GLACIERS--AVALANCHES--MILITARY SKI-ING
A legacy from the past--The formation of glaciers and
atmospheric conditions--Forests and glaciers--Our deficient
knowledge--The upper ice and snow reservoirs--What is the
annual snowfall and what becomes of it?--How glaciers
may be classed--Mechanical forces at work--Moraines and
_séracs_--Avalanches--Periodic avalanches--Accidental
avalanches--The general causes--The statics of snow--What
happens to winter snow--_Strata_--How steep slopes may be
classed--Excusable ignorance of strangers to the Alps--Those
who write glibly in home magazines--Unsafe slopes--Avalanches
when running across slopes--The probing-stick--Avalanche
runs--Military ski-ing--The St. Gothard and St. Maurice
districts--Military raids in the High Alps--The glaciers as
military highways--Riflemen on foot as against marksmen on ski.
On the whole the Mid-European glaciers are a legacy from a distant past.
Their former size and extent corresponded to general meteorological
conditions which have long ceased to exist.
They might--and no doubt did--alternately increase and decrease within
historical times. They nevertheless must be viewed as a bequest, a kind
of heirloom coming from a prehistoric ancestry. They are the survival
of a phenomenon which, in its former compass and intensity, is no longer
compatible with the meteorological _régime_ of Central Europe.
The temperature most suitable for the formation of ice in nature is the
temperature which remains the most steadily around the freezing-point of
water. Extremes of temperature are not favourable to the formation of
snow, which is the form in which water generally passes into glacier ice.
It stands to reason that the oftener the atmosphere can be saturated
with moisture in circumstances which allow a frequent discharge in the
shape of snow falling upon surfaces that are iced--or such as will retain
the snow, assuring the transformation of some of it, ultimately, into
ice--the more will the thermometer readings show a temperature rising and
falling only moderately above and below the freezing-point of natural
water. There is no use in further emphasising this obvious truth.
Everybody will understand that moisture formed in hot tracts of the
atmosphere has little chance of being converted into snow, and that,
while a warm atmosphere may generate water--destructive of ice and snow
surfaces--a very cold atmosphere cannot assist in glacier formation--on
high land, at any rate--for want of vapours to condensate and
precipitate, and for want of water masses to consolidate.
It follows that, within historical times, the Alpine glaciers have
undergone variations according to changes in the quantity of moisture
contained in the atmosphere, theirs being such altitudes and such
climatic conditions as might allow the Centigrade thermometer to swing
pretty steadily between 20 degrees above zero and 20 degrees under, all
the year round and in the course of a day.
These conditions existed more fully in periods when the Alps were
well wooded. Such a period pre-existed the first historical epoch of
Switzerland. Under the Romans, say from 50 B.C. to 500 A.D., this first
historical epoch was marked by the wholesale destruction of forests--the
usual price to be paid for civilisation--and the glacier world retreated
in a ratio commensurate with the process of denudation.
Then came the Early Middle Ages, which for about six or seven hundred
years show a distinct retrogression in Swiss civilisation. The glaciers
now regained some of the ground they had lost, because the wooded
surface, which is the most favourable to the condensation of moisture,
underwent a considerable increase.
In modern times the forest area has again undergone such shrinkage that
it has reached the minimum when artificial means have to be devised for
its preservation. Glaciers have gone back again.
We may therefore define glaciers as ice and snow reservoirs formed
under prehistoric conditions which no longer exist. They are kept alive
on a reduced scale, in a direct ratio to the moisture yielded by the
atmosphere as often as it is conveniently a little above and a little
below the freezing-point of natural water.
[Illustration: THE SONADON GLACIER.
To face p. 266.]
Our knowledge of the glacier world in its formative processes is as yet
extremely deficient. What proportion of the year’s snowfall--within
the glacier region--is actually converted into ice? What proportion
melts away on the surface and passes directly into water, to be carried
away, carrying along with itself some of the ice? What proportion is, by
sublimation and evaporation, returned to the atmosphere, to become again
the toy of winds, in the shape of snow or rain-clouds, never feeding the
glacier at all on which it first fell?
