1. Topics for today Mass Wasting (Ch. 13 418-425) 1. Controlling factors –Soil strength –Hill slope gradient 2 Physical model 3 Natural cases –Rain storms –Timber harvesting –Roads 3. Coefficient of friction Water in soils 4.Mechanisms of movement 5.Mass wasting types 6.Large landslides

2. Mass wasting

3. Mass wasting is the down slope movement of rock, regolith, and soil, under the influence of gravity.

4. Rock fall

7. Landslide

9. Creep

10. Debris flow

12. Coefficient of friction

13. Angle of repose = angle of internal friction in dry, loose material

14. Cohesion

15. Water reduces cohesion, removes frictional contact between grains

16. Landslide

17. Mechanisms of movement Pure flow –Earth flows –Mudflows Pure slide/fall –Rock falls –Avalanches –landslides Creep –Gradual movement - Freezing cycles

19. Dry mass wasting from Slow to fast Creep------->Rock fall

20. Creep

21. Soil Creep

22. Creep

23. Rock fall

27. Talus slope

28. Slow-medium velocity mass wasting from dry to wet

30. Earthflow

31. 6 m/yr Highway 149 The earthflow began 700 years ago. About 350 years ago, a second earthflow Slumgullion Earthflow, CO

32. Solifluction

33. Fasts mass wasting processes from dry to wet

35. Rockfall

36. Debris avalanche

37. Mud flow

38. Blackhawk rockslide, Ca

39. It is a prehistoric landslide ~20,000 years old Source was 4000 ft height 5 miles long X 2 miles wide X 50 feet thick Velocity = 270 miles/hour Traveled time 8 sec

40. Huascaran Debris avalanche, Peru (1970)

41. Huascaran (6768m) Trigger by an earthquake M=8 Buried the city of Yungay, 18,000 people died Traveled 9 miles 175-200 mph

42. Explanations Liquefaction-wet Air cushioning Acoustic fluidization (high vibration)

43. Liquefaction Lost of friction between grain

44. Air cushioning Air layer underneath the slide reduces friction and can travel farther.

45. Acoustic fluidization (high vibration)