Avalanche

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Avalanche

• TMF 2005
• Gymnasium Elišky Krásnohorské

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Task 3 Avalanche

• Under what conditions may an avalanche occur?
  Investigate the phenomenon experimentally.

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Types of Avalanches

• Two basic types
• - loose snow avalanches
• - slab avalanches
• Other types
• - wet loose snow avalanches
• - direct action avalanches
• - ice-fall avalanches
• - fall overhanging snow

ice-fall

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Slab avalanches

• snow consists of few layers
• originate in snow with deficient internal
  cohesion
• induced by the nature of snow deposition or by
  internal metamorphism
• speed 70-130km/hour

after slab avalanche
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Loose snow avalanches

• form in snow with little internal cohesion among
  individual snow crystals
• induced on steep slope, by wind or reduction of
  internal cohesion (by metamorphism or by
  intrusion of liquid water)
• speed up to 300km/hour
• strong blast wave
• wet loose snow avalanches
• occurs at spring

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Good conditions for avalanche

• slope angles between 30 degrees and 45 degrees
• unstable snow with small internal cohesion
• Avalanches are influenced by
• temperature , slope angles, type of snow snow
  density , off-road tread, ground surface
  , snow depth, weather , size of snow
  crystals , intervention of surroundings

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Forecasting Snow Avalanches

• snow cross section - examination of snow cover
  structure for patterns of weakness, examination
  of differences between layers
• Compression test simmilar as snow cross
  section
• analysis of meteorological factors affecting snow
  depositions

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Experimental conditions

• Snow
• is not exactly defined
• it is necessary low temperature
• not easy experiments, not objective results
• BUT snow is a granular stuff
• Experiments are easier and results not so
  affected by conditions with another granular
  stuff
• SAND
• - simplification sand is not compressiable

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Experiments (I)
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Experiments (II)