Deck 7: Snow Avalanches

Question 1

Most skiers,snowboarders,and snowmobilers prefer slope angles where

A) sluffs are frequent.
B) point release avalanches are frequent.
C) slab avalanches are frequent.
D) wet slides are frequent.
E) hoar frost is frequent.

Answer 1

C

Question 2

In general,snowfall is rare

A) at low elevations.
B) on shallowly inclined slopes.
C) on north facing slopes.
D) at low latitudes.
E) around the Great Lakes.

Answer 2

D

Question 3

What was a common trigger for snow avalanches in the Alps during World War I?

A) earthquakes
B) artillery fire
C) cavalry movements
D) refugees crossing snow fields on foot
E) unusual spring weather

Answer 3

B

Question 4

In Canada today,which of the following activities leads to the most deaths from snow avalanches?

A) road building through mountainous regions
B) operating trains through mountainous regions
C) logging in mountainous regions
D) mining in mountainous regions
E) winter recreation in mountainous regions

Question 5

If you were skiing in the backcountry,which of the following observations would indicate the highest local snow avalanche risk?

A) steep, rocky slopes (greater than a 60 degree angle)
B) boulders exposed through the snow surface
C) compacted icy conditions that indicate no recent snowfall
D) thick snow on a sheltered lee slope
E) a fresh dusting of snow over an icy layer on a steep slope

Question 6

Point release avalanches

A) produce a distinct downslope-narrowing trough.
B) have a near vertical crown.
C) have lateral scarps.
D) produce a distinct downslope-widening trough.
E) occur when a slab of snow slips along weak layer.

Question 7

What is the most common trigger for avalanches in recreational accidents?

A) a person's weight added to a slope that is near failure
B) daytime heating of the upper snowpack, which weakens the near-surface layer
C) inflow of warm air funneled upward from a valley, weakening the near-surface layer
D) skiers deliberately attempting to release unstable snow before they ski down a slope
E) bad weather

Question 8

Snow accumulation on the ground

A) is always greater at higher elevations.
B) does not occur at sea level.
C) does not differ over short distances.
D) sloughs away on slopes steep than 45 degrees.
E) is always greater at higher latitudes.

Question 9

Avalanche hazard is commonly increased

A) on slopes greater than 60 degrees.
B) on tree covered slopes.
C) on steep talus covered slopes.
D) at lower elevations.
E) on slopes with gullies or ravines.

Question 10

Wet avalanches

A) do not achieve the high velocities of some dry avalanches.
B) may displace air causing a damaging air blast.
C) only occur at low elevations.
D) generate a cloud of powdered snow.
E) are less dense than dry avalanches.

Question 11

Slab avalanches

A) produce a distinct downslope-narrowing trough.
B) have a near vertical crown.
C) produce a distinct downslope-widening trough.
D) results from the initial failure of a small amount of snow.
E) commonly happen after a heavy snowfall.

Question 12

In mid-latitudes in the Northern Hemisphere,more avalanches happen on

A) sunny leeward slopes where wind deposits alternating weak and strong snow layers.
B) sunny south or southwest facing slopes where the sun weakens the surface snow layers.
C) west facing leeward slopes where weak slabs fail during warm afternoons.
D) west facing windward slopes where variable wind speed creates weak layers.
E) shady north or northeast facing slopes where most avalanches occur during cold weather.

Question 13

In the "snow belts" of central North America,the source of water vapour for the snowfall is

A) the Pacific Ocean.
B) the Atlantic Ocean.
C) Hudson Bay.
D) the Great Lakes.
E) the Arctic Ocean.

Question 14

During which season are snow avalanches the least common?

A) early spring
B) late spring
C) summer
D) fall
E) winter

Question 15

At which of the following slope angles is a point release avalanche most likely?

A) 20 degrees
B) 30 degrees
C) 40 degrees
D) 50 degrees
E) 60 degrees

Question 16

At which of the following slope angles is a slab avalanche most likely?

A) 20 degrees
B) 30 degrees
C) 40 degrees
D) 50 degrees
E) 60 degrees

Question 17

How does hoar form?

