• Reasons for Avalanches
  • The weather
  • The terrain
  • The snowpack
• The Shovel Test

• Avalanche Warning Signs
• If you're caught in an avalanche
• If you're buried in an avalanche

• Avalanche Rescue
• Reporting Avalanches

So think again and be aware of the signs and preventive actions if you are a winter walker, skier or climber. With winter sports becoming more popular and more accessible to the majority, it is important that you do not venture into the hills without the experience or knowledge to notice the signs of danger before you set off and to help yourself and others should the worst occur.

If you have not already done so, we would recommend you attend a winter walking or climbing course so that you fully understand the skills required for the mountains.

• Do not underestimate the power of nature especially in such remote and inaccessible places.

• Don't rely on a mobile phone to keep you safe, build your own skills and this should help in times of trouble on the mountain.

And don't forget - the Mountain Rescue Team is a last resort - it is a team manned by volunteers who rely entirely on donations.....even down to the members buying their own kit to rescue stranded and endangered climbers, walkers or skiers who in most cases where in areas of the mountains where they should not have been and did not have the experience to cope with.

Reasons for Avalanches

As the winter progresses, snow is deposited in successive layers with different physical properties. Avalanches occur when one layer slides on another or the whole snow cover slides along the ground. An avalanche may be dry or wet depending upon whether there is free water in the snow. It may be loose snow starting the avalanche from one point or it maybe a slab avalanche (snow sticks in a slab and separates from the rest of the snow, sliding down the mountain).

90% of all avalanches occur during snow storms.
90% of all avalanches involving human objects are triggered by their victims.

3 main reasons for avalanches

The weather is the most important factor in determining whether an avalanche is likely. The snowpack (layers of snow) is entirely dependent on the weather. Weather reports and avalanche reports from SAIS are available and should obtained before you set out. Also local advice is useful. However, mountain weather is difficult to predict and can change rapidly at any moment.

Terrain

On most hills in Britain, a sensible choice of route can avoid the avalanche risk.

• Slope angle - most large slab avalances run on slopes between 25 and 45 degrees (average angles of coire backwalls and approach slopes to crags are within this range).
• Ground surface - smooth surfaces (i.e. rock slab) is predisposed to avalanches whereas rough ground such as large boulders will tend to anchor base layers. However, once these boulders are covered, surface avalanches are unhindered
• Slope Profile - convex slopes (i.e. bend outwards like the sides of a ball) are more hazardous than uniform or concave slopes

Ridges or buttresses are better choices than open slopes and gullies when avalanches prevail. Lee slopes should be avoided after storms or heavy drifting.

The snowpack

The snowpack can be observed from the roadside and evidence of recent snow movement, accumulation of snow in areas, fresh loading of snow and drifting can be observed from below the mountain. Many other features should be looked out for and it is these skills that a winter walking and climbing course will teach you and that you will build upon these skills as you gain experience in the mountains.
Look out for (amongst other things):

• adjacent layers of different snow hardness
• Very soft layers
• Water drops squeezed out of a snowball etc

The Shovel Test (use your fist or ice axe)

1. Isolate a wedge shaped block, cutting down to the top of the next identified layer.
   • If the top layer slides spontaneously, there is a poor bond between the layers of snow.
   • If the snow layer slides, try to determine the rate of sliding by pulling the layer from behind with your shovel or arm.
2. Do this for each suspect layer on the block. Carrying out this test many times will allow you to assess the stability of the layers and the risk of snow movement.

But remember, these tests only hold for slopes with a similar orientation. Rate the slope as Safe, Marginal or Unsafe and if the slope is Marginl or Unsafe then choose an alternative route round it.

Most avalanches are cornice triggered, where the surface windslabs may be thicker and in general climbing below cornices should be avoided :

1. During snowstorms or heavy drifting
2. Immediately (24-48 Hours) after the above
3. During heavy thaw or sudden temperature rises

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Avalanche Warning Signs

1. If you see avalanche activity on the slope where you intend to go, go somewhere else.
2. Rapid slab/new snow build up (more than 2cm per hour) may produce unstable conditions. More than 30 cm build up is considered very hazardous.
3. Slab lying on ice or neve, with or with out aggravating factor such as thaw.
4. Discontinuity between layers, usually caused by loose graupel pellets or airspace.
5. Sudden temperature rise - the closer to 0 degrees the greater the risk, even if there is no thaw.
6. Feels unsafe - the "seat of the pants" feeling of the experienced observer deserves respect.

Ref. Scottish Mountain Safety Group

Skiers are in greater risk than walkers. The lateral cutting of the skis easily releases unstable snow. If skiing off piste, ensure that you have experience or are with an experienced guide; use and SWITCH ON BEFORE YOU LEAVE avalanche transcievers and carry collapsible probes and shovels.

Direct descent or ascent is safer than traversing. Go one at a time and observe the progress of that person across the slope. Close up clothing and cover your mouth and nose with a scarft or other item. Belay if possible, although rarely possible on wide open slopes.

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If you are caught in an avalanche:

Defensive action is difficult although the following points can be helpful:

1. Try to delay departure by plunging an ice axe into the underside - this should help you to remain at the top of the slide.
2. Shout to other people so that they see you.
3. Try to run to the side or jump above the fracture.
4. If it is a hard slab, try to remain on the top of a block.
5. Get rid of gear, skis etc
6. Try to roll like a log out of the debris
7. Swimming motions can help, but may not.
8. As the avalanche slows, you may be able to get some purchase on the debris. Make a desperate effort to get to the surface while the snow is still moving or at least get a hand through.

If you are buried in an avalanche:

1. Keep one hand in front of your face and try to clear or maintain air space.
2. Try to maintain space for chest expansion by taking and holding a deep breath.
3. Try to avoid panic - conserve energy. Your companions are probably searching for you.

Avalanche Rescue

If you witness an avalanche burial:

1. Observe the victim's progress and if possible, mark the point of entry and point where they were last seen.
2. Check for further avalanche danger
3. Make a quick search of the debris surface - look for any signs of the vicitm, listen for any sounds and probe the most likely burial spots.
4. Make a systematic search probing the debris with axes or poles.
5. Send for help
6. Keep searching unti help arrives - Remember, you are the victim's only real chance of live rescue. Although survival chances decline rapidly with duration of burial, they do not reach zero for a long time.

If you are involved in an incident or witness an avalanche, the contact the SAIS as they keep records of avalanch occurences in Scotland and elsewhere in Britain:
SAIS Co-ordinator
Freepost Glenmore Lodge
Aviemore
Invernessshire
PH22 1BR.