coastal landform development

• how does cliffs and wave cut platforms form?

  • cliffs form as the sea erodes the land , over time , they retreat de to the action of waves and weathering
  • weathering and wave erosion cause a notch to form at the high water mark - develops into a cave
  • rock above cave becomes unstable , nothing to support it with , collapses
  • wave-cut platforms are flat surfaces left behind when a cliff is eroded
• how are headlands and bays formed?

  • form where there are bands of alternating hard and soft rock at right angles to the shoreline
  • soft rock is eroded quickly , forming a bay. Harder rock is eroded less and sticks out as a headland
• how are caves , arches and stacks formed?

  • weak areas in rocks e.g joints are eroded to form caves
  • caves on opposite sides of a narrow headland may eventually join up to form an arch
  • when an arch collapses, it forms a stack
• depositional landforms

  • beaches
  • spits
  • tombolos
  • offshore bars
• how do beaches form?

  form when constructive waves deposit sediment on the shore
• what are shingle beaches?

  steep and narrow - made up of larger particules
• what are sand beaches?

  wide and flat - formed from smaller particules
• when do spits tend to form?

  when the coast suddenyl changes direction e.g across river mouths
• how does a spit form?

  1. longshore drift deposits material across river mouth , leaving bank of sand and shingle sticking out at sea. Forms simple spit
  2. occasional changes to to dominant wind and wave direction may lead to a spit having a curved end (recurved end)
  3. overtime , several recurved ends may be abandoned due to waves returning to OG direction. Forms compound spit
  4. are behind spit is sheltered from wave and often develops into mudflats and saltmarshes
• how are tombolos and offshore bars formed?

  • bars are formed when a spit joins two headlands together. Can occur across a bar or river mouth
  • A lagoon forms behind a bar
  • bars also form off the coast when material moves towards the coastes (normally as sea levels rises) Remain partially submerged by the sea - offshore bars
  • a bar thar connects the shore to an island is called a tombolo
  • E.G St Ninian's isle in the Shetland Islands
• what are barrier islands?

  long , narrow islands of sand or gravel that run parallel to the shore and are detached to it.

  • form in areas with good supply of sediment , gentle slope offshore , powerful waves and small tidal range