Chapter 15
Which of the following is a reason the Gros Ventre rockslide took place?
Because the river eroded material at the valley base, there was no support of the material upslope.
How are debris avalanches and flows related?
Debris avalanches are large, rapid flows of rock.
Which of the following types of flows will have the largest particle sizes?
Debris flow
Describe how a soil particle moves downhill during the freeze-thaw process.
During the freeze, a soil particle moves at a right angle away from the surface, and thawing causes the particle to fall back to a slightly lower level.
How is a fall different from creep?
Falls occur rapidly and in areas with high slope, whereas creep occurs slowly in areas with low slope.
Grasses will create more slope stability than trees because there are more individual plants.
False
Which of the following is not a way an earthquake can trigger mass wasting?
Friction from the fault blocks grinding against each other reduces the angle of repose of slope sediments
Which of the following factors does not influence mass wasting?
Geologic age
Which sediment size has the steepest angle of repose?
Gravel
Which of the following landslides was caused in part because the underlying sedimentary bedrock was oriented parallel to the slope that failed?
Gros Ventre Landslide (Wyoming)
What combination of factors was responsible for the Vaiont Dam disaster in Italy in October 1963?
Heavy rains and the drawing down of the reservoir led to a landslide that filled the reservoir and displaced the water
________ is the downslope movement of rock, regolith, or soil under the direct influence of gravity.
Mass Wasting
Which of the following will not oversteepen a slope and lead to mass wasting? Construction Quarrying Coastal erosion
None of the above
Which of the following locations would be most likely to see large-scale, rapid mass wasting?
Rocky Mountains
Drag the appropriate labels to their respective targets.
Slump: Triggered by curved oversteepened slopes Flow: Triggered by large amounts of water and steep slopes Creep: Triggered by repeated freezing and thawing of soils on gentle slopes Fall: Triggered by ice wedging or plant activities on steep slopes
How are slumps and slides related?
Slumps are a type of slide in the special case where the rupture surface is curved.
Which of the following statements is true regarding the aftermath of the Gros Ventre rockslide?
The rockslide debris dammed up the river and formed a lake.
What is the angle of repose?
The steepest angle at which a material remains at rest
What would likely happen to a fence on a hill over time if the fence were built perpendicular to the hill's slope?
The top of the fence would likely bend uphill as creeping rocks moved under the fence and pushed the fence bottom downslope.
Why would trees be J-shaped?
The trunks become tilted in the downhill direction due to creep, but continue to grow toward the sun.
Which of the following scenarios best describes the creation of the lahars associated with the eruption of Mt. St. Helens in 1980?
The volcanic dome exploded, depositing fine ash in the Toutle River
How can the addition of water make a slope fail, creating a landslide? Select all that apply.
Water in pore spaces reduces cohesion between particles. Water makes the slope material heavier. Water can easily flow downslope.
The Gros Ventre slide is evident today by __________.
a scar, runout area, and landslide debris filling the valley
A __________ is a common result of creep.
broken retaining wall
A __________ acted as a sliding surface across which material moved downhill during the Gros Ventre Slide.
clay layer
What is the slowest form of mass wasting?
creep
___ are very gradual mass movements in which the whole slope moves downhill slowly.
creep
The 2005 mass-wasting event in La Conchita, CA, can be classified as a ______.
debris flow
Which of the following triggers generated the 1958 landslide and tsunami at Lituya Bay, Alaska?
earthquake
When large rocks become dislodged and drop down a steep slope, the mass movement is called a ___
fall
Which of the following are classifications describing how rock and other material move downslope?
fall, slide, slump, creep, flow
When unconsolidated material moves downslope as a viscous fluid it is called a ___
flow
Which type of mass movement event requires the addition of water?
flow
Massive, rapid mass wasting typically occurs in _____.
geologically young mountains
Which of the following is the major contributing factor in all landslides?
gravity
Creep is __________.
mass wasting by the gradual downhill movement of sediment, influenced by freeze-thaw or wet-dry cycles
Which landscape is most prone to generating landslides?
mountains
What is mass movement?
movement of material under the influence of gravity alone
Solifluction would most likely occur in ____.
regions underlain by permafrost
What is the fastest form of mass wasting?
rockfall
Heavy rainfall caused the clay to lubricate and the sandstone to become __________.
saturated and heavy
What is the crescent-shaped mark found at the top of a slump block?
scarp
A mass movement in which a cohesive block of earth or rock slips downhill relatively quickly in one piece along a zone of weakness is called a
slide
Which of the following is associated with creep?
slow and subtle movement of material
Mass movements that move blocks of materials and unconsolidated materials down a curved surface creating scarps on a slope are known as ___
slump
Creep is the most widespread mass-wasting process.
true
Post-fire debris flows are most common in the first two years after a fire.
true
Rapid mass-wasting events do not always need a trigger.
true
Rockfalls are the primary way in which talus slopes are built and maintained.
true
Solifluction is a slow type of mass wasting that moves at a rate of a few centimeters per year.
true
Solifluction occurs during the warmer months of the melt season.
true