Coastal Processes & Landforms

Coastal Processes & LandformsMs Carr5th year Geography

Learning IntentionUnderstand how coastal processes transform the landscapeExamine the landforms created by these coastal processesFEEDs for these landformsFeatureExplanationExampleDiagramIdentify coastal landforms on OS Maps and in Photographs

Today we will......Recall what we already know about coastal processes.Examine what influences coastal erosion.Discuss two types of waves.Recap on processes of coastal erosion.

Textbook pages 122-124.

Mind Map..What I already know..

Chapter 12: Coastal Processes, Patterns & Associated Landforms, & Human Interaction WavesResponsible for erosion, transportation and deposition of material along coastlinesGenerated by wind passing over the surface of the seaFetch is the open area of the sea that a wave travels overThe longer the fetch, the stronger the wind speed, the stronger and greater the waves generated

Factors affecting the rate of coastal erosion

Where the breaking of a wave occursHighest energy at moment of collapseIf it hits a cliff before or after it breaks it wont erode as much

- Steepness of the wave- Formed nearer coast, steeper & stronger

- Rock resistance

Chapter 12: Coastal Processes, Patterns & Associated Landforms, & Human InteractionTypes of WavesConstructive wavesDeposit more than they erodeCarries material in Swash up the shoreMost common in summerDestructive wavesErode more than they depositSteep wavesStrong BackwashMost common in winter

Chapter 12: Coastal Processes, Patterns & Associated Landforms, & Human InteractionWave RefractionWaves slow down as water becomes shallow.This change in speed causes the wave to bend and change their direction as they approach the shore, this is called Wave Refraction.This causes waves to move towards the headland where their erosive force is released.Erosion is stronger on the headland and deposition occurs in the bay.

Change of wave directionDebrisProcessesErosionTransportationDeposition

Chapter 12: Coastal Processes, Patterns & Associated Landforms, & Human InteractionProcesses of coastal erosion Hydraulic ActionCompressionAbrasion/CorrasionAttritionSolution/CorrosionErosionHydraulic Action; direct force of the waves on the coast.Abrasion; rock debris is hurled by the waves against the coastline.Attrition; fragments of stone are rounded and eroded by hitting off each other.Solution; minerals in certain rocks are dissolved by water.Air Compression; breaking of rock as a result of being trapped by waves in rocks.Wave Refraction; bending of waves concentrates erosion at headlands, this then leads to the formation of cliffs, caves, arches and stacks.Chapter 12: Coastal Processes, Patterns & Associated Landforms, & Human InteractionLongshore drift a process of coastal transportationThe sea transports its load of sand and shingle in two main ways:Up the shore in swash Back down the shore in backwash

TransportationLongshore DriftMovement of material along the coastZig zag pathSwash and Backwash

Constructive WavesDestructive WavesWave RefractionLongshore Drift???Deposition occurs because the swash is more powerful than the backwash.Erosion occurs because the backwash is more powerful than the swashThe movement of material along the coastline in a zig zag manner due to the angle of the approaching waves and the slope of the coastline.The bending of waves due to a headland causing the waves to lose energy and deposition to occur.Learning IntentionRecap on coastal processes.Examine landforms of coastal erosion.Answer a FEED style question on one landform.

RecapThe return movement of water downshore is called _____________.____________________ deposit more than they erode and are most common in summer.When a wave slows down, bends and changes direction it is called _________________.__________________ is the zig-zag movement of material along the coast._____________ happens when fragments of rock are rounded and eroded by hitting off each other.When rock breaks as a result of being trapped by waves in rocks, it is called ____________________.Landforms of Marine ErosionCliffsWave-cut PlatformBayHeadland

CaveBlowholesSea ArchesSea Stacks

Chapter 12: Coastal Processes, Patterns & Associated Landforms, & Human InteractionCliffsCliffs are vertical slopes on a coastlineForm as a result of a combination of coastal processes of erosion, such as hydraulic action, compression, abrasion, solution and attritionDestructive waves attack an area of weakness in rocksCrack/joint formsCrack/joints are attacked by hydraulic force of the water and by compressionNotch forms

Chapter 12: Coastal Processes, Patterns & Associated Landforms, & Human InteractionNotch gets bigger, eventually the rocks above the notch (overhang) are unsupported and collapse to form a cliffShattered rock falls into the seaSea uses this shattered rock to further erode the cliff through abrasionSolution also erodes the cliff faceThese events continue over time and the cliff face retreatsWave-cut platforms surface of rock that remains in front of the retreating cliffWave-built terraces deposited pieces of rockthat are deposited below low-tide level

CliffsExample; Cliffs of Moher, Co ClareHook Head, Co Wexford

OS Map- Textbook page 125

Chapter 12: Coastal Processes, Patterns & Associated Landforms, & Human InteractionBays and HeadlandsDifferential erosion rocks along coastlines are eroded at differing rates depending on whether they are soft or hardSections of coastline that are composed of soft rock will erode faster than areas composed of hard, more resistant rockStretches that are composed of soft rock will form baysHarder more resistant rock will take longer to erode and will remain jutting out into the sea as headlands27Bays and Headlands

