Mass Wasting

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Mass Wasting

• Or Stuff Rolls Downhill!

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Mass Movements

• Rock and soil moves down hill under the influence
  of gravity

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Factors in slope stability.

• 1) Material strength
• 2) Internal friction
• 3) External support
• Together these are a slopes shear strength

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Shear Stress

• The component of gravity dragging a rock down
  hill is the.

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• Slopes are in dynamic equilibrium
• Angle of repose slope angle where shear strength
  equals forces of gravity

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Factors favoring movement

• Slope angle -- steep
• Weather and climate -- highly weathered
• Water content - - High
• Vegetation -- little vegetation
• Overloading -- caused by humans

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Types of Mass Movements

• Classified based on movement rate, type (falling
  sliding, flowing), and material
• Falls
• Rockfall rocks falling through air, form talus
• Slides
• Slump slow, along curved surface
• Rockslide fast, along planar surface
• Flows (plastically or as a viscous fluid)
• Mudflow fast, 50 silt and clay
• Debris Flows larger size particles, more viscous
  (less water)
• Earthflows slower
• Creep slowest, extremely slow movement of
  material

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Rockfall
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Rockfall with Talus
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Rock Slide
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Rock Slide
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Midterm 3

• A step back?
• A 89
• 79 B 88
• 64 C 78
• 55 D 63
• F 54
• HW Less than 89, turn in the right answers Due
  next Thurs.

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Types of Mass Movements

• Classified based on movement rate, type (falling
  sliding, flowing), and material
• Falls
• Rockfall rocks falling through air, form talus
• Slides
• Slump slow, along curved surface
• Rockslide fast, along planar surface
• Flows (plastically or as a viscous fluid)
• Mudflow fast, 50 silt and clay
• Debris Flows larger size particles, more viscous
  (less water)
• Earthflows slower
• Creep slowest, extremely slow movement of
  material

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Mudflow

• Estes Park, CO

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Earth Flow

• Baraga, MI.

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EarthFlow

• Slumgullion Earth flow
• This old stable flow descendes from an elevation
  of 11,500 feet to 8,500.
• 4 miles in length and covers about 1,000 acres
• Outside Lake City, CO
• Drunken Forest - trees not vertical!

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Slumgullion Earth Flow
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Creep

• Marathon, Texas

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Creep

• Wyoming

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Creep

• Champion, MI

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Rock Slide and Slumping

• Point Fermin, CA

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Group Exercise

• Identify the following

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Minimizing Effects

• Geological mapping to determine active landslides
  and rock types (soil and bedrock), and map sudden
  change in vegetation
• Develop slope stability maps
• Develop effective drainage
• Stabilize slopes
• Cut and fill method
• Benching
• Retaining walls
• Rock bolts