COASTAL LANDFORMS
FEATURES OF SEA
EROSION AND DEPOSITION
WAVES
Size and type of wave will depend on the
FETCH and wind speed.
Destructive waves – BACKWASH is stronger
than the SWASH.
Destructive waves form features of erosion.
Constructive waves – SWASH is stronger than
the backwash.
Constructive waves form features of deposition.
EROSIONAL PROCESSES
Hydraulic Action – power of wave carries
away any loose material.
Abrasion – Waves use their load to break
rock down into smaller fragments.
Solution – water dissolves soft rock.
Compressed Air- tiny little explosions
within cracks due to trapped air.
Erosion rates depend on:
Rock Type
Degree of exposure
Amount of protective interference by man
Wave Type
Slope of shoreline
Features of sea erosion
Bay and Headland
Cave / Arch / Stack
Sea Cliff
Formation of bay and headland
Bands of hard and soft rock eroded at different
rates – Differential Erosion.
Processes at work : hydraulic action / abrasion /
solution / compressed air.
Hard rock stands out as headlands and soft rock
retreats inland to form bays.
Wave refraction occurs as bays retreat so
headlands receive more high energy waves.
Example – Howth Head and Dublin Bay.
Formation of cave, arch, stack.
Waves attack weak areas of exposed rock.
Processes at work?????
Cave cut into base of cliff/ deepened by
abrasion.
Cave extends through to other side of headland
forming an arch.
Erosion and gravity cause roof of cave to
collapse forming a stack.
Continuous erosion creates a sea stump.
Example – Old Head Of Kinsale, Co. Cork.
Formation of Sea Cliff.
Destructive waves attack coast.
Processes at work ????
Notch carved out and enlarged.
Upper slope unsupported/ undermining occurs.
Due to erosion, weathering and gravity, slope collapses
forming a steep face.
Cliff retreats and increases in height.
Rock left at base of retreating cliff is a wave cut platform.
The bigger the platform – the less rate of erosion.
Example – Cliffs of Moher, Co. Clare.
SEA CLIFFS
Marine Transportation
Longshore Drift – movement of material
along the coast in a zig-zag pattern.
Swash moves material up the beach.
Backwash moves sediment back into the
sea.
Formation of a Beach.
Formed by constructive waves.
Weak backwash allows material to build
up higher up the shore and finer material
is left closer to shoreline.
Beach forms between high and low water
marks.
Sections of beach include sandy area/
shingle area and storm beach.
Example – Skerries.
Formation of Sand Spit.
Long ridge of sand and shingle deposited along
entrance to sheltered bay.
Constructive waves and longshore drift.
Waves hit obstacle/ lose power / deposit load.
Builds up above sea level across entrance to
bay.
Wave refraction may cause spit to curve inwards
towards bay= Recurved spit.
Example – Portmarnock, Dublin.
Formation of a Tombolo.
Island connects to mainland due to
deposition.
Constructive waves and longshore drift.
Wave refraction at island causes currents
to converge / deposit load.
Example – Howth to Sutton.