MASS WASTING AND MASS MOVEMENT mass movement - a general term used to describe the downhill movement...

MASS WASTING AND MASS MOVEMENT• mass movement - a general term used to describe the downhill movement of material that are known as slides, falls, slumps, flows, and creep

MASS WASTING AND MASS MOVEMENT1. unconsolidated material - those that are loose or uncemented, such as sand and soil2. consolidated material - those that are compacted, cemented, or vegetated soils

• Factors That Influence Mass Movement1.slope of material - the steepness of a slope influences instability in mass

movementi. the steepness of a pile of loose material such as sand has a distinct limit -

angle of reposeii. once the angle of repose is reached, addition of more sand will make the

pile broader but not taller

• Factors That Influence Mass Movement2. internal friction - a material’s total resistance to movement

i. consolidated dry materials are held together by cohesion (attraction of like particles) and adhesion (attraction of unlike particles)

ii. cementation

iii. plant roots

• Factors That Influence Mass Movement3. surface tension

4. moisture contenti. too little limits vegetationii. too much can push grains apart, add weight, or provide lubrication

• Factors That Influence Mass Movement

• Triggers of mass movement1. sudden addition of moisture

• Triggers of mass movement

2. shaking of the ground - liquefaction

• Classification of mass movement1. Based upon

i. nature of the material (rock or unconsolidated) ii. speed of movementiii. nature of movement (sliding, falling, or flowing)

• Rock Mass Movement1. rockfall - free fall of boulders from a cliff

• Rock Mass Movement2. rockslides - sliding of rock down an incline

i. usually due to rock breaking from its host material along a bedding plane, joint, or other structural weakness

• Rock Mass Movement3. talus - debris at the bottom of the slope in a broken mass due to rockfalls and rockslides

• Rock Mass Movement4. rock avalanche - rock becomes broken into pieces before it reaches the foot of a slope

• Unconsolidated Material Mass Movement1. creep - extremely slow, almost imperceptible downslope movement of soil and rock debris

• Unconsolidated Material Mass Movement2. solifluction (soil flowage) - special type of creep that is common in polar regions where groundwater in the pore spaces of soil and rock is permanently frozen

• Unconsolidated Material Mass Movement

3. earthflows and debris flows - consist of mixtures of rock fragments, mud, and water that flow downslope as viscous fluids

• Unconsolidated Material Mass Movement3. earthflows and debris flows - consist of mixtures of rock fragments, mud, and water that flow downslope as viscous fluids

• Unconsolidated Material Mass Movement4. mudflows - a variety of debris flow that consist mostly of small silt and clay-sized particles

i. usually occur after heavy rainii. as much as 30% water content

• Unconsolidated Material Mass Movement5. debris avalanche - fastest unconsolidated mass movement

i. on steep slopes in humid areas

6. slumps and debris slide - movement of material in which the material is not rearranged

Debris Slide

• Plate Tectonics1. OC - CC boundary

i. causes steep slopes

ii. volcanic activity and earthquakes

Gros Ventre

•1925•80 km / hr•Buried 30 m thick

• Impact of Human Activities on Mass Movement1. road construction

2. reservoirs