Mass movement/mass wasting Flashcards
(139 cards)
1
Q
why does mass wasting take place AFTER weathering
A
because the rock is now weakened and more susceptible to gravity
2
Q
mass movement AKA
A
mass wasting
3
Q
mass movement
A
the process where a BODY OF MATERIAL is moved downslope by GRAVITY
4
Q
does transport for mass movement involve incorporation of water, air or ice
A
NOT USUALLY
5
Q
forces on a horizontal surface
A
Fn (normal force)
Fg (gravity)
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
7
Q
what are the forces working on a slope
A
- Fn
- Fg
- Fp
- Normal reaction force
- Reaction force
- Ff
8
Q
fp is the
A
component of gravity PARALLEL to the slope
9
Q
Ff is the
A
force that resists movement (friction)
10
Q
what happens to Fp and Ff as the slope increases
A
both become greater
11
Q
Fp is equal to
A
Ff
12
Q
when is Fp equal to Ff
A
when there is NO movement
13
Q
Ff depends on
A
the object and the surface material
14
Q
what happens once a critical angle is reached
A
failure occurs (when driving forces overcome resisting forces)
15
Q
when a slope is at 90 degrees, then ____ and _____ are equal
A
fp and fg
16
Q
what is the result when Ff and Fp are equal
A
no movement
17
Q
driving force
A
gravity
18
Q
resisting force
A
friction
19
Q
angle of repose
A
steepest angle that ca be attained by loose material WITHOUT moving downslope
20
Q
what is balanced in the angle of repose
A
friction and gravity
21
Q
typical angle range of the angle of repose
A
33 to 37 degrees
22
Q
angle of sliding friction
A
angle at which dry and unconsolidated materials fall
23
Q
what is the angle called when sliding starts
A
angle of sliding friction
24
Q
four factors that affect the angle of repose and sliding friction
A
- size of particles
- shape of particles
- sorting
- water content
25
what type of particle has the LARGEST angle of repose and what has the SMALLEST
LARGEST - pebbles (45)
SMALLEST - find sand )35)
26
what sand condition is MOST cohesive?
damp sand
27
what sand is the LEAST cohesive
water-saturated sand
28
order of sand from MOST to LEAST cohesive
1. damp sand
2. dry sand
3. water-saturated sand
29
stress
force/area
30
stress can also be called
pressure
31
what becomes the Coulomb equation
Ff=Fp=Fn(tan of the angle)
32
Coulomb equation
S = Ђ = Sn tan Фi + C
33
S in Coulomb equation
shear strength (force trying to STOP failure and resisting movement)
34
Ђ in Coulomb equation
shear stress (force trying to cause movement)
35
Sn in Coulomb equation
normal stress (as slope increases, sn gets lower)
36
what angle does the normal stress work on in the Coulomb equation
right angles
37
Фi in Coulomb equation
angle of internal friction (property of slope and material)
38
C in Coulomb equation
cohesion (sticky it is)
39
if S = Ђ then there is _____
NO movement
40
what does water affect
the soil cohesion (C)
41
when is cohesion LOW in soil
1. when very DRY
2. when very saturated
42
when is cohesion HIGH in soil
1. when pores are partly full and under suction
43
Coulomb equation in regards to water
S = Ђ = (Sn – Sp) tan Фi + C
44
Sp in Coulomb equation in regards to water
porewater pressure
45
what does the modified Coulomb equation in regards to water explain
WHY landslides take place often heavy rainfall
46
C in the Coulomb equation in regards to water is the ______
NOT constant
47
what does C follow in the Coulomb equation in regards to water
Sp (porewater pressure)
48
what affects _____ in Coulomb equation in regards to water
normal stress
49
how does water affect Sn in the Coulomb equation in regards to water
particles are supported by water (aka become bouyant)
50
A
reaction force
51
B
normal reaction force
52
C
Fp
53
D
Fg
54
E
Fn
55
F
Ff
56
factor of safety
shear strength/shear stress
57
if FoS is less than 1 the slope is
unstable
58
if FoS is greater or equal to 1 the slope is
stable
59
is Fos static
NO- it changes over time
60
what are 6 triggers that can cause slope movement
1. precipitation
2. weathering
3. earthquakes
4. changes in loading
5. changes in slope (undercutting)
6. vegetation changes
61
what are the 5 broad categories of mass movements
1. discontinuous creep
2. flows
3. slides
4. falls
5. complex movements
62
discontinuous creeps include
1. discontinuous creep
2. needle-ice creep
63
types of flows in mass movements
1. continuous creep
2. solifluction
3. earthflow
4. mudflow
5. debris flow
6. quick clay flow
7. slushflow
64
of the 7 different types of flows, what are the SLOW MOVING flows
1. continuous flows
2. solifluction
65
types of slides
1. slump
2. rock slide
3. debris slide
66
type of falls
1. rockfall
2. blockfall
67
what type of mass movement is this
ratchet-like movement
discontinuous creep
68
why do discontinuous creeps have a ratchet-like movement
due to soil expansion and contraction
