Snow safety

Avalanches are a danger of mountain areas. At winter resorts the risk of avalanches is monitored and warnings given when the risk is high.

Avalanches are not an abnormality; steep slopes can hold only so much snow, and the excess volumes will come down as avalanches. The problem is that snow is sticky, so it needs some triggering to come down, and some snow coming down can be the triggering event for the rest. Sometimes the original trigging event is the sun warming the snow, sometimes some more snowfall, sometimes other natural events, often a human. The risk for avalanches depends also on the structure of the snow. Layering can facilitate upper layers gliding down on lower layers, or a middle layer can collapse (progressing over a large area) causing the upper layers to glide down.

Most accidents happen when people go downhill off piste – the risk of being a victim of a spontaneous avalanche is much smaller than the risk of actually causing an avalanche (or getting in the way of one started by others). When the risk is high, also spontaneous avalanches will still happen.

In addition to off piste skiing, other disturbances may start an avalanche e.g. driving a snowmobile.

If going off piste despite warnings 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 would you be unlucky.

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. If you go back-country skiing or off-piste skiing, learn how to gauge the steepness. If in doubt, don't do it. 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. Avalanche hazard depends on local conditions, ask locals for advice.

Those moving in terrain prone to avalanches can reduce risks by choosing their path: avoiding weak areas where it is easy to cause an avalanche, and avoiding 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!

Where an avalanche is possible, 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 call for help, and start searching or give first aid. 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.

Snow covers features of the landscape, including clefts, streams and other dangers. Make sure you know where you are to avoid them, rather than relying on what you see. On glaciers rope is used to stop somebody falling into a cleft, but this requires some know-how, for best protection and to avoid everybody being dragged into it. Do not go near the rim of a drop, as the snow may extend further than the cliff, or may collapse.

On boulder fields, snow covers the gaps, but may not support your weight. This is especially a problem when the snow cover is thin. Of course, if there are real clefts, snow bridges may or may not collapse even in thick snow.

In areas with significant snow cover, going near trees can be dangerous. The loose snow arround the tree might trap people falling in, leading to suffocation.

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 the exposure. Treatment is covering the eyes to let them rest, and possibly pain relief (remove contact lenses). Trekking as 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). The eyes usually recover in one to three days.

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