A) when the temperature hovers around the freezing point, snow that melts during the day refreezes at night
B) when the air is dry and cold, ice crystals grow on the surface of the snowpack
C) feather-shaped snowflakes bond together when they hit the surface of the snowpack
D) wind carries away unconsolidated snow, leaving behind small grooves and needle shaped ice crystals
E) when the air is wet and cold, water vapour transforms directly into ice

Question 18

Point-release avalanches

A) occur at the heads of valleys and widen as they travel down-valley.
B) occur when several small avalanches from different points converge into a larger avalanche.
C) begin with a small avalanche of snow, which causes adjacent failures as it moves downslope.
D) begin when icy slabs fall off steep cliffs and pick up more snow as they travel downslope.
E) erode the snow away to the rock underneath, leaving V-shaped snow valleys.

Question 19

What human activities are likely to increase the snow avalanche hazard in the future?

A) increased use of remote areas for winter recreation
B) increased use of off road vehicles
C) development on snow fields
D) increased hunting in mountainous areas
E) deforestation

Question 20

The run-out for a medium-sized snow avalanche

A) stops on the slope.
B) is less than 100 m from its starting point.
C) continues to the bottom of the slope.
D) continues until the slope angle is zero.
E) continues up the lower part of the opposite slope.

Question 21

Over the past decade,on average,________ people die in avalanches every year in Canada.

A) less than 5
B) 8
C) 10
D) 12
E) over 15

Question 22

In Canada,avalanches are rare in which region(s)?

A) The Gaspe region of Quebec
B) The Prairies and the Arctic mainland
C) Labrador and the Arctic Islands
D) Alberta and British Columbia
E) Atlantic Canada

Question 23

Which of the following structures are designed to slow avalanches?

A) avalanche sheds
B) mounds
C) berms
D) splitting wedges
E) snow fences

Question 24

Avalanche risk can be estimated by determining the

A) speed, thickness and size of avalanches.
B) distribution, frequency and size of avalanches.
C) speed, thickness and duration of avalanches.
D) the size of the avalanche path.
E) the thickness of the snow.

Question 25

Which of the following structures is designed to allow avalanches to run over a road or railway?

A) deflecting berms
B) splitting wedges
C) mounds
D) snow fences
E) avalanche sheds

Question 26

If caught in an avalanche,the chance of surviving burial at greater than 1.5 metres is

A) almost zero.
B) 2%.
C) 5%.
D) 5 - 10%.
E) 10 - 20%.

Question 27

The number of avalanches that occur annually in western Canada and that are large enough to bury a person is

A) 150.
B) 1500.
C) 15000.
D) 150000.
E) 1500000.

Question 28

Explosions in the start zone of an avalanche path

A) always release avalanches.
B) usually release avalanches.
C) always produce slab avalanches.
D) guarantee that the snowpack will not fail naturally.
E) guarantee that the snowpack will not be triggered by a person afterward.

Question 29

The motion of the snow itself kills about

A) 5 percent of avalanche victims.
B) 10 percent of avalanche victims.
C) 25 percent of avalanche victims.
D) 40 percent of avalanche victims.
E) 75 percent of avalanche victims.

Question 30

Which of the following structures is designed to allow avalanches to move around a structure?

A) splitting wedges
B) mounds
C) snow fences
D) avalanche sheds
E) berms

Question 31

An avalanche danger level of extreme will be indicated by the colour symbol

A) orange.
B) red.
C) yellow.
D) red with black border.
E) orange with black border.

Question 32

The mountains in Chile and Argentina are not at high risk of avalanches because

A) they are in a warm, equatorial region.
B) they lie east of the Atacama desert and receive little snowfall.
C) they lie west of the Atacama desert and receive little snowfall.
D) they are near the Pacific Ocean.
E) they are too steep.

Question 33

Which of the following is the most effective means to minimize snow avalanche risk to human infrastructure?

A) Build deflecting structures to funnel the snow avalanches elsewhere.
B) Reinforce buildings on the side facing the avalanche hazard.
C) Trigger controlled avalanches with explosives to minimize surprises.
D) Develop programs to close roads and railways when avalanche danger is high.
E) Avoid placing human infrastructure in expected avalanche paths.

Question 34

If you were backcountry skiing and wanted to conduct a rutschblock test to assess the avalanche risk,what would you do?

A) dig a hole one metre deep and examine the character of the snow layers
B) pull back the upper part of a column of snow with your shovel and observe the fractures produced
C) push on the snow with the back of your shovel and observe fractures on the exposed vertical face
D) push on the snow with your skis, then jump on it and assess the force necessary to set the snow in motion
E) throw a fist-sized rock or larger snowball at the slope you're testing and observe the resulting pattern

Question 35

When the avalanche danger level is high

A) human triggered avalanches are possible.
B) human triggered avalanches are likely.
C) natural avalanches are possible.
D) natural avalanches are certain.
E) human triggered avalanches are certain.

