Snow Structure - A Few Tips

I remember (some 35 years back!) being very confused by Colin Fraser's book "The Avalanche Enigma" which is a great book but not really an idiots guide - which it needed to be for me.  The stumbling block was always getting my head around "constructive metamorphism", "destructive metamorphism" etc.  It took me years to realise you only need to group crystals into 3 distinct types: ROUNDING, FACETING and MELT/FREEZE

Rounding is where the branched stellar snow crystals change shape into smaller more rounded shapes and the pores between the crystals get smaller.  This is often observed as the settling of the snowpack making it more stable over time.  The closer the temp is to 0c the faster this process is BUT, if it get colder the process slows proportional to the decrease in temp.  Increased pressure from subsequent snowfall can accelerate the process.

Faceting comes from large temperature gradients within the snowpack. A temperature gradient is simply how fast temperature changes over a certain distance within the snowpack. Why? Because it's a fact that warm air holds more water vapor than cold air. This means that temperature gradients also create "vapor pressure gradients"  -  more water vapor in one place than another. And what happens when you concentrate something  -  especially a gas? It wants to diffuse  -  move from areas of high concentration to areas of low concentration.

When water vapor rapidly diffuses it changes rounded crystals into faceted ones  -  changes strong snow into weak snow. In other words: temperature gradients create potential weak layers that can kill us. That's why we pay so much attention to them. The point is that this is a completely reversible process.

Strong gradient turns rounds to facets. Weak gradient turns facets back to rounds, the process in reverse. However, it occurs much more slowly because it takes so much more energy to create a faceted crystal and when we take the energy source away (the strong temperature gradient) it takes some time for the crystal to return to its equilibrium state (rounds). In other words, it might take a week or two of a strong temperature gradient to form large faceted crystals but after you take the temperature gradient away, it can take weeks or months for them to stabilize, depending on the ambient temperature of the snow and how much compressive load is on top. In cold climates without much load on top of the faceted snow, it may never gain much strength  -  even without a temperature gradient. The point here is: small temperature gradients make the snow stronger -  large temperature gradients make the snow weaker. Got that?

So, large temperature gradient  -  how large is large? For snow of an average snowpack temperature, say around -5 degrees C, the critical temperature gradient is about one degree centigrade per 10 centimeters (1 deg C / 10 cm). In cold snow, say colder than -10 deg. C you need a higher temperature gradient to cause faceting, and in warm snow you need slightly less.

For example, let's stick two thermometers into a snowpit wall, one 10 centimeters above the other. Say we measure a difference of only 1/2 deg. C in 10 cm,  it means that equilibrium snow is growing (snow is getting stronger). If we measure a temperature difference of 2 deg. C. in 10 cm, it means that faceted snow is growing (snow is getting weaker). All you have to do is to find a faceted layer in the snowpack, measure the gradient and you know whether the layer is gaining strength of loosing strength.

This is a powerful forecasting tool. Ever wonder why the SAIS pit profile shows a red line giving the temperature profile of the crystal types and layers within the pit? Now you know!

 

Size 3 Avalanche Glencoe

22nd Feb 2016 Large Avalanche "Fly Paper" Piste Glencoe Mountain

One of the rights of passage for many of those venturing into steeper ground this is an excellent run when open, but it's often closed because of ice and avalanche danger. The same applies to the two other steep lines off the ridge to the side of it . Heed the warnings, don't duck the ropes to ski it, and if you want to ski the mellower "East Ridge" talk to the ski patrol first when this side of the mountain is closed. Take advice from them. The concern is always that less well equipped riders and skiers will follow your tracks and not make the safe drop in decisions and choices of an experienced Freerider. Have a care for others less equipped and experienced. 

Piste Closed!

Spontaneous Release

Crown Wall 2.5m+

Crown Width 50m

Vertical Travel 250m

Distance Travel 900m+

Size 3

click images for bigger size

Classic avalanche terrain at 43 deg on Scotland steepest piste. Upper section can be steeper!

Lower debris pile and runout with bench terrain trap visible above

A small part of  the upper debris pile and greatest depth on a natural bench and terrain trap.  Both Beacon and Recco Sweeps done.

SAIS Glencoe Snow pit profile from previous day while wind was moving snow

Day after with the morning sun showing the now partially filled in crown wall. This crown is much lower than previous slides on this slope which tend to occur  slightly higher, propagating from the rocks top left and up and right. This web cam is 3km away.

Airbag Refill System

I have x 2 brand new BCA Float Airbag Cylinders for sale at £100 each. Also I am selling a Float Cylinder Refill system. This includes a certificated and tested dive tank and the refill adapter to connect to the above cylinders and refill them. The tank is full. I would be looking at £200 for this. I am too out the way for doing the refills. My last customer drove over from Aberdeen as I am the only place doing it and he said next time it would be eaiser just bying a new cylinder! Maybe an opportunity for someone more central.

In the Shadow of Ben Nevis

I can't wait until I can order a copy of this book. My second pair of boots came from  "Nevisport" with it's big husky on the roof in about 1972 when I was 15/16. A proper climbers shop. My first boots (bought for me by Hamish from George Fishers for acting as a runner on rescues) were taken from the front porch at Kingshouse after coming off Ravens Gully and getting drunk. They also sent a duvet jacket I had ordered by letter with postal order over with Dave Knowles on the Ballachulish ferry one Friday, and the next night was spent out with Euan Grant below and right of Ossians cave and it saved my life. Without doubt the best climbers shop ever as started and run by mountain men.

Ian will be speaking at this years FW Mountain Film Festival.  Don't miss it.

