05 June Rainier Avalanche

FYI, some more information.

I feel sad for this young man's parents

...and for his 5-year old kid.

NWAC has posted more photos of the avalanche.  I can think of two interpretations: it could have been climber-triggered at a deficit zone, lookers right, then propagated left. I believe the route normally climbs the gut of the glacier, then traverses right onto the top of the DC. But the slide looks like it stepped down in the center of the path, and that doesn't make sense to me in terms of being triggered at thin spot, that should have ripped the deepest weak layer at that point. Alternately, maybe serac fall triggered it in the center of the path. Is there anyone who is more knowledgeable about avalanche kinetics who can comment?

On the southwest side of Baker, Tuesday 6/8, the only thing we got to move were a couple of slow, predictable loose, wet slides in the heat of the afternoon on 40+ degree slopes at ~6000'.  There was 3-4 inches of fresh windpack (probably from Monday night) that skied very nicely above 8500'.  The fresh snow felt hollow, but was shallow and below it lay a thick, bombproof crust.  Lower on the mountain, nice corn to about 6k, then mush, much of it quite sticky.  The bare patches nearer to the car skied quite well with my current wax job.

Anyone who's been higher have any conditions to report?

This is very sad. From the article, Mark sounded like a pretty amazing guy.

I've seen small slides start *much* bigger slabs lower down once they got moving and gained some mass. So the idea that this thing started on the far R at a weak spot and then entrained a much bigger slab lower down, even on lower angled maybe less loaded terrain, is very plausible. It also looks like a smaller release on the RH side of the photo might have undercut the support for larger slabs near the center of the photo, where the biggest crowns are. I have no idea if any of that made a difference in this case. But it does happen.

Regardless of how exactly this slide ran, its a terrible event. Sincere condolences to the family & Mark's son.

Outwardly, the taxonomy of avalanches is very simple: loose / slab, hard / soft, wet / dry. The reality of avalanches is that these terms are very general approximations of very complex phenomena.

To this point, in many small, dry snow avalanches, especially events with a short vertical fall, or events on a gentle slope, the slab simply disintegrates as it falls. There is no core, there is no powder cloud, and the snow grains might not even rub together enough to produce rapid freezing. This type of event, while still dangerous, is not what happened here.

Stepping down wouldn't have mattered, as the areal size of the initial fracture was almost certainly large enough to produce a large avalanche. Once flowing snow attains enough mass and velocity, its behaviour changes. This type of avalanche is referred to as a mixed-motion avalanche, AKA a "Hollywood Avalanche". These avalanches are much more diffult to reconstruct, especially in an area with a chaotic, high-altitude snowpack that overlays perennial ice.

In a mixed-motion avalanche, is is thought that the core itself slides downhill like a brick, but the fluidisation of the outer part of the core ( the air/snow mixture ) allows for strange behaviour, most of which is poorly understood. Additionally, the fluidised external layer is responsible for producing the powder cloud that gives the avalanche its "Hollywood" appearance.

Rank Speculation:

The deposit is visible all the way up to the serac, which suggests the upper part of the fracture ( on the right side of my image ) produced snow that flowed downhill and stopped immediately. Flowing snow originating in the left side of the image accelerated rapidly and entrained more snow as it traveled downhill. At some point, probably in first few seconds, the flowing snow became fluidised and then the proverbial material hit the proverbial fan.

I'm very surprised that there were 11 humans in the way of this avalanche and only a single fatality. Does anyone know if most of the climbers were caught at the edge of the slide? I can't imagine that 11 people could be hit by the front of this avalanche without at least 10 more fatalities. The forces produced at the front of this type of avalanche would be more than enough to kill most people, even if they weren't buried.

I am truly sorry for the young man and his family. This really was mostly chance and not a lot of choice.

Looking at telemetry... was there really an 18 degree warm up between 3am and 5am at Muir? Wow.

Given that the avy hit at 4:45a, I can belive it. Very odd. ???