On the other hand, who can tell how much ice is formed on the glacier
surface by the direct absorption of the air moisture collecting upon such
a condensator? And would it be alien to our subject to ask what effect
may have on the present glaciers the loss of pressure consequent upon the
enormous reduction in bulk and height which they have undergone? Is the
glacier ice formed under the present rate of pressure capable of offering
anything like the same resistance to disintegration as its prehistoric
congener? What are its powers of self-preservation under the vastly
inferior pressure which it experiences in the very places in which ice
was once packed to a height and in a bulk we should not like to express
in figures, even if we possessed competent data?
The broad fact seems to be that as much snow as falls on the glaciers
throughout the year is taken back into the atmosphere, and that the snow
congealed and fixed in the upper basins is as nothing compared with the
quantity of water that evaporates or runs away at the nether end of the
mass every summer. What is the capacity of the ice-forming _firn_ of the
Aletsch basin compared to the extent of its melting surface? And how much
snow does the _firn_ receive every year from the atmosphere? And how much
of that snow is incorporated?
There are now so many approaches to the glacier world of Switzerland that
it should be easy to determine, at the outlet of a few typical glaciers,
the amount of water thaw conveys to the valleys below. According to the
season, it is quite easy to distinguish between rain-water, water from
springs, and glacier water. Such observations would lead to results
reciprocally verificatory.
My provisional conclusions are that:--
1. The snow falling on the Swiss glaciers is a mere fraction of the
quantity wanted to assure their stability.
2. The average snowfall of any year returns to the atmosphere.
3. The source and means of congealation are not proportionate to the
exigencies of ice-formation, even for the maintenance of the _status quo_.
4. The glaciers, regressing as they are now doing, are not being
replenished to any appreciable extent from the so-called everlasting snow
storage, and certainly not at all in proportion to their wastage.
In other words:--
1. In a number of years X the whole glacier mass of Switzerland is
dissolved and reconstituted in proportions that are less than in the
preceding X period.
2. The snow fallen during the period X--if present conditions are
accepted--is pumped back by the atmosphere during the same period.
3. The quantity of water flowing from those glaciers in the time is
greater than the means of glacier recuperation.
4. Yet the glaciers do recuperate in some proportion to their former size.
5. Consequently the condensation and congealing of atmospheric moisture
must be much more effective an agent than hitherto suspected, for there
is no reason why, upwards of 9,000 feet, snow should be less liable to
thaw on ice than on rock surfaces. Rock and ice areas are conterminous.
Glaciers may be classed, according to their physical conformation, under
the following headings:--
1. _Circular Schema._--They are then enclosed in a basin more or less
irregular in shape. The enclosed mass of ice remains concave as long
as it is lower than the rim of the basin. But it becomes convex in the
centre when it rises above the horizontal line joining the opposite rims
of the basin.
2. _Longitudinal Schema._--A. On the flat, or approximately, those
glaciers show convex surfaces.
B. When resting on a slope they are concave in the upper basin, which
feeds them and become convex as they reach lower and wider channels.
This second type is the normal glacier type.
A diagram or section of the convex portion of the glacier--an ideal
diagram of course--would show the mechanical and static forces at work
in a fan-shaped formation radiating from a point on the not geometrical,
but mechanical, centre line of the glacier, this point being situated on
its bed, where the side-pressures converge and annihilate each other’s
progress.
From this point the bottom ice works its way up to the
melting-surface--but obliquely, being the whole time carried down by the
slope--and throws up side moraines and one or several spinal moraines in
the process. The spinal moraines always rest on pure ice. The ice seams
have been thrown up from the inside.
Crevasses may occur in an outward, open, surface-formation, as in
_séracs_ when they are grouped together, or else they are the result of
accidental deflections or temporary oppositions in mechanical and static
forces at work in the ice.
We said a while ago that there was no reason why, at the height of 9,000
feet and upwards, snow accumulations should be more stable and constant
on ice surfaces than on rock. The cause for this is simply that rock and
ice are too near to each other and at altitudes too closely alike for
serious differences in temperature.
Let us now pass to the matter of avalanches. If snow is utterly unstable
on rock, so it is on ice. Rock and ice constitute an avalanche area,
which in winter extends down so as to include all steepnesses on which
snow may lodge and whence it may be dislodged by the forces of Nature.
Avalanches may be periodic or accidental.
A periodic avalanche is the kind that comes down regularly at a known
spot, each time sufficient cause is brought into play. Maps of the Alps
exist on which those periodic avalanches are noted. Almost every Alpine
village has a periodic avalanche on its territory. The peasants know
when and where to expect it. It is called _the_ avalanche of so and so,
and your business is to find out, each time you propose going out on an
expedition, whether it has come down or not, and all about it.
