3.1.2
Geological Structure
Concordant vs Discordant Coastlines
Concordant vs Discordant Coastlines
The shape of a coastline is continually changing due to the surrounding geology which contributes to its morphology. Coasts are either concordant or discordant.
Concordant coastlines
Concordant coastlines
- Concordant coastlines have alternating bands of hard and soft rock parallel to the coast.
Discordant coastlines
Discordant coastlines
- Discordant coastlines have alternating bands of hard and soft rock at 90o to the coast.
- Erosional landforms are more common on discordant coastlines because erosion happens at different rates along their length.
Example of a discordant coast
Example of a discordant coast
- In Dorset, the coastline consists of Portland limestone and Greensands.
- The Greensands is less resistant to erosional processes, and so retreats at a faster rate than the Portland limestone.
- This has resulted in the creation of a bay and headlands.
- The Greensands is less resistant to erosional processes, and so retreats at a faster rate than the Portland limestone.
Coastal Morphology
Coastal Morphology
The shape of a coastline is continually changing because of the surrounding geology, which contributes to its morphology.
Pacific coasts
Pacific coasts
- Concordant coastlines, also referred to as Pacific coasts, lead to the formation of Dalmatian coasts.
- Dalmatian coasts are made up of offshore islands and coastal inlets running parallel to the coastline.
- E.g. Lulworth Cove, located on the south-west Dorset coastline. Here, the more-resistant rock (e.g. limestone) acts as a barrier to protect the less-resistant rock.
Atlantic coasts
Atlantic coasts
- Headlands and bays often form on discordant coastlines (also referred to as Atlantic coasts).
- As the faster eroding, less-resistant rock retreats (e.g. the clays at Swanage Bay), this leaves behind the more-resistant rock as headlands.
Bays and headlands
Bays and headlands
- On discordant coastlines, the retreating, less resistant rock and the exposed resistant rocks cause a change in the shape of the coastline. This leads to wave refraction.
- This change in the way in which waves approach the coastline can cause an increase in the rate of erosion on the headlands.
- This leads to the formation of headland features like caves, arches, stacks and stumps.
Geological Structure
Geological Structure
The shape of a coastline is continually changing because of the surrounding geology, which contributes to its morphology.
Joints and faults
Joints and faults
- The geological structure of rocks (the formation of joints, the angle of the dip, faulting and folding) is caused by the deformation and stress placed on them from tectonic processes.
- Rocks with the presence of more joints and faults, like sedimentary rocks, are more susceptible to the processes of erosion and weathering. This is because these processes exert forces on the weaknesses found in the layers of the rocks.
Dip
Dip
- The angle the rock layer forms with the horizontal bedding plane is referred to as the dip. Rocks can dip either towards land or towards the sea.
- Bedding planes that dip towards the sea create a gentler cliff profile. But these cliffs are vulnerable to mass movement processes, like rockfalls.
- Bedding planes that dip towards land tend to create a steeper cliff profile. But these cliffs are more vulnerable to erosion processes, like hydraulic action and abrasion.
