Avalanche path A terrain feature in which an avalanche occurs, this is normally split into the start zone, track and runout zone
Avalanche terrain  Any terrain which has the potential to form or be part of a snow avalanche
Bonding  Refers to a snowpack which has undergone some metamorphism and has many links between the individual snow grains, generally leading to a stronger “bonded” snowpack
Cornice  An overhanging mass of wind sculpted snow projecting beyond the crest of a ridge
Crust  A hard surface layer which can be formed by solar radiation, wind or rain which has the potential to cause instability when buried
Destructive Scale of Avalanches D1: Relatively harmless to people.  Typical mass: less than 10 tons.

D2: Could bury, injure or kill a person.  Typical mass: 100 tons.

D3: Could bury and destroy a car or truck, destroy a wood frame house, or break a few trees.  Typical mass: 1000 tons.

D4: Could destroy a railway car, several buildings, or a substantial amount of forest.  Typical mass: 10,000 tons.

D5: Could gouge the landscape; the largest known avalanches.  Typical mass: 100,000 tons.

Freezing level  The elevation at which the air temperature is at 32° Fahrenheit or 0° Celsius
Half (1/2)  Used with compass directions, e.g. “lee to the easterly half” refers to the aspects facing west from north through to south
Instability                                              A weakness or lack of stability indicating that additional loads will result in a given probability of avalanche occurrence
Lee (leeward)  The side of a mountain protected from the wind (where snow is deposited by the wind and loading occurs)
Loose snow  A type of avalanche which originates at a point and spreads out as it descends (aka “sluff” or point release)
Melt-freeze A metamorphic process when snow changes from a solid to a liquid and back again and may result in the formation of a crust.
Pockets  Small isolated terrain features
Quarter (1/4)  Used with compass directions, e.g. “lee to the easterly quarter” refers to the aspects facing northwest through to southwest
Runout zone  The area at the bottom of an avalanche path where an avalanche starts to decelerate and comes to rest; this is where the debris is located after an avalanche has occurred
Safe travel technique                 The use of appropriate terrain to move given the posted danger scale (e.g. stick to ridges and well away from runout zones, or slopes less than 30°)
Shady aspect  The side of a mountain protected from the sun
Slab  A cohesive layer of snow
Sliding hazard  A hazard posed by very hard or icy conditions, also known as “slide-for-life conditions”
Solar aspect  The side of a mountain exposed to the sun
Start zone  The area at the top of an avalanche path in which unstable snow may fail; most commonly has an angle greater than 25°
Terrain traps  Terrain features which in the event of an avalanche could compound the danger (e.g. gullies, depressions)
Track  The area which connects the start zone and runout zone, which can be either confined or unconfined
Unsupported slope  Slopes which are not supported by the terrain (e.g convex rollovers)
Weak layer  A layer in the snowpack identified as a possible failure plane
Wet snow  Snow with a water content greater than 3% and temperature of 32° fahrenheit or 0° Celsius
Whumphing  The sounds associated with rapid settlement or collapse of the snowpack, when weighted
Wind loading  The transport of snow by the wind causing additional build up of snow on lee terrain or in deposition areas
Wind slab  A cohesive layer of snow caused by wind loading
Windward  The side of a mountain exposed to wind (from which snow is transported to lee aspects or deposition areas)

Leave a Reply