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This second part of the Beginners Guide to Alpine Mountaineering deals travel on glaciers, how to deal with crevasses, and avalanches.

 


A Beginner's Guide to Alpine Mountaineering – Part 2

Part 2 of Rob Collister's guide to alpine mountaineering looks at glaciers, crevasses, glacier travel and avalanches.

If you've missed Part 1 (Alpine scale, altitude, weather and descents) go back there now.

Glaciers and glacier travel
cravasse travelIt is glaciation, cloaking the mountains in snow and ice and splintering the rock into fantastic shapes through the freezing and thawing of water in cracks, that makes Alpine mountains so spectacular, exciting and of a siren beauty. Glaciers are the bodies of permanent snow, hardened by time and pressure into ice, that flow out of the mountains. They are fed by the heavy snowfall of winter and melt in the warm temperatures of summer. When the rate of melt is greater than the natural rate of advance due to gravity, the glacier is said to be retreating.

For 150 years the glaciers of the Alps, and indeed of everywhere except Antarctica, have been retreating, growing steadily smaller and becoming covered with rock or moraine, that falls on to the ice from the surrounding mountainsides. A moraine-covered glacier is in effect a rubbish tip of the mountains, and about as much fun to walk on. As few can fail to be aware, that process has speeded up dramatically in the last 30 years, radically altering many climbs.

Crevasses
Glacier ice is a plastic substance. It is soft enough to flow downhill, but stiff enough to crack open when stressed. Such stress occurs on the outside of a bend, for example, or whenever there is a steepening of the valley floor, or sometimes at the sides, simply because friction is causing the ice to flow slower than in the centre. In all these cases, the glacier will split open to form crevasses. These can be anything from an inch to fifty yards across. The smaller ones are usually the nastiest because less obvious. Glaciologists tell us that crevasses cannot form to a depth greater than 150 ft, but there is scant consolation in that.

In summer, the lower parts of most glaciers, when not covered with moraine, become bare of snow, revealing so called dry ice. Here crevasses are quite without malice and provide useful places to practise ice-climbing and rescue techniques. Higher up the mountain, however, they become masked by snow and a very different proposition. Immediately in front of you a crevasse may be invisible, but to the right or left a faint dimpling of the surface is often discernible, and it may prove to be the continuation of an open hole some distance away. In winter, or after fresh snow, these signs are hidden and great care is needed.

Glaciers are probably at their safest in Spring when there is still a lot of snow about but freeze/thaw is strengthening the bridges. In summer, crevasses are usually safe early in the morning when the snow is frozen hard, but by the afternoon it will have softened, and the bridges will be in a precarious state. As the season goes on, crevasses become increasingly open. By the end of August, glaciers and icefalls which were straightforward ski runs in April can be all but impassable.

It is a good rule always to rope up, even on a well-tracked glacier, unless you know from personal experience that there are no crevasses. Tracks in the snow or other parties wandering about un-roped are no guarantees that the glacier is safe. If hollow, probe it with your axe (easier if you have one of a sensible length, say 55–65 cms, rather than a pterodactyl) or a ski-stick. If your axe goes straight through, or the bridge collapses into the depths, try again elsewhere! It is not unusual to have to weave back and forth across a glacier, crossing or jumping each individual crack at its safest point. Late in the season, the only bridges remaining may be wildly improbably cantilevers of dripping ice. Often they are stronger than they look, but take no chances. Arrange a strong belay and cross on all fours to spread your weight as much as possible. (For constructing snow anchors, see The Handbook of Climbing, Fyffe & Peter.)

Crevasses, what happens when you fall?
Sooner or later, however, you will go through a crevasse whose existence you never suspected. Whether you plunge to the bottom, find yourself dangling at the end of a rope contemplating a bright circle of daylight somewhere above you, or merely feel your legs kicking in space while icicles tinkle far below, will depend entirely on your partner. The key to safe travel on glaciers is a tight rope at all times. Coils held in the hand will only increase the distance of a fall and the difficulty of stopping it. The most effective way of checking a fall is to throw yourself onto the snow in a self-arrest position. Body weight, combined with the friction of the rope biting into the lip, are normally sufficient – but only if there is no slack rope. It all happens very quickly and there are no substitutes for alertness, quick reactions, and a tight rope.

