M o u n t a i n T r a i n i n g T r u s t

A v a l a n c h e A w a r e n e s s

Starting Point

Trig

ger

Terrain

Snow

pack

•Simplistic

•Snow consolidates through melt & freeze

•Icy layers a hazard

•Graupel layers a hazard

•Soft layers potential hazard

•Profiles look for “different layers”

•Stability tests look for “IF” but not so much “WHY”.

M o u n t a i n T r a i n i n g T r u s t

A v a l a n c h e A w a r e n e s s

Outdoor professionals are more likely to get avalanched

than anyone else

•Increased probability – time spent in avalanche terrain

•Avalanche terrain approaching routes and “getting off”

•Route choice (visibility)

•Group management conflict

M o u n t a i n T r a i n i n g T r u s t

A v a l a n c h e A w a r e n e s s

Build on existing knowledge

•Not so simple any more

•Understand “why we make bad decisions”

•“Heuristic Traps”

•Make better decisions about the snow

•Develop understanding

•Jargon Buster

•Help find (and understand) further info

M o u n t a i n T r a i n i n g T r u s t

A v a l a n c h e A w a r e n e s s

Atkins (2001) – In 41 accidents involving “avalanche aware” victims, 83% were due to

decision making errors rather than subtleties of terrain or snowpack.

Why might Instructors make poor decisions?

Heuristic Traps

M o u n t a i n T r a i n i n g T r u s t

A v a l a n c h e A w a r e n e s s

Heuristic Trap - Commitment

•Cue: Prior commitment•Behaviour: Consistency•Trap: Critical change

“They’ve paid me a lot for a good day out”

“I promised them a walk to a peak this week”

M o u n t a i n T r a i n i n g T r u s t

A v a l a n c h e A w a r e n e s s

Heuristic Trap - Scarcity

•Cue: Limited opportunity•Behaviour: Desire +/ Competition•Trap: Increased risk taking

“Let’s get up before that other team beat us”

“I haven’t seen good snow on that for 15 years”

M o u n t a i n T r a i n i n g T r u s t

A v a l a n c h e A w a r e n e s s

Heuristic Trap - Familiarity

•Cue: Familiar setting•Behaviour: Same as last time•Trap: Conditions change

“I can’t see it but I know there’s nothing above us”

“You can always get to the easy track down here . . . . ”

M o u n t a i n T r a i n i n g T r u s t

A v a l a n c h e A w a r e n e s s

Heuristic Trap – Social Proof

•Cue: Other people’s behaviour•Behaviour: Imitation•Trap: They make a bad decision

“If they’re going up there it must be okay”

“I bet the other team are getting to a peak”

M o u n t a i n T r a i n i n g T r u s t

A v a l a n c h e A w a r e n e s s

How snow “changes“ (made simple)

•The “Melt + freeze” process is easy to understand

•Fresh snow “settles” even if it doesn’t melt – How? Why?

•Process often called “destructive metamorphism” or:

Equi-temperature Metamorphism

M o u n t a i n T r a i n i n g T r u s t

A v a l a n c h e A w a r e n e s s

Fresh snow to Firn snow

• Equi = “same”• Temperature• Metamorphism = “change”

•Temperature <0°C

•Snow never “melts”

•Firn snow is “real” nevé

Equi-temperature Metamorphism

M o u n t a i n T r a i n i n g T r u s t

A v a l a n c h e A w a r e n e s s

Equi-temperature Metamorphism

Reproduced from “Winter Skills” by permission from MLTUK

(“Same Temperature Change”)

M o u n t a i n T r a i n i n g T r u s t

A v a l a n c h e A w a r e n e s s

Equi-temperature Metamorphism

Reproduced from “Winter Skills” by permission from MLTUK

Sublimation Sublimation

temperature< 0°C

firn snowSintering or “necking”

Sublimation Sublimation

temperature< 0°C

firn snowSintering or “necking”

M o u n t a i n T r a i n i n g T r u s t

A v a l a n c h e A w a r e n e s s

Often called “destructive metamorphism”

M o u n t a i n T r a i n i n g T r u s t

A v a l a n c h e A w a r e n e s s

Different snow types

• Fresh snow rounds easily (Stellar dendrite)

