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43 Cards in this Set
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Mass Wasting |
the downhill movement of masses of bedrock, rock debris, or soil driven by the pull of gravity. |
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Gentle Slopes & Horizontal Surfaces |
Most Stable Situation: Slope Angle |
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Low |
Most Stable Situation: Local Relief |
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Slight Thickness (usually) |
Most Stable Situation: Thickness of Soil over Bedrock |
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Planes at right angles to hillside slopes |
Most Stable Situation: Orientation of Planes of Weakness in Bedrock |
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Temperature stay above freezing |
Most Stable Situation: Climatic Factors: Ice in ground |
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Film of water around fire particles |
Most Stable Situation: Climate factors: Water in Soil or Debris |
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Frequent but light rainfall |
Most Stable Situation: Climate factors: precipitation |
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Heavily Vegetated |
Most Stable Situation: Vegatation |
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Steep or Vertical |
Most Unstable Situation: Slope Angle |
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High |
Most Unstable Situation: Local Relief |
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Great Thickness |
Most Unstable Situation: Thickness of Soil in Bedrock |
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Planes Parallel to Hillside Slopes |
Most Unstable Situation: Orientation of Planes of Weakness in Bedrock |
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Freezing and thawing for much of the year |
Most Unstable Situation: Climate Factors: Ice in Ground |
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Saturation of Soil with Water |
Most Unstable Situation: Climate Factors: Water in Soil or Debris |
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Episodes of Heavy Precipitation |
Most Unstable Situation: Climate Factors: Precipitation |
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Sparsely Vegetated |
Most Unstable Situation: Vegetation |
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Gravity |
the driving force of mass wasting |
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Landslide |
this happens when the shear force is greater than the shear resistance |
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Steep slopes |
shear forces maximized by gravity |
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Shear Strength |
resistance to movement or deformation |
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Saturation |
this reduces the soil’s shear strength due to increased pore pressure |
Saturated Soil |
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Water |
A small amount with this in a soil can prevent downslope movement |
Like building a sand castle |
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1. Earthquake or Seismic Activity 2. Heavy Rainfall 3. Construction 4. Lack of Vegetation |
Mass Wasting Triggers |
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Lack of Vegetation |
there are no roots to hold rock/soil in place |
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1 cm/year –> 100 km/hr |
Rate Movement of Mass Wasting |
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Rock or Debris |
Type of Material in Mass Wasting |
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Debris |
unconsolidated material at earth’s surface |
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flow, slide, or fall |
type of movement of mass wasting |
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Creep (soil creep) |
very slow downslope movement of soil |
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Flow |
descending mass moves downhill as a viscous fluid |
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Earthflow |
debris moves downslope, slowly, or rapidly, as a viscous fluis |
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Solifluction Permafrost |
flow of water-saturated soil over impermeable material that is common in colder climates. |
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Debris Flow & Mudflow |
flowing mixture of debris and water, usually down a channel. |
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Mudflow |
flowing mixture that consists only soil and water |
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Debris Avalanche |
a very rapid and turbulent debris flow |
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Falls |
material free-falls or bounces down a cliff |
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Rockfall |
a block of bedrock breaks free and falls or bounces down a cliff |
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Slides |
descending mass remains relatively intact, and descends along well-refined surfaces |
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Translational Slide |
type of slide movement along plane parallel to motion |
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Rotational Slide (Slump) |
type of slide movement along a curved surface |
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Rockslide & Rock Avalanche |
the rapid sliding of a mass of bedrock along an inclined surface of weakness |
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Turbidity Currents & Tsunamis |
underwater landslides can create |
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