Posts Tagged ‘ridge line’

Hangfire

Hangfire

The www.mtavalanche.com forecast for the day said it all: “If there was ever a day to stay out of the backcountry – today is it.” Still the intreptied travelers that we are (read: oft thought of as brain-less), Arthur and I skinned up Beehive Basin for an early morning lap before venturing onto the relatively safer confines of Big Sky Resort. The plan was tentatively to make the east Beehive Basin ridge line and ski back down the skin track. Possibly digging a pit up top to add to my developing profile of the upper reaches of Bear/Middle Basin confluence ridge lines.

Strong westerly winds at mid-slope behind Arthur.

Strong westerly winds at mid-slope behind Arthur.

When we arrived on top we were met by strong winds from the west. When I say “met” I mean we had been practically blown up the Beehive Basin skin track by them. Down low the wind effected snow was everywhere. The ava report had placed wind loaded slopes at “high” risk for the day, meaning the descent would be a cautious one, with eyes glued on slopes above, particularly on staying out from under ALL slopes above us, including the recent culprit in a slide a few weeks ago, which covered part of the far left up-track (I tend to stick to the middle benches and avoid that slope before venturing onto the “skinners-right” ridge line above the “Exit Chute”). In addition to high winds Arthur and I found large cornices forming down the ridge line, growing in size. They began just to the left of where the up-track gains the ridge, forming off the steep knob to skinners left of the skin track. They had added a huge amount of size to the large cornice that has been sitting at about mid slope as well as creating a whole slew of new ones.

I moved just the edge of the base of the aforementioned steep knob, at which often people will set the skin track out and around onto the Bear Basin side to continue up the ridge (in the last photo you can see the old small cornice under which this track has been set a few times this year). The snow was firm and there was no new cornice growing at about the spot where the skin track might normally swing off the ridge and onto the east facing slope. I then stepped down about 2-3 feet down the ridge line to a small cornice that I observed as a new growth. I kicked off one small piece of it with ease. (We were the only car in the lot at 7:30am, allowing us the relative certainty that no-one would be below us) The chunk was about 18″ long and 12″ in width, it broke and tumbled down the slope entering only the new snow around it, not running far and not stepping down into old snow at all (new sluff-ing only). I moved down again to break off a piece of about the same size. I stepped with one foot firmly a few times, getting no movement off the cornice chunk. I fastened my heel piece in place (skins still on) and tried again, on the second stomp the (desired) piece broke loose (maybe 24″ by 12-18″) as the entire slope propagated (undesired). About 15 feet up ridge from me to about 100-150 below me the cornice line cracked. The slope below ran in two spots, one immediately below me was about 50 feet wide, with a crown of about 3′ feet

Propagation up-ridge

Propagation up-ridge

Another sympathetic release that was about the same size in width at the crown, but appeared to be smaller in height also went down the ridge (We did not feet comfortable venturing down giving the cracking FAR back from the edges of the cornices).

Sympathetic release further down ridge.

Sympathetic release further down ridge.

Pieces of cornice and wind slabbed snow that ran down to the trees below (50′) were easily 5 feet long and 3 feet in height. Being pinned against the trees by these would have been miserable, and would have resulted in life threatening injuries, if not much worse.

Debris pinned against the trees below

Debris pinned against the trees below

The entire cornice laced ridge line below cracked at the same time, easily a few feet back from what might be considered a “safe” zone. By now, with wind loading we both hopefully predict that these time bombs have collapsed down-slope on their own.

Shooting cracks 150 yards down ridge

Shooting cracks 150 yards down ridge

I am thankful that we paused and didn’t venture onto the lee slope to move up the ridge, a common practice at this feature. I also think in hindsight we were too closely grouped together on the ridge which, had the entire ridge line disintegrated, could have been disastrous. Arthur was back further behind me, and was not next to me on the ridge, but still…better safe than sorry. We took a few photos, conversed about the happenings, stripped our skins, tucked our tails between our legs, made our way to the safety of Big Sky Resort after retreating from Beehive Basin.

3 foot crown where the skin track often wraps around the knob on the ridge.

3 foot crown where the skin track often wraps around the knob on the ridge.

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