69
describe the movement of discontinuous creeps
shallow and very slow
70
what are three reasons for the ratchet-like movement of discontinuous creeps
1. wetting and drying
2. freezing and thawing
3. heating and cooling
71
where are needle-ice creeps favoured
in areas with high levels of freeze-thaw cycles
72
what force acts on a flow
shear occurs throughout
73
is there a single shear plane in flows
NO
74
where is the max shear in flows
at the base
75
What is typically present in flows
water
76
flow vs slide
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
examples of flows
1. river
2. mudflow
3. earthflow
78
are avalanches a flow (why or why not)
NO - they are not made up of earth material (like soil- they are made from ice/snow)
79
is continuous creep fast or slow
slow deformation of soil
80
what produces a continuous creep
gravity acting downslope
81
where can continuous creeps occur
in permafrost
82
what type of mass movement is this
combination of frost creep and gelifuction
solifluction
83
gelifluction
the slow movement of saturated soil over frozen ground during the SPRINg and SUMMER
84
what can solifluctions form
1. tongue like lobes
2. solifluction sheets
85
what type of mass movement is this
do NOT have a scar upslope
solifluction
86
of the 7 types of flows, what are the FAST moving ones
1. earth flows
2. mudflows
3. debris flows
4. quick clay flows
5. slushflows
87
flows are the movements incorporating
viscous fluid OR plastic motion
88
what is the slowest RAPID moving flow
earthflow
89
what type of mass movement is this
vegetation cover usually intact
earthflows
90
fastest flow
mudflow
91
what type of mass movement is this
the most fluid flow
mudflow
92
the most dangerous flow
mudflow
93
the flow that causes the least amount of damage
earthflow
94
what separates a mudflow from a debris flow
debris flows have LARGE PARTICLES while mudflows are mostly fluid like substances
95
what moves slower: a mudslide or a debris slide
debris flow
96
what often causes debris flows
heavy precipitation
97
what type of mass movement is this
horse-show shaped forms
quick clay flow
98
what develops a quick clay flow
Leda clay (produced by depositions of glacial material in the Champlain sea)
99
how does a quick clay flow form
marine salts are leached out of reducing soil = flow occurs following above-normal precipitation OR an earthquake
100
quick clay flow
101
debris flow
102
mudflow
103
flows
104
LEFT
slide
105
RIGHT
flow
106
Needle-ice creep
107
Discontinuous creep
108
where can a slushflow occur
in mountain-environments and down EXISTING river channels
109
describe the debris in a slushflow
it is non-sorted and piled up randomly
110
slides are the movement along
one or more DISCRETE FAILURE SURFACES (aka shear planes)
111
main causes of slumps
1. steeping of slopes by basal erosion, heavy precipitation or earthquakes
112
rock slide
failure along a FLATE PLANE parallel to the ground
113
where do rock slides occur
where bedding planes and slopes dip in the SAME direction
114
debris slides
failure of NON-CONSOLIDATED MATERIAL along a plane PARALLEL to the ground
115
special case of debris slides
active-layer detachments (occur over permafrost because of a rapid-thaw of icy soils over still frozen material)
116
falls
vertical or near vertical movement of particles through the air
117
most rapid of ALL the mass movements
rockfall
118
rockfall
free-falling, bouncing or rolling of blocks down slopes
119
what do rockfalls produce at the base
talus
120
what causes rockfalls
the freeze-thaw weathering
121
blockfall
vertical movement of an ENTIRE piece of slope
122
where do blockfalls often happen
in frozen sediments undermined by thermal erosion
123
complex movements
a mixture of ANY of the other types of mass movements
124
rockfall
125
blockfall
126
active-layer detachements
127
rock slide
128
slump
129
natural causes for mass movements
1. slope becoming saturated
2. oversteepening
3. volcanic eruptions
4. earthquakes
130
anthropogenic causes of mass movements
1. deforestation
2. building on steep gradient
3. road construction
4. mining and undercutting
131
steps of a quick clay flow
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
what holds the quick clay together
the salt content
133
what causes quick clay to liquefy
when the water leeches salt from it - it becomes unstable and liquefies
134
does a tallus move in rock falls
NO
135
what forces act on a rock fall
only FRICTION and NOT gravity
136
does the rock have to be uniform in a rockfall
NO
137
what causes a mudflow
heavy precipitation
138
what mass movements are seen as SATURATED
1. earthflow
2. mudflow
3. debris flow
4. quick clay flow
139
what mass movements are seen as UNSATURATED
1. rock slide
2. slump
3. rock falls
4.
