ASC Avalanche Forecasting & Danger Ratings 2 — Questions and Answers
Question 1: Which avalanche problem type is associated with a weak layer buried deep in the snowpack that persists for weeks or months?
- Storm Slab
- Wind Slab
- Persistent Slab (Correct answer)
- Wet Slab
Correct answer: Persistent Slab
Persistent Slab problems involve a weak layer buried beneath one or more strong snow layers that can remain reactive for an extended period.
Question 2: A 'Storm Slab' avalanche problem is most likely to occur during which period?
- Weeks after new snowfall
- During or shortly after a significant snowstorm (Correct answer)
- During spring melt cycles
- During early-season temperature inversions
Correct answer: During or shortly after a significant snowstorm
Storm Slab avalanche problems develop during or shortly after heavy snowfall when new snow bonds poorly with the surface beneath it.
Question 3: What characteristic best describes a 'Wind Slab' avalanche problem?
- Large wet avalanches on sun-exposed slopes in spring
- Dense, stiff slabs deposited by wind on lee aspects and cross-loaded ridges (Correct answer)
- Loose snow sliding from a point source after warming
- Deep slab releases triggered by remote loading
Correct answer: Dense, stiff slabs deposited by wind on lee aspects and cross-loaded ridges
Wind Slabs form when wind transports snow and deposits it as dense, cohesive slabs on lee aspects, cross-loaded ridges, and terrain features downwind of the prevailing wind.
Question 4: The 'Wet Slab' avalanche problem is most commonly associated with which triggering mechanism?
- Cold overnight temperatures
- Rapid warming, rain, or solar radiation that introduces liquid water into the snowpack (Correct answer)
- Explosive control work
- Deep wind loading
Correct answer: Rapid warming, rain, or solar radiation that introduces liquid water into the snowpack
Wet Slab problems are driven by liquid water infiltrating the snowpack, reducing friction between snow layers and triggering large, heavy avalanches.
Question 5: Which of the following best describes a 'Loose Snow' (or 'Point Release') avalanche?
- A large slab fracturing across a wide area
- An avalanche that starts from a single point and fans outward, involving cohesionless snow (Correct answer)
- A deep slab triggered remotely
- A wet avalanche on a north-facing slope in winter
Correct answer: An avalanche that starts from a single point and fans outward, involving cohesionless snow
Loose Snow avalanches start from a single point and fan outward downslope, typically involving dry, unconsolidated snow or wet surface snow.
Question 6: What is a 'Cornice Fall' avalanche problem?
- An avalanche triggered by falling ice from a glacier
- An overhanging mass of wind-deposited snow that breaks off and can trigger avalanches below (Correct answer)
- A slab avalanche on a convex roll
- A dry slab caused by temperature gradient metamorphism
Correct answer: An overhanging mass of wind-deposited snow that breaks off and can trigger avalanches below
Cornice Fall occurs when overhanging masses of wind-deposited snow break off from ridgelines and can trigger additional slab avalanches on the slopes below.
Question 7: How does aspect affect which terrain features are most prone to Wind Slab avalanche problems?
- Windward (upwind) aspects accumulate the most wind slab
- Lee (downwind) aspects and cross-loaded terrain features accumulate drifted snow (Correct answer)
- South-facing slopes always have more wind slab regardless of wind direction
- Aspect has no significant effect on wind slab distribution
Correct answer: Lee (downwind) aspects and cross-loaded terrain features accumulate drifted snow
Wind transports snow from windward slopes and deposits it as slabs on lee aspects and cross-loaded terrain features, making those the primary locations of Wind Slab problems.
ASC Avalanche Forecasting & Danger Ratings 2
Which avalanche problem type is associated with a weak layer buried deep in the snowpack that persists for weeks or months?