COASTAL LANDFORMS FEATURES OF SEA EROSION AND DEPOSITION.

COASTAL LANDFORMSCOASTAL LANDFORMS

FEATURES OF SEA FEATURES OF SEA EROSION AND DEPOSITIONEROSION AND DEPOSITION

WAVESWAVES

Size and type of wave will depend on the Size and type of wave will depend on the FETCH and wind speed.FETCH and wind speed.

Destructive waves – BACKWASH is stronger Destructive waves – BACKWASH is stronger than the SWASH.than the SWASH.

Destructive waves form features of erosion.Destructive waves form features of erosion.

Constructive waves – SWASH is stronger than Constructive waves – SWASH is stronger than the backwash.the backwash.

Constructive waves form features of deposition.Constructive waves form features of deposition.

EROSIONAL PROCESSESEROSIONAL PROCESSES

Hydraulic Action – power of wave carries Hydraulic Action – power of wave carries away any loose material.away any loose material.

Abrasion – Waves use their load to break Abrasion – Waves use their load to break rock down into smaller fragments.rock down into smaller fragments.

Solution – water dissolves soft rock.Solution – water dissolves soft rock.

Compressed Air- tiny little explosions Compressed Air- tiny little explosions within cracks due to trapped air.within cracks due to trapped air.

Erosion rates depend on:Erosion rates depend on:

Rock TypeRock Type

Degree of exposureDegree of exposure

Amount of protective interference by manAmount of protective interference by man

Wave TypeWave Type

Slope of shorelineSlope of shoreline

Features of sea erosionFeatures of sea erosion

Bay and HeadlandBay and Headland

Cave / Arch / StackCave / Arch / Stack

Sea CliffSea Cliff

Formation of bay and headlandFormation of bay and headland

Bands of hard and soft rock eroded at different Bands of hard and soft rock eroded at different rates – Differential Erosion.rates – Differential Erosion.

Processes at work : hydraulic action / abrasion / Processes at work : hydraulic action / abrasion / solution / compressed air.solution / compressed air.

Hard rock stands out as headlands and soft rock Hard rock stands out as headlands and soft rock retreats inland to form bays.retreats inland to form bays.

Wave refraction occurs as bays retreat so Wave refraction occurs as bays retreat so headlands receive more high energy waves.headlands receive more high energy waves.

Example – Howth Head and Dublin Bay.Example – Howth Head and Dublin Bay.

Formation of cave, arch, stack.Formation of cave, arch, stack.

Waves attack weak areas of exposed rock.Waves attack weak areas of exposed rock.Processes at work?????Processes at work?????Cave cut into base of cliff/ deepened by Cave cut into base of cliff/ deepened by abrasion.abrasion.Cave extends through to other side of headland Cave extends through to other side of headland forming an arch.forming an arch.Erosion and gravity cause roof of cave to Erosion and gravity cause roof of cave to collapse forming a stack.collapse forming a stack.Continuous erosion creates a sea stump.Continuous erosion creates a sea stump.Example – Old Head Of Kinsale, Co. Cork.Example – Old Head Of Kinsale, Co. Cork.

Formation of Sea Cliff.Formation of Sea Cliff.

Destructive waves attack coast.Destructive waves attack coast.Processes at work ????Processes at work ????Notch carved out and enlarged.Notch carved out and enlarged.Upper slope unsupported/ undermining occurs.Upper slope unsupported/ undermining occurs.Due to erosion, weathering and gravity, slope collapses Due to erosion, weathering and gravity, slope collapses forming a steep face.forming a steep face.Cliff retreats and increases in height.Cliff retreats and increases in height.Rock left at base of retreating cliff is a wave cut platform.Rock left at base of retreating cliff is a wave cut platform.The bigger the platform – the less rate of erosion.The bigger the platform – the less rate of erosion.Example – Cliffs of Moher, Co. Clare.Example – Cliffs of Moher, Co. Clare.

SEA CLIFFSSEA CLIFFS

Marine TransportationMarine Transportation

Longshore Drift – movement of material Longshore Drift – movement of material along the coast in a zig-zag pattern.along the coast in a zig-zag pattern.

Swash moves material up the beach.Swash moves material up the beach.

Backwash moves sediment back into the Backwash moves sediment back into the sea.sea.

Formation of a Beach.Formation of a Beach.

Formed by constructive waves.Formed by constructive waves.Weak backwash allows material to build Weak backwash allows material to build up higher up the shore and finer material up higher up the shore and finer material is left closer to shoreline.is left closer to shoreline.Beach forms between high and low water Beach forms between high and low water marks.marks.Sections of beach include sandy area/ Sections of beach include sandy area/ shingle area and storm beach.shingle area and storm beach.Example – Skerries.Example – Skerries.

Formation of Sand Spit.Formation of Sand Spit.

Long ridge of sand and shingle deposited along Long ridge of sand and shingle deposited along entrance to sheltered bay.entrance to sheltered bay.

Constructive waves and longshore drift.Constructive waves and longshore drift.

Waves hit obstacle/ lose power / deposit load.Waves hit obstacle/ lose power / deposit load.

Builds up above sea level across entrance to Builds up above sea level across entrance to bay.bay.

Wave refraction may cause spit to curve inwards Wave refraction may cause spit to curve inwards towards bay= Recurved spit.towards bay= Recurved spit.

Example – Portmarnock, Dublin.Example – Portmarnock, Dublin.

Formation of a Tombolo.Formation of a Tombolo.

Island connects to mainland due to Island connects to mainland due to deposition.deposition.

Constructive waves and longshore drift.Constructive waves and longshore drift.

Wave refraction at island causes currents Wave refraction at island causes currents to converge / deposit load.to converge / deposit load.

Example – Howth to Sutton.Example – Howth to Sutton.