become unstable.
Storm surges and rising sea levels increase wave attack, leading to faster erosion.
Jurassic Coast:
Freeze-thaw weathering in chalk cliffs causes expansion of cracks, leading to rockfalls.
Salt weathering weakens limestone cliffs over time.
Development:
Temporal variation: Climate change means erosion rates may increase in the future.
Spatial variation: Different climates influence erosion processes (e.g., wetter climates increase slumping).
Paragraph 5: Human Influence on Cliff Erosion
Point:
Human actions (coastal defences, land use) can increase or decrease erosion rates.
Evidence (Case Studies):
Holderness Coast:
Groynes at Mappleton protect some areas but increase erosion further south due to sediment starvation.
Sea walls protect towns but cause stronger wave energy at unprotected cliffs.
Jurassic Coast:
UNESCO protection means fewer hard defences; instead, managed retreat and beach nourishment are used.
Soft engineering helps preserve natural landscapes while reducing erosion.
Development:
Temporal variation: Human interventions can change erosion rates over decades.
Spatial variation: Some areas are protected while others erode faster.
Conclusion
Rock type and structure are key factors in determining how cliffs erode, their stability, and their shape.
Holderness Coast demonstrates how soft, weak rocks erode quickly, while the Jurassic Coast shows how hard, structured rocks resist erosion and form distinct landforms.
However, marine processes, weathering, and human activity also shape coastal cliffs.
The importance of rock type varies depending on location (spatial variation) and timescale (temporal variation).
Overall judgment: While rock type is a fundamental factor, it must be considered alongside waves, climate, and human actions to fully explain coastal cliff characteristics.
‘Sea-level rise affects coastal depositional landforms more than coastal erosional landforms.’ How far do you agree with this view?
Paragraph 1: Impact on Coastal Depositional Landforms (Tombolos, Barrier Beaches, and Barrier Islands)
Topic Sentence: Depositional landforms, made of loose sediments, are highly vulnerable to sea-level rise.
Key Examples and Evidence:
Tombolo at St Ninian’s Isle (Shetland):
Impact: Increased overwash events and sediment displacement.
Evidence: Narrowing of the tombolo due to rising seas and stronger wave action.
Slapton Sands (Devon):
Impact: Erosion rates of about 1 meter per year due to direct wave impact and reduced sediment supply.
Explanation: Rising seas push waves further inland, increasing erosion.
Outer Banks (North Carolina):
Impact: Retreat of 1.5–2.5 meters annually.
Cause: Higher sea levels and storm surges intensifying erosion.
Development Points:
Explain why loose sediment and low elevation make these landforms more susceptible.
Mention spatial variation: Barrier islands in subtropical regions face higher risks due to storm intensity.
Link: Connect to next paragraph by suggesting that other depositional features, like dunes and saltmarshes, also face severe impacts.
Paragraph 2: Impact on Sand Dunes, Saltmarshes, and Mudflats
Topic Sentence: Sand dunes, saltmarshes, and mudflats, which rely on vegetation and sediment balance, are heavily impacted by rising seas.
Key Examples and Evidence:
Formby Sand Dunes (Liverpool):
Impact: Retreating at 4 meters per year due to stronger waves and sediment removal.
The Wash (East England):
Impact: Increased inundation and vegetation loss, altering sediment dynamics.
Explanation: Higher sea levels lead to more frequent flooding, damaging saltmarsh plants.
Morecambe Bay Mudflats:
Impact: Increased erosion and sediment redistribution.
Cause: Higher tides spreading mud over a wider area.
Development Points:
Discuss temporal variation: These impacts are predicted to worsen with future sea-level rise.
Mention scale: Large-scale depositional areas (like deltas) face compounded risks due to human activities (e.g., dam construction reducing sediment supply).
Link: Suggest that depositional landforms formed by longshore drift, like spits and cuspate forelands, face similar threats.
Paragraph 3: Impact on Spits, Cuspate Forelands, and Low-Lying Beaches
Topic Sentence: Spits, cuspate forelands, and low-lying beaches, which depend on longshore drift, are extremely vulnerable to sea-level rise.
Key Examples and Evidence:
Spurn Head (Humber Estuary):
Impact: Eroding by over 3 meters per year in some parts.
Cause: Increased wave action and altered longshore drift patterns.
Dungeness (Cuspate Foreland):
Impact: Loss of sediment due to disrupted wave and current patterns.
