Deck 13: Mass Movements and Snow Avalanches

Question 1

The sum of all the underlying causes can push a slope to the brink of failure,and then an immediate cause may trigger the movement.All but,which of the following triggers can initiate mass movements?

A) Heavy rains
B) Earthquakes
C) Thawing of frozen ground
D) Construction projects
E) Heavy snow falls

Answer 1

E

Question 2

Many hill slope masses are weak due to preexisting geologic conditions such as _________________.

A) structures within the rocks,such as fractures,ancient faults,and soft rock layers
B) rock layering dipping at angles greater than the hill slope
C) low water tables
D) all of these are correct

Answer 2

A

Question 3

Freshwater passing through uplifted sediments containing quick clay changes the sea salt content leaving quick clay with all but which of the following?

A) Weak structure
B) Grains mostly less than 0.002 mm diameter
C) Water contents commonly in excess of 50%
D) A high salt content
E) All of these are correct

Answer 3

D

Question 4

The stability of a hillslope is improved by __________________.

A) increasing pore water pressure
B) decreasing the weight of hillslope materials
C) steepening the slope
D) removing support from the base
E) dissolving the cement between soil or rock grains

Question 5

Before a hillside begins to move downslope,it must overcome __________________.

A) inertia and friction
B) inertia and gravity
C) gravity and friction
D) gravity and creep

Question 6

Of the following types of mass movements,which can move fastest?

A) Creep
B) Translational rockslide
C) Earth flow
D) Mudflow
E) Avalanche

Question 7

The Ottawa and St.Lawrence River valleys have extensive deposits of quick clay which when triggered by ____________ can become unstable and flow like a liquid.

A) earthquake
B) excessive amounts of water
C) vibrations from construction equipment
D) all of these are correct

Question 8

External processes that increase the odds of a slope failure include __________________.

A) adding mass high on a slope,as in sediment deposition
B) steepening the slope,as by fault movements
C) removing support from low on a slope,as by stream or ocean-wave erosion
D) all of these are correct

Question 9

The water content varies markedly in different types of mass movements.Which of the following are in the correct sequence going from saturated to driest?

A) Creep,translational slide,rock fall
B) Earth flow,rotational slump,rock fall
C) Mudflow flow,earth flow,landslide
D) Creep,rock fall,landslide

Question 10

The presence of talus slopes indicate that _______ have occurred in the past.

A) snow avalanche
B) rotational slump
C) creep
D) rock fall

Question 11

Internal causes of slope failure include all but which of the following?

A) Inherently weak materials
B) Water in different roles
C) Increasing cohesion
D) Adverse geologic structures
E) All of these are correct

Question 12

Mass movement is the movement of earth materials downslope due to __________________.

A) the Earth's internal energy
B) solar energy
C) gravity
D) the impact of extraterrestrial bodies

Question 13

Which of the following statements regarding clay minerals is false?

A) Clay minerals from the side view are thin and flat,and they commonly form book-like structures.
B) As clay minerals take in new elements and lose others,they increase and decrease in strength.
C) Clay minerals expand and contract as they absorb and lose water.
D) Clay minerals are typically angular and rounded,which allows them to pack tightly.

Question 14

Water weakens earth materials in all but which one of the following ways?

A) Through interplay with clay minerals
B) Decreasing the cohesion of rocks
C) Decreasing pressure in pores of rocks and sediments
D) Congelifraction
E) All of these are correct

Question 15

Inertia is __________________.

A) the resistance to motion due to surface roughness
B) the tendency of a body to remain stationary until an external force is applied
C) the acceleration in velocity as materials move downslope
D) the force of gravity pulling materials downslope

Question 16

Clay crystals ____________________.

A) are very large
B) are very small
C) range from very large to very small
D) are amorphous
E) do not exist in nature

Question 17

The speed of movement varies markedly in different types of mass movements.Which of the following are in the correct sequence going from slow to rapid movement?

A) Creep,translational slide,rock fall
B) Rotational slump,rock fall,mudflow
C) Mudflow flow,earth flow,landslide
D) Creep,rock fall,landslide

Question 18

Rock falls occur where __________________.

A) rocks are not cemented together
B) rock masses split along joints in rock layers
C) rock masses separate along fractures
D) all of these are correct

Question 19

The materials most commonly associated with earth failures are ________________.

A) clay minerals
B) quartz
C) granite
D) basalt

Question 20

Clay minerals may have their strength lessened by water ___________________.

A) adsorbed to the exterior of clays,thus spreading the grains apart
B) absorbed between the interlayer sheets,with resultant expansion
C) none of these are correct
D) both adsorbed to the exterior of clays,thus spreading the grains apart and absorbed between the interlayer sheets,with resultant expansion

Question 21

The 1903 Frank slide is an example of ________________________.

A) a rotational slide
B) a debris avalanche
C) a rock fall
D) an earth flow

Question 22

Several hypothesizes have been proposed to explain the movement of struzstroms.Which of the following statements is not one of these hypotheses?

