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Coastal Processes, Patterns and Landforms

Coastal Processes, Patterns and Landforms. Objectives. Discuss the processes of coastal erosion, transportation and deposition. Understand the formation of coastal landforms and identify these on diagrams, maps and photographs.

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Coastal Processes, Patterns and Landforms

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  1. Coastal Processes, Patterns and Landforms

  2. Objectives • Discuss the processes of coastal erosion, transportation and deposition. • Understand the formation of coastal landforms and identify these on diagrams, maps and photographs. • Describe how human activities can affect natural coastal processes. • Discuss and describe the threats to the coastline and the methods used to protect it. • Explain how changes in sea levels affect coastal landforms.

  3. Activity • Mind map everything you remember about the coast!

  4. Waves • Two types of waves – Constructive and Destructive • The size of the wave is influenced by the fetch. The distance a wave has to travel before it reaches land. • When waves break water rushes up the beach called the swash. When the water goes back to the sea its called backwash.

  5. Destructive Waves • (i) the strength and speed of the wind – when the wind is fast, more energy is transferred and therefore the bigger the wave is produced. • (ii) the duration of the wind –when the wind remains strong over long periods- the longer the wind blows, the more energy is transferred to the wave • Destructive waves = erosion • The backwash digs into the land removing large quantities of rock, sand and earth.

  6. Destructive waves • Weak swash • Strong back wash • Operate during storm conditions • Erosion

  7. Constructive Waves • Powerful swash that can carry debris up the beach but have little energy left in the backwash to drag the debris away again. • Constructive waves = deposition

  8. Constructive waves • Strong swash • Weak backwash • Make storm beaches • Deposition

  9. Wave Refraction • Wave refraction is the bending of the waves. • The waves approaching the coast are straight. Friction with the sea bed causes part of the wave near the headland to slow down while the rest of the wave continues at the same speed. • The difference in speed makes the wave curve towards the headland.

  10. Coastal Erosion • Processes • Landforms (Essay Questions) • Identifying on OS and Aerial Photograph

  11. Sea Erosion • http://www.bbc.co.uk/schools/gcsebitesize/geography/coasts/coastal_processes_rev3.shtml Can any one guess what the processes of sea erosion are? Hint: very similar to river erosion.

  12. Processes of Coastal Erosion • Hydraulic Action • Compression • Abrasion • Attrition • Solution

  13. Hydraulic Action • When strong waves crash against the coast they break rocks off the cliff face.

  14. Compression • Air Compression – The waves trap air in crack in the rocks. As the waves retreat the trapped air expand quickly and can crack the rock.

  15. Abrasion • This is erosion caused by small rocks carried in the sea water hitting against the coastline. p99 *Very similar to Hydraulic Action. Difference = water contains suspended rock material.

  16. Attrition • Erosion caused by the small stones hitting each other breaking themselves into smaller pieces.

  17. Solution • Salts in the sea water dissolve rock by chemical means. Chalk and limestone coasts are most easily eroded this way.

  18. Activity • Write the processes of erosion into your copies. Learn for homework.

  19. Examples of coastal landforms formed by erosion and deposition

  20. Landforms of Sea Erosion • Like rivers, the sea creates many features or landforms as a result of erosion. These include, • Cliffs and blowholes. • Bays and Headlands • Sea caves, sea arch, sea stack, sea stump Each of these will be a long answer essay. You will also be required to recognise these on a map/photo and diagram.

  21. The Sea/ The Coast • Cliff – close contour lines at the edge of the land near water.

  22. How are cliffs and wave-cut platforms formed?

  23. Cliffs and Wave-cut platforms • The waves attack the base of the cliff through the processes of abrasion, compression, hydraulic action and attrition. • Over time the cliff will be undercut and a wave-cut notch is formed. • Eventually the cliff becomes unstable and collapses. Further cliff retreat will form a wave-cut platform.

