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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.
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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
It 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 5565 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, 810 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
If 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. |
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