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Physical Geography 1000 > Mass movement/mass wasting > Flashcards

Mass movement/mass wasting Flashcards

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1
Q

why does mass wasting take place AFTER weathering

A

because the rock is now weakened and more susceptible to gravity

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2
Q

mass movement AKA

A

mass wasting

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3
Q

mass movement

A

the process where a BODY OF MATERIAL is moved downslope by GRAVITY

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4
Q

does transport for mass movement involve incorporation of water, air or ice

A

NOT USUALLY

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5
Q

forces on a horizontal surface

A

Fn (normal force)
Fg (gravity)

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6
Q

describe the relation between the forces working on a horizontal surface

A

fg and fn are equal which means there is NO movement

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7
Q

what are the forces working on a slope

A
  1. Fn
  2. Fg
  3. Fp
  4. Normal reaction force
  5. Reaction force
  6. Ff
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8
Q

fp is the

A

component of gravity PARALLEL to the slope

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9
Q

Ff is the

A

force that resists movement (friction)

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10
Q

what happens to Fp and Ff as the slope increases

A

both become greater

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11
Q

Fp is equal to

A

Ff

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12
Q

when is Fp equal to Ff

A

when there is NO movement

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13
Q

Ff depends on

A

the object and the surface material

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14
Q

what happens once a critical angle is reached

A

failure occurs (when driving forces overcome resisting forces)

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15
Q

when a slope is at 90 degrees, then ____ and _____ are equal

A

fp and fg

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16
Q

what is the result when Ff and Fp are equal

A

no movement

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17
Q

driving force

A

gravity

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18
Q

resisting force

A

friction

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19
Q

angle of repose

A

steepest angle that ca be attained by loose material WITHOUT moving downslope

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20
Q

what is balanced in the angle of repose

A

friction and gravity

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21
Q

typical angle range of the angle of repose

A

33 to 37 degrees

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22
Q

angle of sliding friction

A

angle at which dry and unconsolidated materials fall

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23
Q

what is the angle called when sliding starts

A

angle of sliding friction

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24
Q

four factors that affect the angle of repose and sliding friction

A
  1. size of particles
  2. shape of particles
  3. sorting
  4. water content
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25
Q

what type of particle has the LARGEST angle of repose and what has the SMALLEST

A

LARGEST - pebbles (45)
SMALLEST - find sand )35)

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26
Q

what sand condition is MOST cohesive?

A

damp sand

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27
Q

what sand is the LEAST cohesive

A

water-saturated sand

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28
Q

order of sand from MOST to LEAST cohesive

A
  1. damp sand
  2. dry sand
  3. water-saturated sand
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29
Q

stress

A

force/area

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30
Q

stress can also be called

A

pressure

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31
Q

what becomes the Coulomb equation

A

Ff=Fp=Fn(tan of the angle)

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32
Q

Coulomb equation

A

S = Ђ = Sn tan Фi + C

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33
Q

S in Coulomb equation

A

shear strength (force trying to STOP failure and resisting movement)

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34
Q

Ђ in Coulomb equation

A

shear stress (force trying to cause movement)

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35
Q

Sn in Coulomb equation

A

normal stress (as slope increases, sn gets lower)

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36
Q

what angle does the normal stress work on in the Coulomb equation

A

right angles

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37
Q

Фi in Coulomb equation

A

angle of internal friction (property of slope and material)

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38
Q

C in Coulomb equation

A

cohesion (sticky it is)

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39
Q

if S = Ђ then there is _____

A

NO movement

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40
Q

what does water affect

A

the soil cohesion (C)

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41
Q

when is cohesion LOW in soil

A
  1. when very DRY
  2. when very saturated
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42
Q

when is cohesion HIGH in soil

A
  1. when pores are partly full and under suction
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43
Q

Coulomb equation in regards to water

A

S = Ђ = (Sn – Sp) tan Фi + C

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44
Q

Sp in Coulomb equation in regards to water

A

porewater pressure

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45
Q

what does the modified Coulomb equation in regards to water explain

A

WHY landslides take place often heavy rainfall

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46
Q

C in the Coulomb equation in regards to water is the ______

A

NOT constant

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47
Q

what does C follow in the Coulomb equation in regards to water

A

Sp (porewater pressure)

