Tag Archive for 'avalanche'

Developing an Eye for Angles - Part 2

Published
by
Andrew
on January 2, 2009
in 07 Avalanche Avoidance
. 6 Comments

Part of the challenge of correctly identifying slope angles by eye is that they often look much steeper when viewed straight-on than they do from the side.  (This is also a good photography trick - shooting straight-on, like from a helicopter or across a valley makes the slopes look lots steeper).  A classic case of this is Mt. Superior, which when viewed directly across the canyon from Alta or Snowbird, looks really steep, but when you actually ski it, it’s about like a black diamond run at a resort - not too bad. 

The steep looking Monte Cristo Headwall as seen head-on from Mt. Superior. Photo by Carl Skoog
The same 30-degree headwall as seen from the side. Alex Lowe digging a pit.

Something to keep in mind is that your angle-sense changes when you move to different areas.  For instance, the snow in Alaska sticks to steeper slopes than in the Wasatch, so all of those little visual clues you subconsciously pick up on are off.  As a result, I often underestimate my maritime snowpack angles and overestimate the continental ones.

Any way you physically measure a slope is better than nothing, although the generally agreed on best method is to sight down it with an accurate clinometer, or get it from a distant side view.  Measuring it directly on the snow, or on a pole on the snow (as shown in yesterday’s post) may pick up unwanted dips or roll-overs.  Keeping a compass/clinometer in a chest pouch or front zipper pocket makes it easy and painless to grab a quick angle.

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Developing an Eye for Angles - Part 1

Published
by
Andrew
on January 1, 2009
in 07 Avalanche Avoidance
. 0 Comments

An experienced car mechanic can look at a nut or bolt from ten feet away and instantly tell you what size it is down to the 64th of an inch.  It is not magic, but more a case of repetitive familiarity within a certain range.  Cars tend to use bolts in the 1/4″ to 1″ range, so after a few hundred times of fitting sockets to them, you start to develop a eye for what size they are.

The same idea applies for slope angles, which in terms of avalanche danger, is a key factor.  Although my eyes/brain are not accurately calibrated for the sub 25-degree range, or over 50-degrees, I can usually pick out a slope angle in the 30-45 degree range to within a degree or so at a glance.  Like a mechanic, this is more the result of first making a guesstimate, then trying it (with a clinometer in the case of a slope).  After doing this a few hundred times you start to get pretty accurate at it.  If I’m with a group, I make everyone guess (including myself) before taking the actual measurement, just for the fun of it.

Checking the slope angle in the Tetons. Photo by Doug Coombs.

The significance of developing an eye for angles is that often, just a few degrees can make a huge difference.  For instance, say you are skinning up a 30 degree ridgeline, which then contours around into a slightly steeper bowl.  In this case, you will be changing aspects (north/south/east/west) AND bumping the angle up towards the prime 38-degree avalanche strike zone.  It is subtle, but within a few feet you can go from relative safety to dangerous.

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Deciphering the Avalanche Rose

Published
by
Andrew
on December 23, 2008
in 07 Avalanche Avoidance
. 9 Comments

The idea of an “avalanche rose” has been around for a while, but has been making its way into avalanche forecasts where it is one of my favorite quick-hit summaries of the current avalanche stability.  The “rose” part come from the concept of a compass rose (north, south, east & west pointers with sub quads) and the avalanche part comes from, well, avalanches.  I like the avalanche rose as it is a very quick, graphical overview.  I wouldn’t ski a slope based only on the info gleaned from an avalanche rose diagram, but it would give me a big head-start on where to start looking for trouble or safe skiing for the day.

As the skier sees Little Cottonwood Canyon…
… the same view through the eyes of the avalanche rose. In the above illustration, the skier probably would have triggered an avalanche up in the red zone.

The avalanche rose is a stylized top view of a mountain which splits the world into aspects and elevations, then assigns an avalanche danger accordingly.  It is a rough estimate and not like you can suddenly cross the 10,000′ foot line, or from NW to North and have the danger dissipate, but it gives a good general idea.  Much like a traffic light, red means “stop - high danger”  (beyond that is extreme/black, which is rare), and green is “go - low danger,” which makes it easy to figure out. 

