Mass Wasting Flashcards
1
Q
It is the downslope movement of rock and
regolith near the Earth’s surface mainly due
to the force of gravity.
A
Mass Wasting
2
Q
Any perceptible downslope movement of
rock or regolith is often referred to in general terms as a
A
Landslide
3
Q
The Cherry Hills Landslide’s complex
slide started out as a ______ and developed into a _______ near the base.
A
slump; debris flow
4
Q
Knowledge about the relationships between these two can lead to better planning that can reduce
vulnerability to such hazards.
A
local geology and mass wasting processes
5
Q
The material that is (practically) still in place and
adjacent to the highest parts of the main scarp.
A
Crown
6
Q
A steep surface on the undisturbed ground at the
upper edge of the landslide, caused by movement of the displaced material away from the undisturbed ground. It is the visible part of the surface of rupture.
A
Main scarp
7
Q
The highest point of contact between the displaced
material and the main scarp.
A
Top
8
Q
The upper parts of the landslide along the contact
between the displaced material and the main scarp.
A
Head
9
Q
A steep surface on the displaced material of the landslide produced by differential movements within the
displaced material.
A
Minor scarp
10
Q
The part of the displaced material of the landslide
that overlies the surface of rupture between the main scarp
and the toe of the surface of rupture.
A
Main body
11
Q
The portion of the landslide that has moved beyond the
toe of the surface of rupture and overlies the original ground
surface.
A
Foot
12
Q
The point of the toe farthest from the top of the landslide.
A
Tip
13
Q
The lower, usually curved margin of the displaced
material of a landslide, it is the most distant from the main
scarp.
A
Toe
14
Q
The surface that forms (or has formed) the lower boundary of the displaced material below the original ground surface.
A
Surface of rupture
15
Q
The intersection (usually buried)
between the lower part of the surface of rupture of a landslide and the original ground surface.
A
Toe of surface of rupture
16
Q
The part of the original ground surface overlain by the foot of the landslide.
A
Surface of separation
17
Q
Material displaced from its original position
on the slope by movement in the landslide. It forms both the
depleted mass and the accumulation.
A
Displaced material
18
Q
The area of the landslide within which the displaced material lies below the original ground surface.
A
Zone of depletion
19
Q
The area of the landslide within which
the displaced material lies above the original ground surface.
A
Zone of accumulation
20
Q
The volume bounded by the main scarp, the depleted mass and the original ground surface.
A
Depletion
21
Q
The volume of the displaced material that overlies the rupture surface but underlies the original ground
surface.
A
Depleted mass
22
Q
The volume of displaced material that lies above the original ground surface.
A
Accumulation
23
Q
The undisplaced material adjacent to the sides of the rupture surface. Compass directions are preferable in
describing these, but if left and right are used, they refer to these as viewed from the crown.
A
Flank
24
Q
The surface of the slope that existed
before the landslide took place
A
Original ground surface
25
True or False: Slump is the term for translational landslide
False; rotational
26
State of a mass wasting that refers to the ongoing or currently occurring movement of materials down a slope. It is characterized by the continuous displacement of material due to the force of gravity.
Active
27
A state of mass wasting where the movement of material down a slope has temporarily ceased, often due to a decrease in the driving forces (e.g., reduced rainfall) or an increase in resisting forces (e.g., vegetation growth).
Suspended
28
A state of mass wasting that occurs when previously stable materials on a slope are suddenly mobilized due to changes in conditions. These changes can reinitiate movement after a period of suspension.
Reactivated
29
A state of mass wasting where there is no current movement of materials down a slope. The slope may have fully stabilized, or the conditions necessary for movement are not currently met.
Inactive
30
A state of mass wasting that where a mass wasting feature, such as a landslide or slope failure, is not currently active but has the potential to become active again under the right conditions.
Dormant
31
A state of mass wasting that have undergone movement in the past but are no longer active and are not expected to become active again. These features have reached a state of long-term stability.
Abandoned
32
A state of mass wasting that features have been actively managed or engineered to reduce or eliminate the risk of further movement. Stabilization measures aim to secure the slope and prevent future mass wasting events.
Stabilized
33
A state of mass wasting where features are remnants of ancient or long-past mass wasting events. These features are no longer active and are often found in older geological formations.
Relict
34
Mass Movements can be classified according to:
1. Type of movement: flow, slide, slump, etc.
2. Type of material involved: rock, debris,
earth, and mud
3. Relative proportions of material and water
4. Velocity of movement: slow<>rapid
5. Thickness: shallow or deep seated
6. Type of triggering factor: rain-induced,
earthquake-induced
35
A type of movement that comprise a detachment of soil or rock
from a steep slope and the more or less free and extremely rapid descent of the material.
