coastal landforms

• cliffs and wave cut platform : part 1 (notch, cave and cliff)

  • wave erosion such as hydraulic action and abrasion attack the lines of weaknesses, forming a notch
  • further erosion enlarges the notch, forming a hollow space, a cave
  • the cave enlarges with continued erosion. The roof of the cave becomes unstable and collapses into the ocean, forming a steep cliff.
  • collapsed material deposited on the foot of the cliff
• cliffs and wave cut platforms : part 2 (wave cut platform)

  • sediments are repeatedly thrown against the coast --> abrasion
  • results in cliff retreating inland
  • gentle gradient formed where the base of cliff used to be
  • known as wave cut platform, submerged during high tide
• headlands and bays part 1

  • waves attack exposed discordant coast with alternating bands of resistant and less resistant rocks that occur at right angles along the coast
  • erosion is uneven due to the difference in rock resistance
  • rapid erosion of less resistant rocks form bays
  • less rapid erosion of resistant rocks form headlands
• formation of cave, arch

  • waves attack along the lines of weakness of the headlands, forming a notch
  • notch enlarges with further erosion into a cave
  • cave enlarges, arch is formed when a cave cuts through the headlands and meets with another cave on the other side of the headland
• formation of stack, stump

  • due to weathering and mass wasting, arch becomes unstable and collapses, leaving behind an isolated pillar of rock --> stack
  • continued erosion of stack reduces its height, forming a stump
• wave refraction

  • waves move faster in deeper waters than shallow waters
  • change in speed results in refraction of waves(change in direction)
  • wave refraction refers to the change in direction of waves as they approach the coast
  • converge on headlands, resulting in deposition
  • diverge at bays, reducing wave energy, resulting in deposition
• formation of spit

  • longshore drift transports materials in a zig zag fashion parallel to the coast
  • even when there is an abrupt change in coast, the longshore drift will continue to transport materials in the original direction
  • over time, accumulation of materials with appear on the surface of the water
  • formation of a long narrow ridge of sand and pebbles with one end attached to the mainland --> spit
• formation of hooked spit

  • due to wave refraction or occasional changes in wind direction, the free end of the spit might curve, forming a hooked spit
• formation of tombolos

  • when a spit meets another island
  • when a spit connects two islands