Coastal Zones

Coastal Zones

1. WEATHERING

   • Mechanical
     • breakdown of rock without changing its chemical composition - freeze thaw weathering
       • 1. temperature alternates above and below 0'C
       • 2. Water gets into cracks
       • 3. When water freezes it expands, puts pressure on the rock
       • 4. When water thaws it contracts, releasing pressure
       • 5. This process repeats and widens the crack causes rock to break up
   • Chemical
     • break down of rock by changing chemical composition - carbonation weathering (warm and wet conditions)
       • 1. Rainwater has carbon dioxide dissolved in it- makes it weak carbonic acid
       • 2. Carbonic acid reacts with rock that contain calcium carbonate so rocks dissolve by rainwater (limestone)

2. MASS MOVEMENT

   • shifting of rocks and loose material down a slope.
     • causes coasts to retreat rapidly
     • more likely to happen when material is full of water
   • 2 types
     • material shifts in a straight line
     • material shifts with a rotation

3. PROCESS OF EROSION

   • Hydraulic Action - waves crash against rock, compress air in crack. Pressure on rocks- process repeats widens the crack, rocks fall off
   • Abrasion - eroded particles in water scrape and rub against rock, removing small pieces
   • Attrition - particles smash into eachother and break into smaller fragments - edges round off
   • Solution - particles dissolve in water

4. WAVES

   • Constructive
     • carry and deposit material
       • low and long
       • swash is more powerful than the backwash
         • material is deposited instead of taken away
   • Destructive
     • carry out erosional process
       • high and steep
       • backwash is more powerful than the swash
         • material removed from beach