Fall
36
Triggering factors of a fall
lateral pressures (roots, crystallization pressures, ice wedging, etc.) or by lost of underlying support (erosion on cliffs)
37
A forward rotation out of the
slope of a mass of soil or rock about a
point below the center of gravity of
the displaced mass.
Topple
38
A _____ is defined as a
moving slab of soil or
bedrock that moves
downslope as a whole,
remaining in contact
with the underlying
material.
Slide
39
A type of slide movment which have a more or less circular failure surface.
Rotational
40
A type of slide movement where the sliding mass moves along a pre-existing failure plane (e.g. bedding, schistosity, joint, discontinuity between slope debris and the underlying rock).
Translational
41
True or False: The total displacement along translational slide plane is generally shorter than rotational's. Also, translational slides are also frequently showing a considerable smaller width than a rotational slide.
False; longer and larger
42
It is a shallow translational movement in soil material
Soil Slips
43
This type of movement involve
great internal deformation;
inter-granular movements
dominate over shear
surface movements.
Flow
44
It is a type of slow flow movement, in which the rate of internal
deformation is limited.
Earth flow
45
It is a type of a fast moving flow. The material is (over)saturated with
water.
Mudflow
46
Debris from falls and high-energy slides can also behave as a flow called ____, especially if air or water is entrained in the initial movement.
Debris flow
47
An extension of a cohesive soil or rock mass combined with a general subsidence of the broken mass of cohesive material into softer underlying material.
Spread
48
______ is the slow
movement of soil or
bedrock down slope. It
occurs where the stresses
on the slope material are
too small to create a
rapid failure, or as a
result of thawing/freezing
effects.
Creep
49
It is a combination of two principal types of movement.
Complex
50
True or False. As the slope increases, so too does the gravitational component acting parallel to the slope.
True
51
In addition to steepness, what are other factors that may
trigger mass wasting:
Nature of Slope Material
Oversteepened Slopes
Climate and Vegetation
Earthquakes and Volcanic Activity
52
It is the steepest angle at which a sloping surface of
unconsolidated sediments is stable. Provide the degree of angle.
Angle of repose (less than 35 degrees)
53
True or False: Frictional forces within loose or unconsolidated sediments are usually higher than solid rock, making
sediment more prone to mass wasting and less able to form vertical slopes.
False; lower
54
True or False: Resistant to weathering rocks tend to form gentler slope than weaker rocks
False; steeper
55
It is formed from the undercutting of stream banks
due to the natural migration of stream channels
which results to destabilizing/overhanging of riverbanks.
Cutbanks
56
_____ also determines the types of
vegetation we see blanketing the various slopes, which influences the fraction
of rain or snow that infiltrates into the subsurface.
Climate
57
Geological causes of mass movement
• Weak material
• Sensitive material
• Weathered material
• Sheared material
• Jointed or fissured material
• Adversely oriented mass discontinuity (bedding, schistosity,
etc.)
• Adversely oriented structural discontinuity (fault,
unconformity etc.)
• Contrast in permeability
• Contrast in stiffness (stiff, dense material over plastic
material)
58
Morphological causes of mass movement
• Tectonic or volcanic uplift
• Glacial rebound
• Erosion of slope toe
• Erosion of lateral margins
• Subterranean erosion (solution, piping)
• Deposition of load on the slope or its crest
• Vegetation removal
59
Physical causes of mass movement
• Intense rainfall/ Prolonged exceptional precipitation
• Rapid snow melt/ Thawing/ Freeze-and-thaw weathering
• Earthquake/ Volcanic eruption
60
Human causes of mass movement
• Excavation of the slope or its toe
• Deposition of load on the slope or its crest
• Drawdown (of reservoirs)
• Deforestation
• Irrigation
• Mining
• Artificial vibration
• Water leakage from utilities
61
Observations needed in identifying Landslides
•Vegetation cover: intact/disrupted
•Presence of cracks or scars •Disturbance of the drainage pattern. •Excessive soil moisture or abrupt soils moisture changes.
•Terrain form (e.g. hummocky, niche-lobe sequence)
62
Morphological Diagnostics of a Landslide:
Semicircular niches
Back tilting of slope face
Hummocky relief
Formation of cracks
Steepening of slopes
Vegetational clearances on steep scarps
Irregular linear clearances along the slope
63
This sequence or part of a slope is associated with landslide niches and associated deposits. In the stereo model this appears as concave/convex anomalies.
Concave/convex
64
A ________________ is related to retrogressive sliding.
step-like morphology
65
____________ are associated with the head part of a slide with the
outcrop of the failure plane. On photographs recognizable as a light toned scarp, with small light curved lineaments.
Semicircular niches
66
________________ indicates rotational movement of slide blocks. This feature appears as oval or elongated depressions with imperfect drainage conditions.
