ASC Avalanche Formation & Terrain Recognition 3 — Questions and Answers
Question 1: Which avalanche type is characterized by a single point of origin that fans out in a triangular shape as it descends?
- Slab avalanche
- Loose-snow avalanche (Correct answer)
- Glide avalanche
- Cornice fall avalanche
Correct answer: Loose-snow avalanche
Loose-snow avalanches start at a single point and widen as they gather more snow, forming a characteristic inverted-V or triangular shape.
Question 2: What is the typical critical slope angle range where most slab avalanches release?
- 5–20 degrees
- 30–45 degrees (Correct answer)
- 50–65 degrees
- 70–90 degrees
Correct answer: 30–45 degrees
Most slab avalanches release on slopes between 30 and 45 degrees, where gravitational stress exceeds the snowpack's strength most efficiently.
Question 3: A persistent slab avalanche problem is particularly dangerous because:
- It only occurs on north-facing slopes
- Buried weak layers can remain reactive for weeks or months after burial (Correct answer)
- It always produces the largest avalanches
- It can only be triggered by cornices
Correct answer: Buried weak layers can remain reactive for weeks or months after burial
Persistent weak layers can be re-activated long after they are buried, remaining a hazard even when surface conditions seem stable.
Question 4: What does a 'shooting crack' propagating away from your ski or board mean?
- The snow surface is too icy to avalanche
- The slab is fracturing and conditions are highly unstable (Correct answer)
- You are on safe, well-bonded snow
- Wind crust is breaking underfoot, which is normal
Correct answer: The slab is fracturing and conditions are highly unstable
Shooting cracks are a critical red flag indicating that slab layers are fracturing and propagating, signaling imminent avalanche danger.
Question 5: What term describes an avalanche that occurs when the entire snowpack slides on the ground surface?
- Soft slab avalanche
- Glide avalanche (Correct answer)
- Wind slab avalanche
- Surface hoar avalanche
Correct answer: Glide avalanche
Glide avalanches occur when the full snowpack moves along the ground, often over smooth rock or grass, and can release with little warning.
Question 6: Which observation most strongly indicates that a slope has recently avalanched?
- Fresh animal tracks crossing the slope
- A smooth, scoured bed surface with debris at the bottom (Correct answer)
- A thick, uniform snow surface without any wind features
- Dense frost flowers on the snow surface
Correct answer: A smooth, scoured bed surface with debris at the bottom
A scoured crown, smooth bed surface, and debris pile (runout zone) are classic evidence of a recent avalanche cycle.
Question 7: How does rain affect avalanche hazard in winter snowpack?
- Rain stabilizes the snowpack by freezing into a supportive crust
- Rain adds weight and lubricates layers, dramatically increasing wet avalanche danger (Correct answer)
- Rain has no significant effect on avalanche hazard
- Rain only affects surface conditions, not buried layers
Correct answer: Rain adds weight and lubricates layers, dramatically increasing wet avalanche danger
Rain rapidly weakens snow strength by adding weight and introducing free water that lubricates failure planes, causing an abrupt spike in avalanche hazard.
ASC Avalanche Formation & Terrain Recognition 3
Which avalanche type is characterized by a single point of origin that fans out in a triangular shape as it descends?