Bays and Headlands

Bays and Headlands

Malin Head, DonegalBays & HeadlandsExample;Dublin BayWicklow Head

OS Map; Textbook page 126

Chapter 12: Coastal Processes, Patterns & Associated Landforms, & Human Interaction Sea Caves, Sea Arches, Sea Stacks and Sea Stumps

Caves form in an area of weakness on a cliff face or headlandProcesses of coastal erosion act on this area of weakness and enlarge it to form cavesCaves are further eroded by abrasion, resulting in them becoming largerSea arches form when continued erosion occurs in a sea cave causing it to extend right through the headlandA sea arch may also form when two sea caves form back to back on the opposite sides of a headlandCave, arch, stack, stump

Cave, arch, stack, stump

Chapter 12: Coastal Processes, Patterns & Associated Landforms, & Human InteractionA sea stack is a rock which is standing out in isolation in the sea away from the coastlineSea stacks form when erosion continues on a sea arch, widening the sea arch and causing the roof of the sea arch to eventually collapseWhen the roof of the sea arch collapses, it leaves the former section of headland isolated or cut away from the main headland/coast. What remains standing out in the sea in isolation is called a sea stackA sea stump is the eroded remains of a sea stack

Cave, Arch, Stack, StumpExamples;Hook Head, Co Wexford

Caves; Ballybunion, Co KerryArch; The Bridges of Ross, Co ClareSea Stack; Dun Briste, Co Mayo

Chapter 12: Coastal Processes, Patterns & Associated Landforms, & Human InteractionBlowholes

Blowholes form at areas of weakness, for example, where a hole forms on the surface of a cliff top joins with a roof of a sea cave. They are formed as a result of compression.Air may become trapped in a sea cave by waves.Results in a build up of pressure which leads to rock shattering the rocks of the cave roof.Rock eventually collapses creating a blowhole.During stormy weather, sea spray blasts out through the blowhole.Example; Hook Head, Co Wexford.Geo: a long narrow inlet that forms when the roof of a cave, that was once connected to a blowhole collapses.

Landforms of Coastal Erosion on OS MapsTextbook- page 128.Pairwork Quick QuestionsList 5 processes of coastal erosion.List the 3 main landforms of coastal erosion.Name an Irish example of each of the above landforms.What does a sea stack look like on an OS map?Explain the term differential erosion.What is a geo?

Caves, arches, stacks, stumps and blowholes are features of coastal erosion.

Caves: what are they?Type of rock they are formed inWhy hard rock?Hydraulic Action (P)Compressed Air (P)Weakness in the roof of the caveFormation of a blowholeContinued erosion on roof and back wallFormation of an archWeathering and erosion of the roof of archCreation of a stackErosion of stack Abrasion (P) of stack whyCreation of a stumpExam Question; FEEDE:Caves are open hollows usually found near the base of a headland on the cliff face. They tend to form in areas of hard rock along the coastline. Soft rock erodes too quickly for a cave to maintain its shape therefore they tend to form slowly in hard rock and can be deep and large. Caves occur due to the main marine processes of erosion such as hydraulic action (the power and the force of the seas waves pounding the coastline) and Compressed air (where air is trapped between the cliff face and the wave and causes the air to expand. This in turn causes the cracks to enlarge and the coastline to erode). Over time the sea will continue to erode the back wall of the cave and in stormy times cracks in the roof of the cave will be further eroded by solution and compressed air. This creates an area of weakness such as a tunnel or vent in the roof all the way to the surface of the headland. If a vent opens from the roof of the cave to the top of a headland a blowhole is now formed. During times of high tide or storms water will force its way up the vent and spray out on the surface. As this feature is formed the cave continues to erode backwards through the headland. Sometimes one cave will erode the whole way through or sometimes two caves will meet from either side of the headland. As this happens an arch is formed. However, the roof of the arch (with the blowhole) is weakened and continuous erosion will cause the roof to collapse. Once an arch collapse the headland appears smaller and the remaining outer wall is called a stack. However there is an increase of broken rocks and debris in the area and the processes of abrasion (the scraping of the seas load against the coastline) will continue to erode the stack. Over time it is eroded down to a stump. This is an area of rock barely visible over the waves and dangerous for incoming boats.The creation of these features are responsible for the coastline appearing to retreat and appear smaller on maps/photographs.E:Examples x 3D:Diagram (frame, title, details, colour, labels)

