EOSC 114 Landslides Exam Questions and Answers Pass Guaranteed Latest Update
What is a fall - Answer- a sudden, vertical movement of material
Where do falls occur - Answer- on steep slopes with loose rock that may periodically detach from a surface on which little or no shear/sliding is taking...
EOSC 114 Landslides Exam Questions
and Answers Pass Guaranteed Latest
Update
What is a fall - Answer- a sudden, vertical movement of material
Where do falls occur - Answer- on steep slopes with loose rock that may periodically
detach from a surface on which little or no shear/sliding is taking place
How do fall material descend - Answer- mainly through the air by falling, bouncing, or
rolling
What are the characteristics of falls - Answer- very fast moving, usually involve rocks,
and are often related to the geologic structure of the slope
How are areas of active rock falls identifiable - Answer- by the formation of talus cones
and aprons at the base of the cliffs
What is the greatest influence on falls that require almost new vertical cliff faces in order
to occur - Answer- gravity
What is the equation for the velocity of fall - Answer- v = square root of 2*g*z (z = height
of fall; g = gravity)
What plays a significant role in creating situations where falls will occur - Answer-
mechanical weathering and absorption of water without chemical changes
What is mechanical weathering - Answer- physical breakup of material by freeze-thaw
cycles, salt crystal growth, root wedging, and penetration
What is an example of a fall that mechanical weathering and absorption of water without
chemical changes played a big role - Answer- 1996 Yosemite rock fall where the
plutonic rocks that compose the steep glaciated valley were gradually weakened by
years of freeze-thaw cycling of water in pervasive joints
What do topples require - Answer- the forward rotation of material (rocks) about a pivot
point below the center of gravity of the unit or in the slope; require fractured material
oriented perpendicular and parallel to the slope face, which allows the materials to be
broken up into coherent pieces that roll forward down a slope
,Why is there no such thing as a debris topple - Answer- because debris is unsorted and
consists of material of a variety of sizes which usually does not remain in coherent
blocks upon failure
What do slides involve - Answer- large volumes of rock or soil material moving as an
initially coherent mass on a sliding surface
How may slides occur as - Answer- rotational slides or translational slides
What are rotational slides - Answer- where blocks of soil or weak rock move along a
curved rupture surface that forms due to the shear forces in the slope exceeding the
shear strength of the soils/rocks -- during failure, blocks of material rotate and lift
What are translational slides - Answer- where blocks of strong rock move upon a weak
plane or pairs of intersecting weak planes in the rock (joints, faults, bedding, etc.)
What are slide velocities usually like - Answer- slide velocities vary from slow to fast,
usually involving soil, rock, or debris moving along a surface of failure (curved or
straight)
What are lateral spreads - Answer- lateral spreads occur where there is a slow to rapid
extensional movement of rock or soil -- usually related to the sudden liquefaction of
weak soil layers (eg. quick clays); such spreads can occur on relatively shallow slopes
What are lateral spreads usually triggered by - Answer- earthquakes or explosions
What areas can cause water pressure to increase dramatically - Answer- in areas
where loose soils are saturated with water, seismic shaking (from earthquakes) can
cause water pressure to increase dramatically
What is liquefaction - Answer- the sudden loss of strength in the soil transforming its
behavior into that of a liquid
What was the most significant cause of damage in the Alaska M 8.6 earthquake -
Answer- liquefaction of saturated sands and lateral spreads
What occurs to the factor of safety during liquefaction - Answer- it decrease to a very
small number due to the dramatic increase in the pore water pressure
Why is Richmond and Delta highly vulnerable to earthquakes and damage due to
liquefaction and lateral spreads - Answer- because Richmond and Delta are underlain
by deep water-saturated, loose, silty sand deposits
What are sensitive clays - Answer- quick clays -- young marine clays that are deposited
with a House of Cards like structure
, What happens to quick clays during an earthquake - Answer- the card-house structure
may collapse and liquefy
Where are Canada's quick clays - Answer- the St. Lawrence river valleys -- lined with
thick beds of sensitive marine clays known as Leda clays
Upon disturbance, what happens to the Leda clays - Answer- Leda clays may undergo
a significant loss of shear strength, liquefying and flowing as a viscous mud, rapidly
devastating large areas of relatively flat terrain
What do water-saturated clay particles flow like - Answer- a liquid
When do flows occur - Answer- when there is a relatively large volume of water present
in a mixture of soil and debris
How does material flow downhill - Answer- rather than moving downslope as a coherent
mass, material will flow downhill as a chaotic, viscous mixture
What are flows differentiated based off of - Answer- flows are differentiated based off
their velocity and the type of sediment involved
What is the difference between flows and slides - Answer- slides require the material to
stay in coherent blocks while a flow moves in a rather chaotic, viscous way
What is a rock or soil creep - Answer- a type of flow where soil and upper bedrock
zones move downslope extremely slow
What is movement of rock or soil creeps usually measured as - Answer- mm or cm per
year
What creates the most long-term economic problems compared to any other landslide -
Answer- creeps because it usually goes undetected until the damage is already done
What is a debris flow - Answer- a rapid flow of fully saturated debris (organic matter,
sand, gravel, boulders) in a steep channel
What do debris flows form - Answer- a distinctive debris fan at the mouth of the channel
or gulley as the material spreads out because it is no longer confined (debris flows from
the point of initiation through the transport zone or gorge and results in a debris/colluvial
fan)
Where are debris fans common in BC - Answer- in the BC coastal mountains because
heavy rains fall on steep slopes covered by loose sediments
What is a debris avalanche - Answer- a rapid and shallow flow of partially to fully
saturated debris on a steep slope that is not confined to an established channel [starts
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