1.COASTAL EROSIONLesson 4

2. 2 3. Tides Rising and fallingof the sea level Cause : pull of themoon & sun,rotation of theearth Each coastal areareceive two hightides and two lowtides daily3 4. The shaping influencing factors: 5. 5 6. LESSON OBJECTIVE Todescribe and explain the 4 coastal erosion processes 6 7. ErosionCorrasion3 COASTAL PROCESSES Abrasion Solution Hydraulic actionTransport Longshore driftDeposition Factors: -Supply of sediment -Gradient of slope -Coast position 7 8. COASTAL EROSIONMore erosion Less erosionTypes of waves-Destructive waves -Constructive(more energy)waves (less energy)Structure and - Numerous lines of - No crackscomposition ofweakness- Hard rockscoastal rocks - Soft rocksPosition of the - Open coast - Protected andcoastsheltered by8 structures 9. Waves can be destructive or constructive..1. Destructive waves: operate in storm conditions arecreated from big, strong waves when the wind is strong and has been blowing for a long time occurwhen wave energy is high and the wave has traveled for a long time tendto remove material from the coast and associated with erosion backwash is stronger than the swash. 10. 2. Constructive waves: operate in calm weather are less powerful waves break on the shore and tend to deposit material, building up beaches are responsible for transporting material . swash is stronger than the backwash. 11. Plunging Spilling 12. HYDRAULIC ACTION Direct impact of the waves againstthe coast. Compress air and exertpressure in the cracks of rocks (pg92) Enlarges lines of weaknesses afterrepeated crashes of waves Cavitation: water surges intocracks, joints, faults. Results incompressed air and builds pressure.Water retreat releases pressure andtrapped air which breaks the rockup.13 13. The constant force ofwaves crashing on theshore damages it. Thisis called hydraulic action. 14. CORRASION/ABRASION Impact of the materials carriedby the waves scraping againstthe coast Turbulence of the currentsproduce a scouring effect Chiselling effect / grindingaction on the coast Cutting and breaking the rockson the coasts 15 15. ATTRITION Rocks rub or hit againsteach other, breaks downinto small round smoothpieces(pg 93) Materials from the wavescollide with materials on thecoast Impact causes materials tobreak into smaller pieceswhich becomes sand16 16. SOLUTION/CORROSION Waves react chemically with soluble minerals in the rocks and dissolve them (pg 93) Corrosion of rocks by seawater Wave action increases the rate of reaction by removing the reacted chemical solution Eg limestone17 17. Coastswhere the geology alternatesbetween strata (or bands) of hard rocksand soft rocks is called a discordantcoastline. Discordant coastlines will have alternatingheadlands and bays. Concordant coastline is where the rockremains the same along the coastline. Concordant coastlines tend to have lessbays and headlands. 18. Alongthe coastline of the Isle of Purbeck in Dorset (south coast of England), there are both discordant and concordant coasts. Thediscordant coast has been formed into Studland Bay (soft rock), Ballard Point (hard rock), Swanage Bay (soft rock) and Durlston Head (hard rock). AfterDurlston Head the rock remains hard. This concordant coast has less features. 19. Coastal features Created byerosionAlong a coastline there are often many features created by erosion. The most common of these are: 1.Cliffs 2.Headlands and Bays 3.Caves4.Arches 5.Stacks6.Stumps 20. COASTAL LANDFORMS FORMED BY WAVE/MARINE EROSION: SEA CAVES, ARCHES, STACKS AND STUMPS(C) Sea caves, arches, stacks and stumps1. Sea caves a tunnel-like opening at the base of the cliff.2. Erosional processes such as hydraulic action, abrasion and corrosion by destructive waves act at the base of a cliff/headland along a line of weakness in the rock to form a hole called a notch.3. Continual erosion enlarging the notch to form a cave.4. Prolonged wave erosion enlarges and lengthens a sea cave until it finally cuts right through the headland and form an arch.5. Further erosion of the arch causes it to collapse and an isolated pillar of rock called a stack is formed.6.The stack can be further eroded and weathered. It is finally worn down to astump which is covered during high tide. 21. Formation of Cave, Arch, Stack andStump 22. 1. Cliffs One of the most common features of the coastline in Britainand around the world are cliffs. Cliffs are shaped through a combination of erosion andweathering. The weather attacks the cliff top. The wavesattack the cliff foot, causing a wave-cut notch at the bottom. Soft rock erodes easily and creates gently sloping cliffs. Hardrock is more resistant and erodes slowly and creates steepcliffs. 23. Sea cliffs A tall, steep rock face,formed by the undercuttingaction of the seaSeven Sisters chalk cliffs on the East Sussex coast 24. Wave-cut notchesA rock recess at the foot of a sea cliff where the energy of waves is concentrated 25. The formation of sea cliff and wave-cut platform 26. 2. Headlands andbays Headlands are formed when the sea attacks a section of coast consisting of alternating bands of hard and soft rock. Thebands of soft rock, such as sand and clay, erode more quickly than those of more resistant hard rock, such as chalk. Thisleaves a section of land jutting out into the sea; this is called a headland. Theareas where the soft rock has eroded away, next to the headland, are called bays. 27. Headland and bay: Myrtos Bay, Kefalonia 28. Erosion can create caves, arches and stacks along a headland. Againweathering can also help to create these landforms. 3- Caves occur when the waves force their way into cracks in the cliff face. The water contains sand and other materials that help to grind away at the rock until the cracks become a cave.4- If the cave is formed in a headland, it may eventually break through forming an arch.5- The arch will gradually become bigger and bigger until it can no longer support the top of the arch. When the arch collapses, it leaves the headland on one side and a stack (a tall column of rock) on the other. 29. Old cliffline Original Land su rface stack stumpNaturalWave-cut platform Arch 30. Erosional Features 31. SUMMARY Describe the characteristics of 4 coastalerosional process: CASH Explained how the erosional processes occur State the coastal erosional features and explainhow they form 40 32. Sources: Source: http://www.slideshare.net/shoaib1982/marine-system by shoaib 1982 Source: http://www.slideshare.net/esteeseetoh/coastal-proce by estee seetoh hoaib1982