ASC Avalanche Formation & Terrain Recognition

Question 1

What is the most common trigger for avalanches?

Accepted Answer

Human activity

Answer

While natural factors like snowfall and wind can contribute to avalanche formation, human activity is the most common trigger for avalanches that involve people. Skiers, snowboarders, snowmobilers, and hikers often inadvertently trigger slides by adding weight to unstable snowpacks or disturbing weak layers. This highlights the importance of human decision-making in avalanche safety.

Question 2

Which slope angle range is most prone to avalanches?

Accepted Answer

30–45 degrees

Answer

Slopes between 30 and 45 degrees are considered the most dangerous for avalanches because they are steep enough for snow to slide but not so steep that snow cannot accumulate. Below 30 degrees, snow generally doesn't slide easily, and above 45-50 degrees, snow tends to sluff off frequently, preventing large, deep slabs from forming. This range represents the critical balance for slab avalanche formation.

Question 3

What terrain feature can increase avalanche risk?

Accepted Answer

Convex slopes

Answer

Convex slopes are particularly dangerous because they often have a shallower snowpack near the top, which can act as a weak point, and the snowpack is under tension. As the slope steepens, the snowpack is stretched, making it more prone to fracturing and releasing an avalanche. The change in slope angle can also make it harder to assess snow stability.

Question 4

What is a 'persistent weak layer' in avalanche terms?

Accepted Answer

An old snow layer prone to collapse

Answer

A persistent weak layer is a buried layer of snow, often formed early in the season, that remains weak and unstable over time. These layers, like faceted crystals or surface hoar, can persist for weeks or months, acting as a failure plane within the snowpack and making it prone to collapse under new snow loads.

Question 5

Which sign indicates potential avalanche conditions?

Accepted Answer

Whumpfing sounds

Answer

Whumpfing sounds are a clear indicator of a weak layer collapsing within the snowpack, often accompanied by the ground settling underfoot. This audible sign signifies that the snowpack is unstable and that an avalanche could be triggered by additional stress.

(ASC) Avalanche Safety Certification Practice Test

(ASC) Avalanche Safety Certification Practice Test

ASC Avalanche Formation & Terrain Recognition