AVALANCHES
Many of the most terrible accidents in the Alps have been due to
avalanches, and perhaps, as avalanches take place from different
causes and have various characteristics, according to whether they are
of ice, snow, or _débris_, some account of them may not be out of
place.
We may briefly classify them as follows:--
1. Ice avalanches, only met with on or near glaciers.
2. Dust avalanches, composed of very light, powdery snow.
3. Compact avalanches (_Grund_ or ground avalanches, as the
Germans call them), consisting of snow, earth, stones,
trees, and anything which the avalanche finds in its path.
These take place only in winter and spring, while the two
other kinds happen on the mountains at any season.
An ice avalanche is easily understood when it is borne in mind that a
glacier is always moving. When this river of ice comes to the edge of
a precipice, or tries to crawl down a very steep cliff, it splits
across and forms tottering crags of ice, which lean over more and more
till they lose their balance and go crashing down the slope. Some of
the ice is crushed to powder by its fall, yet many blocks generally
survive, and are occasionally heaped up in such huge masses below that
they form another glacier on a small scale. If a party of mountaineers
passes under a place overhung by threatening ice, they are in great
danger, though at early morning, before the sun has loosened the
frozen masses, the peril is less. Sometimes, too, if the distance to
be traversed is very short and the going quite easy, it is safe enough
to dash quickly across.
[Illustration: A TUNNEL 300 FEET LONG THROUGH AN AVALANCHE.
Tree trunks, etc., can be seen embedded in it.]
[Illustration: AN AVALANCHE NEAR BOUVERET, LAKE OF GENEVA.]
Dust avalanches occur when a heavy fall of light, powdery snow takes
place on frozen hillsides or ice-slopes, and so long as there is no
wind or disturbance, all remains quiet, and inexperienced people would
think there was no danger. But in reality dust avalanches are the most
to be feared of any, for they fall irregularly in unexpected places,
and their power is tremendous. While all seems calm and peaceful,
suddenly a puff of wind or the passage of an animal disturbs the
delicately-balanced masses, and then woe betide whoever is within
reach of this frightful engine of destruction. First, the snow begins
to slide gently down, then it gathers pace and volume, and even miles
away the thunder of its fall can be heard as it leaps from ledge to
ledge. Covered with a cloud of smoking, powdery dust, it is a
veritable Niagara of giant height, and as it descends towards the
forests, it carries with it whatever it finds in its path. Trees are
mown down with as much ease as the tender grass of spring. Houses are
lifted from the ground and tossed far away.
An avalanche is preceded by a blast even more destructive than the
masses of snow which it hurls along. As it advances with
ever-increasing rapidity the air in front is more and more compressed
as the avalanche rushes on with lightning-like speed behind it. The
wind sweeps everything before it, and many are the tales related by
those who have survived or witnessed a display of its power. On one
occasion more than a hundred houses were overwhelmed by a huge
avalanche at Saas (Prättigau, near Davos), and during the search
afterwards the rescue party found amidst the ruins a child lying
asleep and uninjured in his cradle, which had been blown to some
distance from his home, while close by stood a basket containing six
eggs, none of which were broken. I have myself seen a row of telegraph
posts in an Alpine valley in winter thrown flat on the ground by the
air preceding an enormous avalanche, which itself did not come within
300 yards of them. It is a very wonderful thing that persons buried
beneath an avalanche can sometimes hear every word spoken by a search
party, and yet not a sound that they utter reaches the ears of those
outside. A great deal of air is imprisoned between the particles of
snow, and so it is possible for those overwhelmed by an avalanche to
live inside it for hours. Cases have been known where a man, buried
not far below the surface, has been able to melt a hole to the outer
air with his breath, and eventually free himself from his icy prison.
On 18th January, 1885, enormous avalanches fell in some of the
mountainous districts of northern Italy, houses, cattle, crops, and
granaries being carried away, and many victims buried beneath the
ruins. Some touching episodes of wonderful escapes were related. "For
instance, at Riva, in the valley of Susa, a whole family, consisting
of an old woman of seventy, her two daughters, her four nieces, and a
child four months old, were buried with their house in the snow,
exposed apparently to certain death from cold and hunger. But the
soldiers of the Compagnie Alpine, hearing of the sad case, worked with
all their might and main to save them, and at last they were found and
brought out alive, the brave old grandmother insisting that the
children should be saved first, and then her daughters, saying that
their lives were more precious than her own." The soldiers, who worked
with a will above all praise, were obliged in several cases to
construct long galleries in the snow in order to reach the villages,
which were sometimes buried beneath 40 feet of snow.
Compact avalanches, though very terrible on account of their
frequently great size, can be more easily guarded against than dust
avalanches, because they always fall in well-defined channels. A
compact avalanche consists of snow, earth, stones, and trees, and
comes down in times of thaw. Many fall in early spring in Alpine
valleys, and though it is not unusual for them to come right across
high roads, the fatal accidents are comparatively few. The inhabitants
know that wherever, high up on the hills, there is a hollow which may
serve as a _reservoir_ or collecting-basin for the snow, and below
this a funnel or shoot, there an avalanche may be expected. Often they
take means to prevent one starting, for an avalanche, whose power is
irresistible when once it has begun to move quickly, is very easily
kept from mischief if it is not allowed a running start. The best of
all ways for preventing avalanches is to plant the gullies with trees,
but where this cannot be done, rows of stakes driven into the ground
will serve to hold up the snow, and where the hillside is extremely
steep, and much damage would be caused if an avalanche fell, stone
walls are built one above another to keep the soil and the snow
together, very much as we see on precipitous banks overlooking English
railways.
The driving roads over Alpine passes are in places exposed to
avalanches in winter. At the worst spots galleries of stone are built,
through which the sleighs can pass in perfect safety, and if an
avalanche fell while they were inside it would pass harmlessly over
their heads. On the Albula Pass, in Switzerland, as soon as the
avalanches come down, tunnels are cut in the snow through them, and
are in constant use till early summer.
Occasionally houses or churches are built in the very path of an
avalanche. A V-shaped wall, called an avalanche-breaker, is put
behind, and this cuts the snowy stream in two parts, which passes on
harmlessly on either side of the building. Sometimes avalanche-breakers
of snow, hardened into ice by throwing water over them, are constructed
behind barns which have been put in exposed places.
In order that an avalanche may get up speed enough to commence its
swift career, the slope the snow rests on where it starts must be at
an angle of from 30° to 35° at least.