COAST海岸
Where is erosion active?•   Long fetch•   Headland – wave energy concentrates•   Line of weakness on rocks•   Deep water• ...
Short fetch              Long fetch
Waves• Swash - Water  moves up the  beach• Backwash -  Water moves  down from the  beach
Wave erosion
Erosion on exposed coasts
What are coastal erosion              features?•   Cave•   Geo•   Arch•   Stack•   Platform
Platform• Ping Chau• Cliff• Platform
Wave Cut Platform• Cliff• Platform
Notch•Wavesundercut thecliff•Hydraulicaction,abrasion•Notchformed atthe base
FormationNotch collapsesCliff retreatsLeave a rocky platform behind
Caves on Basalt Island
Geo and cliff• A small inlet• Steep slopes on both  sides
Geo on Yuen Kong• Inlet• Cliff on both sides
Geo on Wan Lan Island
Formation•   Waves attacks base of cliff•   Erosion along lines of weakness•   Notch is formed•   Then a cave along the li...
Arch on Tiu Chung Chau
Tiu Chung Chau
Arch on Basalt    Island
Coastal Erosion
Formation• Line of weakness cutting across a headland• Two caves formed on the same line• Meet and join together  or• Cave...
Stack
Stack on Tai A Chau
Formation• Two caves meet and the roof collapses• Two geos meet
Transportation• Long shore drift• This happens when the prevailing wind is  not perpendicular to the coastline.• Grains mo...
Beach / Long shore driftWind direction
Favourable conditions of             deposition•   Erosion / delta provides sediment•   Sheltered coast•   Shallow water o...
Spit at Pui O
Spit
Spit
Tombolo: spit between twoislands / an island and mainland
Tombolo on Soko Islands
Tombolo on Sha Chau
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Hk coast

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Hk coast

  1. 1. COAST海岸
  2. 2. Where is erosion active?• Long fetch• Headland – wave energy concentrates• Line of weakness on rocks• Deep water• Destructive waves
  3. 3. Short fetch Long fetch
  4. 4. Waves• Swash - Water moves up the beach• Backwash - Water moves down from the beach
  5. 5. Wave erosion
  6. 6. Erosion on exposed coasts
  7. 7. What are coastal erosion features?• Cave• Geo• Arch• Stack• Platform
  8. 8. Platform• Ping Chau• Cliff• Platform
  9. 9. Wave Cut Platform• Cliff• Platform
  10. 10. Notch•Wavesundercut thecliff•Hydraulicaction,abrasion•Notchformed atthe base
  11. 11. FormationNotch collapsesCliff retreatsLeave a rocky platform behind
  12. 12. Caves on Basalt Island
  13. 13. Geo and cliff• A small inlet• Steep slopes on both sides
  14. 14. Geo on Yuen Kong• Inlet• Cliff on both sides
  15. 15. Geo on Wan Lan Island
  16. 16. Formation• Waves attacks base of cliff• Erosion along lines of weakness• Notch is formed• Then a cave along the line of weakness• Cave collapses
  17. 17. Arch on Tiu Chung Chau
  18. 18. Tiu Chung Chau
  19. 19. Arch on Basalt Island
  20. 20. Coastal Erosion
  21. 21. Formation• Line of weakness cutting across a headland• Two caves formed on the same line• Meet and join together or• Cave formed on a line and extends to the other side
  22. 22. Stack
  23. 23. Stack on Tai A Chau
  24. 24. Formation• Two caves meet and the roof collapses• Two geos meet
  25. 25. Transportation• Long shore drift• This happens when the prevailing wind is not perpendicular to the coastline.• Grains move up the shore obliquely• Then move down under gravity• Net movement
  26. 26. Beach / Long shore driftWind direction
  27. 27. Favourable conditions of deposition• Erosion / delta provides sediment• Sheltered coast• Shallow water offshore• Constructive waves• Vegetation on the coast
  28. 28. Spit at Pui O
  29. 29. Spit
  30. 30. Spit
  31. 31. Tombolo: spit between twoislands / an island and mainland
  32. 32. Tombolo on Soko Islands
  33. 33. Tombolo on Sha Chau

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