Lecture #11 - Snow Avalanches

Question 1

What is a snow avalanche?

Answer 1

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

Question 2

What is the intensity of a snow avalanche dependant on?

Answer 2

Slope steepness
Snowpack stability
Weather

Question 3

What are the 2 types of snow avalanches?

Answer 3

1. Avalanche travelling as a coherent block

2. Avalanche that becomes wider as it travels downslope

Question 4

What % of avalanches are seen?

Answer 4

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

Question 5

when does snow accumulate on a mountain slope

Answer 5

When the slope angles are less than 60 degrees

Question 6

What are Point release avalanches?

Answer 6

They begin as an initial failure after a heavy snowfall

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

Question 7

What are slab avalanches?

Answer 7

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

Question 8

what kind of snow is more susceptible to sliding?

Answer 8

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

Question 9

Which kind of snow is left likely to slide?

Answer 9

Wet compacted snow

Question 10

What isa requirement for a slab avalanche?

Answer 10

A buried weak layer

-layer can form from wind or hoar

Question 11

where can a failure occur?

Answer 11

The boundary between 2 layers

Question 12

What is a Hoar?

Answer 12

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

Question 13

How fast are avalanches?

Answer 13

~35km/h leaving a cloud of powdered snow

-some powerful enough to travel up opposing slopes

Question 14

When are avalanches most likely to occur?

Answer 14

right after a snowstorm

Question 15

How do people get hurt form avalanches?

Answer 15

Humans trigger the avalanche by skiing over it usually

Question 16

What are the 3 zones of an avalanche?

Answer 16

Start zone
Track
Runout zone

Question 17

What is the slope range at which most avalanches occur?

Answer 17

25-60 degrees

-main area of concern is 30-45 degrees

Question 18

which slopes are more prone to daytime avalanches?

Answer 18

Slopes facing the sun

Question 19

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

Answer 19

~50cm snowpack

Question 20

Where do avalanches cause the most damage?

Answer 20

In forests, property damage is minor

Question 21

Chilkoot avalanche

Answer 21

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

Question 22

What other hazards can avalanches cause?

Answer 22

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

Question 23

what are some natural service functions of avalanches?

Answer 23

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

Question 24

What has helped increase the number of deaths from avalanches?

Answer 24

Toursim and skiing

-more people on the hills to disturb the snow

Question 25

How do you minimize the risk of avalanches?

Answer 25

- 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

Question 26

What is a compression test?

Answer 26

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

Question 27

What is a shovel test?

Answer 27

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

Question 28

What is the Rutschblock test?

Answer 28

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

Question 29

When is there never a chance of an avalanche?

Answer 29

There is always a chance for an avalanche

Question 30

What is your best chance of survival?

Answer 30

if rescued within 15mins 90% survive - 30% 35 mins - 0% within 2 hours

Question 31

What is an avalanche cord?

Answer 31

10m rope drags behind a person while skiing/snowboarding

Question 32

What us an avalanche transceiver?

Answer 32

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

Question 33

Why are large scale diseases different?

Answer 33

Because the effect people only and not property

Question 34

What is an outbreak?

Answer 34

a simultaneous, related occurrence of several cases

Question 35

What is an epidemic?

Answer 35

An uncontrolled outbreak of communicable disease

Question 36

What is a Pandemic?

Answer 36

Internation or wide-travelling simultaneous epidemics of the same condition

Question 37

What is the bubonic Plague?

Answer 37

Black Death | -spread by rodents among ship back then

Question 38

How many pandemics has the black plague caused?

Answer 38

``` 3 542 1300 1894 tallying 163 million deaths ```

Question 39

What is Cholera?

Answer 39

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

Question 40

What is HIV/AIDS

Answer 40

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

Question 41

What are the 4 different influenzas?

Answer 41

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

Question 42

Swine flue facts

Answer 42

- 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

Question 43

What is Malaria?

Answer 43

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 -

Question 44

What is West Nile virus?

Answer 44

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

Question 45

What are some characteristics of pandemics?

Answer 45

- 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