Maldives (Low-Lying Beaches):
Risk: 80% of islands less than 1 meter above sea level face complete submersion.
Development Points:
Spatial variation: Low-lying tropical regions face higher risks due to storm surge and limited sediment supply.
Explain why longshore drift is disrupted by higher sea levels (increased depth changes wave energy and direction).
Link: Move to erosional landforms, suggesting that while these face less risk, they are not immune to rising seas.
Paragraph 4: Impact on Coastal Erosional Landforms (Cliffs, Wave-Cut Platforms, Headlands, Bays)
Topic Sentence: Erosional landforms, though more resistant, are also affected by sea-level rise, particularly softer rock types.
Key Examples and Evidence:
Holderness Coast (Yorkshire):
Impact: 2 meters per year of erosion due to soft clay cliffs and rising sea levels.
Kaikoura Wave-Cut Platforms (New Zealand):
Impact: Longer submersion periods increasing erosion rates.
Dorset Coast:
Features: Headlands, bays, arches, caves, stacks (e.g., Old Harry Rocks).
Impact: Higher sea levels intensifying wave attack on exposed rock faces.
Development Points:
Temporal variation: Erosional landforms take longer to show significant changes due to their harder structure.
Spatial variation: Softer coasts (e.g., Holderness) erode faster than rocky coasts (e.g., Dorset).
Link: Introduce submergent and emergent landforms to discuss more diverse impacts of sea-level rise.
Paragraph 5: Impact on Submergent and Emergent Landforms (Rias, Fjords, Raised Beaches, and Mangroves)
Topic Sentence: Submergent landforms face increased flooding, while emergent landforms show limited impacts unless they are low-lying.
Key Examples and Evidence:
River Fal Ria (Cornwall):
Impact: Increased saltwater intrusion and flooding.
Sognefjord (Norway):
Impact: Altered tidal dynamics due to rising sea levels.
Portland Raised Beach:
Limited Impact: Elevated above current sea levels, reducing direct impact.
Sundarbans Mangroves:
Impact: Losing 200 km² per year due to root submersion and erosion.
Development Points:
Temporal variation: Mangrove loss accelerating due to combined effects of sea-level rise and reduced sediment from rivers.
Scale: Large-scale mangrove systems (e.g., Sundarbans) face more severe impacts than isolated patches.
Link: Prepare for the conclusion by summarizing how depositional landforms face more immediate and severe risks.
Conclusion
Restate Thesis: Depositional landforms are more affected by sea-level rise than erosional landforms due to their unconsolidated nature and sediment dependence.
Key Summary:
Depositional landforms face faster and more significant changes.
Erosional landforms are impacted but at a slower rate.
Judgement: Strongly agree with the view that depositional landforms are more severely impacted.
Assess the relative importance of the factors influencing the formation of coastal saltmarshes and mangroves.
Paragraph 1: The Importance of Low-Energy Environments and Sediment Deposition
Point:
Both saltmarshes and mangroves require calm waters for sediment to accumulate, but mangroves can tolerate higher-energy environments.
Saltmarshes (The Wash example)
Sheltered locations: Develop in estuaries, behind spits, or in bays where waves and currents are weak.
Fine sediment: Need silt and clay deposition, brought in by rivers and tides.
The Wash (UK):
Large embayment in Eastern England
Tidal currents slow down, allowing fine mud deposition.
Mudflats gradually transition into saltmarshes as plants colonise the area.
Mangroves (The Sundarbans example)
More adaptable to moderate wave energy:
Mangroves can trap and stabilise sediment even in higher-energy environments.
Root adaptations:
Stilt roots (Rhizophora) slow down water, allowing sediment deposition.
Prop roots and pneumatophores help anchor trees in unstable mud.
Sundarbans (Bangladesh and India):
Located in a river delta, affected by strong tides but still supports vast mangrove forests.
Mangroves trap sediment, helping land build-up despite tidal fluctuations.
Evaluation:
Saltmarshes only develop where conditions are calm enough, while mangroves can survive a wider range of environments, making them more resilient in different coastal settings.
Paragraph 2: The Role of Halophytic (Salt-Tolerant) Vegetation in Stabilisation
Point:
Both ecosystems rely on vegetation to stabilise sediment and reduce tidal submergence.
Saltmarshes
Pioneer species (e.g., Spartina anglica) grow on mudflats, trapping sediment.
