Cliffs

• A sea cliff is a vertical or almost vertical section of coastline that has been formed by sea erosion
• The Cliffs of Moher in Co. Clare are an example of a sea cliff
• The processes of hydraulic action, abrasion, solution and compression are important in the formation of sea cliffs
• Wave refraction occurs when waves bend and change direction as they approach the shore
•  As a result of wave refraction, the power of waves is focused on headlands
• Hydraulic Action is erosion by the power of water as waves pound against the coast
• Destructive waves are particularly powerful, especially during storms when they can exert enormous pressure, up to 25 tonnes per square metre
• The constant battering by the sea weakens the rock and loosens it
• Abrasion is erosion by stones, pebbles and sand particles that are hurled by the waves against the coast
• Solution also plays a role in coastlines that are made of limestone, as it can be dissolved in the water and carried away in solution
• As a result of the processes, cracks will appear in the rock and every time a wave breaks against it, air is compressed in the rock
• As the wave withdraws, the air expands rapidly with explosive force
• This is known as compression and is a very powerful method of erosion especially during storms when waves can hit the coastline several times a minute
• These processes first erode an opening called a notch in the coastline
• This is formed between high and low tide mark, which is where sea erosion is most concentrated
•  As the notch grows deeper, the land above overhangs and will eventually collapse
• After a cliff has been formed the waves will then erode another notch in the cliff, causing another collapse of overhanging rock
• As this cycle continues the cliff retreats inland
• The exposed base of the cliff forms a flat area in front of the cliff called a wave cut platform
• the wave cut platform will be covered at high tide and exposed at low tide
• As the wave cut platform grows wider, it helps to break the power of the waves before they reach the cliff thus slowing down cliff erosion
• The cliff may eventually become inactive
• Inactive cliffs often have vegetation growing on the cliff face
• The cliff debris falls to the bottom of the cliff and is broken up by the forces of erosion