An accidental avalanche arises from general causes taking effect
fortuitously.
The general causes are:--
1. A quick rise in the temperature.
2. A sudden fall of the barometer.
3. A change of wind.
4. A fresh fall of snow.
5. Slopes of a certain angle and conformation.
6. Differences of density, moisture, and consistency in superposed layers
of snow.
A study of the statics of snow is the royal road to the understanding of
avalanches.
On a slope snow is in a state of more or less pronounced instability.
A first fall of dry winter snow upon dry slopes is extremely avalanchy,
provided it be heavy enough. If it be a fall of wet snow on a porous
surface--that is, neither frozen ground nor hard rock--the snow will as
it were flop together in a slithering mass, but is not likely to form
itself into a dangerous compact floe.
As soon as a second fall of snow comes to adhere to what is left of
the first, it may happen that the second layer does not get properly
welded to the first. The thoroughness of the attachment depends on the
adhesiveness of the snow and on weather conditions. A foundation is
therefore laid for the slipping of the new snow upon the surface of the
old.
In the course of the winter the snow gets consolidated in one mass, but
the process takes each time from two to three days, during which caution
is necessary. A homogeneous layer of snow, hardened from the outside by
wind pressure, or freezing over after a slight thaw, may then break up
into slabs which slide down on the older snow, should one with ski, or in
any other fashion, cut that snow away--at any point--from its support.
A _stratum_ of snow on a steep open slope is like a piece of cardboard
balanced on your finger. There is a limit to the inclination of the
cardboard beyond which it will slip off its pivot. So it is with snow.
Newly fallen snow soon ceases to be an amorphous mealy mass. Its bottom
layer models itself on the surface on which it lies and, if turned over,
would show that surface _en relief_. The next _stratum_ adheres to the
first more or less, and finds points of support for itself, such as rocks
protruding through the first _stratum_, trees, shrubs, fences, dykes, &c.
Every ensuing layer is less shored up than the one beneath. Should there
be a rise in the temperature, an increase of moisture brought on by a
change in the wind, the snow becomes heavier and may start down; as a dry
sponge on an inclined board, gradually absorbing water, must slide down
when the inclination of the board and the quantity of water reach the
critical point.
Our illustration from the cardboard balanced on a finger-tip, and from
the sponge on an inclined plane, makes it clear that it is impossible to
state at what definite angle the equipoise of a snow _stratum_ must be
lost or is sure to be kept. That angle depends on the finger-tip, on the
weight and size of the cardboard, on the sponginess of the sponge, on the
slipperiness of the plank, on your holding your breath, or mischievously
blowing upon the suspended object, &c. When about to capsize, the
cardboard may meet some external point of support, such as your raised
hand, which, in the case of the snow _stratum_, would be a pre-existing
prop and maintain an otherwise impossible stability.
A fall in the barometer almost always means an increase of moisture which
is unfavourable to the steadiness of old snow. A dry, hot wind--such
as _foehn_--is worse, because its heat penetrates the snow to the very
bottom and sets it moving throughout its thickness.
New snow is dangerous till it has had time to set--that is, for two or
three days.
Runners are generally agreed to call steep the slopes on which avalanches
may occur.
Steep slopes are either concave, convex, or straight.
They are concave when the slopes converge towards a central dividing line
lying deeper, to the eye, than their sides; these are scooped out of the
hill.
Concave slopes are:--
1. Funnel-shaped, when the funnel may be either upright or upside down.
If it is upright, the wide opening is at the top. If the slope affect the
shape of a reversed funnel, it opens out at the bottom, but it may also
be choked up in the middle, opening up again above, like an hour-glass.
Concave slopes are quite safe if strewn with rocks, overgrown with
shrubs, or wooded. They are untrustworthy if the sides have been planed
down, as it were, by what we may call natural wear and tear.
The reader sees here how the indications of nature may be properly
interpreted. It is quite clear that a gorge which is a natural shrubbery,
for instance, has not been visited by avalanches for a time at least as
long as the plants took to grow to their visible size.
