Flashcards in Lecture #11 - Snow Avalanches Deck (45):
What is a snow avalanche?
A mass of snow many cubic metres in volume that separate from a snowpack and flows downslope
What is the intensity of a snow avalanche dependant on?
What are the 2 types of snow avalanches?
1. Avalanche travelling as a coherent block
2. Avalanche that becomes wider as it travels downslope
What % of avalanches are seen?
1% because they occur in high altitude areas where no one lives
when does snow accumulate on a mountain slope
When the slope angles are less than 60 degrees
What are Point release avalanches?
They begin as an initial failure after a heavy snowfall
-sliding snow causes more failures in the adjacent snowpack, causing the trough to widen
What are slab avalanches?
happen when a snow pack fractures along a weak layer parallel to the surface
-moves as a cohesive block
what kind of snow is more susceptible to sliding?
New snow that haven't been able to bond with the previous layer
Which kind of snow is left likely to slide?
Wet compacted snow
What isa requirement for a slab avalanche?
A buried weak layer
-layer can form from wind or hoar
where can a failure occur?
The boundary between 2 layers
What is a Hoar?
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
How fast are avalanches?
~35km/h leaving a cloud of powdered snow
-some powerful enough to travel up opposing slopes
When are avalanches most likely to occur?
right after a snowstorm
How do people get hurt form avalanches?
Humans trigger the avalanche by skiing over it usually
What are the 3 zones of an avalanche?
What is the slope range at which most avalanches occur?
-main area of concern is 30-45 degrees
which slopes are more prone to daytime avalanches?
Slopes facing the sun
How much snow do we need for an avalanche to form?
Where do avalanches cause the most damage?
In forests, property damage is minor
caused 60 deaths
the trail was heavily used at the time because of the gold rush
What other hazards can avalanches cause?
-they can be cause by earthquakes
-climate change may increase snowfall in some areas
-colder climates= longer winter season
what are some natural service functions of avalanches?
-ecological disturbance, increasing local animal and plant diversity
-maintain open areas for grazing
What has helped increase the number of deaths from avalanches?
Toursim and skiing
-more people on the hills to disturb the snow
How do you minimize the risk of avalanches?
-Build buildings and houses outside of the avalanche zone
-use hazard maps
-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
What is a compression test?
A vertical force is placed on the top of the snowpack to detect weak layers
What is a shovel test?
Assesses the strength by isolating a column of snow and applying force on the uphill slide
What is the Rutschblock test?
Skier pushes and jumps on a column of snow to detach cohesion of the snow pack
When is there never a chance of an avalanche?
There is always a chance for an avalanche
What is your best chance of survival?
if rescued within 15mins 90% survive
-30% 35 mins
-0% within 2 hours
What is an avalanche cord?
10m rope drags behind a person while skiing/snowboarding
What us an avalanche transceiver?
Portable device that emit a radio signal to assist in finding the location of a victim
Why are large scale diseases different?
Because the effect people only and not property
What is an outbreak?
a simultaneous, related occurrence of several cases
What is an epidemic?
An uncontrolled outbreak of communicable disease
What is a Pandemic?
Internation or wide-travelling simultaneous epidemics of the same condition
What is the bubonic Plague?
-spread by rodents among ship back then
How many pandemics has the black plague caused?
tallying 163 million deaths
What is Cholera?
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
What is HIV/AIDS
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
What are the 4 different influenzas?
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 facts
-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
What is Malaria?
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
What is West Nile virus?
Affects birds mainly, animals and humans through mosquito bites
-Get fever and weakness for 2 days then goes away