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Geology > Chapter 11 -- Mass Wasting > Flashcards

Chapter 11 -- Mass Wasting Flashcards

0
Q

Mass Wasting includes these 7 things…

A

Landslides, Earthflows, Mudflows, Rockfalls, Debris and Snow Avalanches, and Subsidence.

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1
Q

is the downslope of movement of material resulting from the force of gravity.

A

Mass Wasting

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2
Q

Slopes shear strength
Depends on forces called ______ ______ that oppose downward movement and help maintain slope stability.

Material’s strength and cohesion
Internal friction between grains.
External support of the slope.

A

Resisting Forces

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3
Q

Is a driving force which opposes a slope’s shear strength and moves material down slope.

A

Gravity

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4
Q

Driving Forces Include 3 things…

A

Weight of slope material
Vegetation
Structures on the Slope

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5
Q

Probably the major cause of slope failure.

The steeper the slope, the less stable it is.

A

Slope Angle

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6
Q

Maximum angle at which unconsolidated material on slope is stable. ~##-##°
Controlled by coarseness, shape, size and uniformity of size of fragments water content, etc..

A

Angle of Repose

30-35°

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7
Q

Mass wasting is more likely to occur in highly weathered slope material than in bedrock.

A

Weathering

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8
Q

Characteristic weather at a specific place over time. This includes, the average temperature and precipitation which affects vegetation and therefore affects slope stability.

A

Climate

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9
Q

Almost always involved with mass movements.
_____ fills pore spaces between sediments, reduces internal resistance, and adds weight.
Effects: Decreasing stability when slope becomes saturated. Slumps or slides can occur years after deep water infiltration. Can erode base or toe of slope decreasing it’s stability.

A

Water

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10
Q

Stream or wave _______ may remove material creating steeper slope thus reducing safety factor. This may reactivate old landslides.

A

Erosion

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11
Q 
Pros and Cons of Vegetation
\+
\+
\+
-
A

+ Shields soil thus mitigates runoff.
+ Helps absorb water from the rains
+ Roots help fix soil in place.
- Adds weight to the slope.

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12
Q

Almost always from human activity such as dumping, filling, or piling up of material
Can increase water pressure within the slope material.
Decreases shear strength and thus weakens the slope material.

A

Overloading

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13
Q

Triggers of Mass Wasting (6)

A 
Earthquakes
Heavy precipitation
Volcanic Eruptions
Thunder
----If the slope is sufficiently unstable.
Gunshot or Loud Shout
Some Avalanches
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14
Q

_____ _______ depends on the driving and resisting forces that act on the slope.

A

Slope Stability

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15
Q

Types of Mass Wasting

Extremely Rapid
Rocks of any size free fall through the air.

A

Falls

16
Q

Types of Mass Wasting

Variable rate
Downslope movement of material along one or more surface of failure.

A

Slide

17
Q

Types of Mass Wasting

Slow to moderate
Occurs along a curved surface of rupture

A

Slump

18
Q

Types of Mass Wasting

Rapid
Occurs along planar surface.

A

Rockslide

19
Q

Types of Mass Wasting

Rapid downslope movement of snow and ice sometimes with rock, soil, and trees.
Can travel as much as 62 mph.
Tend to travel down chutes where previous _________ have flown.

A

Avalanches

20
Q

Downslope movement of unconsolidated Earth material saturated with water.

Main types are:

A

Flows

Mud Flows, Debris Flows, Earth Flows

21
Q

> 50% of particles are finer than sand
Up to 30% water
Common in arid and semiarid climates after severe storms.

A

Mudflows

22
Q

> 50% of particles are coarser than sand.
Contains less water and larger particles than mudflows
More viscous than mudflows and move more slowly.

A

Debris Flows

23
Q

Move downslope as thick, viscous masses of wet regolith

Move more slowly than debris flows or mudflows

A

Earth Flows

24
Q

These spontaneously liquefy and flow when disturbed.

A

Quick Clays

25
Q

Mudflow produced when large volumes of volcanic ash and ejecta becomes saturated with water.

A

Lahar

26
Q

Types of Mass Movement

Mass of rock and ice frozen together and flowing downslope.

A

Rock Glacier

27
Q

Types of Mass Movement

Slow, imperceptible downslope movement of unconsolidated Earth material.
Often related to seasonal effects and/or precipitation rates.

A

Creep

28
Q

Types of Mass Movement

Sinking of mass of Earth material below level of surrounding materials.

A

Subsidence

29
Q

Types of Mass Movement

Complex combinations of sliding and flow

A

Landslide

30
Q

Anchored to bedrock and supports base of slope

A

Retaining Walls

31
Q

Fastens potentially unstable rock masses to into underlying stable bedrock

A

Rock Bolts

32
Q

Material relocated from upper slope to base.

A

Cut and Fill

33
Q

Cutting a series of ________.

A

Benching

Geology (13 decks)

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