Avalanche Safety Study Notes
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Questions and Answers

What is the primary cause of fatal avalanches?

  • Movement of loose, dry, fresh snow
  • Accumulation of storm snow
  • Strong solar radiation
  • Victim or their party activities (correct)

    • Which type of avalanche is characterized by a dense layer of snow sliding on a weaker layer?

  • Cornice collapse
  • Loose snow avalanche
  • Slab avalanche (correct)
  • Icefall avalanche

    • What effect does surface hoar have on the snowpack?

  • Creates a solid bond in the snowpack
  • Acts as a protective crust
  • Increases avalanche stability
  • Forms a weak layer once buried (correct)

    • What initiates a loose snow avalanche?

    <p>Poorly bonded surface layer snow</p> Signup and view all the answers

    Which factor is NOT a primary trigger for natural avalanches?

    <p>Human weight</p> Signup and view all the answers

    What is a cornice in the context of avalanche formation?

    <p>Overhanging mass of wind deposited snow</p> Signup and view all the answers

    What type of avalanche starts from a point and spreads out like a teardrop?

    <p>Loose snow avalanche</p> Signup and view all the answers

    Which type of weak layer can last for months at the base of shallow snow packs?

    <p>Depth hoar</p> Signup and view all the answers

    What happens to the weak layer in a slab avalanche when overlaid by a stronger layer?

    <p>It collapses when support is lost</p> Signup and view all the answers

    Which weather condition is NOT a common factor in avalanche formation?

    <p>Consistent sunlight</p> Signup and view all the answers

    What is a sign that a wet slab may be present?

    <p>Dripping trees</p> Signup and view all the answers

    What is the primary danger associated with deep persistent slabs?

    <p>They typically involve old persistent slab layers.</p> Signup and view all the answers

    Which condition increases the risk of loose wet avalanches?

    <p>Direct sunlight on slopes</p> Signup and view all the answers

    When performing a signal search in avalanche rescue, what is the first step?

    <p>Turn your transceiver to search mode.</p> Signup and view all the answers

    What should NOT be done when trying to spot a cornice?

    <p>Trust visible snow formations without verification.</p> Signup and view all the answers

    What is the ideal team size for an avalanche rescue operation?

    <p>4-5 people to balance effectiveness and safety.</p> Signup and view all the answers

    What indicates that snow is likely in a dangerous unstable state?

    <p>Recent snowfall combined with warming.</p> Signup and view all the answers

    What should a companion do while another performs a fine search?

    <p>Assist with probing and shoveling.</p> Signup and view all the answers

    In which cases should you call for help during a rescue effort?

    <p>After ensuring all victims are accounted for.</p> Signup and view all the answers

    What is the correct method for probing during an avalanche rescue?

    <p>Insert the probe perpendicularly to the slope.</p> Signup and view all the answers

    What is the primary purpose of using explosives in avalanche control?

    <p>To deliberately release smaller avalanches</p> Signup and view all the answers

    What class of avalanche is classified as having the potential to bury and injure a person?

    <p>Class 2</p> Signup and view all the answers

    What angle range is considered most common for avalanche-prone slopes?

    <p>30 to 45 degrees</p> Signup and view all the answers

    What does the term 'runout zone' refer to in avalanche terminology?

    <p>The area where the slide runs and loses momentum</p> Signup and view all the answers

    What impact do terrain traps generally have in an avalanche situation?

    <p>Increase the severity if caught in one</p> Signup and view all the answers

    How does wind exposure affect snow on slopes?

    <p>It can create dangerous wind slabs</p> Signup and view all the answers

    What is the primary rating system used for evaluating the exposure of backcountry terrain to avalanches?

    <p>Avalanche Terrain Exposure Scale (ATES)</p> Signup and view all the answers

    Which attribute is commonly measured to classify slopes in avalanche forecasting?

    <p>Slope shape and size</p> Signup and view all the answers

    What avalanche danger rating indicates a high likelihood of large avalanches occurring?

    <p>High</p> Signup and view all the answers

    In avalanche terms, how is 'cross loading' defined?

    <p>Snow being carried to the lee side of a slope</p> Signup and view all the answers

    What is an important feature of simple terrain in the ATES classification?

    <p>Exposure to low angle or forested terrain</p> Signup and view all the answers

    Why can slopes facing the sun lead to avalanche formation?

    <p>They often develop hard layers from melting and refreezing</p> Signup and view all the answers

    What is the significance of having no ATES rating for a backcountry area?

    <p>Advanced knowledge is required to assess risk</p> Signup and view all the answers

    Study Notes

    Avalanche Safety - Study Notes

    • Avalanche Causation: Over 90% of fatal avalanches are caused by the victim or their group.

