Avalanches Flashcards
Two types of avalanches
Point release and slab
slab avalanche
cohesive layers
triggered by people/victims
wind drifted snow or loading
they have a strongly packed top layer but a very thin and weak bottom layer.
Point release avalanches
loose, cohesionless snow
entertainment from side walls as it rolls
dry snow makes it small
wet snow makes it large
Dry avalanches
caused by too much stress
triggered by victims
loading of wind drifted snow or loading
fast
wet avalanches
decreasing in strength
mostly natural
rain or prolonged melting
slower
triggers for avalanches
snow accumulation over surface hoar vehicles and humans increase the weight or 'normal force' surface heating gravitational creep shaking
avalanche preconditions
loading through snow or wind packing
cornice
aspect to sun
characteristics of northern/southern aspect to the sun
North is colder, south is sun facing and warmer
characteristics of eastern/western aspect to the sun
West is warmer in the afternoon
East is warmer in the morning
Surface Hoar formation
rapid deposition of water that goes into ice without wet phase, its formed on cold surface with humid air
Tests for snow stability
copression test: Shoulder->elbow->wrist
cornice test
Slope modifications/mitigation
snow umbrellas, snow fences and nets
signs of avalanches
cracks in snow snowfall previous snow activity temperature rising strong winds
Depth Hoar formation
depth hoar forms from temperature gradients between warm ground and cold snow surfaces.
avalanche path is divided into which 3 parts
start zone
track
run-out zone