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48
Q

what affects _____ in Coulomb equation in regards to water

A

normal stress

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49
Q

how does water affect Sn in the Coulomb equation in regards to water

A

particles are supported by water (aka become bouyant)

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50
Q

A

A

reaction force

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51
Q

B

A

normal reaction force

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52
Q

C

A

Fp

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53
Q

D

A

Fg

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54
Q

E

A

Fn

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55
Q

F

A

Ff

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56
Q

factor of safety

A

shear strength/shear stress

57
Q

if FoS is less than 1 the slope is

A

unstable

58
Q

if FoS is greater or equal to 1 the slope is

A

stable

59
Q

is Fos static

A

NO- it changes over time

60
Q

what are 6 triggers that can cause slope movement

A
  1. precipitation
  2. weathering
  3. earthquakes
  4. changes in loading
  5. changes in slope (undercutting)
  6. vegetation changes
61
Q

what are the 5 broad categories of mass movements

A
  1. discontinuous creep
  2. flows
  3. slides
  4. falls
  5. complex movements
62
Q

discontinuous creeps include

A
  1. discontinuous creep
  2. needle-ice creep
63
Q

types of flows in mass movements

A
  1. continuous creep
  2. solifluction
  3. earthflow
  4. mudflow
  5. debris flow
  6. quick clay flow
  7. slushflow
64
Q

of the 7 different types of flows, what are the SLOW MOVING flows

A
  1. continuous flows
  2. solifluction
65
Q

types of slides

A
  1. slump
  2. rock slide
  3. debris slide
66
Q

type of falls

A
  1. rockfall
  2. blockfall
67
Q

what type of mass movement is this
ratchet-like movement

A

discontinuous creep

68
Q

why do discontinuous creeps have a ratchet-like movement

A

due to soil expansion and contraction

69
Q

describe the movement of discontinuous creeps

A

shallow and very slow

70
Q

what are three reasons for the ratchet-like movement of discontinuous creeps

A
  1. wetting and drying
  2. freezing and thawing
  3. heating and cooling
71
Q

where are needle-ice creeps favoured

A

in areas with high levels of freeze-thaw cycles

72
Q

what force acts on a flow

A

shear occurs throughout

73
Q

is there a single shear plane in flows

A

NO

74
Q

where is the max shear in flows

A

at the base

75
Q

What is typically present in flows

A

water

76
Q

flow vs slide

A

slide
1. has a UNIFORM depth and velocity profile in relation to the shear plane
2. friction with the surface is the SAME throughout
3. moves at the SAME speed
4. LACK of liquid (water)

Flows
1. DO NOT have a uniform depth and velocity profile in relation to the shear plane
2. acts like a liquid (there IS usually water)
3. MORE friction with a surface at the BOTTOM (moving up = LESS friction)
4. Bottom moves SLOWER = there is more friction

77
Q

examples of flows

A
  1. river
  2. mudflow
  3. earthflow
78
Q

are avalanches a flow (why or why not)

A

NO - they are not made up of earth material (like soil- they are made from ice/snow)

79
Q

is continuous creep fast or slow

A

slow deformation of soil

80
Q

what produces a continuous creep

A

gravity acting downslope

81
Q

where can continuous creeps occur

A

in permafrost

82
Q

what type of mass movement is this
combination of frost creep and gelifuction

A

solifluction

83
Q

gelifluction

A

the slow movement of saturated soil over frozen ground during the SPRINg and SUMMER