A) Water provides lubrication for the fluid like flow.
B) Steam liquefies and fluidizes the moving mass.
C) The falling mass traps a volume of air beneath it and then rides atop this cushion of air (like an air hockey puck).
D) The knocking together of fragments as they travel down slope set up vibrations resulting in acoustic fluidization.
E) Earthquakes or volcanic eruptions release geological vibrations that result in geo-fluidization of the falling mass.

Question 23

The land beneath Mexico City is sinking because of ___________________.

A) volcanic activity
B) earthquakes
C) tectonic rifting
D) groundwater withdrawal
E) pumping of oil wells

Question 24

In __________________,masses move down and out by sliding on planes of weakness,such as faults,bedding,or clay rich layers.

A) rockfalls
B) debris flows
C) rotational slides
D) translational slides
E) struzstroms

Question 25

Slope stability is increased by _________ and decreased by ___________.

A) supporting the base or toe of the slope;increasing slope angle
B) positive pore pressure;inserting rock bolts
C) removing weight from the top of the slope;benching the slope
D) all of these are correct

Question 26

Snow avalanches like earthen mass movements have the same classes with the exception of ____________.

A) falls
B) flows
C) subsidence
D) slides
E) creep

Question 27

Catastrophic subsidence into sinkholes tends to occur more often in areas underlain by _______________.

A) limestones
B) sandstones
C) shales
D) granite

Question 28

The number of fatalities due to rockfall in Quebec City since 1775 is ______________.

A) 6
B) 12
C) 26
D) 88

Question 29

Avalanche forecasting is based on ______________.

A) weather conditions
B) assessment of the snow pack
C) observations of recent avalanches
D) all of these are correct

Question 30

Slab avalanches can be triggered by all but which of the following?

A) A heavy snow fall
B) Skiers
C) Snowmobiles
D) Acoustic vibrations
E) Solar warming

Question 31

The underlying cause of the Saint-Jean-Vianney,Quebec lateral spread was ________________.

A) dissolution of salt in sensitive clays
B) too much gypsum in the soil
C) over-steepening of slopes
D) freezing and thawing of the soil

Question 32

Leda clay was formed when Champlain Sea (a body of water that occupied the depression formed during the last glaciation)gradually shrank,leaving the marine clays ________________.

A) very stable for constructional work.
B) soft even today
C) vulnerable to leaching by rainwater.
D) vulnerable to lateral spread
E) both C and D are correct

Question 33

Translational slide masses behave in all but which of these different fashions?

A) They may remain basically coherent as block slides.
B) The sliding mass may deform and disintegrate to form a debris slide.
C) Lateral spreading may occur where the underlying material fails and flows,thus causing the overlying coherent material to break apart and move.
D) Their movement is predominately vertically downward.

Question 34

Mitigation methods designed to prevent mass movement events include all but which of the following?

A) Improved drainage
B) Rock bolts
C) Spraying the slope with shotcrete
D) building tunnels or snow sheds

Question 35

Catastrophic subsidence into sinkholes tends to occur more often in areas underlain by __________________.

A) acidic freshwater flowing through limestone
B) basic freshwater flowing through limestone
C) acidic saltwater flowing through granite
D) basic freshwater flowing through sandstone
E) basic saltwater flowing through sandstone

Question 36

The Italian city of ____________ is trying to save itself from slow subsidence and sea level rise.

A) Rome
B) Florence
C) Turin
D) Pisa
E) Venice

Question 37

The best mitigation strategy for snow avalanches in the back country __________.

A) the use of explosive charges
B) the use of artillery shells
C) avoidance of these areas
D) all of these are correct

Question 38

In Quebec City in 1841,heavy rains caused an enormous rock mass of the Cap-aux-Diamants to detach and crash into the city.This event would best be classified as ________________.

A) a fall
B) a rotational slide
C) a flank collapse
D) subsidence

Question 39

The mechanism that drives creep is _______________________.

A) freezing and thawing of the surface
B) wetting and drying of the surface
C) heating and cooling of the surface
D) all of these are correct
E) only A and B are correct

Question 40

The Sea-to-Sky highway north of Vancouver is one of the most active landslide regions in Canada because of ___________.

A) heavy rains
B) steep terrain
C) abundant glacial sediments overtop of bedrock
D) all of these are correct

Question 41

A 21-year review,covering 1994-2005 showed that __________ form the great majority of victims of snow avalanches,and that most of them who die of _______________.

A) train commuters;trauma
B) recreationists;hypothermia
C) recreationists;asphyxiation
D) train commuters;hypothermia
E) recreationists;trauma

Question 42

Water is both absorbed (internally)and adsorbed (externally)by clay minerals with resultant increases in strength.

Question 43

In this figure (Figure 13.21)the grey (Leda clay)and dark (sand)layers are not horizontal because:

A) sand is easily deformed by the weight of Leda clay.
B) Leda clay was deformed by the weight of an observer.
C) of the soft sediment deformation processes.
D) sand will flow and deform if it is in contact with rainwater.

