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Wave action and coastal landforms

Wave action and coastal landforms. PART TWO!. Yesterday, we learned about…. Waves  friction Wave length , height , crest , trough Wave action: constructive and destructive Swash and backwash Longshore drift Wave refraction. Coastline Erosion. Four types: 1) Corrosion

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Wave action and coastal landforms

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  1. Wave action and coastal landforms PART TWO!

  2. Yesterday, we learned about… • Waves  friction • Wave length, height, crest, trough • Wave action: constructive and destructive • Swash and backwash • Longshore drift • Wave refraction

  3. Coastline Erosion • Four types: • 1) Corrosion • 2) Corrasion/ Abrasion • 3) Attrition • 4) Hydraulic action

  4. Corrosion (also sometimes called solution) • A type of chemical weathering where material is dissolved by seawater • There are weak acids in the sea which wear rock down (especially some types of rock such as chalk or limestone) http://www.bbc.co.uk/schools/gcsebitesize/geography/coastal/coastalprocessesrev3.shtml

  5. Corrasion/ Abrasion • Scouring of the rock • Sand and rock particles in waves wear down rock surfaces (usually at the base of a cliff) • Leaves rock very smooth • Like sandpaper http://www.bbc.co.uk/schools/gcsebitesize/geography/coastal/coastalprocessesrev3.shtml

  6. Attrition • Rock particles in suspension erode each other • Rock hits rock  particles break down • Hitting each other and getting smaller in size http://www.bbc.co.uk/schools/gcsebitesize/geography/coastal/coastalprocessesrev3.shtml

  7. Hydraulic Action • When waves hit the base of a cliff, air is compressed into cracks. When the wave retreats the air rushes out of the gap  cliff material breaks away. • Basically, water and air are compressed into rock fractures  water and air in and out of the rock breaks it apart http://www.bbc.co.uk/schools/gcsebitesize/geography/coastal/coastalprocessesrev3.shtml

  8. Undercutting (52-53) • Rock eroded and removed at the base of a cliff • Creates a very steep, vertical cliff

  9. Cliff erosion features • Caves • Bays • Headlands • Tunnels • Arches • Stacks • Wave-cut platforms

  10. Caves, Bays, Headlands • CAVES: Indentation in the weakest rock surface of cliff caused by wave refraction and hydraulic action • BAYS: soft rock wears away faster  bay between headlands • HEADLANDS:Hard rock more resistant to erosion  erodes into jagged shape that juts out from land

  11. Erosion of cliffs caves  bays and headlands  caves tunnels  arch  stack  wave-cut platform • Arch: hole in headland caused by wave refraction • Stack: isolated rock pillar after arch caves • Wave-cut platform: undercutting creates a rock debris platform in water http://www.geography.learnontheinternet.co.uk/topics/coasts_erosional_landforms.html#baysandheadlands

  12. Shoreline depositional features • Spits • Tombolos

  13. Spit •  Long ridge of sand created by longshore drift • Linear accumulation of sediment attached to land at one end. • Spits are typically elongate, narrow features built to several dozen feet by wind and waves. • Where there is an obstruction or the power of the waves is reduced the material is deposited. The sediment which is deposited usually builds up over the years to form a long ridge of material

  14. Tombolo • When sand spit grows long enough that it joins an island to the mainland

  15. Types of coasts (54) • Ria: lower part of V-shaped valley flooded with water  A drowned river valley that remains open to the sea • Fjord: Lower part of U0shaped valley flooded with water • Estuary: lower part of a river valley filled with sediment and submerged by the sea depending on the tides; mix of salt and fresh water; funnel shape with gently sloping sides

  16. Ria

  17. Coastal Protection • 1) Sea wall: man-made wall to prevent wave erosion • 2) Groynes: artificial barriers built into ocean to stop movement of sand by longshore drift

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