Admittedly, that is easier said than done at the end of a long, tiring day and on a glacier there is definitely safety in numbers. In a party of three or more, 8–10 metres of rope between climbers will suffice, with spare rope carried around the shoulders and tied off. If anyone falls, it will usually be quickest to haul them out from the top, either with a straight heave if there are plenty of hands available, or by improvising a pulley-hoist. However it will often be necessary to drop the victim another end of rope first and arrange this over a rucksack at the lip so that the rope does not bite into the snow.

The more usual, and the more hazardous situation is two climbers roped together. Here, it is always possible that one will drag the other into the same hole. To reduce the chance of this happening, a longer distance between climbers – 12 to 15 metres – is advisable. When climbing as a pair, it is essential that you can both prusik efficiently, since even with the most elaborate improvised hoists it is extremely difficult, and may prove impossible, for one person to hoist another when so much friction is involved. Little gadgets like a Ropeman, a Tibloc or a Petzl pulley can all help, but in general prusik knots or similar but more efficient variations, work quite well enough.

Whatever the temperature on the surface – and the combination of ultra-violet radiation and reflected glare from the snow can be quite literally scorching to skin and eyes without protective cream, lip-salve and dark glasses – the inside of a crevasse is a bitterly cold place. Snow is, moreover, highly abrasive. It is worth always wearing gloves or mitts on snow, and preferably a long-sleeved shirt.

Avalanches in alpine mountaineering
avalancheIf crevasses are an ever-present danger in summer alpinism, avalanches are perhaps less of a hazard than at other times of the year. The greatest danger is from ice-avalanches. When a glacier flows over a projection or rock hard enough to withstand the crushing, grinding weight of ice above it, be it high up on the side of a mountain or in the flow of a valley, the ice will split open into ice-cliffs or seracs, which are continually collapsing and changing shape as the ice behind presses inexorably forward. The dangers of working through an unstable icefall are usually obvious and when the instability is not great, they can be fun to climb, presenting a series of technical problems to overcome.

Not such an obvious hazard, and easily overlooked, are hanging glaciers poised hundreds, sometimes thousands of feet above. There are many approaches to routes, and even hut walks, that pass beneath such hanging masses of ice. Seracs seem more prone to collapse in the heat of the afternoon when melt water acts as a lubricant within cracks in the ice. Bonatti, on his frequent excursions to the Brenva Face and the Grand Pilier d'Angle on Mont Blanc, both of which are threatened by enormous seracs on the approach, used to carry a thermometer and did not bother to leave the hut unless the temperature at night was well below freezing. That he is still alive seems to justify his caution.

Nonetheless, seracs can and do fall at all times of day and night and at all times of the year; gravity will always have its way in the end. The best policy is always to look above you before stopping for a break, and to accelerate whenever you are in the vicinity of hanging ice, even if you are plodding wearily along much-used descent routes like the Nantillons or Violettes glaciers.

Snow, as opposed to ice, avalanches are less common in summer. Nonetheless, after prolonged bad weather, conditions will always be potentially dangerous for at least 24 hours, especially on lee slopes where windslab can form. Wet snow avalanches can occur almost anywhere in the heat of the afternoon, though fortunately they usually don't. A layer of snow lying on ice becomes so saturated with water that it suddenly slides away with a hiss, even on easy-angled slopes. The depth may not be great, but it will still knock you off your feet, and if there is steep ground below, the result could be fatal. Moral – try to avoid long, open slopes facing south or west in the middle of the afternoon.

Part 3: Mountain huts, gear and trip planning >>

Text © Rob Collister and travel-quest 2006, all photos © Rob Collister 2006

FACT FILE
Rob Collister is available for mountaineering guiding trips in the Alps, including glacier journeys, introduction to Alpine climbing, classic climbs and more serious one-to-one Alpine ascents, Rob is a qualified Mountain Guide (IFMGA/UIAGM).

Part 3 of A Beginners Guide to Alpine Mountaineering is now available and discusses mountain huts, alpine mountaineering gear, trip planning and selecting the right climbing grade.