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Landslides

Landslides. Causes. Is landslide a natural process?. Climatic graph of Hong Kong. Any relation between rainfall and landslides?. Rain washes away the soil. Describe and explain the rainfall characteristics of Hong Kong. Heavy Prolonged Intense

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Landslides

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  1. Landslides Causes

  2. Is landslide a natural process?

  3. Climatic graph of Hong Kong

  4. Any relation between rainfall and landslides?

  5. Rain washes away the soil

  6. Describe and explain the rainfall characteristics of Hong Kong. • Heavy • Prolonged • Intense • Because HK belongs to tropical monsoon climate, which is hot and wet.

  7. How does rain cause landslides? • Rain acts as a lubricant • which reduces friction • Soil becomes loose • Soil becomes saturated • Weight increases •  unstable slopes

  8. Water acts as a lubricant

  9. Unweathered & weathered granite

  10. How is granite weathered?

  11. Thick layer of soil

  12. Rocks change to soil by weathering

  13. Soil is removed by water or rain

  14. Let’s do a demonstration

  15. Steep slopes are common in Hong Kong

  16. Houses are built on steep slopes

  17. Houses are so close to steep slopes

  18. Can you recognize this place?

  19. Can you recognize this place?

  20. Slopes are oversteepened

  21. Landslides usually occur on steep slopes

  22. Should human be responsible for landslides?

  23. Trees on the slope are removed. Slope lacks protection.

  24. Heavy traffic causes vibration.

  25. Road cutting oversteepens the slope.

  26. Can you name some highways running beside steep slopes?

  27. Leakage of water pipes reduces the strength of slopes.

  28. Buildings add weight to the slopes.

  29. Summary: Conditions for landslides • Physical Factors – amount + duration + intensity of rain, thickness of soil layer, steepness of the slope • Human Factors – removal of vegetation, urban development, lack of maintenance, road cutting

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