84
Q

what can solifluctions form

A
  1. tongue like lobes
  2. solifluction sheets
85
Q

what type of mass movement is this
do NOT have a scar upslope

A

solifluction

86
Q

of the 7 types of flows, what are the FAST moving ones

A
  1. earth flows
  2. mudflows
  3. debris flows
  4. quick clay flows
  5. slushflows
87
Q

flows are the movements incorporating

A

viscous fluid OR plastic motion

88
Q

what is the slowest RAPID moving flow

A

earthflow

89
Q

what type of mass movement is this
vegetation cover usually intact

A

earthflows

90
Q

fastest flow

A

mudflow

91
Q

what type of mass movement is this
the most fluid flow

A

mudflow

92
Q

the most dangerous flow

A

mudflow

93
Q

the flow that causes the least amount of damage

A

earthflow

94
Q

what separates a mudflow from a debris flow

A

debris flows have LARGE PARTICLES while mudflows are mostly fluid like substances

95
Q

what moves slower: a mudslide or a debris slide

A

debris flow

96
Q

what often causes debris flows

A

heavy precipitation

97
Q

what type of mass movement is this
horse-show shaped forms

A

quick clay flow

98
Q

what develops a quick clay flow

A

Leda clay (produced by depositions of glacial material in the Champlain sea)

99
Q

how does a quick clay flow form

A

marine salts are leached out of reducing soil = flow occurs following above-normal precipitation OR an earthquake

100
Q
A

quick clay flow

101
Q
A

debris flow

102
Q
A

mudflow

103
Q
A

flows

104
Q

LEFT

A

slide

105
Q

RIGHT

A

flow

106
Q
A

Needle-ice creep

107
Q
A

Discontinuous creep

108
Q

where can a slushflow occur

A

in mountain-environments and down EXISTING river channels

109
Q

describe the debris in a slushflow

A

it is non-sorted and piled up randomly

110
Q

slides are the movement along

A

one or more DISCRETE FAILURE SURFACES (aka shear planes)

111
Q

main causes of slumps

A
  1. steeping of slopes by basal erosion, heavy precipitation or earthquakes
112
Q

rock slide

A

failure along a FLATE PLANE parallel to the ground

113
Q

where do rock slides occur

A

where bedding planes and slopes dip in the SAME direction

114
Q

debris slides

A

failure of NON-CONSOLIDATED MATERIAL along a plane PARALLEL to the ground

115
Q

special case of debris slides

A

active-layer detachments (occur over permafrost because of a rapid-thaw of icy soils over still frozen material)

116
Q

falls

A

vertical or near vertical movement of particles through the air

117
Q

most rapid of ALL the mass movements

A

rockfall

118
Q

rockfall

A

free-falling, bouncing or rolling of blocks down slopes

119
Q

what do rockfalls produce at the base

A

talus

120
Q

what causes rockfalls

A

the freeze-thaw weathering

121
Q

blockfall

A

vertical movement of an ENTIRE piece of slope

122
Q

where do blockfalls often happen

A

in frozen sediments undermined by thermal erosion

123
Q

complex movements

A

a mixture of ANY of the other types of mass movements

124
Q
A

rockfall

125
Q
A

blockfall

126
Q
A

active-layer detachements

127
Q
A

rock slide

128
Q
A

slump

129
Q

natural causes for mass movements

A
  1. slope becoming saturated
  2. oversteepening
  3. volcanic eruptions
  4. earthquakes
130
Q

anthropogenic causes of mass movements

A
  1. deforestation
  2. building on steep gradient
  3. road construction
  4. mining and undercutting
131
Q

steps of a quick clay flow

A
  1. the land was under water with glaciers pushing them down which sinks it down
  2. once the water is gone, the land bounces back up
132
Q

what holds the quick clay together

A

the salt content

133
Q

what causes quick clay to liquefy

A

when the water leeches salt from it - it becomes unstable and liquefies

134
Q

does a tallus move in rock falls

A

NO

135
Q

what forces act on a rock fall

A

only FRICTION and NOT gravity

136
Q

does the rock have to be uniform in a rockfall

A

NO

137
Q

what causes a mudflow

A

heavy precipitation

138
Q

what mass movements are seen as SATURATED

A
  1. earthflow
  2. mudflow
  3. debris flow
  4. quick clay flow
139
Q

what mass movements are seen as UNSATURATED

A
  1. rock slide
  2. slump
  3. rock falls
    4.

Physical Geography 1000 (21 decks)

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