Headlands, Bays and Cliff Features
This section covers the formation of major coastal landforms through erosion processes.
Formation of Headlands and Bays
Headlands and bays form along discordant coastlines due to differential erosion. Higher geography coastal formation and erosion occurs more rapidly in softer rock through processes like:
- Hydraulic action: Wave force breaks rock
- Solution: Acidic seawater dissolves rock
- Abrasion: Sand in waves erodes rock
This creates sheltered bays in soft rock areas, while hard rock remains as headlands jutting into the sea.
Example: Swanage Bay and headlands demonstrate this process.
Cliff, Wave-cut Notch and Platform Formation
Erosion is strongest at a cliff base between high and low tide marks. This creates a wave-cut notch through:
- Solution from acidic seawater
- Abrasion from sand particles
- Hydraulic action forcing air into cracks
As the notch grows, the unsupported rock above eventually collapses, causing cliff retreat. This leaves a gently sloping wave-cut platform at the cliff base.
Highlight: Biological weathering of the cliff face also contributes to instability and collapse.
Cave, Arch, Stack and Stump Evolution
Headlands experience erosion on three sides. Weak points like fault lines erode faster through hydraulic action, solution and abrasion to form sea caves. As caves enlarge, they may form blowholes or erode through the headland to create arches.
Example: Durdle Door is a famous coastal arch formation.
Continued erosion and weathering eventually cause arch roofs to collapse, leaving isolated rock pillars called stacks. Further erosion reduces stacks to stumps.
Example: Old Harry Rocks demonstrate the stack and stump stages.
