mass wastage
Post on 24-Feb-2016
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Mass wastagePart One
What exactly do we mean when we say “mass wastage”?Mass wastage = Mass wasting =
Mass movement
It is the down slope movement of weathered materials (rock, regolith, and soil) under the direct influence of gravity
It can be slow, or rapid, sudden and catastrophic
GravityThe effectiveness of gravity is
determined by the steepness of the slope and thickness of loose materials
In other words, steeper landscape = greater force to move objects downslope
Greater the thickness of moving mass = greater speed
Causes of mass wasting1) Natural: Expansion of soilExpanding and contracting of soil
Water gets into soil soil gets heavier expansion makes soil move slightly instability!
Causes of mass wasting2) Logging practices
Clear-cutting trees (most or all trees in an area are uniformly cut down) leaves a slope with little vegetation stability
Logging roads cut deeply into mountain sides
Causes of mass wasting3) Urbanization
Removed vegetation and altered natural drainage patterns creates flash floods
Methods of stabilizing slopes1) VegetationPlant roots can
help to anchor the soil
Leaves and roots can help protect the soil from being washed away by heavy rains
Methods of stabilizing slopes… on Highways!
Bolts
(See textbook diagram on page 37)
Concrete spray
People working on the Sea to Sky construction project
Wire mesh
Drainage pipes and Retaining walls
(See textbook diagram on page 37)
Terracing
Snowsheds
(See textbook diagram on page 37)
Tunnels
Types of Mass Wasting:1) Scree/ talusOn very steep slopes, soils do not
have the chance to form and blocks of rock become loosened
Frost shatter causes the regolith to loosen and tumble down
Blocks are mostly large and sharp-edged and so do not travel far
They build a pile of loose rocks at the bottom called scree or talus
Types of Mass Wasting:2) Soil Creep
Slow, almost imperceptible downhill motion of soil particles
Common in humid areas
Helped by soil expansion and contracting
Most common
Types of Mass Wasting:3) LandslideRapid
movement of soil down slope
Rock is weathered into soil
Heavy rainfall often triggers it
Freeze-thaw action
http://www.youtube.com/watch?v=f19Onak6KC0
Types of Mass Wasting:4) Mudflow
Soil absorbs so much water that it literally flows downhill
Everything in it mixes thoroughly
http://www.youtube.com/watch?v=8mKC3eID074&feature=related
http://www.youtube.com/watch?v=SrYqJlCuppA&feature=related
Types of Mass Wasting:5) SlumpA slab of land breaks away and
slips a short distance
See page 38 for a lovely diagram!
Types of Mass Wasting:6) AvalancheA mass of snow and ice that
breaks away and slides down a slope
Heavy accumulation of snow
Air temperatures make them unstable
Can be very dangerous
http://www.youtube.com/watch?v=bJ0osmXOfvs&feature=related
Types of Mass Wasting:7) Soil SolutionSoil materials transported by
water
Very small particles in seeming less transparent water
TIME FOR REVIEW!!!
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