Log Cabin Mountain ATES
Chilkoot Trail National Historic Site
|Exposure to low angle or primarily forested terrain. Some forest openings may involve the runout zones of infrequent avalanches. Many options to reduce or eliminate exposure. No glacier travel.
|Exposure to well defined avalanche paths, starting zones or terrain traps; options exist to reduce or eliminate exposure with careful routefinding. Glacier travel is straightforward but crevasse hazards may exist.
|Exposure to multiple overlapping avalanche paths or large expanses of steep, open terrain; multiple avalanche starting zones and terrain traps below; minimal options to reduce exposure. Complicated glacier travel with extensive crevasse bands or icefalls.
The technical model has been designed for users trained and skilled in the subtle nuances of avalanche terrain.
|1 - Simple>
|2 - Challenging
|3 - Complex
|Angles generally < 30º
|Mostly low angle, isolated slopes >35º
| Variable with large % >35º
|Primarily treed with some forest openings
|Mixed trees and open terrain
|Large expanses of open terrain. Isolated tree bands
|Minimal, some creek slopes or cutbanks
|Some depressions, gullies and/or overhead avalanche terrain
|Many depressions, gullies, cliffs, hidden slopes above gullies, cornices
|1:30 ≥ size 2
|1:1 for < size 2
1:3 for ≥ size 2
|1:1 < size 3
1:1 ≥ size 3
|Start zone density
|Limited open terrain
|Some open terrain. Isolated avalanche paths leading to valley bottom
|Large expanses of open terrain. Multiple avalanche paths leading to valley bottom
|Runout zone characteristics
|Solitary, well defined areas, smooth transitions, spread deposits
|Abrupt transitions or depressions with deep deposits
|Multiple converging runout zones, confined deposition area, steep tracks overhead
|Interaction with avalanche paths
|Runout zones only
|Single path or paths with separation
|Numerous and overlapping paths
|Numerous, terrain allows multiple choices
|A selection of choices of varying exposure, options to avoid avalanche paths
|Limited chances to reduce exposure, avoidance not possible
|None, or limited exposure crossing runouts only
|Isolated exposure to start zones and tracks
|Frequent exposure to start zones and tracks
|Generally smooth with isolated bands of crevasses
|Broken or steep sections of crevasses, icefalls or serac exposure
Using this scale
Any given piece of mountain terrain may have elements that will fit into multiple classes. Applying a terrain exposure rating involves considering all of the variables described above, with some default priorities:
- Terrain that qualifies under an italicized descriptor automatically defaults into that or a higher terrain class.
- Non-italicized descriptors carry less weight and will not trigger a default, but must be considered in combination with the other factors.
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