  24. This is a passage that links the roof of a cave to the cliff top. Air trapped by waves erodes away the rock. This continues to create a tunnel called a blowhole. http://www.youtube.com/watch?v=bWC_g2XfuQU Blowhole

  25. Activity • Read the formation of a cliff in your groups. Hightlight the important information. • Homework: Write out a sample answer of a cliff and wavecut platform. Use F.E.E.D • Name the feature, example, explain and diagram.

  26. Sea Cave, Sea Arch, Sea Stack • http://www.boardworks.co.uk/media/2132de4b/ALevel%20Geography%20Sample/2_9_stacks_stumps_animation.swf

  27. Sea Caves, Sea Archs, Sea Stacks • As the water smashes up against the headland rock, the erosion process begins. • Waves chisel away at the rock and over time a cave is formed. • The cave will give way and the water will drill its way on through the back of the cave, thus creating an arch. • Overtime the arch collapses to reveal one large stack of rock. This is the sea stack.

  28. Sea Stacks

  29. Sea Caves, Arches, Stacks and Stumps. • Stack little islands – green with blue outline. • Stumps underwater, smaller, grey. *Difficult to see an arch or cave.

  30. For Homework • Write out sample answers on Sea cave, arch and stacks using the FEED principal. • F = State the Feature • E = Explanation/Formation • E = Examples • D = Labelled Diagram

  31. Bays and Headlands http://www.youtube.com/watch?v=C_4DEkz9CCU • In your groups read how bays and headlands are formed. Highlight the important parts.

  32. For Homework • Write out sample answer on Cliffs and Sea Stacks using the FEED principal. • F = State the Feature • E = Explanation/Formation • E = Examples • D = Labelled Diagram

  33. Deposition

  34. Constructive Waves Powerful swash that can carry debris up the beach but have little energy left in the backwash to drag the debris away again. Constructive waves = deposition

  35. Before we talk about deposition we have to mention how the eroded material is carried along the coast. • What do you remember about longshore drift?? • Movement of material along the coast. • Occurs because the coastline is irregular and waves do not break parallel to the coast (wave refraction). • Swash moves material to the shore at an angle and the backwash pulls the sediment back out to sea at a right angle.

  36. http://www.youtube.com/watch?v=U9EhVa4MmEs

  37. Longshore Drift • http://www.youtube.com/watch?v=rCpZYlPqn6E Activity: Read your book - page 55. Draw the diagram no.6 on page 55 of your book.

  38. Longshore Drift • http://www.youtube.com/watch?v=U9EhVa4MmEs&feature=related • Activity: Using the above information and notes in your book. Summarise longshore drift into your copies

  39. Landforms of coastal deposition • Beaches • Sand Spits, Sand Bar and Lagoon • Tombolos

  40. Beaches form in sheltered environments, such as bays. When the swash is stronger than the backwash, deposition occurs.

  41. Beach • Can be seen on an OS map – coloured yellow at the coast • Beaches have other landforms such as Berms, Cusps and Runnels and Ridges. • Berms: are long steps or terraces which form on shingle beaches when constructive waves push beach sediment into long low ridges. They mark the junction between the backshore and foreshore. • Cusps: Crescent shaped hollows formed where shingle changes to sand. Generally occur on pebble beaches • Runnels and Ridges: Runnels are wide depressions in the sand of the foreshore. Ridges are gentle rises in it. Formed by the action of constructive waves.

  42. Activity • Read the notes in book about the formation of a beach. • Complete a sample answer into your copies using F.E.E.D and remember at least 13 SRPS.

  43. Sand Spit • A long deposit of sand attached to the land at one end. • Example: Portmarnock and North Bull Island in Dublin. • Created when the process of longshore drift is interrupted in some way either by a change in the shape of the coast or by human activity such as building a sea wall . • They are commonly found attached to the headland.

  44. Sand Bar and Lagoon • When a spit grows and reaches out to the other side the spit is called a sand bar. • If it cuts water off from the sea a lake is formed called a lagoon.

  45. Tombolo • When a spit grows out into the ocean and joins to an island its called a tombolo.

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