1Tectonic Processes & Hazards
1.1Tectonic Processes & Hazards
1.2Natural Disasters
1.3Natural Disaster Case Studies
1.4Trends & Patterns
2Option 2A: Glaciated Landscapes & Change
2.1Glaciated Landscapes Over Time
2.2Periglacial Landscapes
2.3Glacial Processes
2.4Glacial Landforms
3Option 2B: Coastal Landscapes & Change
3.1Coastal Landscapes
3.2Coastal Erosion & Deposition
3.3Coastal Risks
4Globalisation
4.1Globalisation
4.2Negatives of Globalisation
4.3Global Shift
4.5Culture
4.6Measuring Development
5Option 4A: Regenerating Places
5.1Types of Economies
5.2Function of Places
5.3Regeneration
5.4Regeneration Case Studies
6Option 4B: Diverse Places
6.1Population Structure
6.2Past & Present Connections
6.3Urban & Rural Spaces
6.4Diversity
6.5Urban & Rural Case Studies
6.6Case Study - Tower Hamlets
6.7Case Study - Sturton-le-Steeple
7The Water Cycle & Water Insecurity (A2 only)
7.1Hydrological Processes Global to Local
7.2Influences on the Water Cycle
7.3Water Insecurity
8The Carbon Cycle & Energy Security (A2 only)
8.1The Carbon Cycle
8.2Energy Consumption
8.3Alternative Energy
8.4Growing Demand for Resources
9Superpowers (A2 only)
9.1Superpowers
9.2Hard & Soft Power
9.2.1Hard & Soft Power
9.2.2Emerging Powers - China Rivalry
9.2.3Emerging Powers - Chinese Sources of Power
9.2.4Emerging Powers - Brazil
9.2.5Emerging Powers - Russia
9.2.6Emerging Powers - India
9.2.7Theories of Development
9.2.8Power Case Studies: Chinese One Belt One Road
9.2.9Power Case Studies: Pakistan Nuclear Arms
9.2.10Power Case Studies: OPEC
9.3IGOs, TNCs & Alliances
10Option 8A: Health & Human Rights (A2 only)
10.1Human Development
10.2Role of Governments & IGOs
10.3Human Rights
10.4Interventions
11Option 8B: Migration & Identity (A2 only)
11.1Globalisation & Migration
11.2Consequences of Migration
11.3Nation States
11.4Responses to Global Migration
Jump to other topics
1Tectonic Processes & Hazards
1.1Tectonic Processes & Hazards
1.2Natural Disasters
1.3Natural Disaster Case Studies
1.4Trends & Patterns
2Option 2A: Glaciated Landscapes & Change
2.1Glaciated Landscapes Over Time
2.2Periglacial Landscapes
2.3Glacial Processes
2.4Glacial Landforms
3Option 2B: Coastal Landscapes & Change
3.1Coastal Landscapes
3.2Coastal Erosion & Deposition
3.3Coastal Risks
4Globalisation
4.1Globalisation
4.2Negatives of Globalisation
4.3Global Shift
4.5Culture
4.6Measuring Development
5Option 4A: Regenerating Places
5.1Types of Economies
5.2Function of Places
5.3Regeneration
5.4Regeneration Case Studies
6Option 4B: Diverse Places
6.1Population Structure
6.2Past & Present Connections
6.3Urban & Rural Spaces
6.4Diversity
6.5Urban & Rural Case Studies
6.6Case Study - Tower Hamlets
6.7Case Study - Sturton-le-Steeple
7The Water Cycle & Water Insecurity (A2 only)
7.1Hydrological Processes Global to Local
7.2Influences on the Water Cycle
7.3Water Insecurity
8The Carbon Cycle & Energy Security (A2 only)
8.1The Carbon Cycle
8.2Energy Consumption
8.3Alternative Energy
8.4Growing Demand for Resources
9Superpowers (A2 only)
9.1Superpowers
9.2Hard & Soft Power
9.2.1Hard & Soft Power
9.2.2Emerging Powers - China Rivalry
9.2.3Emerging Powers - Chinese Sources of Power
9.2.4Emerging Powers - Brazil
9.2.5Emerging Powers - Russia
9.2.6Emerging Powers - India
9.2.7Theories of Development
9.2.8Power Case Studies: Chinese One Belt One Road
9.2.9Power Case Studies: Pakistan Nuclear Arms
9.2.10Power Case Studies: OPEC
9.3IGOs, TNCs & Alliances
10Option 8A: Health & Human Rights (A2 only)
10.1Human Development
10.2Role of Governments & IGOs
10.3Human Rights
10.4Interventions
11Option 8B: Migration & Identity (A2 only)
11.1Globalisation & Migration
11.2Consequences of Migration
11.3Nation States
11.4Responses to Global Migration
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