edu290 ppt1koch
DESCRIPTION
This is an assignment for EDU 290. This PowerPoint gives a basic understanding of types of mass-wasting.TRANSCRIPT
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Processes of Mass Wasting
Janet KochEDU 290
PowerPoint Presentation
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Definition•Mass wasting is the down-slope movement of material under direct influence of gravity
•Water influences the effects of mass wasting but gravity is the most important factor
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Determining Factors of Mass Wasting
•Slope Stability
Gravity
Friction
Angle of Repose
•Type of Material (Rock, soil, sediment)
•Water saturation (increases slope failure)
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How Does it Happen?
Rock
Slide component
Stick component
Shear stress vs. shear strength
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When Gravity Wins
•When the force of gravity exceeds the friction of the slope, material begins to move
•Shear strength resists movement, if gravity is too strong the object loses friction
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Angle of Repose
The steepness of a slope is an important factor
Steeper the slope increase in the amount of gravity pulling on the object
The angle of repose is the steepest angle a slope can maintain without collapse
Around 25-40 degrees
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Weathering and Climate•Weathering: wind and water erosion weakens surfaces
•Weathering decomposes material and reduces the strength of the slope
•Loose materials are most susceptible as they are not stable
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Triggering Events
Events that encourage mass wasting:› Earthquakes› Snowmelt› Heavy rainstorms
› Why?
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Vegetation
Increases slope stability!
Absorb water from rainfall and roots stabilize within soil
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Criteria for Mass Wasting
Type of material…
Type of movement…
Rate of movement…
Rock, debris, soil, mud
Fall, slide, slump, flow, creep
Fast, slow, not visible
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Falls
Very rapid movement, talus formation, often triggered by earthquakes.
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Slump
Movement along a curved surface, caused by steepening of the slope
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Flow
Slow to rapid movement but often appears to have a plastic movement (Debris-flow vs. Mudflow)
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Solifluction
Common in areas of permafrost, very slow movement when frozen surface melts in summer
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Creep
Slowest flow, visible through features such at tilted trees or telephone poles
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How do we control masswasting?
1. Improve drainage› Ditches, gutters, vegetation, drainpipes
2. Decrease slope› Cut and fill, benching
3. Build retaining walls› Provide support at the bottom of a slope
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References
Text and FiguresSchaetzl, Randy, 2011, Masswasting, Environmental Geomorphology 306
Steinbis, Martin, 20ll, Masswaste pdf, Geology 100
PicturesClip art images