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Geology > Mass Wasting > Flashcards

Mass Wasting Flashcards

1
Q

Mass wasting is due to __________

A

Slope Failure.
Slopes can become unstable when they are over steepened or comprise of unconsolidated material.

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2
Q

Mass Wasting refers to ______________

A

Downhill movement of masses of soil, rock, mud or other unconsolidated materials due to gravity

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3
Q

Triggers for Mass Wasting?

A
  • Vibrations from Earthquakes or man-made events
  • heavy rainstorms
  • volcanic activity
  • freeze- thaw action
  • Tectonically uplifted areas
  • the oversteepening of a slope
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4
Q

The basics of slope stability can be determined by _____________

A
  1. the angle of the slope
  2. material strength
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5
Q

Slope failure (Mass wasting) occurs when ___________

A

the gravitational force on a slope exceeds its resisting force.

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6
Q

Slope’s shear strength = ______________

A

The slope material’s strength, cohesion, and the amount of internal friction helps to maintain slope’s stability

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7
Q

What is Angle of repose?

A
  • Maximum angle at which a slope of unconsolidated materials will remain stable
  • its shear strength perfectly counterbalances the force of gravity
  • function of: particle size, particle shape, moisture content
  • Important for stability of unconsolidated materials.
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8
Q

Cohesion of the material is __________

A

attractive forces that bind the material together

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9
Q

Shear strength or internal friction = _______

A

The resistance to movement due to cohesion

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10
Q

Unconsolidated: ______________
Consolidated: ______________

A

Unconsolidated: any loose and un-cemented material such as soil, sediments
Consolidated: Rocks and cemented, vegetated.

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11
Q

Mass movement are classified based on:

A
  • Type of material that move: Consolidated (Rock) or Unconsolidated
  • Nature of movement: Fall or Slide or Flow
  • Speed of movement: Slow (mm/yr) or Fast (km/hr)
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12
Q

Rock Mass Movements include:

A
  • Rock Falls
  • Rock Slides
  • Rock Avalanches
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13
Q

Unconsolidated Mass Movements include:

A
  • Creep
  • Earthflow
  • Mudflow
  • Debris flow
  • Debris Avalanche
  • Slump
  • Solifluction
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14
Q

What is Rock Fall?

A
  • Sudden and rapid free fall movement of rock
  • Occur on steep slopes
  • Freeze thaw action
  • Forms Talus piles
    Talus: accumulation of rocks at the foot of a steep bedrock cliff
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15
Q

What is Rock Slides?

A
  • Rocks slide rapidly down a slope rather than free falling
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16
Q

Rock Avalanche

A
  • Rock Flows
  • One of the most destructive forms of mass movements
  • Very fast, large volume
17
Q

Creep

A

very slow downhill movement o soil and other debris

18
Q

Earthflow

A
  • fluid movement of fine grained soils and sediments
  • fast
19
Q

Debris flow

A
  • fluid movement of rock fragments supported by muddy matrix
  • contain coarser materials, faster than earth flow
20
Q

Mudflows

A
  • flowing masses fine-grained material containing large amounts of water
  • fast movement due to the high water content
  • often initiated after a high rainfall in dry region
21
Q

Slump

A

slow slide of unconsolidated material that moves as a unit

22
Q

Solifluction

A
  • only in cold regions when water in the surface of layers of the soil freeze and thaw
  • When surface layers thaw, they become saturated because the water cannot flow down into the frozen layers below
  • so upper layers of the soil flow downhill
23
Q

The occurrence of mass wasting is influenced by _____________

A
  • slope material
  • water content
  • slope steepness
24
Q

What is Liquefaction?

A
  • process whereby a water‐saturated material liquefies into a fluid slurry
  • one consequence of earth quakes vibration
25
Q

How does water content affect the stability of unconsolidated materials?

A
  • A thin film of water increases surface tension and increases angle of repose
  • However excessive amounts of water will saturate the material and reduce the strength.
26
Q

What does failure of consolidated materials require?

A

Overcoming cohesion and shear strength of the material

27
Q

Engineering Solution?

A
  • Planting vegetation
  • Drainage ditches
  • Retaining walls
  • Rock bolts
28
Q

The dip angle of bedded rocks has a big effect on slope stability. True or False?

A

True

29
Q

Briefly explain why freeze-thaw action can be important in initiating a rock fall?

A

freeze-thaw action weakens rocks through the expansion and contraction of water within fractures.

30
Q

The steeper the slope the stronger the shear force. True or False?

A

True

31
Q

Earthquake vibrations can cause ______ in water-saturated material.

A

liquefaction

32
Q

What causes solifluction?

A

Seasonal freeze and thaw of surface material

33
Q

A slope of unconsolidated sand may have the same angle of repose as angular boulders if ________

A

the sand is damp

Geology (4 decks)

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