…it seemed like a sensible idea; the BT forecast for the day predicted considerable danger up high, moderate danger at the mid levels and low danger for the 6000′-7500′ range, so stay low. Plus, they had seen this open rib at low elevation just south of the mouth of West Pine Creek, where you can turn in and park on the road into the Girl’s Camp, and it offered a few hundred feet of turns on a moderate angle just a few hundred feet off the road. But, it’s the fine print you’ve got to read too; “low danger except for isolated pockets of unstable snow”…
Mark, Rick, Dean and I headed to West Pine Creek, aka Girl’s Camp, off of Pine Creek, with new information to help us pinpoint the avalanche that occurred there last Thursday, Feb. 24th.
The avalanche was on the northeast side of a subridge, north of the main ridge separating West Pine Creek from Fleming Canyon and was just a few hundred feet west from the highway and south of the road into the Girl’s Camp.
…so the boarder, the skier and his dog boot-packed up through the trees, emerging into a narrow clearing in front of a cornice overhanging the ridgeline before them. As they worked forward to climb over a thin spot in the cornice, the ground around them began to move and there was a “crack” like thunder and in a blink of an eye, the solid slab of snow they had been standing on broke into blocks that slid past them and with them downslope…
We traced a boot track up-slope until it disappeared under the lower edge of the debris pile at about 6100′. We then moved across a couple hundred feet of slab blocks ranging from cinder block to refrigerator size, looking up at a 3-4′ “crown” where the cornice had broken away for a distance of 200′-300′.
…they came to rest moments later after getting tumbled in the fracturing slab, thankfully missing trees and the larger blocks; shaken but intact. After collecting themselves, they snapped a few pictures and retreated down to the road and their car, learning that “low danger doesn’t mean ‘no’ danger”…
We dug two pits, one in the slide path and one further up the ridge above the crown to be able to compare layers. Being wind impacted, there is wide variability of depth within relatively short distances; next to the cornice the snow depth is greater than a probe’s length but drops to 100cm about 50′ out.
Both pits showed a substantial “base” of cold-impacted snow; facets about 40-50cm thick. Above that, both pits show the evidence of warming events from late January through mid-February; ice/melt-freeze layers, separated by surface hoars and thin snow layers. The surface of this sequence formed the bed-surface for this avalanche. The upper pit showed the wind slab that formed last week with our region’s return to snowfall and high winds; this layer was missing in the lower pit…it slid.
The lower pit was an ECT x, failing in the facets below the ice layers while isolating it.
The upper pit had CT 11(x3), also failing in the facets about 100cm down.
The newer wind slab of the upper pit showed Q1 shears on buried surface hoars, separating the multiple wind/snow events of last week.
It is our speculation that the wind slab triggered as the two crossed it, sliding on the older ice layer, pulling out what little support it offered the overhanging cornice, which then also broke, forming the larger blocks seen in the debris pile.
This is the second year in a row an avalanche has occurred in what we call the “Girl’s Camp Bowl” area. Both have been human triggered and carried someone. It is low elevation and therefore is often considerd “low danger” but it is proving to be an area that demands full respect!
Those of us that ski the Kelly Canyon off-piste should note the similarities to the west slope of Moose drainage, particularly south of the “Baugher Special” and the cross-loaded ribs across the road from the ski hill!!