Lecture 9

Question 1

Define the term Snow avalanche?

Answer 1

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

Question 2

The intensity of the hazard is dependent on what?

Answer 2

Slope, steepness, snowpack stability and weather

Question 3

List the two types of ways a avalanche travels

Answer 3

• Travels as a coherent block

- becomes wide as it travels downslope

Question 4

Snowfall accumulation depends on what variables?

Answer 4

Latitude, altitude and proximity to bodies of water

Question 5

List the types of avalanches

Answer 5

• Point release avalanche

- slab avalanche

Question 6

Discuss the term point release avalanche?

Answer 6

• they begin as an initial failure after a heavy snowfall

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

Question 7

Discuss the term slab avalanche?

Answer 7

Occurs when a snowpack fractures along a weak layer parallel to the surface
- move as a cohesive block

Question 8

Slab avalanches require a buried weak layer, name the two ways this layer can be formed?

Answer 8

Wind or Hoar

Question 9

Explain how wind can form a layer on slab avalanches

Answer 9

• Blowing snow can accumulate on the lee slope of mountains

- Wind can deposit a layer of light ice crystals on a layer of more compacted snow

Question 10

Explain how hoar can form a layer on slab avalanches

Answer 10

Hoar can form deep in the snowpack (in air pockets) or on the snow surface.
- Hoar changes little over time; therefore, overlying snow can leave the buried hoar as a weak layer

Question 11

Rapidly moving avalanches often generate what?

Answer 11

Rapid moving avalanches (speeds of over 35km/h) often generate clouds of powdered snow

Question 12

Fastest avalanches have been measured at speeds of ?

Answer 12

200km/h

Question 13

When do most avalanches most occur

Answer 13

Soon after snowstorms

Question 14

Which avalanches are triggered by people?

Answer 14

Avalanches that cause injuries or fatalities

Question 15

Mention the three avalanche paths?

Answer 15

• Start Zone
• Track
• Run-out zone

Question 16

Explain the start zone?

Answer 16

• The area where the snowpack first fails

Question 17

Explain the track?

Answer 17

• the area along which the avalanche accelerates and reaches maximum velocity

Question 18

Explain the run - out zone?

Answer 18

The area of deceleration and snow deposition