The Coastal Zone

The Coastal Zone

1. WAVES

   • Constructive
     • Stronger SWASH
     • Push sand and pebbles UP the beach
       • Backwash not strong enough to remove these
     • SUMMER
   • Destructive
     • Stronger BACKWASH
     • Pull sand and pebbles DOWN the beach
     • STEEP, HIGH waves
     • SURFING waves
     • WINTER

2. WEATHERING

   • Freeze-Thaw
     • Water in crack...
       • water freezes...
         • pushing the crack apart...
           • until it BREAKS
   • Salt wedging
     • Salt from the sea...
       • salt EXPANDS...
         • making a HOLE
   • Chemical
     • Alkali rock, acid rain...
       • rock is DISSOLVED....
         • more...
           • and more...
   • Mass movement
     • Rotational slip
       • Slabs of cliff fall away
       • Particularly common on CLAY
     • Slumping
       • Cliff collapse
       • When cliffs collapse in large blocks

3. COASTAL EROSION

   • Hydraulic action
     • When WAVES hit against the cliffs
   • Attrition
     • Pebbles hit each other, turning them into sand
   • Corrosion
     • When CHEMICALS erode the rock
   • Corrasion
     • Stones are thrown against the cliff by the waves

4. COASTAL TRANSPORTATION

   • Traction
     • Pebbles are ROLLED
   • Suspension
     • Fine sediments FLOAT
   • Solution
     • Dissolves materials FLOAT
   • Saltation
     • Smaller pebbles are BOUNCED

5. COASTAL DEFENCES

   • Hard engineering
     • Sea wall
     • Groynes
     • Rip Rap
     • Gabions
     • Breakwater
   • Soft engineering
     • Managed retreat
     • Dune fixing
     • Beach nourishment

6. COASTAL HABITAT

   • Supply of sand...
     • wind blows inland from the sea...
       • sand trapped behind small obstacle...
         • dune grows as more sand is trapped...
           • at 35 degrees the dune collapses...
             • cycle begins again, but moves further inland