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SnowFlurry 10 2019/20 | Nanu, some snow profiles are not complete

Why are these often not entered or not recorded at all?

by Stefanie Höpperger 01/25/2020
You often see that the lower snow layers are missing from profiles, but aren't these also important? Basically yes, but since you can't assess an entire slope with a profile, but "only" (and yet very much) locate the snow layers, snow forms, weak layers, etc., as well as observe fracture initiation and fracture propagation, you don't necessarily have to dig a three-metre-deep hole.

You can always get a feel for what is going on in the snowpack.

Profiles down to the ground are interesting in spring, for example, when there is a risk of the snowpack becoming completely soaked, which can reactivate deeper-lying weak layers. Or if there is a pronounced weak layer near the ground that could be disturbed in areas with less snow or that you want to observe.

In high winter, on the other hand, when a thick layer of snow prevails, it is sufficient to dig a hole about 100 -150 cm deep. This is because a single skier can only disturb the snow cover up to a certain depth. With soft, unbound snow, the penetration depth is approx. 80 -100 cm, with bound snow it is max. 50 cm.

Note: The softer the snow, the greater the penetration depth. The harder the snow, the larger the surface area and shallower the penetration depth.

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It is unlikely that a winter sports enthusiast will disturb an even deeper weak layer. In places with less snow, however, the distance from the weak layer to the snow surface becomes smaller and smaller and must therefore be taken into account again. Avalanches can therefore be triggered more easily at the transitions from much to little snow. As has been mentioned several times this winter in the avalanche report:

"New and drifting snow lies mainly on shady slopes on an unfavorable old snow surface. There are weak layers in the snowpack, especially there with an angular structure. The snowpack varies greatly on a small scale"

The load of an avalanche can initiate a break in deeper weak layers (more than 60 cm).

Snow profile from 19.1.2020 Rietzer Grieskogel | SW | 2446m

A little information first: When digging a snow profile, choose areas with less snow, as these are more informative. However, there can also be several meters of snow cover at the profile location - it is sufficient to shovel out approx. 1.5 meters, unless you like to shovel, in which case of course you should shovel right down to the ground.

It is important that the total snow depth is indicated. You start picking up the layers at the snow surface and work your way down layer by layer as far as you have shoveled. What is underneath is left free (see profile).

Blue:

Cold, loose fresh snow with beautiful dendrites (snow stars) from 18.1. to 19.1.2020

It snowed with only a light wind, so the crystals were not destroyed.

Green:

Snowfall on 18.1.20, bound fresh snow

Red:

Edged crystals due to the accumulating transformation before the snowfall on 18.01.2020

Yellow:

Crust formation in the fair weather phase from the beginning of January.

The angular layer between the two crusts is a possible weak layer as soon as a suitable board lies above it.

Purple:

From the crust downwards you can find a few to many frozen water columns.

In the fair weather phases, the snow surface became moist, allowing water to seep in. This made its way down and froze again in the colder layers. This creates small, large, thin and thick frozen columns in the snowpack.

The layers were not recorded from 0 - 80 cm

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This article has been automatically translated by DeepL with subsequent editing. If you notice any spelling or grammatical errors or if the translation has lost its meaning, please write an e-mail to the editors.

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