Vegetation succession:
More plants grow → marsh builds up → becomes less frequently submerged.
Over time, it transitions from mudflat → low marsh → high marsh.
Example: The Wash
Saltmarshes are expanding due to continuous sediment trapping.
However, high tides and storm surges can erode these areas, limiting long-term stability.
Mangroves
Greater stability due to deep-rooted trees:
Aerial roots (pneumatophores) allow gas exchange in waterlogged soils.
Buttress roots and prop roots prevent erosion, even in high-energy settings.
Example: The Sundarbans
Mangroves protect coastal areas from flooding and erosion, helping to stabilise an area that experiences high tidal action.
Dense root systems slow down water and encourage sediment accumulation.
Evaluation:
Mangroves provide more long-term stability than saltmarshes because they can survive stronger wave action.
Saltmarshes rely on vegetation succession, which can be reversed by erosion, while mangroves can maintain stability even in extreme conditions.
Paragraph 3: The Influence of Temperature and Climate
Point:
Temperature is a key spatial control: Saltmarshes dominate in cooler temperate regions, while mangroves dominate in warm tropical climates.
Saltmarshes (The Wash example)
Restricted to temperate climates (below 20°C year-round).
Plants like Spartina thrive in cool temperatures, but mangroves cannot survive in such climates.
Mangroves (The Sundarbans example)
Require temperatures above 20°C year-round.
Sundarbans average temperature: 26°C, perfect for mangroves to thrive.
More heat = faster plant growth, allowing faster land stabilisation.
Future changes (Climate Change impact)
Saltmarshes may retreat if rising temperatures allow mangroves to spread poleward.
Mangroves could expand into temperate regions, replacing saltmarshes.
Evaluation:
Mangroves are more climate-dependent, but they could outcompete saltmarshes in a warming world.
Saltmarshes are more restricted by temperature, making them less adaptable.
Paragraph 4: Tidal Range and Rising Sea Levels
Point:
Tidal range controls submersion and plant survival.
Both ecosystems are at risk from sea-level rise.
Saltmarshes (The Wash example)
Tidal range: 6.5m (moderate, ideal for saltmarsh growth).
Sea-level rise could flood marshes permanently, leading to retreat.
Mangroves (The Sundarbans example)
Tidal range: Up to 5m, but mangroves can survive periodic flooding.
Mangroves naturally adapt by increasing sediment deposition, helping them keep pace with sea-level rise.
However, too much sea-level rise can drown even mangroves.
Evaluation:
Mangroves are more resilient to tidal fluctuations, while saltmarshes retreat faster under rising sea levels.
Paragraph 5: The Impact of Storms and Extreme Weather
Point:
Mangroves provide greater protection against extreme weather than saltmarshes.
Saltmarshes (The Wash example)
Storms cause erosion and remove sediment.
Saltmarshes provide some wave reduction but are not strong against powerful storms.
Mangroves (The Sundarbans example)
Absorb wave energy and protect inland areas.
Cyclone Amphan (2020): Sundarbans reduced flooding damage significantly.
Mangroves act as a natural buffer against hurricanes and tsunamis.
Evaluation:
Mangroves are far superior for coastal protection.
Saltmarshes are vulnerable to storm damage and cannot provide the same level of defence.
Conclusion
Summarise key points: Both saltmarshes and mangroves rely on sedimentation and plant adaptation, but mangroves are more resilient to storms, sea-level rise, and tidal variations.
Make a judgement: While saltmarshes are vital in temperate zones, mangroves provide better long-term coastal stability and protection.
Future outlook: As climate change alters global temperatures, mangroves may expand while saltmarshes shrink.
Assess the Role of Longshore Drift in the Formation of Depositional Landforms in Coastal Environments
Paragraph 1: Spits and Tombolos – Landforms Primarily Shaped by Longshore Drift
Key Points
Spits: Form when longshore drift moves sediment along the coast and deposits it when wave energy decreases.
Tombolos: Created when longshore drift connects an island to the mainland.
Case Studies & Evidence
Spurn Head (UK):
5.5 km long spit on the Holderness Coast.
Sediment is moved southward at a rate of 400,000 tonnes per year.
Forms a sheltered area behind it where salt marshes develop.
Temporal aspect: Spits can be breached by storms and may shift over time.
St Ninian’s Tombolo (Shetland, Scotland):
Bidirectional longshore drift transports sand from both sides to create a connection between the island and the mainland.
