Glide crack

Ok, that's just weird. Stuff like that doesn't just "happen", given how cold it has been. I know it's a smooth heather slope and all, but it isn't really any different from other slopes in the area.

Anyone? Anyone? ???<br><br>Any avy experts wish to offer an explanation? Coldest temps of the year, avy danger low, and that slope cracks and slides?<br>Given the weather and snow conditions, I would have been comfortable climbing up under that thing to go have a look at it. Clearly wouldn't have been a good idea.

My first guess would be faceting on the ground that finally weakened the bed surface interface to the point that it failed...the flanks were basically all left holding the slab, and failed. Since it is smooth and treeless (I think) there were no anchors.<br><br>I have seen faceting beneath deep snowpacks in the area right on the ground. Kind of interesting.<br><br>Ever read about moguled slopes in Colorado that weaken by faceting above the ground and then avalanche?<br><br>We in the PNW are accustomed to thinking about hazard as direct action, while in the cold regime faceting below that causes failure is not seen unless in a pit study.

Wouldn't the snowpack be a little thick for depth-hoar formation? I guess it could have formed during the cold spell in December when it was still thinner.<br><br>But what would have triggered the release now? I think we had some hot sunny days the week before last... maybe moisture trickled down and it started gliding then?<br><br>Pete's picture almost makes it look like there is a big gap under the snowpack. Probably just the colour of the heather, partly covered with snow dust and partly not.

If TG metamorphism occurred it would not be hindered by the depth, Snow is an ice skeleton with communicating air spaces. With cold weather, a temperature gradiant can occur thus driving the migration of H2O vapor that builds facets. Also clear nights enhance telestial radiation which also removes heat from the ground up (makes corn snow too in summer.<br><br>Check an avalanche text, there may be better infrmation. I have not looked at mine for a while, may check it later.

but if faceting was to blame, then wouldn't the slab have failed rather soon after the crack first began to appear since that means the snowpack is now moving on the layer of faceted snow?  I would've thought that climax slab released on depth hoar and glide cracks were two different animals.  But I guess the layer could've failed when Phil saw the crack and then the sidewalls of the snowpack held it in place for a couple days...maybe?<br><br>Although I guess depth hoar is more common in thin snowpacks like Colorado, I've seen it in relatively deep snowpacks before.  A few years ago at Fairy Meadows in the Selkirks we dug a pit to the ground on the first day of skiing, and below about eight feet of snow we found about 12" of faceted junk between the snowpack at the ground.<br><br>Here's another shot of the crown, more off to the side of the slidepath:<br> www.cascadeclimbers.com/plab/data/503/125avy_side_view.jpg

Although its was really cold up in the cascades, on sunday it was windless and sunny, we actually found some reasonable corn on south facing aspects around 5500ft in the afternoon. I wonder if the combination of very cold weather and some faceting along with moisture percolating through the snowpack from the solar radiation would've been enough to cause the failure.

Still doesn't explain how this slope would fail every year as Randonnee mentioned.