Answers to questions: Physical Geology
lecture outline - Mass Wasting
What are critical factors that influence whether mass
wasting occurs or not, whether a slope is stable or not?
- topography and slope angle, undercutting
destablizes.
- strengths of slope material: sruface slip
strength, material viscosity.
- orientation of potential slip planes.
- earthquakes.
- water saturation: two factors here 1)
decrease in viscosity, 2) hydraulic lift (the influence of fluid
pressure on forces on a slip plane).
What are major
classification factors for types of mass wasting?
- velocity of movement, from creep to catastrophic
slip or flow.
- coherence of moving body, slip vs. flow.
- types of material involved, sediment vs.
bedrock.
- all three are related.
What are typical slip planes, planes of failure?
- bedding planes (e.g. Gros Ventre slide).
- specific weak layers: shale, weathered
ash, salt.
- joint surfaces.
- foliations or metamorphic surfaces.
- faults.
- soil-bedrock interface.
For what geologic features is mass wasting important?
- sea cliffs.
- valley incision.
- volcanic eruptions.
- alpine lake formation.
- alluvial fan formation.
- deposition of turbidites.
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