The avalanche rose in action on a daily UAC forecast:

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Wild Weekend in Store for the Wasatch Mtns

Published
by
Andrew
on December 19, 2008
in current conditions
. 1 Comment

Rat-a-tat-tat, hang on to your hat!  There’s going to be some very wide spread and dangerous avalanche activity in the Wasatch Mountains today and this weekend.

One of my favorite snow stability comments comes from Bob Athey - “When it comes to snow, it all depends.”  If there’s no loose snow to transport, then high winds are not necessarily that bad.  Sometimes 30″ of new snow can be very stable.  Shallow snowpacks are generally weak… but not always.

And then there are times like this where all of these elements come together and go in the opposite direction to create a VERY dangerous snowpack - high winds blowing lots of light density snow onto a weak, shallow snowpack with a variety of slick crusts buried in it.  And lots of powder starved skiers/triggers.

The avalanche danger rose from today - that’s a whole lotta red!

Bruce Tremper of the Utah Avalanche Forecast Center issued today’s advisory, which is noteworthy as it is only a few times per year (hopefully no more) that the danger jumps up this high.  “Extreme” avalanche danger is very rare and may only happen once a year, if that, so to see this much red (High danger) over so many aspects and elevations says something about the conditions.  Having forecast for the Wasatch Mountains for decades, Bruce’s assessments always seem very accurate, at least to me.  If we get a ton of new snow, but it is stable, Bruce will give you the straight scoop.  Conversely, if Bruce mentions wid-spread high-danger, I’d pay attention.

Kitchen window forecasting: lots of wind and transport, and this isn’t even a very windy spot. The mountains are going to be rocking.
I still get out on days like these, but more in a manner of practicing extremely safe route finding rather than looking for good turns.  In conditions like these, if it is steep enough to ski, it will probably be steep enough to slide.
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Ditch the Plastic Shovel

Published
by
Andrew
on September 11, 2008
in 02 Gear
. 5 Comments

By the numbers, plastic shovels are supposedly as strong (or stronger) than steel and able to withstand incredibly low temperatures.  Their big selling points are that they are lighter and cheaper than metal.  The weight claims are a bit suspect as plastic shovels tend to be on the small side, which naturally makes them lighter, but also less functional.  When it comes to cost, there is no denying they are less expensive, but is $30 really worth it?

A plastic shovel which shattered catastrophically while digging a tent out. The tent survived, but a buried partner probably would not have.
A plastic shovel which shattered catastrophically while digging a tent out. The tent survived, but a buried partner may not have.

The biggest issue with plastic shovels is that they fail catastrophically without warning.  A metal blade on the other hand usually gives you some warning (if you are paying attention) in the form of bending or cracking, and can be nursed through an expedition and/or replaced before they have a chance to fail in the field.

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Inside Info - Part II

Published
by
Andrew
on July 31, 2008
in 07 Avalanche Avoidance
. 0 Comments

The snowpack is the third major factor and also the trickiest one.  Like the weather, its history is more important than its immediate surface conditions. The plot thickens with the snowpack as there are almost always weaknesses in it, but they are difficult to quantify.  Snow is the building block of avalanches, but it is these tiny weaknesses between the blocks that actually cause them. Assessing the snowpack is difficult because these paper-thin layers are hard to identify and quantify amidst many feet of snow.

An avalanche triggered by a very surprised mountain lion in the Wasatch Mountains. No cats were hurt during the making of this photo and the tracks led away from the debris.
An avalanche triggered by a very surprised mountain lion in the Wasatch Mountains. No cats were hurt during the making of this photo and the tracks led away from the debris.

Thinking of avalanches in terms of terrain, weather and snowpack simplifies the decision process as you need all or a combination of these elements to have a slide.  If the weather and snowpack are unstable, but you are on flat terrain, you won’t have an avalanche.  Or, if you are in avalanche terrain, but the weather and snowpack are stable, you probably won’t have an avalanche. 

Thinking in terms of this triad also makes it easier to extrapolate decisions when you are unsure of one of the factors.  If you are in a) avalanche terrain and know it has been b) storming for the last two days, it’s a safe bet that you will trigger some slides, even if you know nothing about c) the stability of the snowpack.

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Inside Info - Part I

Published
by
Andrew
on July 30, 2008
in 07 Avalanche Avoidance
. 0 Comments

(continued from Monday’s ABC’s of avalanche train of thought)

With so many variables hidden under a blanket of white, where do you even begin?  Simplify the process by breaking it down into the big three categories; terrain, snowpack and weather.

