Question

Based on their triggering mechanism, snow avalanches can be further classified into which two categories?

• A. Natural action and Artificial action avalanches
• B. Direct action and Delayed action avalanches
• C. Surface layer and Deep layer avalanches
• D. Wind-triggered and Gravity-triggered avalanches

Answer 1

Answer:

B. Direct action and Delayed action avalanches

Based on their triggering mechanism, snow avalanches can be further classified into two categories:

1. Direct Action Avalanches:

   • Trigger: These avalanches occur during or immediately after a snowfall or storm.

   • Cause: They are typically caused by the fresh load of new snow exceeding the strength of the underlying snowpack or by strong winds rapidly loading slopes.

   • Timing: They happen very quickly in response to the immediate weather event.

2. Delayed Action Avalanches:

   • Trigger: These avalanches occur some time after a snowfall, often during periods of fair weather between storms.

   • Cause: They are primarily triggered by internal weaknesses or structural instabilities that develop within the snowpack over time, such as the formation of weak layers (like "depth hoar" or "surface hoar") due to temperature changes and metamorphism.

   • Timing: There's a delay between the snowfall event and the avalanche release, as the snowpack evolves and internal stresses build up.