The trouble here is that Londoners, for example, having to deal with
a gorge which they have not seen free from snow, cannot be expected
to tell whether it is safe or not. The local man alone--a permanent
eye-witness--possesses the information required, and failing actual
acquaintance with the place, a practised mountaineer alone can form an
opinion.
Slopes are convex when the centre line, to the eye, rises above their
sides. These stand out from the hill, diverging from its top.
Convex slopes should be ascended and descended along the dividing-line.
This line, as a dominating centre, will always be sought out by the good
High Alp runner. It is both the shortest and surest path from point to
point, and great is the delight to see at one’s feet the avalanche runs.
If the coping is occupied by rocks, the runner will keep to the snow near
to the rocks, but he has no business there at all if the rock ridge is
considerable enough to harbour avalanche snow. A practised eye sees at
a glance whether snow in excess of the capacity of the gullies is still
suspended above the runner’s head, or whether it lies in cakes and balls
at his feet.
Here again the native will know. It would help you but little to say
that you have found him out to be an unconventional runner, that he is
slow and not at all the handy man you expected. However much you may
be entitled to fancy yourself or your skill as a conventional runner,
he is the better mountaineer, and should your conventional style leave
you in the lurch, he is the fellow to do the right thing for you. It is
then just as well to remember, when one writes in a home magazine, that,
on the spot, one was the incompetent person of the party. “He of the
ice-axe,” your guide, would do that second job, too, far better than you,
if the use of the pen in that periodical was not inconsistent with his
inferior social standing and extremely imperfect education.
The straight slope is the slope on which every point is on the same plane
as another. These slopes are safe when they abut on to ground which
obviously is locally viewed as not exposed to avalanches: vineyards,
potato-fields, woods, hay-lofts, &c.
They are unsafe when undermined by a trickle of water--springs, for
instance--and when the layer of snow next to the ground has melted
away without affecting the upper layers; or when the slope rests upon
a protruding ledge over which it bulges out; or when it is cut by
longitudinal ribs of blown-out snow which you may break open unawares,
letting out the mealy contents upon yourself.
All slopes may be traversed--that is, you may run across them obliquely.
When about to traverse, look to the foot of the slope, and then look to
the head of the slope. If all is right, sound the snow with your stick
and glance into the conic hole made by it. In time you will acquire
an ability to tell by the feel whether the snow is mealy, or set, or
damp, and how many layers your stick breaks through before coming to a
standstill upon frozen ground, or against rock, or before sinking into
the hollow space that may exist between the nethermost layer of snow and
the soil.
Of course, all this you cannot do with a short, light bamboo,
conveniently fitted with an osier disk within three inches of the point!
To go forth so simply equipped means that you are leaving your brains at
home on that day--a thing I often do myself--but, I assure you, only when
out for mere play!
A stick that cannot be used on an emergency either as an anchor or
as a sounding-line to take castings with, is a poor friend. It is
instructive to look curiously into the hole made by one’s stick. What
would be the use of a sport practised simply as an opportunity for being
scatter-brained with impunity, so long as luck lasts?
On the hill-side, slopes--concave, convex, and straight--are joined
to one another by linking surfaces varying in shape and inclination,
but of too limited a development and too irregular a build to offer
to avalanches any opportunity of spreading over them; or else slopes
are separated from one another by breaks in the ski-ing surface, such
as ravines. In these, masses of snow gather most conveniently. The
longitudinal gaps opened up by landslips, torrent beds, or even only the
slides made by wood-cutters through forest and pasture land to launch
felled trees into the valley, are very distinctly avalanche runs. Efforts
are now being made to bar such runs by artificial plantations, fencings,
or walls.
The centre of military ski-running in Switzerland is in the environment
of the permanent Alpine forts which defend the St. Gothard knot of
trans-Alpine and sub-Alpine (railway tunnels) lines of communication
from Italy into Switzerland, betwixt the sources of the Reuss, Ticino,
Rhine, and Rhône. Another centre is situated in the Rhône Valley, at the
point where a natural defile bars the line of communication between the
upper Rhône Valley, at St. Maurice, and the Lake of Geneva, commanding to
some extent the roads converging upon that point from Northern Savoy and
leading to it from Italy over the St. Bernard pass or through the Simplon
tunnel.
The opening of the Loetschberg tunnel on the new short railway route
between Berne and Milan will, however, make it advisable to erect some
kind of additional works about Brigue.