The tombolo is vulnerable to storm erosion and rising sea levels, showing long-term changes in landform stability.
Paragraph 2: Barrier Beaches and Barrier Islands – Dynamic Coastal Landforms
Key Points
Barrier beaches: Form when longshore drift deposits sediment offshore, creating a ridge that protects the coastline.
Barrier islands: Large-scale versions that are constantly shifting due to tides, storms, and sea-level rise.
Case Studies & Evidence
Slapton Sands (UK):
Formed from post-glacial sediment deposits and shaped by longshore drift.
Provides coastal protection but is vulnerable to erosion.
Example of temporal change: Storm events and rising sea levels are reshaping the feature.
Outer Banks (USA):
A series of barrier islands stretching over 320 km along the east coast.
Longshore drift and ocean currents move sand continuously, causing the islands to migrate.
Some parts are retreating by 30+ meters per year due to storms and sea-level rise.
Spatial variation: Some sections are more stable, while others erode quickly.
Paragraph 3: Sand Dunes and Salt Marshes – Indirect Influence of Longshore Drift
Key Points
Sand dunes: Form inland from beaches due to wind-blown sand.
Salt marshes: Develop in sheltered, low-energy environments where fine sediment accumulates.
Case Studies & Evidence
Formby Sand Dunes (UK):
Longshore drift supplies the sand, but wind is the dominant force in shaping dunes.
Retreating at a rate of 4 meters per year due to human activity and climate change.
Temporal variation: Dunes can grow, shift, or erode depending on changes in sediment supply.
The Wash (UK):
Largest salt marsh in England, formed behind depositional landforms.
3mm per year sea-level rise is altering sediment deposition.
Longshore drift contributes some sediment, but rivers and tides are more significant.
Paragraph 4: Mudflats and Cuspate Forelands – A Mix of Processes
Key Points
Mudflats: Form in sheltered coastal areas where fine sediment settles.
Cuspate forelands: Develop where waves push sediment together from two different directions.
Case Studies & Evidence
Morecambe Bay (UK):
One of the largest mudflats in the UK, formed by sediment deposits from rivers and tidal currents.
Longshore drift plays a secondary role in sediment transport.
Vulnerable to rising sea levels and erosion.
Dungeness (UK):
A 12 km² cuspate foreland formed by sediment transported from two different directions.
Longshore drift is a key process, but wave refraction also plays a role.
Constantly evolving as new material is deposited and eroded.
Paragraph 5: Low-Lying Beaches and Mangroves – Minimal Influence of Longshore Drift
Key Points
Low-lying beaches: Mainly shaped by coral reef erosion and deposition.
Mangrove forests: Depend more on river and tidal processes.
Case Studies & Evidence
The Maldives (Indian Ocean):
Low-lying coral beaches mainly formed by biogenic sediment (coral and shell fragments).
Longshore drift redistributes sediment locally but does not form the beaches.
Rising sea levels pose a major threat.
Sundarbans (Bangladesh and India):
Largest mangrove forest in the world, created by sediment from the Ganges-Brahmaputra river system.
Longshore drift plays a minor role, as fluvial and tidal processes are dominant.
Temporal change: Climate change and increased cyclone activity are altering sediment deposition.
Conclusion
Longshore drift is a major force in shaping many depositional landforms, such as spits, tombolos, barrier beaches, and cuspate forelands.
However, it is not the only process at work. Other forces, such as wind (for dunes), tides (for salt marshes and mudflats), and rivers (for mangroves and mudflats), play a greater role in some environments.
Spatial variation: Some coastal areas experience stronger longshore drift due to prevailing winds and wave energy, while others are dominated by tidal or fluvial processes.
Temporal variation: Climate change, rising sea levels, and storm events are altering the way sediment is deposited and reshaped.
Final judgement: While longshore drift is a crucial process, its influence is not universal—it interacts with many other coastal forces, making each landform unique.
Evaluate the role of wind in the formation and characteristics of coastal dunes
Paragraph 1: How Wind Forms Coastal Dunes
🡪 Key Point: Wind transports and deposits sand, creating dunes.
Aeolian (wind) processes: Wind picks up and moves sand inland through saltation (bouncing), surface creep (rolling), and suspension (carried in the air).
At Formby:
South-westerly winds (from the Atlantic) are the dominant force, regularly exceeding 4.5 m/s (minimum speed needed to move dry sand).
