Coastal Landscapes

• • Wave processes depend on the wind speed and the fetch (length of sea that passes over) 
  • Waves are ripples formed by the wind moving across the surface of the water 
• Swash: Water that moves up the shore while carrying sediments up 

  Backwash: Water that moves back down the shore while carrying sediments down
• Constructive waves

  • Stong swash weak backwash 
  • Deposits sediments on the shore 
  • Occurs in calm weather summer 
  • Waves have less energy 
• Destructive waves 

  • Weak swash strong backwash 
  • Erodes sediments from the shore 
  • Occurs in poor weather in winter 
  • Waves have more energy – stormy wave
• Hydraulic acid: The force of waves on the coast. Rocks and sand are removed by force. Rock can be thrown.
• Compressed air: When air becomes trapped in the cracks of rocks. Incoming waves compress the air. Air expands when the waves retreat creating pressure breaking rock. 
• Abrasion: When pebbles and stones are thrown against the coast by the force of waves. This breaks rocks smaller.
• Attrition: Pebbles and stones rub against one another becoming worn down and breaking down into sand. 
• Solution: Seawater containing salt dissolves the rock gradually
• Longshore Drift 

  • Sediments along the coast are transported in a zig-zag movement along the coast. 
  • Waves approach the sea at an angle from prevailing winds bringing sediments in – swash 
  • The waves then retreat carrying sediments back down the shore at a right angle to the sea - backwash 

   
• Sediments are deposits when waves loose energy when: 

  1. Entering shallow waters 
  2. Crossing wide beach
• Cliffs and wave-cut platforms 

  • Cliffs form when destructive waves erode the coast 
  • At high tide many erosion processes such as compressed air erode a wave-cut notch. A wave cut platform develops at the base of a cliff 
  • Sediments from the notch are transported and deposited below low tide 
  • Over time the notch becomes bigger from erosion. The rocks above eventually collapse forming a cliff 
  • Erosion is reduced when crossing the wave-cut platform 
  • Eg. Cliffs of Moher 

   
• Bays and headlands 

  • Forms in areas where a combination of soft and hard rock facing the sea lie 
  • The soft rock is eroded quicker than the hard rock by hydraulic action and abrasion leaving and indent in the coast – bay 
  • The hard rock jutting out on either side is the headlands 
  • Eg. Tralee bay Co. Kerry 
• Blowhole 

  • It is a passage that goes through a roof of a cave to the surface above 
  • Waves force air to the back of the cave and it becomes trapped and compressed 
  • Pressure builds up and the air expands causing the rock to shatter. Over time this repeats, and it creates a passage – stormy weather water will splash through. 
  • Eg. Downpatrick Head Co. Mayo 
• Sea caves, arches, stacks and stumps 

  • Caves start as crack or wave-cut notches and is eroded by incoming waves – compressed air, hydraulic action etc. 
  • Eventually a sea cave formed. If the erosion continues it cuts through the other side to form a sea arch 
  • When the roof of the sea arch collapses it forms a sea stack. Overtime the stack will erode or collapse into a sea stump 
  • Eg. Great Pollet Sea Arch, Co. Donegal