•Graupel rounds more slowly (rimed snowflakes)

• Depth hoar struggles to round (facets)

M o u n t a i n T r a i n i n g T r u s t

A v a l a n c h e A w a r e n e s s

Surface Hoar

Some crystals grow:

•On the surface (surface hoar)•In the Snow pack (depth hoar)

In prolonged cold conditions

Not all snow falls from the sky

M o u n t a i n T r a i n i n g T r u s t

A v a l a n c h e A w a r e n e s s

Surface Hoar

M o u n t a i n T r a i n i n g T r u s t

A v a l a n c h e A w a r e n e s s

Surface Hoar

•Like dew after an Autumnal frost•Moisture in the air condenses on the cold surface•Slowly grow into pure crystals•Only forms in prolonged clear and cold weather (with no wind)

M o i s t a i r

M o u n t a i n T r a i n i n g T r u s t

A v a l a n c h e A w a r e n e s s

M o u n t a i n T r a i n i n g T r u s t

A v a l a n c h e A w a r e n e s s

Surface Hoar

•Forms (or “grows”) slowly on the surface in cold clear conditions

•Only becomes a problem if and when it is buried by another layer

•May have been destroyed by the sun on sunny slopes

•May have become a substantial layer on shady slopes

M o u n t a i n T r a i n i n g T r u s t

A v a l a n c h e A w a r e n e s s

Photo Case Study Crown wall

M o u n t a i n T r a i n i n g T r u s t

A v a l a n c h e A w a r e n e s s

Photo Case Study

M o u n t a i n T r a i n i n g T r u s t

A v a l a n c h e A w a r e n e s s

Photo Case Study

M o u n t a i n T r a i n i n g T r u s t

A v a l a n c h e A w a r e n e s s

Photo Case Study

Buried surface hoar (glinting crystals)

Super smooth sliding surface

M o u n t a i n T r a i n i n g T r u s t

A v a l a n c h e A w a r e n e s s

Snow profile

M o u n t a i n T r a i n i n g T r u s t

A v a l a n c h e A w a r e n e s s

Depth Hoar

•Similar process to surface hoar

•Moist air from ground or wet snow pack

•Meets cold air from above

•Crystal growth within the snow pack

M o u n t a i n T r a i n i n g T r u s t

A v a l a n c h e A w a r e n e s s

Temperature Gradient Metamorphosis

M o u n t a i n T r a i n i n g T r u s t

A v a l a n c h e A w a r e n e s s

Detached Crust

How did this crust form?

Why is it not “stuck” to the snow beneath?

M o u n t a i n T r a i n i n g T r u s t

A v a l a n c h e A w a r e n e s s

Depth Hoar case study

How come this was safe to decend

Why did it release just here?

M o u n t a i n T r a i n i n g T r u s t

A v a l a n c h e A w a r e n e s s

Depth Hoar case study

Nothing easily visible in profile

M o u n t a i n T r a i n i n g T r u s t

A v a l a n c h e A w a r e n e s s

•Deep snow pack

•Homogenous

•Less gradient

•Shallow snow pack

•Depth Hoar layer

•Steeper gradient

Depth Hoar case study

M o u n t a i n T r a i n i n g T r u s t

A v a l a n c h e A w a r e n e s s

Further reading

Jill Fredston & Doug FeslerAlaska Mtn Safety Center

Bob Barton & Blythe WrightScottish Mountaineering Trust

David McClung & Peter SchaererThe Mountaineers

M o u n t a i n T r a i n i n g T r u s t

A v a l a n c h e A w a r e n e s s

A Few Facts

The colder it is…….

The longer its cold for………..

Depth of snow

M o u n t a i n T r a i n i n g T r u s t

A v a l a n c h e A w a r e n e s s

So What?

Hidden layers

Thin layers

Prolonged cold – worse not better

M o u n t a i n T r a i n i n g T r u s t

A v a l a n c h e A w a r e n e s s

How to predict

Quiz?

M o u n t a i n T r a i n i n g T r u s t

A v a l a n c h e A w a r e n e s s

Snow profiles