Will it stay, or will it go now? New snow, steep slope and a clear day... what to do?
Will it stay, or will it go now? New snow, steep slope and nice weather…

Terrain is the easiest.  If golf courses are too flat to avalanche and vertical walls won’t hold snow, the prime avalanche angle must be somewhere right in between.  As it happens, 38 degrees is the magic/tragic angle where avalanches are most likely to occur.  For reference, this is about as steep as an expert slope at a ski resort, or in other words, perfect ski mountaineering terrain.

Weather is the next factor and has a direct correlation with avalanches.  Stable weather means stable snow, and turbulent weather means turbulent snow.  The important weather information is its history, not necessarily what it is doing at the moment.  Statistically, most avalanche accidents happen just after a storm when the weather has cleared, but the snowpack is still adjusting to its new loading.  New snow is the big, obvious ogre, but wind is the evil villain that lays hidden deadly traps.  Rapid warming creates unusual avalanches and rain would be far more dangerous if it wasn’t so unpleasant to ski in.

continued tomorrow…
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Snap, Crackle & Pop – The ABC’s of Avalanches

Published
by
Andrew
on July 28, 2008
in 07 Avalanche Avoidance
. 5 Comments

The physics of an avalanche is as easy to understand as placing one book on top of another, then tipping the lower book up until the top one slides off.  Voila - a bookalanche!  The grip or amount of friction between the books will determine how easily they slide apart.  If they are both dry and glossy, they’ll slide apart at almost any angle, but, if they have somehow bonded together through heat, humidity or moisture, you can turn them upside down and they may not come apart. 

 

One of my all time favorite avalanche education tools was this demonstration by the Alaska Avalanche School where layers of flour and sand are piled up on a flat board, which is then tipped up to 38 degrees where it rips loose and crushes the toys below.
One of my all time favorite avalanche education tools was this demonstration at the Alaska Avalanche School where layers of flour and sand are piled up on a flat board, which is then tipped up to 38 degrees where it rips loose and crushes the toys below.

This book example illustrates two important concepts of avalanches.  One, avalanches occur when a bond (friction) fails, and two; it can be difficult, if not impossible to predict exactly when that bond will fail without some additional information.  At times you could turn a mountain range over and shake it without the snow moving and at other times it will avalanche if you gently poke it with a ski pole.

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Photo Gallery - Shishapangma 1999

Published
by
Andrew
on July 23, 2008
in Events
. 0 Comments

After discussing avalanche avoidance for the last few days, it seemed like a good time put up some photos from one of my worst avalanche experiences - Shishapangma 1999, where Alex Lowe and David Bridges died in a massive slide while scouting a route near the base of the line we were hoping to ski.

The event was covered by MountainZone.com and is still available on their website at:

http://classic.mountainzone.com/climbing/99/shishapangma/

Avalanche Avoidance - Salvation Through Education

Published
by
Andrew
on July 22, 2008
in 07 Avalanche Avoidance
. 4 Comments
It would be ideal of avalanche education was like driver’s education, where you studied and learned about the activity before physically doing it.  But alas it is not, and some skiers go their entire lives without taking a class.  Bad idea!  A lack of avalanche education should not be considered a backcountry badge of honor.  To make matters worse, the longer a skier goes without taking a class, the less likely they are to do so.  Someone who has been skiing for fifteen years is not going to be seen dead in an Avalanche Level 1 course.
Pitting out. Like a college degree, the actual information you learn in an avalanche class is secondary to learning the terms and methodology.
Pitting out. Like a college degree, the actual information you learn in an avalanche class is secondary to learning the terms and methodology.

Avalanche education has a constantly changing curriculum that is worth keeping up on.  It is important to get in the habit of continuing education with avalanches, and the pros do it all the time through seminars, meetings and trade journals. 

More than anything, classes force you to think about avalanches, practice safe skiing, familiarize yourself with your beacon and look critically at snow.  Plus, they are often good places to meet partners with similar levels of enthusiasm and skills.

Avalanche education also helps to develop your vocabulary, which in turn is useful for deciphering avalanche forecast reports.  Learning that a “westerly front produced significant cross-loading on mid elevation ridgelines” doesn’t help you much if you have no idea what they are talking about!

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