Snow safety Voyage Tips and guide

Snow safety includes precautions in snowy terrain, beyond what is needed for cold weather.

Snow covers features of the landscape, making it impossible to see clefts, streams and other dangers underneath.

Snow bridges form across streams, rocks, boulder fields, gaps in the ground or places where snow melts from underneath. The surface snow covering these up may not support your weight, collapse under your feet, and trap or injure you. This can occur even in thick snow.

Tree wells form around evergreen trees, where the branch canopy prevents snow from accumulating close to the tree. If you step too close to a tree, the loose snow around the tree might give way and trap you, leading to suffocation.

Cornices form along cliffs, thick snowbanks that sometimes extend past the edge of the rim. Do not go near the rim of a steep drop, as a cornice collapse could be catastrophic.

Glaciers form crevasses, cracks in the ice that can swallow a person. Groups traveling across ice typically use a rope, so that if one person falls in, the others have a chance of stopping the fall and pulling them back up. This requires a great deal of skill to pull off.

Avalanches are a danger of mountain areas. Steep slopes can hold only so much snow before excess volume will release and come down as a wave of snow.

At winter resorts the risk of avalanches is monitored and warnings given when the risk is high. It is exceeding rare for avalanches to occur in-bounds. Most accidents happen when people go downhill off piste. In addition to skiing, other disturbances may start an avalanche e.g. driving a snowmobile. Most deadly avalanches are human-triggered, on days with predictably high risk, on unmanaged terrain.

Avalanches start on slopes steeper than 30° (50%) grade, roughly the same as traditional, moderately pitched roofs in Norway and the rest of Northern Europe. Once started, the avalanche can run down 20–30° slopes, and some distance over level terrain or even uphill. An avalanche never reaches further than 20° from the starting point.

If going into avalanche terrain, you should know how to evaluate the current risks, avoid them where possible, and have safety equipment and know-how to increase your survival chances.

• Learn how to gauge the steepness of a slope. If in doubt, don't do it.
• Choose your path carefully: avoid weak areas where it is easy to cause an avalanche, and avoid areas where getting hit is easy or especially dangerous because of likeliness of getting trapped, hurt by obstacles, swept over cliffs etc. Narrow river valleys or gullies can be "avalanche traps" and even small avalanches can be fatal. Wind-swept ridges with little snow are among the safest places to move – but watch out for the cornices!
• A group should move one by one, so that only one is likely to be hit if it does occur, leaving the others ready to help. A tight group of skiers is also more likely to cause an avalanche than several individual ones. Ensure good communication, so that everybody is aware of and understands decisions made.
• Avalanche hazard depends on local conditions, ask locals for advice.

Snow is sticky, so it needs a trigger to come down. Once one patch starts to fall, it can be the triggering event for the rest of the slope. Triggers can include:

• warming from the sun or air
• new snowfall (or rainfall)
• wind loading snow onto a surface
• a cornice collapse
• movement from a human. The risk of a spontaneous avalanche is smaller than the risk of a self-caused avalanche (or getting in the way of one started by others).

The risk also depends on the structure of the snow. When a layer of loose snow forms between two consolidated slabs, an upper layer can glide down on a lower layer. A middle layer can also collapse (progressing over a large area) causing the upper layers to glide down.

• Warm clothing, to delay hypothermia if buried
• Avalanche transceiver (beacon): sends signals at regular intervals, enabling locating you under the snow; use purpose-made modern ones and get at least some training in how to use them
• Collapsible probe
• Sturdy shovel: avalanche debris is dense and hard, even when the snow was powder before

(Avalanche cords are obsolete.)

Get away from the path of the avalanche! Have a wide stand, ski in a 45° angle to the slope and aim for high ground.

If you are caught, get rid of skis, poles and large packs. Fight for the surface and create an air pocket in front of your face. When the avalanche stops, the snow will suddenly freeze, making movement nearly impossible. Stay calm and wait for rescue. If you are very close to the surface you may be able to get a hand through the snow, but this is unlikely.

If your company is hit, work quickly to find anyone buried; after 10 minutes, odds of survival start to plummet. Assess whether there is a risk of further avalanches and take safety measures as appropriate. Check how many are missing and where they were last seen. Call for help. Check any clues about where they might be buried, mark the position. Plan how to search and whether some areas should be prioritized. Be systematic without unnecessarily losing time.

Use a beacon to locate a buried victim. The signal should be quite reliably received from about 20 m. Switch your beacon to 'receive' instead of 'transmit', and follow the indicator on the screen; they are designed to be intuitive while panicking, but will take you on an arc instead of a straight line. When you get with 1 meter of the victim's beacon, pull out and assemble your probe, and begin probing the snow for buried objects, in a spiral or other consistent pattern. Dig out a "V" downhill from the victim, with a height 1–2 times the depth depending on terrain steepness. Digging snow is time-consuming and exhausting; if possible, switch out with another rescuer every few minutes.

Performing these steps efficiently under pressure requires training and practice. If you will be entering avalanche terrain, consider taking a formal education course.

• American Institute for Avalanche Research and Education (AIARE) is the standard curriculum for the United States and Canada, and is increasingly offered in Europe as well.

Thick snowfall can bring visibility down to a few metres. Even light snowfall considerably lessens visibility, so that distant landmarks can get out of sight. Wind-drift lowers visibility in a similar manner near the ground.

See also: Eye care

Snow blindness is a variant of ultraviolet keratitis, caused by extreme levels of ultraviolet light reflected by snow, similar to sunburn. Sunglasses with good UV protection are the very least you should do to protect yourself. Emergency lenses can be made by cutting slits in dark fabric or tape folded back onto itself.

Symptoms usually come hours after exposure. Treatment is covering the eyes to let them rest, and possibly pain relief (remove contact lenses). Trekking blind is not nice, but may be better than worsening the condition. Consider stopping as soon as you can at safe shelter to recover (with eyes covered). Eyes usually recover in one to three days.

• Ice safety
• Severe weather
• Winter driving
• Winter sport