[Nmap] Northern Glide Cracks

[sean fraser]

Hi Folks...so some of you may be looking at the recent LFH and NW MOT posts on  the infoex regarding Glide Crack failures during -25 in Dec, and think we are on crack. Well, after 3 years of seeing this in the Ningunsaw area, this year is definetly the worse, and I am interested to hear anyones thoughts on this. IT is widespread at TL and BTL, all aspects from Treaty Ck in the W, to well up the Bell Irving River in the E. Some BTL terrain actually looks like a crevasse field, and there are some real hazards with skiing into these over a blind roll. These things seem to be moving more on low angle terrain, even as low as 15deg.
Had a chat with Dr. Jamieson the other night, here is my theory, wondering what others have experienced.
So, I believe with a certain smooth wet soil type, such as heather moss/clay, which I hear is notorious up this way for poor soil stability snow aside, That with heavy precip in the form of rain before winter the earth is super saturated. Then, copious amounts of moist/wet snowfall insulate this layer, and above normal amts of HN fall, and things start to glide. Early Nov rain at low elevation probably does not help. The localized glides start to open, and glide creep. Then with a sudden, intense blast of arctic air, they become brittle, much like a cornice, or icefall and collapse/fail. The resulting slab often only involves the area of glide, and does not propogate over wide areas.
I dug a 320cm full profile to ground in the Bell Irving the other day, and was able to squeeze half a cup of water out of a handfull of dirt/moss.
Last year this same sort of thing occurred, except it was almost a full month earlier, as the cold snap was in November. Glides failed, but not as widespread as this.
 
Anyways, just curious what others in the area have seen past or present, and if they feel this is localized phenomena for the type of soils for the area. I have seen many glide cracks in spring on wet lubricated rock slabs, that looked much riper for failure than these, and even coaxing them with copious amounts of An/Fo  for several days fails to release them.
 
Have a good holiday season folks, hope your fire is a burning!
 
Cheers;
seanSean FraserACMG Ski GuideCAA Professional Member/ Avalanche ConsultantSmithers, BC250-847-5537
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