Question 36

Which of the following provides the most direct evidence of avalanche risk?

A) weather observations
B) snowpack observations
C) snow stability tests
D) observations of recent avalanches
E) slope measurements

Question 37

Before modern recreation,the greatest loss of life due to avalanches was due to the

A) gold rush.
B) building of towns in avalanche prone regions.
C) building of the Canadian Pacific Railway.
D) lack of trained rescue dogs.
E) inability to properly forecast.

Question 38

If you're snowshoeing in the backcountry with a group and one of your group is swept away and buried by an avalanche,what should you do first?

A) call for professional help
B) conduct a search immediately to dig the person out
C) divide the group and have half go for help and the other half stay and wait
D) mark the spot and evacuate the rest of the group to safety
E) start a stove or build a fire to warm the victim once he/she is recovered

Question 39

Fences or nets installed in the start zone of an avalanche path

A) are effective in protecting all infrastructure.
B) are inexpensive.
C) are common in North America.
D) inhibit tree growth in the avalanche path.
E) can help support the snow pack.

Question 40

One of the deadliest avalanches in North American history occurred in 1898 during

A) the gold rush to the Klondike.
B) the building of the Canadian Pacific Railway.
C) the introduction of recreational skiing.
D) the gold rush to Alaska.
E) increased mining activity in the Rocky Mountains.

Question 41

The west coasts of Northern Hemisphere continents get considerable snow cover to latitudes as low as 35 degrees.

Question 42

Avalanche hazard is commonly greater at low elevations because snowfall and winds are greater there.

Question 43

Most snow avalanches are not witnessed by humans because they occur primarily in remote areas.

Question 44

A dry snow avalanche will move faster than a wet snow avalanche.

Question 45

A point release avalanche results from initial failure of a small amount of snow.

Question 46

Very few dry avalanches occur on slopes less than 30 degrees.

Question 47

Compacted snow is more likely to move than light powdery snow.

Question 48

The most dangerous snow avalanches occur on slopes at angles greater than 60 degrees.

Question 49

Slab avalanches move slowly and therefore are not very dangerous.

Question 50

Slopes less than 25 degrees and greater than 60 degrees have a low avalanche risk.

Question 51

In a slab avalanche,the slab stays intact as it moves downslope.

Question 52

Avalanches are more common on concave slopes and less common on convex slopes.

Question 53

New snow is not susceptible to sliding.

Question 54

The run-out zone is the part of the avalanche path along which the avalanche accelerates.

Question 55

Snow avalanches behave the same as rock avalanches.

Question 56

Point-release snow avalanches commonly occur after heavy snowfall because the snow crystals have little time to bond.

Question 57

In most recreational accidents wind triggers the avalanche.

Question 58

Slab avalanches disintegrate into smaller fragments soon after failure.

Question 59

Most avalanches occur during or soon after a snowstorm.

Question 60

Avalanches rarely initiate in tree-covered areas.

Question 61

The highest incidence of avalanches in Canada occurs in the Arctic.

Question 62

Avalanches are only considered a hazard when humans interact with them.

Question 63

The most important terrain factor for avalanche formation is slope steepness.

Question 64

What happens to snow that falls on slopes steeper than about 60 degrees?

Question 65

Why is there little snowfall on Antarctica?

Question 66

What are the four most important factors determining how much snow will be in a particular place?

Question 67

Avalanches are destructive and offer no environmental benefit to a region.

Question 68

There have been no avalanche related fatalities in eastern Canada.

Question 69

As long as you have a transceiver,it is better to travel through the backcountry alone so there is less chance of triggering an avalanche.

Question 70

Observations of past avalanches help forecast future avalanches under similar conditions.

Question 71

A rough surface,such as a talus slope,will anchor snowpack better than a smooth rock surface.

Question 72

Currently,Canada has no consistent policies delineating snow avalanche hazard zones.

Question 73

Traffic delays,due to avalanches,can result in high economic losses.

Question 74

No buried avalanche victim has ever been found alive by search dogs in Canada.

Question 75

Slab avalanches are usually more dangerous than point avalanches.

Question 76

Slopes less that 25 degrees only produce wet slides.

Question 77

What is the primary force that drives an avalanche?

Question 78

Why does the amount of snow on the ground vary considerably over short distances?

Question 79

In the early 20th century,transportation-related activities accounted for most snow avalanche deaths.

Question 80

Avalanche dogs are responsible for most live recoveries of avalanche victims.