Avalanche Awareness

Question 1

Name the 4 principle types of avalanches.

Answer 1

1. Loose snow avalanches 2. Slab avalanches 3. Cornice collapses 4. Ice avalanches

Question 2

What is a loose snow avalanche?

Answer 2

An avalanche that starts with a small amount of cohesionless snow and typically picks up more snow as it descends. Also called “sluffs” and “point releases”

Question 3

What is a slab avalanche?

Answer 3

An avalanche that occurs when one or more layers of cohesive snow release as a unit.

Question 4

What is the upper boundary of a slab avalanche called?

Answer 4

Fracture line or crown face

Question 5

What is the area immediately above a slab avalanche fracture line called?

Answer 5

Crown

Question 6

What are the sides of a slab avalanche called?

Answer 6

Flanks

Question 7

What is the bottom boundary of a slab avalanche called?

Answer 7

Stauchwall

Question 8

What is the main sliding surface under a slab avalanche called?

Answer 8

Bed surface

Question 9

What are the 3 variables that determine whether or not an avalanche is possible?

Answer 9

Terrain, snowpack, and weather

Question 10

What are the four critical questions to answer when traveling through mountains in the winter?

Answer 10

1. Is the terrain capable of producing avalanches? 2. Is the weather contributing to instability? 3. Could the snow slide? 4. What are my alternatives and their possible consequences?

Question 11

What are the 3 parts of an avalanche path?

Answer 11

Starting zone, track, and runout zone

Question 12

What is the most important terrain variable for determining whether or not it is possible for a given slope to avalanche?

Answer 12

Slope angle

Question 13

Slab avalanches in cold snow generally possible between what range of slope angles?

Answer 13

20-60+ degrees

Question 14

What factors influence what slope angles are likely to avalanche?

Answer 14

Slab depth, distribution, and structure; as well as, the type of weak layer

Question 15

What is this a picture of:

Answer 15

Top loading caused by wind

Question 16

What is this a picture of:

Answer 16

Side loading caused by wind

Question 17

What are the 4 requirements for a slab avalanche?

Answer 17

A slab, a weak layer, a slope steep enough to slide, and a trigger

Question 18

What is the critical issue in snow stability?

Answer 18

The relative cohesiveness of the snow layers and how well they are bonded to each other

Question 19

What are the bull’s-eye snow stability questions?

Answer 19

1. Is there an unstable snow structure (slab/weak layer combination)?
2. If so, what is its depth and distribution?
3. How well are the layers bonded?
4. How much force will it take to make the slope avalanche?

Question 20

What are the bull’s-eye clues to snow instability?

Answer 20

1. Recent avalanche activity on similar slopes
2. Whumping noises
3. Shooting cracks
4. Recent wind-loading
5. Hollow sounds

Question 21

What are the avalanche field tests?

Answer 21

1. Ski pole/hand pit test
2. Snowpit tests
   
   • Compression Test (CT)
   • Extended Column Test (ECT)
   • Rutschblock Test (RB)