Avalanche Awareness

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  1. Avalanche anatomy:
    • 1. Crown
    • 2. Flank
    • 3.Stauchwall
    • 4. Deposition zone
    • 5. Bed Surface
  2. 1. Crown
    Upper margin where the slide broke away from the rest of the snow pack
  3. 2. Flank
    The left and right borders of the slide.
  4. 3. Stauchwall
    The bottom (downslope) boundary of a slab where it rides up over the snow below. Usually difficult to impossible to identify after an avalanche.
  5. 4. Deposit zone
    where the slide stops moving and ost debris is deposited
  6. 5. Bed surface
    the surface on which the snow slides.
  7. 2 Main Avalanche Types:
    • 1. Loose Snow
    • 2. Slab
  8. 1. Loose Snow
    • Dry: usually caused by fresh snow >12''. often referred as sluffs, can run fast and far depending on terrain.
    • Wet: Similar to dry loose avalanche, however conditions are caused by rain or rapidly warming temperatures.
  9. 2. Slab Most dangerous and devastating
    Wet: usually caused by rain or prolongd warming on dry snow.

    Storm Slab: usually caused by >12'' of new snow in 24hrs or less
    • Wind Slab: usually caused from moderate winds (10-20mph) transporting snow which loads the leeward aspects.
    • Persistant Slab: aused by persistent layers of strong hard slabs surrounded top and bottom by weak snow.
    • Deep Slab: caused by weak layer buried deep (3') in the snow pack. usually triggered by a large load such as a cornice fall or explosive.
  10. Relative to Path:
    • R1: very small (0-20%)
    • R2: small (20-40%)
    • R3: medium (40-60%)
    • R4: Large (60-80%)
    • R5: Major (80-100%)
  11. Destruction Potential:
    • D1: Too small to injure of bury a person
    • D2: Could bury, injure or kill a person
    • D3: Could bury, destroy a car, damage a truck, destroy a small bldg., or break a few trees.
    • D4: Could destroy a truck railway car, several bldgs., or up to 10 acres of forest.
    • D5: could destroy a village or 100 acres or more of forest
  12. Slope Angles: 0-25°
    infrequent wet snow avalanche, green slopes
  13. Slope Angles: 25-30°
    Infrequent slabs in unstable conditions, blue slopes
  14. Slope Angles: 30-35°
    Slabs in unstable condition, Black diamond slopes
  15. Slope Angles: 35-45°
    frequent slabs of all sizes , double black diamond slopes
  16. Slope Angles: 45-55°
    many loose avalanches start, some small slabs, out of bounds
  17. Slope Angles: 55°+
    Few avalanches, climbing terrain
Card Set
Avalanche Awareness
Avalanche Terrain Terminology
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