RECCO Rescues 2015

RECCO Rescues 2015

The following are some rescues where RECCO technology made a difference, or could have. The first two rescues mentioned below occurred in Spain’s Pyrenees and deserve attention as they highlight the importance of being searchable. At Baqueira, RECCO technology quickly located and saved a buried off-piste skier, which then helped rescuers find the second buried skier who was also found alive. In the other accident at Candanchú, the search operation and outcome were very different as the skier was not searchable. Rescuers found the skier dead the next day. 

Baqueira-Beret, Val d'Aran, Spain, 2 February 2015

Located in the Pyrenees, Baqueira-Beret is the largest and busiest ski resort in Spain. On Monday, February 2, a group of 4 off-piste skiers were caught, and 2 with no rescue gear were completely buried in a soft slab avalanche. The ski patrol responded immediately. The RECCO detector operator found the first skier buried 1.4 meters after a 6-minute search. The skier’s cell phone (facing the surface) likely reflected the RECCO signal. Once found, rescuers had the indication where to focus their effort and located the second skier, buried 1.5 meters, about 20 minutes later by probing. Both skiers survived. Mountain rescuers from the Bombers de la Generalitat with their helicopter joined seventeen ski patrollers to rescue the pair. It is not easy (and sometimes it’s impossible) to find a cell phone or other electronic device because of weak signals and short ranges, but this rescue highlights the importance of searching with the RECCO even when the person does not have reflectors.

Special thank you to Francesc Rocher, ski patrol director, for sharing details.

Candanchú, Huesca, Spain, 31 January 2015

At the end of January the Candanchú ski resort was hit by heavy snows and strong winds, which closed parts of the resort. On the 31^st, two backcountry skiers triggered an avalanche in the Rinconada area, an area that was closed at that time because of the severe weather. Neither skier carried any rescue equipment. One was not buried and called 112 (equivalent of 911). Ski patrollers found him suffering from hypothermia. The other skier was buried, and rescuers from the ski patrol and the Guardia Civil searched RECCO, dogs, and probes into the evening before suspending the search because of bad weather and increasing avalanche danger. The search resumed early Sunday morning. As the skier was not searchable he was eventually located – deceased – by probe line some 20 hours after the avalanche.

Special thank you to RECCO Techs (and Bomber instructors) Bernat and Francois Carola for additional information.

Polar Circus, Banff, Canada, 2 February 2015

Late Thursday afternoon in Banff National Park a Canadian Forces search and rescue technician was swept over a cliff while he and his partner descended Polar Circus (700+ m ice climb) on an official military training. The pair had just rappelled the upper portion of the route to a steep, snow-covered bench. The victim triggered an avalanche after moving ahead to set up the next anchor while his partner coiled the ropes. His partner searched the area, but neither had transceivers. Late that night the Parks Canada mountain rescue team received word of the accident. An incoming storm dropped up to 1 m of new snow by Saturday, which prevented any searching on the ground. Extensive mitigation work with explosives on Sunday triggered many big avalanches that spilled down the route. On Monday park rescuers were short hauled by helicopter onto the debris and searched for a few hours with 2 dogs and RECCO. Because the terrain is a technical ice climb, all searching was done while roped. Since it was known the climber was not equipped with a reflector, the RECCO search was done slowly with a tight grid pattern. As the dogs were equipped with reflectors, the operator had to wait for the dogs to move out of a sector before searching with the detector. On Wednesday a detector operator picked up a RECCO signal that was being reflected back by a Mammut headlamp the victim carried in his backpack. He was located under 2.7m of debris. This search is a good reminder to use the detector’s earbud headphones especially when searching for incidental electronic devices. Weak signals can be better heard when using earbuds. 

Zakopane, Poland, 21 February 2015

On Saturday, as strong winds caused heavy blowing snow, two tourists set out for a hut in the Valley of Five Polish Ponds. When they failed to reach the hut by 0100 the hut master called rescuers. Early Sunday morning TOPR rescuers, assisted by rescuers from Slovakia, spotted and started searching several recent avalanches with probes, dogs and RECCO without success. The search continued on Monday. An appeal for information over local television and radio resulted in several photographs showing the pair. While searching a small avalanche (80 x 5 meters) on Tuesday afternoon a RECCO detector operator detected a signal. A probe confirmed the signal. A second signal was detected nearby. The first victim was buried one meter deep, the other 2.5 meters. The pair had followed the summer trail, which is threatened by significant avalanche danger rather than taking the safer and longer winter trail. The first victim was buried one meter deep, the other 2.5 meters. The pair had followed the summer trail, which is threatened by significant avalanche danger rather than taking the safer and longer winter trail. The victims likely triggered the avalanche, and apparently were traveling together when caught. Neither victim had a transceiver. Both victims were found because of their cell phones.

Special thank you to Andrzej Górka of TOPR for sharing details of the SAR operation. 

Orelle, Savoire, France, 3 March 2015

Four skiers were caught in a small slab avalanche that swept 3 skiers over a 15m cliff and buried 1 skier. The alarm was sounded immediately and 2 ski patrollers arrived quickly with transceivers and a RECCO detector. The search area was relatively small (25 x 20m) and one rescuer quickly got a signal with the RECCO detector. This victim was uncovered from a 40cm burial after only a 12-minute burial. The victim was unconscious, but breathing, and had suffered a significant head injury. The mountain rescue team and emergency doctors arrived and treated the patient before he was flown to a Grenoble hospital. The patient was not equipped with a reflector, but was found by a weak signal that likely came from a cell phone. When the RECCO operator did not detect a signal during the first pass, he started to search in microstrips (few meters wide) with the detector just above the snow surface.

Reported by Frederic Gros, Orelle Ski Patrol and Recco operator