CHAPTER IX

MOUNTAINEERING ON SKI

BY ARNOLD LUNN

Winter mountaineering may be said to date from Mr. Moore’s crossing of

the Strahlegg and Finsteraarjoch Passes in January 1865. The first big

peak to be climbed in winter was the Wetterhorn, which was ascended

in 1874 by the Rev. W. A. B. Coolidge and Miss Brevort; a few days

later this party climbed the Jungfrau. These brilliant expeditions

set a fashion which was, however, only followed by a select company

of mountaineers, among whom a place of honour must be given to Mrs.

Le Blonde. It was not until Paulcke crossed the Oberland at the end

of 1897 on the ski that winter mountaineering began to be a popular

sport. To wade up a big peak in deep snow on snow-shoes or on foot only

appealed to a minority, but the number of those who were attracted by

the chance of combining mountaineering with ski-ing steadily increased.

The English were slow to follow the new fashion; the number of British

ski-runners who have a long list of glacier ski tours to their credit

is still small, but abroad hundreds of experienced mountaineers have

explored the High Alps on ski, and abroad the advisability of using the

ski in the High Alps has passed beyond the limits of discussion.

The time is coming when most alpine huts will be provided with ski. A

steadily increasing number of mountaineers realize that such peaks as

Monte Rosa or the Zermatt Breithorn provide excellent ski-ing at all

months of the year, and that the trouble of dragging a light pair of

summer ski to the summit is well repaid by a magnificent run down to

the hut.

There is no month in the year in which the writer has not enjoyed

first-class ski-ing, and there is no season in the whole alpine

calendar in which ski cannot be used on the loftier snow peaks in

the Alps. Ski have come to stay as an indispensable adjunct to

mountaineering. To the rock climber the ski are perhaps mainly useful

in bad seasons; if the weather in summer were uniformly good the

enthusiastic rock climber would have little use for the ski. But long

spells of bad weather are not unknown, and many a climber who has

engaged a guide or a couple of guides for a month has spent a week,

a fortnight, or in some cases even longer without climbing a peak. I

venture to assert that if he took himself and his ski to a club hut

he would at least have the satisfaction of making good use even of an

afternoon’s fine weather. I remember once finding myself at the Egon

von Steiger hut during bad weather. It snowed all day and all night,

and cleared at ten o’clock the next morning. Two parties on foot

attempted the easy Ebnefluh. Both were driven back after a very brief

struggle with deep soft snow. Myself and a friend reached the summit on

ski in more or less normal time, and enjoyed a wonderful run back to

the hut, where the disgruntled foot-sloggers had spent the day.

Let the rock climber learn to ski, and when the big rock peaks are

deep in snow he will be able to snatch a Monte Rosa or Breithorn from

the first fine day. In bad seasons individual fine days are often

sandwiched between two or three days of bad weather. Such isolated days

are useless to the foot-climber but invaluable to the ski-runner.

[Sidenote: Technique.]

I cannot spare the space to explain the technique of ski-ing.[18] Here

I need only attempt to dispel a lingering belief, that dies hard,

to the effect that there is one technique for ordinary ski-runners

and another for mountaineers. This curious superstition is the last

relic of an exploded system of ski-ing taught by an Austrian called

Zdarsky, the main effect of which was to encourage timid, slow and

clumsy ski-ing. The ‘Lillienfeld’ ski were short, and made straight

running very difficult and turning very easy. The Lillienfeld system

taught people to ski very quickly by dodging all difficulties and

encouraged a free use of the stick. It was a bad system, and is now

quite discredited; but there still lingers a curious belief that the

Norwegian style may be all very well for small mountains but is too

dashing and insecure for the High Alps. As a rule, glacier ski-ing is

far easier than ski-ing among the lower mountains; the most difficult

of all ski-ing country is wooded country, such as extends for miles

round Christiania, the home of the ‘Norwegian style.’ Let me therefore

urge the reader to master the free Norwegian style, to make all his

turns and swings without the aid of the stick, and to acquire a free

and dashing style. The mountaineer even more than the low-level

ski-runner should have complete control of his ski, and complete

control is impossible unless you have learned to control your ski not

by means of the stick, but by means of the ski themselves.

[Illustration: SNOW WAYS [JEAN GABERELL]

There are a few occasions on which the use of the stick is permissible

on tour; but it is so dangerous to begin by using the stick as a brake,

that I would advise the beginner NEVER to use the stick until he has at

least passed the ‘THIRD-CLASS TEST’ which is held from time to time in

all ski-ing centres patronized by British runners.

