Landforms of Coastal Erosion (Cambridge (CIE) IGCSE Geography) : Revision Note

Formation of erosional coastal landforms

Cliffs

• Cliffs are sloping or steep rocks with different profiles depending on the topography and geology of the cliff

• The cliff face angle is also affected by geology and wave attack at its base

• Cliffs are shaped through erosion

  • Low-energy waves cause less damage than high-energy ones

  • Soft rock erodes quickly and will form sloping cliff faces

  • Steep cliffs are formed where there is hard rock facing the sea

Wave-cut platforms

• A wave-cut platform is a wide, gently sloped surface found at the foot of a cliff

  • As the sea attacks the base of a cliff between the high and low water mark, a wave-cut notch is formed

  • Abrasion, corrosion and hydraulic action further extend the notch back into the cliff

  • As undercutting continues, the cliff above becomes unsupported and unstable and eventually collapses

  • The backwash of the waves carries away the eroded material, leaving behind a wave-cut platform

  • The process repeats and the cliff continues to retreat, leading to a coastal retreat

Headlands and bays

• Occur where alternating bands of hard and soft rocks run perpendicular to oncoming waves (discordant coastline)

  1. At first, the softer rock (e.g. clay) is eroded backward, forming an inlet

  2. As the inlet continues to erode it curves inwards, and a bay is formed, usually with a beach

  3. The harder rock (e.g. limestone) is left protruding out to sea as a headland

• A headland features usually include:

  • Cliffs along its sides

  • That it projects out to sea

  • It is usually longer than it is wide

  • Geology is of resistant rock

• A bay usually has:

  • A wide, open entrance from the sea

  • A roughly, semi-circular shape extending into the coastline

  • Land that is lower than the headlands surrounding it

  • A bay may or may not have a beach

Caves, arches, stacks and stumps

• These form in a headland because of wave action

• As waves approach the shore, their speed is reduced as they move along the sea floor

• This changes the angle of the waves, and they will turn so the crest becomes parallel to the coast – known as wave refraction

• This refraction concentrates erosive action on all sides of the headland

• Hydraulic action, abrasion, and corrosion take advantage of any weaknesses in the headland

  • As the crack begins to widen, abrasion will begin to wear away at the forming cave

  • The cave will become larger and eventually breaks through the headland to form an arch

  • The base of the arch continually becomes wider and thinner through erosion below

  • Eventually, the roof of the arch collapses, leaving behind an isolated column of rock called a stack

  • The stack is undercut at the base by wave action until it collapses to form a stump