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Edu290 ppt1koch


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This is an assignment for EDU 290. This PowerPoint gives a basic understanding of types of mass-wasting.

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Edu290 ppt1koch

  1. 1. Processes of Mass Wasting<br />Janet Koch<br />EDU 290<br />PowerPoint Presentation<br />
  2. 2. Definition<br /><ul><li>Mass wasting is the down-slope movement of material under direct influence of gravity
  3. 3. Water influences the effects of mass wasting but gravity is the most important factor</li></li></ul><li>Determining Factors of Mass Wasting<br /><ul><li>Slope Stability</li></ul>Gravity<br /><ul><li>Friction
  4. 4. Angle of Repose
  5. 5. Type of Material (Rock, soil, sediment)
  6. 6. Water saturation (increases slope failure) </li></li></ul><li>How Does it Happen?<br />Rock<br />Slide component<br />Stick component<br />Shear stress vs. shear strength<br />
  7. 7. When Gravity Wins<br /><ul><li>When the force of gravity exceeds the friction of the slope, material begins to move
  8. 8. Shear strength resists movement, if gravity is too strong the object loses friction</li></li></ul><li>Angle of Repose<br />The steepness of a slope is an important factor<br />Steeper the slope  increase in the amount of gravity pulling on the object<br />The angle of repose is the steepest angle a slope can maintain without collapse<br />Around 25-40 degrees <br />
  9. 9. Weathering and Climate<br /><ul><li>Weathering: wind and water erosion weakens surfaces
  10. 10. Weathering decomposes material and reduces the strength of the slope
  11. 11. Loose materials are most susceptible as they are not stable</li></li></ul><li>Triggering Events <br />Events that encourage mass wasting:<br />Earthquakes<br />Snowmelt<br />Heavy rainstorms<br />Why?<br />
  12. 12. Vegetation<br />Increases slope stability! <br />Absorb water from rainfall and roots stabilize within soil <br />
  13. 13. Criteria for Mass Wasting<br />Type of material…<br />Type of movement…<br />Rate of movement…<br />Rock, debris, soil, mud<br />Fall, slide, slump, flow, creep<br />Fast, slow, not visible <br />
  14. 14. Falls<br />Very rapid movement, talus formation, often triggered by earthquakes.<br />
  15. 15. Slump<br />Movement along a curved surface, caused by steepening of the slope<br />
  16. 16. Flow<br />Slow to rapid movement but often appears to have a plastic movement (Debris-flow vs. Mudflow) <br />
  17. 17. Solifluction<br />Common in areas of permafrost, very slow movement when frozen surface melts in summer<br />
  18. 18. Creep<br />Slowest flow, visible through features such at tilted trees or telephone poles<br />
  19. 19. How do we control masswasting?<br />Improve drainage<br />Ditches, gutters, vegetation, drainpipes<br />Decrease slope<br />Cut and fill, benching<br />Build retaining walls<br />Provide support at the bottom of a slope<br />
  20. 20. References<br />Text and Figures<br />Schaetzl, Randy, 2011, Masswasting, Environmental Geomorphology 306<br />Steinbis, Martin, 20ll, Masswastepdf, Geology 100<br />Pictures<br />Clip art images <br />