The Gothard and St. Maurice guards use ski, and ski-ing detachments are
about to be attached to the brigades of mountain infantry located all
along the range of the Alps.
Many junior Swiss officers have made themselves proficient in the
new mountaineering by joining military ski courses. Military patrol
competitions meet with much favour at the large ski gatherings.
For all that, the adaptability of ski to military purposes is not very
great in the High Alps. Still they are called upon to become quite a
consideration in border defence or attack. Small troops of skiers could
pass easily from one side to another of the Alps, occupying flying
posts of observation, and even raiding places where the defence would
have preferred to put its own outposts, had it not allowed itself to be
forestalled. The Alpine Club huts afford sufficient shelter for summarily
equipped detachments numbering from twenty to forty men.
Bodies of troops crossing the Alps in winter by the passes available for
considerable military transport would enjoy a distinct advantage if the
outlet of the passes had been previously occupied by half or quarter
companies of bold ski-ing infantry pouncing, as it were, from the skies
upon small snow-bound places with summer hotels ready for occupation and
better stocked with means of subsistence than one would at first be led
to expect. In some Swiss Alpine villages particularly, large supplies
are often accumulated for the next summer season, and in others much
merchandise is stored up to accommodate the Italian smugglers whose
“exports” from Switzerland are all the year round a source of profit to
their purveyors.
[Illustration: AT THE FOOT OF COL D’HÉRENS.
To face p. 279.]
Swiss ski-runners, by expeditions like my own, have proved that the
glaciers may be used, within strict limits, as highways for rapid and
unexpected military movements. Till now it was assumed that crevasses,
iced rocks, and piles upon piles of corniced snow would offer insuperable
obstacles to any military action. But the crevasses--as the reader now
knows--are most hermetically sealed. To the expert and wary runner the
snow opposes no greater barrier than to the pedestrian in summer. Does
not history teach how foot-soldiers have _en masse_, with artillery and
baggage, been moved to and fro across the Alps? Henceforth, military
runners may be trusted to scour the ranges, undetected, cutting
communications one day at the St. Bernard hospice and opening fire three
days later upon the Simplon hospice, hanging alternately on the only two
military roads joining Switzerland and Italy between the St. Gothard
forts and French Savoy.
Those raiding parties could be followed by considerable parties of
transport men, carrying fresh ammunition and supplies.
Such places as Bourg St. Pierre, Fionnay, Arolla, Zinal, Zermatt, Saas,
would be, from the Italian point of view, worth seizing and manning
at the outset of a winter campaign. From the point of view of a Swiss
advance aiming at laying hold of the southern outlets of the military
roads before the enemy could move up its advanced columns, those places
would be valuable bases for the auxiliary services waiting upon the
raiding detachments.
Hitherto forces crossing the Alps in winter could expect to be safe
from attack on their flanks. Henceforth there might be a very different
story to relate. The few experiments hitherto made show that an attack
by skirmishing ski-runners upon columns on the march could not be met
by dispatching against them rifle-men on foot. Across country a man on
foot will take about an hour--on flat ground--to cover a distance which
an average runner on 2 feet of snow will overtake in one-quarter of the
time. Uphill, the advantage of the ski-man is still more marked, and he
may continue much longer. Moreover, he disposes of the whole hill-side,
and may take cover exactly as he pleases, by crossing snows over which
the pedestrian can make no progress at all, and becomes a most convenient
mark. The ski-runner may force his pursuer into any ground he chooses.
For a force developed across an expanse of snow, it is extraordinarily
difficult to carry out an attack upon ski-runners firing from behind
shelter. They occupy probably the higher position, and their field of
vision is absolutely uninterrupted. Rushes from point to point across the
zone of fire are quite out of the question in the absence of any screen
whatsoever.
As for the rifle-men or sharpshooters on foot in charge of a village,
sallying forth to dislodge a party of runners firing into their
position and then withdrawing out of the reach of adversaries firing
from opened-up tracks, spaces, or houses, the idea is not plausible. A
dismounted horse-soldier might just as well advance sword in hand against
marksmen manning rifle-pits, or an infantry man, short of ammunition,
might just as well trust his bayonet to reach a horseman galloping away
out of sight.
Ski-ing patrols of mountain infantry with portable machine-guns could
defend such passes as the Furka or the Grimsel against forces pushed
forward in vastly superior numbers.
[Illustration]