The wide beach at low tide provides an essential sand supply for dune formation.
Obstacles such as driftwood, vegetation, or rocks help sand accumulate, forming embryo dunes.
Spatial variation:
Dunes form in different areas depending on wind exposure and sediment availability.
Temporal variation:
Dunes take years to form but can be eroded quickly during storms.
Paragraph 2: How Wind Shapes the Characteristics of Dunes
🡪 Key Point: Wind determines the size, shape, and structure of dunes.
Types of dunes at Formby:
Embryo dunes (1-2m tall): Very mobile, frequently reshaped by wind.
Yellow dunes (up to 10m): Larger, but still influenced by wind-driven sand movement.
Grey dunes: More stable, as vegetation binds the sand together.
Wind strength and direction affect dune morphology:
Strong winds create steeper dunes, with a slip face on the sheltered side.
Crescent-shaped barchan dunes form where wind blows consistently in one direction.
Seasonal variation:
Winter storms remove sand (erosion).
Summer conditions allow dunes to build up (accumulation).
Long-term change:
Over decades, dunes migrate inland as wind constantly moves sand.
Paragraph 3: The Role of Vegetation in Stabilising Wind-Formed Dunes
🡪 Key Point: Vegetation helps to reduce wind erosion and maintain dune stability.
Marram grass (Ammophila arenaria):
Grows on dunes and traps sand, helping dunes grow higher.
Deep roots bind sand together, reducing wind erosion.
How vegetation changes dunes over time:
Yellow dunes (with little vegetation) transition into grey dunes (covered in plants).
Organic matter from plants creates soil, leading to further stabilisation.
Blowouts:
Gaps in vegetation (caused by human activity or strong winds) expose sand, leading to rapid wind erosion.
Formby has areas where trampling has led to increased blowouts.
Spatial variation:
Some dunes remain stable due to dense vegetation, while others (near footpaths) show more erosion.
Paragraph 4: How Human Activity Affects Wind’s Role in Dune Formation
🡪 Key Point: Tourism, development, and conservation efforts influence wind-driven dune processes.
Trampling by visitors:
Formby receives over 300,000 visitors per year.
Foot traffic damages vegetation, making dunes more vulnerable to wind erosion.
Afforestation (tree planting):
In the past, pine trees were planted to stabilise dunes, disrupting the natural movement of sand.
Coastal management strategies to reduce wind erosion:
Sand fencing slows wind and traps sand.
Boardwalks protect vegetation from trampling.
Replanting marram grass restores stabilisation.
Spatial variation:
Some areas of Formby dunes are well-managed and stable, while others are highly eroded.
Temporal variation:
Human impacts have increased over the last century, requiring more conservation efforts.
Paragraph 5: Climate Change and Future Implications for Wind and Dune Systems
🡪 Key Point: Climate change is altering wind patterns, increasing erosion, and threatening dune stability.
Rising sea levels:
The Formby coastline is retreating at a rate of 4m per year.
Less sand is available for wind transport, reducing dune formation.
More frequent and stronger storms:
Storms remove large amounts of sand in short periods.
Dunes may not recover fast enough between storms.
Potential changes in wind patterns:
Stronger or shifting winds could reshape dunes in unpredictable ways.
Long-term monitoring and management:
Conservationists are studying Formby’s dunes to plan future protection strategies.
Conclusion
Wind is a key factor in forming and shaping dunes, but it does not act alone.
Vegetation, human activity, and climate change influence how wind affects dunes.
Spatial variation: Different areas of Formby dunes show different effects of wind, depending on plant cover and human activity.
Temporal variation: Dune formation takes years, but storms and human impacts can change them quickly.
Judgement: Wind plays the most important role in initial dune formation, but its impact is increasingly modified by human actions and climate change. Managing these other factors is essential to preserving coastal dunes in the future.
‘Sea level change has a very limited role in the formation of coastal landforms.’ How far do you agree?
Paragraph 1: Raised Beaches – Portland Raised Beach (Mainly Sea Level Change)
Point:
Raised beaches form when sea levels fall, exposing former wave-cut platforms and beaches. They indicate past high sea levels, often due to interglacial warming periods.
Portland Raised Beach (Dorset, UK) formed during the last interglacial period (~125,000 years ago) when sea levels were 7–9m higher than today.
As the Earth cooled and entered the last ice age, sea levels fell by ~120m, leaving the old beach stranded above current sea levels.
