lecture 21: avalanches

Question 1

how does snowpack on slopes fail due to gravity

Answer 1

creep
fall
slide
flow

Question 2

avalanche paths

Answer 2

a: starting zone, steepest slope 30-45 degrees
b: track: guided by topography 20-30
c: run out zone <20 degrees

Question 3

snow pack

Answer 3

snowpack deposited by multiple storms leading to snow layers with different properties
- becomes denser and more cohesive with age
frost crystals can grow between layers
boundaries are weaknesses

Question 4

loose powder avalanche

Answer 4

acts like a flow, high speed (65-100km/hr), light snow often buries victims largely unharmed

Question 5

slab avalanche

Answer 5

slab of heavy cohesive snow detaches at weak layer boundary

• act like a translational slide evolving into flow
• speeds of 30-65 km/h but heavy snow can cause casualties and destory buildings and railways
• most dangerous avalanche

Question 6

rogers pass

Answer 6

150 tonne locomotive overturned in 1910 rogers pass slab avalanche

• 58 men losxt their lives
• canadas deadliest avalanche
• workers clearing snow when another slide came roaring down

Question 7

avalanche safety

Answer 7

difficult to outrun avalanche - escape to side

• get rid of backpack skis and poles
• use swimming motion to stay near surface
• maintain air pocket in front of face
• fast location and rescue

Question 8

before

Answer 8

consult and obey avalanche bulletins

- avalanche kit: transceivers, collapsible shovel and probe pole

Question 9

how many people have been killed by avalanches in the past 26 years

Answer 9

more than 200 people

Question 10

impacts of rogers pass

Answer 10

400m of track buried
locomotiev and plow hurled 15m and landed upside down, cars crushed
- abandon route through rogers pass instead go underground

Question 11

present day rogers pass

Answer 11

abandoned line still visible
now used by cross country skiers
studies of avalanches led to detailed maps of where avalanches were occuring and how strong