New Zealand Mountan Safety Council


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Avalanche Advisory Glossary 


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 


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. 


An overhanging mass of wind sculpted snow projecting beyond the crest of a ridge 


A hard surface layer which can be formed by solar radiation, wind or rain which has the potential to cause instability when buried. 

Freezing level 

The elevation at which the air temperature is at 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. 


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 

Loose snow 

A type of avalanche which originates at a point and spreads out as it descends. 


A metamorphic process when snow changes from a solid to a liquid and back again and may result in the formation of a crust. 


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. stay to ridges and well away from runout zones, or slopes less than 30°) 

Shady aspect 

The side of a mountain protected from the sun 


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 250

Terrain traps 

Terrain features which in the event of an avalanche would compound the effect (e.g. gullies, small bowls) 


The area which connects the start zone and runout zone, this can be either confined or unconfined. 

Unsupported slope 

Slopes which are not being supported by the terrain, e.g convex rolls 

Weak layer 

A layer in the snowpack identified as a possible failure plane 

Wet snow 

Snow with a water content greater than 3% and has a temperature of 0° Celsius 


The sounds associated with the rapid settlement or collapse of a snowpack, when weighted. 

Wind loading 

The transport of snow by the wind causing an additional build up of snow on a lee slope 

Wind slab 

A cohesive layer of snow caused by wind loading 


The side of a mountain exposed to a wind 

Avalanche Forecast Regions:
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Mountainf Safety Council websiteAdventure Smart websiteNew Zealand Avalanche Center

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