Back tilting of slope faces
67
It has irregular slope morphology. Micro-relief associated with shallow
movements or small retrogressive slide blocks. On the aero-photo the
coarse surface texture of these terrains stand in contrast with smooth surroundings
Hummocky Relief
68
The ______________ is an indication for recent activity. These occurs with sliding and toppling movement. They appear as
lineaments more or less parallel to the existing scar
Formation of new cracks
69
Morphological diagnostics of a landslide that is coinciding with morphological steps. Headscarps and steps in a slide body often lack vegetation. On photographs this shows as light-toned elongated areas at the crown or on the body of the mass movement.
Vegetational clearances on steep scarps
70
This morphological diagnostics of a landslide has flows and avalanches strip parts of the slope from vegetation; leaving the flowpath uncovered. Slip surface of translational slides as well are usually uncovered. The denudated areas are showing light tones, often with linear pattern in direction of movement.
Irregular linear clearances along the slope
71
What agency and what program under that agency is responsible for the mapping of landslide susceptibility in the Philippines?
MINES AND GEOSCIENCES
BUREAU; NATIONAL GEOHAZARD MAPPING AND ASSESSMENT PROGRAM
72
Interpretation and analysis of these Remote Sensing Data are useful for conducting Geohazard mapping
aerial photographs & satellite images and other thematic maps such as
geologic map, drainage map, slope map, vegetation map
73
__________ in geohazard mapping involves on-site investigations and data collection conducted by geologists, geoscientists, or experts to evaluate and document the physical characteristics, geological features, and potential hazards in a specific geographic area.
Field assessment
74
In geohazard mapping, _____________ refer to firsthand or eyewitness reports and stories provided by individuals or communities who have experienced or observed geohazard events.
Anecdotal accounts
75
What are the Contents of the Geohazard Maps of MGB
DIRECTION
SCALE
LEGEND
SUSCEPTIBILITY CODING
76
What is the degree of angle of this slope classification? "Level to nearly level"
0 to 3 degrees
77
What is the degree of angle of this slope classification? "Gently Sloping to Undulating"
3 to 8 degrees
78
What is the degree of angle of this slope classification? "Undulating to Rolling"
8 to 18 degrees
79
What is the degree of angle of this slope classification? "Rolling to Moderately Steep"
18 to 30 degrees
80
What is the degree of angle of this slope classification? "Steep"
30 to 50 degrees
81
What is the degree of angle of this slope classification? "Very Steep"
>50 degrees
82
Two ways to reduce the risks of mass wasting
Recognizing and Avoiding the Hazard
Applying Engineering Controls
83
These two methods can minimize human activity within the hazard zone
Zoning Laws
Construction Ordinances
84
This engineering control are commonly used whenever a flat or level surface is needed in
sloping terrain, such as for roadways, buildings, and parking lots; involves stabilization
of oversteepened slope thru cutting. It can also be used to gain control over slides or
flows that occur repeatedly.
Retaining Walls
85
This engineering control are commonly used to anchor loose rocks to more massive, solid bodies
of rock; applicable on areas that have highly fractured rocks are exposed on steep
slopes and where weakness planes are inclined in the
same direction as the slope.
Rock Bolts
86
This controlling water engineering technique drains water from within the slope
installing a network of perforated
pipes and/or gravel beds
87
In controlling water engineering control, it may even be necessary to cover large sections of a slope with _______________ to prevent water from infiltrating into unstable materials.
impervious plastic sheeting
88
This engineering control decreases the overall steepness of the slope, but also breaks the slope up into shorter segments
Terracing
89
In covering the steep slope, common way of establishing a blanket of
grass is a technique called ________, where a slurry of seed, mulch, and fertilizer is sprayed onto a
bare slope.
hydroseeding
90
In the case of weakness planes are inclined
in the direction of the slope,
creating a serious hazard that
can require continuous and
costly engineering efforts to
prevent a slide, this engineering control has the advantage
of eliminating both the hazard
and the long-term costs
associated with stabilization
efforts.
Reducing or removing the entire slope materials
91
This protective structure diverts material away from a
building or group of buildings.
Retaining walls
92
To protect an entire village or town, this protective structure can
be placed in a stream valley that will trap material from flows or slides as it moves downslope
Large barriers made of reinforced concrete
93
This protective structure can bypass altogether a troublesome sections of a highway or railroad.
Tunnel
94
What are the two types of mass movement that cause the complex slide in Guinsaugon,
Leyte (February 17, 2006) which claimed at least 1,126 lives and
devastated the Village of Saint Bernard?
rockslide and debris
avalanche
95
What is the run-up height caused by the debris flow in Andap, New Bataan.
1.8 m
96
Fall produces a cone-shaped deposit of rocks at the base of exposed rock bodies called a ______.
Talus pile
97
Creep is usually associated with what type of material of a slope?
Clay-rich
