Sediment Cells And Sources

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Sediment Cells And Sources

  1. 1. Sediment Cells and Sources<br />AS Geography<br />
  2. 2. Learning Objectives<br />Demonstrate an understanding of wave refraction<br />Develop an awareness of littoral cells and different types of sediment<br />Demonstrate a knowledge of coastal processes including erosion<br />Evaluate the concepts behind mass movement<br />
  3. 3. Wave Refraction<br />As waves leave deep water they become affected by frictional drag as they come into contact with the seabed<br />
  4. 4. Sediment Sources<br />Erosion of the cliffs can provide direct sediment input<br />currents bring in material from the sea bed<br />Rivers bring sediment downstream<br />There are several methods by which sediment can reach the sea<br />
  5. 5. What happens to sediment<br />Sediment is either stored as a depositional landform <br />As a nearshore feature such a bank or offshore bar. <br />Alternatively it is transported as a throughput and become outputs from the system being deposited either in deeper water or away from the coastal area in question.<br />
  6. 6. Types of Sediment<br />Clastic and Biogenic sediment<br />Clastic sediments are from rock weathering and erosion<br />Biogenicsediments are the shells and skeletons of marine organisms<br />
  7. 7. Sediment Transport and Deposition<br />What do you think is the main agent of moving sediment and depositation?<br />Waves, currents, tides and wind move sediment from source areas and deposit it in the form of coastal land forms<br />These exist in a state of “Dynamic Equilibrium”<br />
  8. 8. Sediment Cells/ Littoral Cells<br />These depositional landforms (such as beaches, sand dunes, salt marshes and mudflats) act as a dynamic sediment store and sediments are transported onshore, offshore, and alongshore to create them. <br />These stores in turn provide sediment for stores further down the coast.<br />The next slide explains this<br />
  9. 9.
  10. 10. Sediment Cells of the UK<br />
  11. 11. Definitions<br />The movement of sand and shingle in the nearshore zone by longshore drift (littoral drift) has been found to occur in discrete, functionally separate sediment cells.<br />There are 11around England and Wales. Smaller ones are within these. <br />The main cells are defined as a length of coastline and its associated nearshore area within which the movement of coarse sediment (sand and shingle) is largely self contained. <br />Interruptions to movement of sand and shingle within one cell should not affect beaches in an adjacent sediment Cell<br />
  12. 12. Transport<br />As the particles are moved they become rounded by Attrition.<br />Larger sediment is deposited during high energy and form beaches whilst some are also carried in suspension in areas of reduced energy<br />Adjustments to these dynamic environments happen continuously to maintain the flux<br />
  13. 13. Coastal Processes<br />Now for the fun bit<br />Coastlines differ due to differing erosion<br />Coastal Erosion is the wearing away of the land by the sea.<br />Different types of rocks wear away at different speeds and in different ways.<br />
  14. 14. Types of erosion<br />Hydraulic Action. This is the force of water hitting the cliff and squeezing air into the cracks in the rock<br />Abrasion. This is the force of the bits of rock carried in the water blasting into the cliff.<br />Attrition. This is the process of rocks hitting each other and breaking into smaller rocks<br />Corrosion. This is a chemical reaction between the sea water and the minerals in the rocks<br />
  15. 15. The secret art of Coastal kung fu!<br />Hydraulic Action: make punching movements with hand- demonstrates force of water hitting cliff. <br />Abrasion: make a throwing gesture with hands like you are throwing dealing cards very rapidly<br />Attrition: make 2 fists, and then bring them towards each other, hitting each other, then open hand to resemble a stone breaking.<br />Corrosion: have arms out stretched in front of you, waving fingers, and moving arms downwards. Sound effect of something dissolving is needed. <br />Solution: Put arms out in front of you waving fingers and moving down.<br />
  16. 16. Please Don’t be embarrassed<br />Oh OK be embarrassed then<br />Here we go:<br />
  17. 17. Mass Movement<br />Exposed weathered rocks are often susceptible to mass movement<br />
  18. 18. Soil Creep<br />Slow less than 1cm a year<br />Caused by raindrop impacts<br />Wet periods add moisture to soil which swells and expands then falls down slope<br />Freeze thaw<br />
  19. 19. Solifluction<br />Occurs mainly in colder areas, where freeze and then thaw creates movement due to lack of percolation<br />
  20. 20. Earth flows and Mudflows, slides slumps and Rockfalls<br />Faster movements <br />Occur on steep slopes<br />Found often on unconsolidated slopes<br />Can be large or small<br />
  21. 21. Other Mass Movement Reasons<br />Students are to write short paragraphs on the following separate into physical and human causes<br />Runoff<br />Marine Erosion<br />Waves and Beaches<br />Geology<br />Human Activity<br />Sea walls and Coastal Defences<br />Land reclamation<br />Development<br />
  22. 22. Learning Objectives<br /><ul><li>Demonstrate an understanding of wave refraction
  23. 23. Develop an awareness of littoral cells and different types of sediment
  24. 24. Demonstrate a knowledge of coastal processes including erosion
  25. 25. Evaluate the concepts behind mass movement</li>

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