Chapter #5 Flashcards
Relief is…
Differences in elevation between location
Slope is….
Tilted ground between locations at different elevations
Erosion is …
The removal of material due to the movement of ice, water, and air
Name the 4 angles and their degrees
Gentle: < 5
Moderate: 5 - 35
Steep: > 35
Vertical: 90
What is the slope on roads called?
Grade
What is Grade (of land) measured in?
Percentage
Most slopes are of which type?
Complex
Name the 6 types of slopes
Planar
Convex up
Concave up
Complex (convex-concave)
Vertical
Stair-step
Slope Shape depends on what 3 factors?
Strength, Climate, Formation Process
Define Strength, with slope shape
- The ability to avoid failure,
- Coherent material is a continuous solid,
- Unconsolidated material is composed of separate pieces,
- Planes of weakness are weakly attached surfaces
Define Climate, with slope shape
- Long term atmospheric conditions
- Determines running water, flowing ice, and wind
- Controls vegetation and soil characteristics
Define Formation Process, with slope shape
- Different erosion processes create different slope shapes.
Glacial erosion creates what shape?
A “U” shape
Steam flow erosion creates what shape?
A “V” shape
Class Question #1
Why is the event at Yungay, Peru, classified as a secondary disaster?
a) The flood that inundated Yungay was created from volcanism in
Nevado Huascarán that melted a glacier.
b) The primary seismic waves created only minimal damage to Yungay
compared to the surface waves that arrived later.
c) The landslide that buried Yungay was created by an MW 7.9
earthquake.
d) The pyroclastic flow that buried Yungay was created only after a
mafic volcanic eruption.
( NO PROVIDED ANSWER YET)
Vectors indicate what?
Magnitude and Direction (Force direction specifically)
What is the formula for Stress
Stress = Force (divided) Area
What is Normal Stress?
Force that is perpendicular to the surface
What is Shear Stress?
Force that is parallel to the surface
What is Resistance Stress?
Frictional resistance of motion
A slope is unstable when?
Force D > Force R
What is the formula for Safety Factor?
Safety Factor = Force R (divided) Force D
What are joints?
Cracks
Factors causing joint growth
- Increasing σd (downslope shear stress)
- Overburden removal
- Ice and root wedging
- Daily temperature changes
Sedimentary rock joints are often ___ to beds
perpendicular
Igneous rock joints are often _______ to beds
perpendicular or parallel
Exfoliation joints are
joints that are parallel to beds
Cohesion
Weak electrical charges attract grains to each other
Too much what does what to Cohesion?
Eliminates cohesion by seperating grains, eliminating electrical attraction
A cones steepest angle is its?
Repose
Foliation (Specific to this course)
A parallel alignment of materials
Failure surface
Where movement begins on a weak plane
Planes of weak surface definition
A surface with less strength compared to the material above it
Planes of weakness include…
- Layers of wet clay and sand
- Joints in sediment and igneous rock
- Exfoliation joints in igneous rock
- Foliation planes in metamorphic rock
Is the orientation of planes relative to slope matter?
Yes it does matter
If a surface angle is parallel to the orientation of a plane, the surface is ______
Unstable
If a surface angle is perpendicular to the orientation of a plane, the surface is ______
More stable
Class Question #2
Why can the walls of sandcastles stand at 90°?
a) Water’s surface tension creates cohesion between sand grains.
b) Friction between dry grains prevents movement.
c) Water-filled pores create strong electrical charges between grains.
d) The chemical bonds between individual, dry sand grains create an
attractive electrical force.
(NO answer provided)
Mass wasting’s are distinguished by 4 criteria..
- Material type
- Movement velocity
- Moving mass character
- Movement environment
Creep
Regolith’s slow, gradual, downslope movement
Creep is caused by…
Repeated expansion and contraction.
Ex: Freezing and thawing, Wetting and drying, Warming and cooling
Solifluction
Creep in areas with permafrost
Permafrost
Permineately frozen ground slightly below Earth’s surface. Common in polar and high elevation
Slumps (Specific to this course mostly)
Rock and regolith stay mostly coherent during during movement
Transitional slump
Rock and regolith move down a planar failure surface.
