ASC Snowpack Analysis & Weather Interpretation 3 — Questions and Answers
Question 1: What does a wide, flat fracture line with a sharp, cohesive slab indicate about the avalanche that occurred?
- A loose, wet avalanche starting from a point
- A slab avalanche that released on a buried weak layer (Correct answer)
- Wind erosion rather than a snow slide
- A glide avalanche on a grassy slope
Correct answer: A slab avalanche that released on a buried weak layer
A wide, clean crown with a cohesive slab below is the hallmark of a slab avalanche, where an entire layer released simultaneously along a weak layer.
Question 2: In the North American Avalanche Danger Scale, which danger level accounts for the majority of avalanche fatalities?
- Low (1)
- Moderate (2) and Considerable (3) (Correct answer)
- High (4)
- Extreme (5)
Correct answer: Moderate (2) and Considerable (3)
Statistics consistently show that Considerable (3) and Moderate (2) danger levels account for the most fatalities because people underestimate the risk and travel in backcountry terrain.
Question 3: What is 'aspect' in avalanche terrain analysis?
- The steepness angle of a slope measured in degrees
- The compass direction a slope faces (Correct answer)
- The vertical elevation of a starting zone
- The width of a potential avalanche path
Correct answer: The compass direction a slope faces
Aspect describes which direction a slope faces (N, NE, E, etc.) and is critical because it determines sun exposure, wind loading patterns, and temperature effects on snowpack.
Question 4: Which wind speed threshold is generally considered significant for wind slab formation?
- 5–10 mph (8–16 km/h)
- 15–25 mph (24–40 km/h) (Correct answer)
- 40–50 mph (64–80 km/h)
- Only speeds above 60 mph (97 km/h) matter
Correct answer: 15–25 mph (24–40 km/h)
Winds of 15–25 mph and above can transport snow and deposit wind slabs on lee slopes and terrain features, creating one of the most common avalanche triggers.
Question 5: A 'roller ball' or 'pinwheel' on a slope surface is a sign of:
- Increasing snow stability due to consolidation
- Wet, loose surface snow losing cohesion, indicating wet avalanche potential (Correct answer)
- Wind transport creating surface erosion features
- New snow bonding to the old snow surface
Correct answer: Wet, loose surface snow losing cohesion, indicating wet avalanche potential
Rollers and pinwheels form when wet surface snow loses strength and rolls downhill, indicating the surface layer is saturated and wet slides are likely.
Question 6: What is the primary purpose of digging a snow pit?
- To create a sheltered camping spot in the snowpack
- To examine snowpack layering, identify weak layers, and assess stability (Correct answer)
- To measure total snow depth for water content calculations
- To test ski boot penetration depth for trip planning
Correct answer: To examine snowpack layering, identify weak layers, and assess stability
Snow pits expose the stratigraphy of the snowpack, allowing identification of weak layers, crusts, and their relative positions, which informs stability assessment.
Question 7: In avalanche forecasting, 'loading rate' refers to:
- The weight of a skier applied to a slope
- The rate at which new snow, rain, or wind-deposited snow adds stress to the snowpack (Correct answer)
- Speed at which snow crystals transform through metamorphism
- Rate of temperature change in the snowpack per hour
Correct answer: The rate at which new snow, rain, or wind-deposited snow adds stress to the snowpack
Loading rate describes how quickly mass is added to the snowpack; rapid loading (heavy snowfall, wind deposition, rain) overwhelms the snowpack's ability to adjust and increases instability.
ASC Snowpack Analysis & Weather Interpretation 3
What does a wide, flat fracture line with a sharp, cohesive slab indicate about the avalanche that occurred?