    Avalanche Types

    • Slab Avalanche: A dense layer of snow breaks off and slides on a weaker layer within the snowpack. This is highly dangerous, reaching speeds over 130 km/hr. Weak layers can stem from temp fluctuations or are created by storms. Slab avalanches are cohesive at first but break into chunks.

    • Loose Snow Avalanche (or Sluff): A poorly bonded surface layer of snow slides downhill under its own weight. It has a less dangerous nature than slab avalanches, starting at one point and spreading like a tear shape.

    • Cornices: Wind-deposited snow masses protruding from ridges/peaks. They can break off and trigger larger avalanches (or be a trigger for slab avalanches) due to stress from gravity, weather changes, or weight (human or machine).

    Avalanche Formation

    • Weather's Role: Weather is the primary driver of avalanche formation, creating different snowpack layers with varying strengths and weaknesses. Snow crystals bond differently depending on weather conditions over time, thus creating strong and weak layers.

    • Weak Layers: Storm snow, surface hoar (frozen dew that creates feathery crystals), facets (different temp in snowpack, sharp sides of grains, no cohesion b/w snow crystals), depth hoar (persistent, large cup shaped layer), and crusts (melted then refrozen snow- often used as a sliding surface) are all problematic weak layers in snowpacks.

    Avalanche Triggers

    • Natural Triggers: New snow loading, windblown snow, rain, rapid temp increase, and strong solar radiation all initiate natural avalanches.

    • Human Triggers: People and machines trigger many avalanches, and the triggering effect can be from many meters away!

    • Artificial Triggers: Explosives are used (deliberately) to release avalanches in ski areas or highway passes, to keep the size manageable.

    Avalanche Sizes

    • Classification: Avalanches are rated from 1 (smallest) to 5 (largest) based on their destructive potential. Size 1 avalanches are relatively harmless to people but still pose risks. Sizes 2–5 can bury, injure, or kill people/destroy property.

    Avalanche Terrain

    • Terrain Characteristics: Avalanche paths (start zone, track, runout zone; sometimes delineated by trim lines) are critical areas. Slope angle is vital; 30-45 degrees is most common for slab avalanches. Steeper slopes (over 45 degrees) have fewer slab avalanches.

    • Slope Shape: Convex slopes (steepest point near the top) are more prone to fractures.

    • Terrain Traps: Terrain features like rocks, trees, and cliffs increase avalanche severity, as do sudden flat spots, which can lead to deeper burials.

    • Slope Aspect and Wind: Slopes facing winds(windward), have wind slabs formed because they carry the snow to the leeward side of slopes. Solar radiation impacts sun-facing slopes with potential to form hard crusts and weakens the slope.

    Avalanche Exposure Scale

    • ATES: A system for rating backcountry terrain's avalanche exposure into Simple (green), Challenging (blue), and Complex (black) categories. Using 11 different weighted measures!

    Avalanche Forecast

    • Importance: The forecast is a key component of planning any backcountry trip, providing danger ratings (1-5), problems (types of avalanches and terrain), and details (local conditions, weather).

    • Danger Ratings: Based on the North American public avalanche danger scale, which provides the likelihood of avalanches and their size.

    • Avalanche Problems: Storm slab, wind slab (look for stiffness under feet, hollow noises), persistent slabs, wet slabs (rain, temp increase), cornices, loose wet, and loose dry (sluffs) are all discussed in detail to help assess danger.

    Daily Process

    • Group Formation: Create small and efficient groups (3–5 people).

    • Trip Planning: Assess the forecast and create a plan, including plan B.

    • Gear Check: Check and verify all necessary gear (batteries).

    • Condition Verification: Check weather/snow conditions, assess safety, etc

    • Communication and Travel Habits: Maintain communication, have a clear escape plan, and look for signs of instability like drifting/cracking/recent avalanches.

    Companion Rescue

    • Quick Action: Immediate actions are crucial.

    • Leader Selection: Designate a leader.

    • Scene Assessment: Assess safety, overhead hazards.

    • Headcount and Search: Figure out where last seen.

    • Transceiver Search: Signal, coarse, and fine search phases are explained. The transceiver shows distance and direction.

    • Probing and Shoveling: Systematic techniques are given.

    • When to Call for Help: Only if necessary, and don't take up too much rescue time.

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    Description

    Explore the critical aspects of avalanche safety with a focus on the types of avalanches, their causation, and formation factors. Understand the dangers associated with slab and loose snow avalanches, as well as the role of weather in their formation. This comprehensive overview is essential for anyone interested in outdoor safety in mountainous regions.

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