Head scarp
the exposed, upslope edge of the failure surface
Toe (specific to this course, not my toe)
The downslope end of the slump block
Mudflow
a slurry of mud
Debris flow
a mixture of mud and large rocks
What creates a slurry?
Excessive water
Lahar
Muddy slurries of ash, melted snow, and rain. Develop from volcanic ash and water
Saprolite
Soft, porous rock of clay quartz. Mass wasting are common on this
Lateral Spreading
Displacement on a horizontal failure surface
Rockslides
Sudden downslope movement of rock and debris (Note: slope is non-vertical)
Rockfalls
When a mass free-falls down a cliff or slope
Toppling vs Dropping
Toppling: Falling over from the top
Dropping: Dropping from below
Evidence of Rockfalls
Talus slopes accumulate at the cliff base
Wet avalanche
A slurry of solid and liquid water
Dry avalanche
A cloud of powder mixed with air
Class Question #3
Why do some economically-marginalized Brazilian communities live
with a high mudflow risk?
a) Their favelas are commonly located at the base of rockfall-prone
cliff faces.
b) Their homes are frequently built near the peaks of tectonically
uplifted terraces.
c) Their neighborhoods are regularly constructed on top of unstable
solifluction lobes.
d) Their communities are often built upon unstable saprolite slopes.
(NO GIVEN ANSWER)
The 3 types of submarine mass wasting’s are?
- Submarine slumps
- Submarine debris flows
- Turbidity Currents
Submarine slumps
Semi coherent blocks move down slope
Submarine debris flows
Moving layers break apart to form a slurry
Turbidity Currents
Sediment disperses and forms a turbulent cloud
Liquefaction
When wet sediment changes to a slurry
What triggers Liquefaction?
- Human induced ground vibrations
- Seismic waves
- Heavy Rains
- Water table changes
Undercutting
Removal of support at base of slope decreases resistance.
Causes: Stream erosion, Wave erosion, Excavation
What happens to shear stress as we increase the angle of the slope?
As angle of slope goes up, shear stress goes down
The 3 factors that influence a slopes strength
- Weathering: Materials may be weakened by physical and chemical processes
- Vegetation: Roots bind sediments and absorb water, Deforestation and wild fires can cause mass wasting’s.
- Water Content: Increased water pressure may push apart sediment grains
Class Question #4
What do saltwater ions do that stabilizes clay particles?
a) Atomically bond to silica in clay particles to create crystal lattices.
b) Electrostatically bind to clay’s negatively charged flakes.
c) Precipitate a cementing agent that reinforces clay sediment.
d) Inhibit seismic vibrations from passing through clay beds
(NO given answer)
LPM
Landslide Potential Maps
Indications of starting a mass wasting include,
Infrastructure damage (cracked roads, buildings, and pipes)
Visible cracks and elevation changes (indicating slump formation)
Changes in an area’s water drainage patterns
Remotely observed location changes (GPS, lasers, and satellite radar)
Precise surveying data
Mitigation techniques for mass wasting’s include,
Revegetate slopes so plants absorb water and roots bind soil.
Lower water levels in reservoirs and lakes to reduce weight.
Reposition stream channels to prevent slope erosion.
Lower water tables to decrease slope weight.
Construction solutions:
* Excavate benches to remove downslope stress.
* Install drainage culverts and drainage pipes.
* Construct retaining walls.
* Build rockfall and avalanche sheds over roads.
* Spray shotcrete over bedrock slopes.
* Cover slopes with chain link fencing.
* Insert rock bolts into bedrock slopes.
Four Main ways to mitigate mass wastings
- Revegetate slope
- Lower a water table
- Relocate river
- Add riprap
Class Question #5
Why are aerial imagery data and maps useful when identifying mass
wasting risks?
a) They can show water table depth, and thus lead to mitigation
efforts.
b) They can show real-time dilution of saltwater ions, thereby leading
to highly accurate liquefaction forecasting.
c) They may identify areas that experienced past mass wasting events.
d) They can identify failure surfaces underlying regolith.
(No current answer)
