GCSE Geography: The UK's Evolving Physical Landscape

Erosional Features

Cave, Arch, and Stack Formation

• Location: Forms on a headland, typically found on a discordant coastline.
• Process:
  • Erosion occurs on both sides of the headland due to wave refraction.
  • Waves attack the sides of the headland, exploiting cracks and weaknesses in the rock through hydraulic action and abrasion.
  • Hydraulic Action: Air in cracks is compressed by wave action, breaking the rock.
  • Abrasion: Particles in waves wear away the rock.
  • Cracks widen to form caves on either side of the headland.
  • Caves eventually meet to form an arch.
  • Sub-aerial processes (e.g., weathering, vegetation) weaken the top of the arch, leading to collapse.
  • Collapse leaves behind a stack.
  • The stack is further eroded at the base, leading to the formation of a stump.

Types of Coastlines

Discordant Coastlines

• Definition: Rock types run at angles to the sea (not always 90 degrees).
• Formation:
  • Alternating bands of hard and soft rock.
  • Hard rock forms headlands; soft rock forms bays.

Concordant Coastlines

• Definition: Rock layers run parallel to the sea.
• Features:
  • Hard rock at the front, followed by softer rock, then harder rock again.
  • Example: Lulworth Cove on the Dorset coastline.
  • Cove Formation:
    • Initial erosion through a weakness in the hard rock.
    • Once through, waves erode softer rock behind, forming a cove.
    • Further erosion is limited by another layer of hard rock behind.

Key Terms

• Hydraulic Action: Compression of air in rocks by waves leading to rock breakage.
• Abrasion: Mechanical scraping of a rock surface by friction between rocks and moving particles.
• Sub-aerial Processes: Weathering and biological processes occurring above the sea level, weakening cliffs.