Coastline Formation (Cambridge International IGCSE Geography)

Specification link

This page covers section 2.2.2 of the CIE IGCSE specification .

• 2.2.2 - The formation and characteristics of discordant and concordant coastlines.

The influence of geological structure

• Geological structure influences the shape of the coastline
• A coastline made up of softer rocks such as sands and clays will be more easily eroded
• Coastlines of more resistant, harder rock will take longer to erode and produce rugged landscapes
• Joints and faults expose rock to erosion and weathering
• The differences between hard and soft rocks will also impact the shape and characteristics of cliffs

The Effects of Rock Type on the Coastline

• The angle of the rocks at the coastline determines the shape that the coastline will take
• This forms a concordant or discordant coastline, such as the Dorset coastline

Map of Dorset coastline showing a concordant and discordant coastline

• Geology, therefore, determines the coastline vertically through the height and profile of a cliff and horizontally with bays and headlands

Concordant coastlines

Spec point — The formation and characteristics of discordant and concordant coastlines.

• Concordant coastlines are made up of the same rock type, running parallel to the sea

• This causes even rates of erosion along the coastline

• These coastlines typically produce coves

  • An example of a concordant coastline can be found in the area around Lulworth Cove in Dorset
  • More resistant Portland Limestone runs parallel to the sea, with less resistant Purbeck Limestone and Wealden Clay behind it
  • The formation of coves has occurred where the water has broken through at weaker points in the Portland Limestone

Concordant coastline in South Dorset, showing coastal erosion at Durdle Door and Lulworth Cove

Discordant coastlines

Spec point — The formation and characteristics of discordant and concordant coastlines.

• Discordant coastlines have alternating bands of rock perpendicular (90°) exposed to the sea

• This causes uneven rates of erosion along the coastline

• These types of coastlines form headlands and bays

  • For example, to the east of Lulworth Cove in Dorset, the coastline runs north to south and so the rocks meet the coast at an angle, creating a discordant coastline

Headland and bay formations on a discordant coastline