Tuesday, January 3, 2012

Pop Goes The Slab

Conditions are pretty much ripe for skier/sledder/boarder triggered avalanches right now. Around the Nelson Range, somewhere between 110 and 120 cm of snow has covered the mid-December surface hoar/near surface facet layer, and has settled out to a slab with a thickness of 70 to 80 cm. That is getting near the limit of skier triggering, but, there will be plenty of areas where the slab is slightly less thick and thus well within the range of skier triggering.

Digging in the snow, in the right location (look for open gladed areas in the trees sheltered from the wind on E or N aspects at treeline or below), the mid-December surface hoar is up to 18 mm in size and well preserved. On compression and extended column tests, fractures initiate and propagate with sudden fracture character. In other words, that slab pops. Hit it right, and it will pop with you on top.

Check out the videos to see a "pop" on the compression test and the extended column test.

There's also a nasty freezing rain crust on the surface impacting ski quality.
Nasty Freezing Rain Crust

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