Development:
Eustatic fall of sea levels was the main cause of this landform, as water was stored in glaciers during the ice age.
Isostatic rebound also contributed as land rose after ice sheets melted, lifting the beach further.
Counterpoint:
However, wave processes before sea level change shaped the beach, including sediment deposition and wave erosion.
Without these coastal processes, there would have been no beach to become “raised” in the first place.
Judgment:
Sea level change played a major role in forming raised beaches, but it wasn’t the only process.
Without prior wave action and sediment movement, raised beaches would not exist.
Paragraph 2: Fjords – Sognefjord, Norway (Mostly Not Due to Sea Level Change)
Point:
Fjords are deep, U-shaped valleys created by glaciers, later flooded by rising sea levels.
Sognefjord (Norway) is 204km long and 1,308m deep, formed by glacial erosion before sea levels rose.
Development:
During the Last Glacial Maximum (~20,000 years ago), glaciers carved deep valleys.
When glaciers melted, eustatic sea levels rose by ~120m, flooding the valley.
Sea level rise helped shape the modern fjord, but glacial erosion was the primary force.
Counterpoint:
Sea level rise was crucial for transforming these valleys into fjords.
Without rising sea levels, fjords would be dry glacial valleys instead of coastal landforms.
Judgment:
Sea level change had a supporting role in fjord formation, but glaciers did the main work.
This shows that while sea level rise influences coastal landforms, it doesn’t always create them.
Paragraph 3: Rias – River Fal Ria, Cornwall (Mostly Due to Sea Level Change)
Point:
Rias are drowned river valleys, formed by rising sea levels flooding existing fluvial valleys.
The River Fal Ria (Cornwall, UK) is a classic example, formed ~20,000 years ago as sea levels rose.
Development:
Before flooding, the valley was shaped by fluvial (river) erosion when sea levels were lower.
Post-glacial sea level rise (~120m) flooded the valley, creating the ria.
Rias are often navigable and used as harbors (e.g., Falmouth in Cornwall).
Counterpoint:
The valley itself pre-dated sea level rise—it was the river that created the valley first.
If sea level had never risen, the valley would have remained a river valley, not a coastal landform.
Judgment:
Sea level change was crucial for rias, but they depended on earlier fluvial processes.
This shows that sea level change has a significant role in shaping some landforms, but only if the right preconditions exist.
Paragraph 4: Isostatic Change – Local Variation in Land Movement
Point:
Isostatic processes cause local land movement, affecting coastal landforms differently.
In Scotland, land is rising ~1-2mm per year due to post-glacial rebound, exposing raised beaches.
In Southern England, land is sinking ~1-1.5mm per year, leading to coastal flooding and higher erosion rates.
Development:
Some coastal landforms emerge as sea levels fall locally (e.g., raised beaches).
Others are submerged, leading to coastal retreat (e.g., low-lying coastlines eroding).
Counterpoint:
These changes are local, not global, meaning they do not explain the formation of most coastal landforms.
Other processes, such as wave action, are more important in shaping cliffs, spits, and beaches.
Judgment:
Isostatic changes affect some landforms but have limited impact globally.
Other factors like wave erosion and sediment transport often play a larger role.
Paragraph 5: Other Coastal Processes – Why Sea Level Change is Not Always the Main Factor
Point:
Many coastal landforms form without direct influence from sea level change.
Cliffs, stacks, caves, and arches are shaped by wave action and erosion rather than changes in sea level.
Spits and barrier islands are created by longshore drift, which moves sediment along the coast.
Development:
Example: The chalk cliffs of Dover (UK) are shaped by marine erosion, not sea level change.
Example: Spurn Head (Holderness Coast) formed due to longshore drift, not sea level movement.
Counterpoint:
Rising sea levels can accelerate erosion and coastal retreat, indirectly shaping landforms.
However, the landforms themselves are created by other processes.
Judgment:
Many coastal landforms exist independently of sea level change.
Wave action and sediment movement are often more important.
Conclusion
Sea level change is important for some coastal landforms, particularly rias, fjords, and raised beaches.
However, in many cases, other processes such as glacial erosion, fluvial processes, wave action, and sediment transport are more significant.
Spatial variation: Some coasts are more affected than others, depending on location.
Temporal variation: Past sea level changes shaped landforms over thousands of years, but modern coasts are influenced more by wave and sediment processes.