Caves are open hollows usually found near the base of a headland on the cliff face. They tend to form in areas of hard rock along the coastline. Soft rock erodes too quickly for a cave to maintain its shape therefore they tend to form slowly in hard rock and can be deep and large. Caves occur due to the main marine processes of erosion such as hydraulic action (the power and the force of the seas waves pounding the coastline) and Compressed air (where air is trapped between the cliff face and the wave and causes the air to expand. This in turn causes the cracks to enlarge and the coastline to erode). Over time the sea will continue to erode the back wall of the cave and in stormy times cracks in the roof of the cave will be further eroded by solution and compressed air. This creates an area of weakness such as a tunnel or vent in the roof all the way to the surface of the headland. If a vent opens from the roof of the cave to the top of a headland a blowhole is now formed. During times of high tide or storms water will force its way up the vent and spray out on the surface. As this feature is formed the cave continues to erode backwards through the headland. Sometimes one cave will erode the whole way through or sometimes two caves will meet from either side of the headland. As this happens an arch is formed. However, the roof of the arch (with the blowhole) is weakened and continuous erosion will cause the roof to collapse. Once an arch collapse the headland appears smaller and the remaining outer wall is called a stack. However there is an increase of broken rocks and debris in the area and the processes of abrasion (the scraping of the seas load against the coastline) will continue to erode the stack. Over time it is eroded down to a stump. This is an area of rock barely visible over the waves and dangerous for incoming boats.The creation of these features are responsible for the coastline appearing to retreat and appear smaller on maps/photographs.E:Examples x 3D:Diagram (frame, title, details, colour, labels)DepositionCoastal Landforms

Learning IntentionExamine landforms of coastal deposition.Review a sample answer on one landform.Answer a FEED style question on another landform.

Chapter 12: Coastal Processes, Patterns & Associated Landforms, & Human InteractionTextbook page 129-132DepositionCoastal deposition occurs when waves lose energy and therefore their ability to carry materialSea deposits its load on the coastal areaConstructive waves have an ability to move the load inlandWave refraction in bays result in wave energy decreasing and this results in deposition occurringDeposited material may include shingle, sand and sediment

Landforms of Marine DepositionBeachStorm BeachSand SpitSand BarLagoonTomboloChapter 12: Coastal Processes, Patterns & Associated Landforms, & Human InteractionBeachA beach is an area of sand, shingle or gravel Beaches are created by the processes of longshore drift, constructive waves and wave refraction,Located in an area between low tide mark and where the highest storm waves can reachConstructive waves swash is powerfulWaves move up the sea shore, slow down and their load of sand and rocks is depositedHeavier load of rock and shingle is deposited on the backshoreFiner, lighter material such as sand is deposited on the foreshoreOver time a beach is formed

A storm beach is made of pebbles and stonesIt forms when waves are strong enough to push large rocks and boulders above the high tide markA storm beach is usually steeper than a regular beach.

Sand Dunes

Hills of sandSand is dried and blown inlandVegetation can trap the sandMarram grass is sometimes planted to prevent it blowing further inlandEg; Curracloe, Co Wexford

BermsRidges, like steps or terracesGentle constructive waves push sediment into long low ridgesMark the junction between foreshore and backshore

Runnels & RidgesRunnels-depressions on the sand on the foreshoreRidges-the gentle rises between the runnelsFormed by the action of constructive waves

CuspsCresent shaped hollows where shingle changes to sandResult of complex wave actions on pebble beaches

Beach

FeatureExplain ExamplesDiagram

Chapter 12: Coastal Processes, Patterns & Associated Landforms, & Human InteractionSand SpitA sand spit is a long narrow ridge of deposited sand and shingle It is connected to the coast at one endSand spits develop due to longshore drift and depositionSand spits form where the process of longshore drift is interruptedWaves lose energy and slow downLocation of estuary or change in wind directionSediment is deposited in sheltered and shallow waterOver time this sediment builds up and becomes visible above the level of the sea

Chapter 12: Coastal Processes, Patterns & Associated Landforms, & Human InteractionOn the seaward side of the sand spit constructive waves deposit fine sediment such as sand and form a beachOver time the sand spit gets widerAs sand spits grow the area of water behind it is often then sheltered by waves and windThis often leads to the formation of a salt marshWave refraction may occur at the end of a sand spit which results in the sediment being carried around the end of the sand spit to form a recurved spit, this looks like a hook.

SpitExample; Inch Strand, Dingle, Co Kerry

Pairwork RecapBeaches are created by the processes of;1.2.3.Three beach features are;1.2.3.A sand spit is a _______, _________ ____________of deposited _________ and ___________.Sand spits develop due to _______________________and __________________.

Chapter 12: Coastal Processes, Patterns & Associated Landforms, & Human InteractionSand Bar & LagoonA sand bar forms when a sand spit extends across a bay Sand bars will eventually seal off an area of coastlineThe water directly behind the sand bar will then be called a lagoon

Two Types of Sand BarOffshore BarLocated away from the coastlineParallel to the coastlineGenerally only exposed at times of low tideBreaking waves deposit sand on the offshore barSize of the offshore bar increases over timeMay eventually block or close off the bay creating a lagoon

Baymouth barSand spit extends from one side of a landmass across a bay and reaches the other landmassBlocks/closes off the bay

ExampleOur Ladys Island, Co. Wexford.

Baymouth BarClassworkQuick QuestionsPage 132

TomboloTombolos are formed due to wave refraction and longshore driftResult from a sand spit extending out to an island and connecting the island to the mainlandWaves approach the island, wave refraction occursSediment is depositedResults in the spit connecting the island to the mainland and a tombolo is formed

TomboloTomboloExample;Howth, Co Dublin- Sutton is built on the tombolo.

Coastal Landforms on OS MapsTextbook page 133

Exam QuestionsCoastal Processes, Patterns & Landforms