Question 44

In Canada,thousands of mass movements occur every year mostly in the summer.

Question 45

Mass movement occurs when friction overpowers gravity.

Question 46

Water molecules can attach their positive sides against clay minerals because clay surfaces are also positively charged.

Question 47

This figure (Figure 13.58)shows:

A) a new ski technique.
B) the avalanche flotation bag system.
C) a new technique showing how to fall on steep slopes.
D) none of these choices are correct.

Question 48

If you are caught in the rip current shown on this figure (Figure 13.6)your escape tactic will be:

A) swimming along the current.
B) swimming toward shore.
C) swimming parallel to the shore.
D) swimming against the current.
E) not to do anything

Question 49

An example of sediment with high pore-water pressure is quicksand,a geologic hazard that sucks people or other objects down below the surface.

Question 50

In this figure (Fig.13.15)the black arrow points to:

A) stable rock material on steep slopes.
B) unstable rock material on talus slopes.
C) stable rock material on talus slopes.
D) a stable block of cliff.
E) rotational movement called topple.

Question 51

Clay crystals are composed of thin subparallel sheets,like the pages in a book.

Question 52

Removal of large thicknesses of overburden material causes expansion of earth materials,which can lead to decreases in strength.

Question 53

Many mass movements and slope failures result from abnormally high pore-water pressures.

Question 54

This figure (Figure 13.66)shows one of the mitigation strategies from the Contain the hazard category.It _________________.

A) collects extra rainwater which cascades safely at the slope base
B) protects from rock slide debris
C) collects and channels debris flow
D) collects wooden debris from a catchment basin

Question 55

Quick clays are among the least mobile of all deposits and so provide favorable building sites.

Question 56

Based on the landslide susceptibility map of Canada areas of highest risk include all of the following except:

A) Saint-Lawrence River Valley.
B) Yukon.
C) the eastern part of British Columbia.
D) the western part of Alberta.
E) the Canadian Precambrian Shield.

Question 57

There are certain times when a hill containing clay minerals is weaker than at other times,and then gravity has a better chance of provoking a slope failure.

Question 58

Rip currents develop when:

A) tsunamis approach close to the shoreline.
B) especially powerful waves bring water ashore.
C) especially powerful waves bring water offshore.
D) hurricane winds push water ashore.
E) tornadoes develop beside the shoreline.

Question 59

Due to high frequency mass movements events cost Canadian economy between $100 million and $200 million annually.

Question 60

Clays are among the least abundant of all sediments.

Question 61

A Quebec City engineer identified an unstable zone of the Cap-aux-Diamants escarpment years before it failed in the disastrous 1889 rockfall,but his warnings were ignored.

Question 62

Coal miners,trapped underground by the Frank slide,dug through several metres of coal and limestone to escape to the surface.

Question 63

Ground surfaces do not sit still;they move up and down.

Question 64

The geological condition known as day lighted bedding exists where the ends of shallow-dipping rock layers are exposed to daylight on a steeper slope.This condition produces a strengthened condition of the rock layers that is not favorable for failure.

Question 65

Land subsidence is worsened by stopping groundwater pumping,because the additional water that is retained underground weakens the rock,making it subside more easily.

Question 66

The term "creep" refers to slope failures where the material are relatively dry and the term "slow subsidence" when the materials are saturated.

Question 67

Creep is an ultra-slow,almost imperceptible upslope movement of the soil and uppermost bedrock zones.

Question 68

The orientation of rock layering within a hill can either enhance or hinder the chances of slope failure.

Question 69

In the City of Quebec,the responsibility of slope stabilization and mitigation against mass movement events lies with the local government.

Question 70

Slab avalanches can occur when the balanced stress/strength relationship between a slab of relatively stronger snow and an underlying weaker layer is upset by sudden change in load.

Question 71

Flows are mass movements that behave like liquids and are often named based on the particle size the material moving downslope.

Question 72

The volume of soil does not stay constant but instead swells and shrinks.

Question 73

Carbonic acid is produced by the chemical precipitation of limestone.

Question 74

First Nations people would not camp near Turtle Mountain (site of the Frank slide)for fear of falling rock.

Question 75

The Sea-to-Sky highway north of Vancouver is closed due to mass movement on average once per month.

Question 76

A victim engulfed in an avalanche is more likely to be found buried in the steepest slopes,closest to the starting zone than anywhere else along the path.

Question 77

The main types of mass movement are downward,as in falling or subsiding,or downward and outward,as in sliding and flowing.

Question 78

In Canada,avalanche risk is highest in the Rockies,the railway through Roger's Pass has experienced multiple events and by 1910,250 people had been killed.

Question 79

A rotational slide may move as long as it sits on the downward-inclined planar surface and its driving mass still exists whereas translational slides move only short distances.

Question 80

Loose powder avalanches are analogous to rotational slides,starting at a single point and developing an inverted "V" shape upon failure.