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Geo of Hazards > Lecture #11 - Snow Avalanches > Flashcards

Lecture #11 - Snow Avalanches Flashcards

1
Q

What is a snow avalanche?

A

A mass of snow many cubic metres in volume that separate from a snowpack and flows downslope

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2
Q

What is the intensity of a snow avalanche dependant on?

A

Slope steepness
Snowpack stability
Weather

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3
Q

What are the 2 types of snow avalanches?

A
  1. Avalanche travelling as a coherent block

2. Avalanche that becomes wider as it travels downslope

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4
Q

What % of avalanches are seen?

A

1% because they occur in high altitude areas where no one lives

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5
Q

when does snow accumulate on a mountain slope

A

When the slope angles are less than 60 degrees

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6
Q

What are Point release avalanches?

A

They begin as an initial failure after a heavy snowfall

-sliding snow causes more failures in the adjacent snowpack, causing the trough to widen

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7
Q

What are slab avalanches?

A

happen when a snow pack fractures along a weak layer parallel to the surface
-moves as a cohesive block

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8
Q

what kind of snow is more susceptible to sliding?

A

New snow that haven’t been able to bond with the previous layer

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9
Q

Which kind of snow is left likely to slide?

A

Wet compacted snow

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10
Q

What isa requirement for a slab avalanche?

A

A buried weak layer

-layer can form from wind or hoar

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11
Q

where can a failure occur?

A

The boundary between 2 layers

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12
Q

What is a Hoar?

A

Layers composed of hoar have less strength than the rest of the snow pack

  • can form deep in the snowpack or on the surface
  • changes little over time therefore overlaying snow can leave the buried hoar as a weak layer
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13
Q

How fast are avalanches?

A

~35km/h leaving a cloud of powdered snow

-some powerful enough to travel up opposing slopes

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14
Q

When are avalanches most likely to occur?

A

right after a snowstorm

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15
Q

How do people get hurt form avalanches?

A

Humans trigger the avalanche by skiing over it usually

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16
Q

What are the 3 zones of an avalanche?

A

Start zone
Track
Runout zone

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17
Q

What is the slope range at which most avalanches occur?

A

25-60 degrees

-main area of concern is 30-45 degrees

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18
Q

which slopes are more prone to daytime avalanches?

A

Slopes facing the sun

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19
Q

How much snow do we need for an avalanche to form?

A

~50cm snowpack

20
Q

Where do avalanches cause the most damage?

A

In forests, property damage is minor

21
Q

Chilkoot avalanche

A

1898
caused 60 deaths
the trail was heavily used at the time because of the gold rush

22
Q

What other hazards can avalanches cause?

A
  • they can be cause by earthquakes
  • climate change may increase snowfall in some areas
  • colder climates= longer winter season
23
Q

what are some natural service functions of avalanches?

A
  • ecological disturbance, increasing local animal and plant diversity
  • maintain open areas for grazing
  • important habitat
24
Q

What has helped increase the number of deaths from avalanches?

A

Toursim and skiing

-more people on the hills to disturb the snow

25
Q

How do you minimize the risk of avalanches?

A
  • Build buildings and houses outside of the avalanche zone
  • use hazard maps
  • Reinforce structures
  • Fences and nets to keep the snow in place
  • Spliting wedges for force the avalanche around an area
  • Mounds and beams used to deflect snow
  • Avalanch sheds allows for the travel over roads and railroads
  • Controlled triggers
26
Q

What is a compression test?

A

A vertical force is placed on the top of the snowpack to detect weak layers

27
Q

What is a shovel test?

A

Assesses the strength by isolating a column of snow and applying force on the uphill slide

28
Q

What is the Rutschblock test?

A

Skier pushes and jumps on a column of snow to detach cohesion of the snow pack

29
Q

When is there never a chance of an avalanche?

A

There is always a chance for an avalanche

30
Q

What is your best chance of survival?

A

if rescued within 15mins 90% survive

  • 30% 35 mins
  • 0% within 2 hours
31
Q

What is an avalanche cord?

A

10m rope drags behind a person while skiing/snowboarding

32
Q

What us an avalanche transceiver?

A

Portable device that emit a radio signal to assist in finding the location of a victim

33
Q

Why are large scale diseases different?

A

Because the effect people only and not property

34
Q

What is an outbreak?

A

a simultaneous, related occurrence of several cases

35
Q

What is an epidemic?

A

An uncontrolled outbreak of communicable disease

36
Q

What is a Pandemic?

A

Internation or wide-travelling simultaneous epidemics of the same condition

37
Q

What is the bubonic Plague?

A

Black Death

-spread by rodents among ship back then

38
Q

How many pandemics has the black plague caused?

A 
3
542
1300
1894
tallying 163 million deaths
39
Q

What is Cholera?

A

waterborne disease that originates in contaminated water supplies

  • caused by a bacterial infection in the intestines
  • rare in developing countries
  • When it first came about in London they didnt know how it was spread so they used mapping to trace it back to the contaminated water source
40
Q

What is HIV/AIDS

A

Human immunodeficiency virus
Acquired Immune deficiency virus
-frist seen in the 1980’s, but was ignored because it didnt affect the mainstream population
-you don’t die from AIDS, it just weakens your immune system so you die from something else
-No cure, antiretroviral drug to slow the process
-95% of cases are in developing countries

41
Q

What are the 4 different influenzas?

A

Spanish Flue: Spread by soldier travelling home from war
Asan Flue/ HongKong Flue: less death, better medicine
Bird Flue: Killed all the birds to solve the problem
Swine Flue

42
Q

Swine flue facts

A
  • Pandemic
  • virus strain was a combination of all the flues and swine flue
  • Spread from person to person through respiratory droplets
  • couldnt actually be spread through the consumption of pork
  • antiviral drug= Tamiflu
43
Q

What is Malaria?

A

Infectious disease spread by mosquitoes
-multiplication of parasites in red blood cells
-Climate change could increase the number of people affected by malaria
-used DDT to get rid of the mosquitoes but it was banned
-

44
Q

What is West Nile virus?

A

Affects birds mainly, animals and humans through mosquito bites
-Get fever and weakness for 2 days then goes away

45
Q

What are some characteristics of pandemics?

A
  • Unpredictable
  • Rapid surge with quick exponential increase that overcomes populations and capacity to cope
  • Reducing crowding would help reduce transmission
  • Delaying the spread helps reduce stress on the health care system

Geo of Hazards (12 decks)

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