Snow sculptures and subnivian lifePosted on February 8th, 2011 Add a comment >>
“….we see fantastic forms stretching in frolic gambols across the landscape, as if Nature had strewn her fresh designs over the fields by night as models for man’s art.” – Henry David Thoreau from “A Winter Walk”.
We can only wonder if Thoreau knew about “plasticity” in snow. We often think that snow is simply piles and piles of snow flakes that sit on the ground, in the trees, on the roof, or on any other structure we see. To some degree that is true, snow on the ground is made up of gazillions of snow flakes, but what goes on in that snow pile over time can tell us a lot.
The picture above shows a once-vertical column of snow now slowly leaning to one side, but yet it is not breaking or collapsing! How can that be?
This is what’s known as the “plastic behavior” of snow. Even though snow pack is frozen it can still behave in a way that resembles water moving in slow motion. When this pile of snow was vertical it began to deform at the bottom due to the weight of the upper part and gravity working on it. Over time the snow column yields to these pressures in a fluid-like movement and reforms but does not break.
I’m sure many of you have seen snow that looks as if it’s wrapped completely around a branch, like a snake or a vine. That snow was once on top of the branch, where it fell, but over time it gave way to its own weight, deformed and then reformed into the odd shapes we see.
As I was skiing on the trails at the Paul Smiths College “VIC” I saw lots of small mice or vole tracks on top of the snow pack:
However, if you look closely at the picture you can see a couple “tail drags” where the tail hit the snow. This tells us that it was mouse, probably a white-footed or deer mouse (Peromyscus) that made the track while on some dawn or dusk run to a food source.
Even though we play on top of the snow in winter, there’s still lots of serious activity down under the snow, or in the “subnivian zone” (area from the ground up to the snow surface). Here we find mice and voles busy eating their stored food, or happily eating the bark off your favorite ornamental shrub. Mice and voles will often build a nest or bedding area on the ground where they can take a little day or week-long nap depending on the outside conditions.
Ruffed grouse and weasels can often be found burrowing through this zone. For the former, it’s a place to hide and stay warm while a blizzard rages on above them, and for the latter, it’s the source for many yummy dinners!
So often we snowshoe and ski with our minds only on that task, but when you can let your eyes wander over the snow pack and look for the finer details….”the models for man’s art.”
Photo Credits: Brian McAllister
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