Avalanche Courses start tonight for me, so I thought I’d share a quick video of a compression test (at least the second 2/3 of one). 

A compression test is likely the most common of  all bonding tests used when evaluating snow stability. This test is best utilized to a) confirm or deny what you already know and b) to get an idea of the bonding strength between layers and c) to identify a weak layer within the snowpack.

The test is performed as such…

-Identify all layers (using hand hardness)

-Dig your profile at least 1 meter in depth… or to the ground if you live in CO :(.

Completely isolate a 30cmx30cm column using a snow saw (I like the G3 Bonesaw best). Back must be cut at least past the depth of your weak layer in question.

– Lay shovel blade convex side up onto column and begin with 10taps from the wrist. (this step is omitted in the movie) Having as assistant observe for any failures in the column is very helpful. If no result continue to 10taps from the elbow. Layin the elbow on the shovel handle and letting the hand drop. Observe column for any failures. Next do 10 taps from the shoulder, again letting the arm drop rather than using muscle. If still no failure you record a CTN. Compression Test No-Failure. 

-What perhaps is of most importance is recording the Fracture Characteristics of the failure. (for another post.)

[vimeo 2508702]

Thanks!

Mtns tinyMike Bromberg