Snow Science

By Kevin Grove, Chemistry

Figure 1. From Kenneth G. Libbrecht 
www.snowcrystals.com

Have you ever taken a close look at the snow falling from the sky?  Not just a cursory glance – but a good, solid look.  Did you find intricate, six-sided beauty?  Were any two snowflakes exactly the same?

Snow is a magical medium for science, art, and sport to blend into one.  In the past three months, I have talked about snow, thought about snow, studied snow, and experienced all of its ephemeral qualities.  Writing about snow has been the most difficult.  Each time I attempt to start this blog post, something new comes up related to all things snowy, shifting my focus of the post. 

Initially, my intent was to talk about the scientific aspects of snow.  Liquid water droplets freezing on dust particles initiate the process.  Water chemistry – polar covalent bonding, hydrogen bonding, etc. determines the six-sided nature of the snowflake (see figure 2). 

Figure 2. Water molecules attaching to form hexagonal ice.  Chemistry in Context-McGraw-Hill.

After the initial crystallization, snow physics takes over building and defining the snowflake.  Temperature and humidity are the two key variables taking over as the snowflake builds (see figure 3).  Mass transfer (water vapor movement from the space around the flake to the flake), heat transfer (latent heat is given off during hydrogen bond formation), and attachment kinetics (the Lego effect where water molecules can only attach to the snowflake at specific locations) ultimately decide the final size, shape, and beauty of the snowflake.

Figure 3. Ukichiro Nakaya – 1954 from www.snowcrystals.com

Each time a snowflake moves into a different temperature and/or humidity during its formation, the physics change the building block process of the snowflake.  All snowflakes travel through many different temperature and humidity regions before landing on your jacket, ultimately leading to a very high probability that no two snowflakes are alike.  Take a relatively simple task of arranging 15 books on your bookshelf as an example to illustrate this concept.  With over one trillion ways to arrange the 15 books, you can imagine how it is highly probably – considering the extremely complex and variable nature of the building process – that no two snowflakes are alike.  Wilson Bentley first set out to prove the validity of the statement capturing over 5000 images of snowflakes.  Nicknamed the “snowflake man,” Bentley profoundly stated,  “Under the microscope, I found that snowflakes were miracles of beauty; and it seemed a shame that this beauty should not be seen and appreciated by others. Every crystal was a masterpiece of design and no one design was ever repeated.  When a snowflake melted, that design was forever lost. Just that much beauty was gone, without leaving any record behind.”

Figure 4. Wilson ‘snowflake’ Bentley photographing snowflakes.  www.snowflakebentley.com

On January 22, I gave a college hour presentation to a packed house about the science of snow.  Actually, there were only five folks there, but they filled the room with their intrigue, interest, and enthusiasm – making it feel like a packed house.  The talk was about the scientific process of snowflake formation and destruction (what happens to the flakes over time after they fall to the ground).  I pontificated about what happens to snow over time in a snowpack and how this can lead to either amazing downhill skiing/snowboarding, knee-tweaking skiing (breakable crust), amazing Nordic crust cruising (another blog post someday?), and dangerous backcountry conditions regarding avalanching slopes. 

Figure 5. Crust Cruising near Broken Top, self-portrait

Ironically, the next day, I skied onto a slope by Middle Sister in the Cascades, and triggered the largest, most potentially dangerous avalanche I have ever been involved in.  It was still a relatively minor avalanche, on a slope with relatively low consequences, but I did indeed make a mistake.  Luckily, I skied out of the avalanche unscathed. 

Equally as ironic, I already signed up to take a Level II avalanche course with Aaron Lish and Tim Peterson in COCC’s HHP department to further my education on avalanche safety.  Two weeks after I triggered the avalanche, I spent five days with Aaron, Tim, and eight other students learning about all aspects related to avalanche safety. 

I chalked my mistake up to the human element – one of the four factors that contribute to avalanche hazards.  The human element looks at the decision making process, especially where and when it breaks down.  I have made many good decisions in the backcountry over the past ten years and was even making good decisions early in the day of my incident.  I identified a weak layer of near-surface facetted crystals at an interface between a frozen, rock hard, layer and new snow on top.  Performing stability tests on the snow layers, I saw potentially hazardous, high energy, conditions.  Why did I ski the slope?  The human factors taking away from good, sound decision-making included beautiful lighting and cloud conditions for stunning picture taking, fiddling with a new video camera, changing our objective at the last minute and not reassessing the current hazard on the current slope, being out with a new partner. 

I reflected on this incident a great deal before, during, and after taking the avalanche class.  My friend Wray Landon was not so lucky and did not get a second chance.  I did not know Wray well and only met him a couple times, but he was good friends with one of my good friends, Ty.  Ty and Wray skied a lot together over the past two years including a ski descent from the summit of the Grand Teton.  I first met Wray nearing the end of a randonee (uphill-downhill) race at Jackson Hole a couple years ago.  We were battling it out at the end of the brutal 6000 feet of climbing in the race.  I stepped aside to allow Wray to go ahead on the final climb up a ladder exiting one of the most famous ski runs in the country, Corbett’s Couloir.  After another encounter last summer in Driggs, ID, I could clearly tell that Wray was humble, kind, and loved to ski.  On February 28, Wray triggered an avalanche on the Southeast Face of the South Teton in Wyoming that swept him over a 1500-foot cliff.  Human factors were certainly involved, as a group of skiers had skied the same exact slope the day before, perhaps causing Wray to let his guard down. 

Figure 6. Wray Landon from www.tetonat.com

I think back to Bentley’s quote, and see it equally applying to Wray: “Under the microscope, I found that snowflakes were miracles of beauty; and it seemed a shame that this beauty should not be seen and appreciated by others. Every crystal was a masterpiece of design and no one design was ever repeated.  When a snowflake melted, that design was forever lost. Just that much beauty was gone, without leaving any record behind.”  Wray did leave behind a record;  family and friends will remember him forever.

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One Response to Snow Science

  1. Sean says:

    Gorgeous, Grover. I especially like the 15! reference in there. As I was walking through these unique miracles today, I found myself thinking about how, by the time we see them, they have already traveled, what, 3000 feet? We see them for a teeny percentage of their totally morphing journey. Kind of like watching only the finish line at a marathon, I suppose.

    Except the marathoners don’t melt, I guess.

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