coasts

• a coast


  where the land meets the sea
• hong kong's coast is 1178 km long(456 km around main, 722 km around islands)
• offshore


  never exposed
• foreshore


  exposed in low tide
• backshore


  always exposed, the beach
• landforms found at the beach


  caves, cliffs, arches, beaches, tombolos, stacks and headlands
• erosion


  the wearing away of a surface (e.g. a cliff) and the removal of sediment (destructive process)
• sediment


  material at the coast such as sand, rocks and pebbles
• cliff


  a steep rock face, especially at the edge of the sea
• arch


  an arch-shaped feature
• beach


  formed when sediment(sand) is deposited by waves
• headland


  a narrow piece of land that projects from a coastline into the sea
• stack


  a landform consisting of a vertical column of rock in the sea near a coast(was an arch but became disconnected from the coast due to erosion)
• tombolo


  formed when an island is connected to land due to deposition
• abrasion


  waves hit the coastal landforms, wearing them down over time. waves carry rock fragments scraping away the surfaces
• corrosion


  a chemical reaction between the water and the rock surface. weak carbonic acid in seawater dissolves and reacts with minerals like chalk and limestone
• attrition


  rocks or pebbles collide or crash into each other causing them to become smaller and smoother
• hydraulic action 


  waves force air into cracks in the rock surface, causing cracks to widen and break off
• formation of landforms:

  1. a crack forms in the side of a headland due to erosion
  2. the crack expands due to hydraulic action causing a cave to form
  3. abrasion continues to erode the headland from both sides, causing a cave to break through and form an arch
  4. waves and weather cause the roof of the arch to fall, forming a stack
  5. corrosion dissolves the surface of the stack causing it to weaken and collapse to form a stump