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!!!