Final judgment: Sea level change plays a role but is often not the dominant force in shaping coastal landforms. Other natural processes are frequently more important in their formation.
To what extent is sediment supply the most important factor influencing the characteristics and formation of depositional landforms in coastal environments?
Paragraph 1: The Importance of Sediment Supply
Main Point: Sediment supply is a fundamental factor in the formation of depositional landforms because, without sufficient material, features like beaches, spits, and barrier islands cannot develop.
Evidence & Examples:
St Ninian’s Tombolo (Scotland): Formed by the deposition of sand and shingle transported by waves, connecting the mainland to an island. The size and shape fluctuate due to seasonal changes in sediment supply.
Slapton Sands (Devon): A barrier beach created from shingle deposition over thousands of years, but currently at risk due to reduced sediment supply caused by rising sea levels and coastal defenses.
Key Development: Sediment supply is necessary, but without other processes such as wave energy and longshore drift, it would not be distributed effectively.
Paragraph 2: The Role of Wave Energy and Longshore Drift
Main Point: Wave energy and longshore drift determine where and how sediment is transported and deposited, shaping depositional landforms over time.
Evidence & Examples:
Spurn Head (Holderness Coast): Formed due to high rates of coastal erosion (around 2m per year), supplying sediment that is carried south by longshore drift. Without drift, the spit would not extend into the Humber Estuary.
Outer Banks (North Carolina, USA): A system of barrier islands that continuously change shape due to wave action and storm events, demonstrating that high wave energy can both deposit and erode landforms.
Key Development: Even with high sediment availability, depositional landforms would not develop without longshore drift to move the sediment and wave energy to distribute it.
Paragraph 3: The Role of Coastal Configuration and Vegetation
Main Point: The shape of the coastline influences where sediment accumulates, and vegetation helps stabilize landforms, preventing erosion.
Evidence & Examples:
Dungeness (Kent): A cuspate foreland created by sediment being trapped in a triangular shape due to waves converging from different directions. Even with ample sediment, the unique coastal configuration is what allows this landform to exist.
Formby Sand Dunes (Sefton Coast): Stabilized by marram grass, which prevents wind erosion and maintains the structure of the dunes.
Sundarbans (Bangladesh & India): The largest mangrove forest in the world, where mangrove roots trap sediment and protect the coastline from erosion.
Key Development: Sediment alone is not enough—certain landforms require the right physical shape and vegetation to hold the sediment in place over time.
Paragraph 4: Human Activity and Climate Change
Main Point: Human interventions such as dredging, land reclamation, and coastal management affect sediment supply, while climate change is altering long-term coastal sediment dynamics.
Evidence & Examples:
Morecambe Bay (UK): One of the largest intertidal mudflat systems, where dredging and land reclamation have altered natural sediment deposition patterns.
The Wash (Eastern England): Human-controlled flood defenses and managed retreat influence how sediment is deposited and whether salt marshes can expand.
Maldives (Indian Ocean): Low-lying islands with beaches that are threatened by rising sea levels and stronger storms. Without enough sediment deposition, these islands are at risk of disappearing.
Key Development: Even when natural sediment supply is high, human actions and climate change can disrupt deposition, making other factors more significant.
Paragraph 5: How the Importance of Sediment Supply Changes Over Time and Space
Main Point: The significance of sediment supply varies depending on spatial and temporal scales. Some landforms take centuries to develop, while others respond to seasonal changes.
Evidence & Examples:
Barrier islands and spits evolve over centuries, influenced by glacial and interglacial cycles.
Salt marshes and mudflats, like those in Morecambe Bay, change over decades, affected by human activity and rising sea levels.
Sundarbans sediment supply fluctuates due to monsoon cycles and tectonic activity, affecting landform stability over time.
Key Development: The importance of sediment supply is relative—it is more significant in the long term for certain landforms but less crucial for features that are rapidly shaped by external forces.
Conclusion
Summarize that while sediment supply is necessary for depositional landforms, it is not the only or always the most important factor.
Wave energy and longshore drift determine how sediment is transported and deposited.
Coastal shape and vegetation help trap and stabilize sediment.
Human activity and climate change can override natural sediment processes.
The importance of sediment supply varies with spatial and temporal scales—for some landforms, it is dominant, but for others, wave energy or vegetation is more critical.
Final judgment: Sediment supply is essential but only forms depositional landforms when combined with other processes.