Furthermore, though of course it is absurd to take risks in the High

Alps, occasions often arise where speed means safety. With bad weather

or night approaching, the man who can run fast stands more chance

than the man who can not, and, consequently, the higher your speed

consistent with safety the better your chances. Now, a high speed

consistent with safety can only be maintained by those who have lost

no chance on small expeditions of raising the speed at which they feel

comfortable, and this, again, can only be achieved by running just a

little faster than is quite comfortable.

In the High Alps a reckless runner, who is always falling, is a danger

to his companions and himself, but a man who is quite incapable of a

fair speed is always a nuisance on tour, and may sometimes prove a

danger. Steadiness is the first requisite in the High Alps, but speed

is by no means unimportant. Any man with average balance and nerve,

if he is properly taught, can learn to run steadily and to make slow

turns on average snow at the end of a fortnight. To become a really

expert ski-runner is, of course, another matter, but some of the finest

ski-turns in the High Alps have been carried through with success by

men who were not even third-class runners. Let the mountaineer learn

to ski and take such chances as a snowy summer may afford. In a few

hours he will begin to enjoy ski-ing, and his enjoyment will steadily

increase with his experience. It is easy to become a third-class

ski-runner, and very well worth while taking sufficient trouble to

become a second-class runner. First-class ski-ing is, of course, not

within the reach of all.

In order to make much that follows comprehensible to the reader,

who, though a mountaineer, has yet to become a ski-runner, a short

definition of the ski-ing turns and swings is necessary.

The object of every ski-runner is to approximate as nearly as possible

in his course to a straight line between the point of departure and

the goal. Obviously this ideal is impossible of attainment save on

comparatively short open slopes, which can be taken straight. Hence the

regrettable necessity of turns and swings which, unlike skating turns

and swings, are not an end in themselves, and are only incidentally

beautiful and graceful to execute and to watch.

There are three principal turns or swings: the _Stemming turn_, the

_Telemark_, the _Christiania_.

Each of these turns can be used either as a stop turn (i.e. in order

to stop more or less suddenly), or as a means of linking one tack to

another. For instance, a slope may be too steep to take straight; in

this case the good runner descends in a series of linked curves.

According to the condition of the snow, he will make these linked

curves either by means of the Stemming, the Telemark, or the

Christiania turns.

The Stemming turn is the easiest and slowest turn. It is the key

to alpine ski-ing, and can be employed on snow on which a Telemark

or linked Christiania would be either difficult or impossible. The

beginner should try to combine Stemming with Christianias, to begin

his turn as a Stem and to finish with a Christiania. This swing, which

is sometimes called a Stem-Christiania or a ‘Closed Christiania’ (as

opposed to ‘Open Christianias’), or by a natural abbreviation a

‘Closti,’ is the most generally useful of ski-ing swings.

The Lillienfeld system placed exclusive reliance on the Stemming turn

and dismissed the other two as fancy tricks. This was absurd, for in

many kinds of snow the Telemark or Christiania is much the more useful

manœuvre. Either of these latter turns can be executed at a very high

speed, whereas the Stemming turn cannot be done at a high speed.

The Telemark is mainly useful in deep soft snow or in soft breakable

crust; in either of which the Stemming turn and the linked Christiania

is difficult or impossible.

The Christiania, as a stop turn, is the safest method of stopping

at high speed. Linked open Christianias are not easy to master, but

are very satisfactory when mastered. Wherever a linked series of

Christianias can be executed, linked Stem-Christianias are easier, and

safer. The power to make a series of continuous non-stop turns with the

Christiania marks out the expert; nothing is more beautiful than fast

descent on glacier snow, film crust or crust slightly softened by means

of a series of swift-running Christianias.

For the High Alps I consider that the Stemming turn and the Christiania

should always be used in preference to the Telemark, excepting in very

deep soft snow--rare in the High Alps--or in soft breakable crust.

The Telemark is a one-foot turn; all the weight is on the leading foot;

consequently the Telemark is less powerful and less sure than the

Christiania, which is a two-foot turn. Furthermore, the falls resulting

from a Telemark which has gone wrong are more dangerous than from any

other turn. From a faulty Christiania or Stemming turn one is usually

thrown backwards or sideways against the slope; from a faulty Telemark

one is often thrown on to one’s head or outwards from the slope.

Further, the ski have a nasty habit of crossing behind in a badly timed

Telemark.

To sum up: Use the stick as little as possible. Make all your linked

turns by Stem-Christianias, except in deep soft snow or breakable

crust, where the Telemark should be used. For a sudden stop use the

Christiania in preference to the Telemark.

[Sidenote: Equipment.]

In addition to the ordinary mountaineer’s equipment, the ski-runner

must have ski, sealskins, ski-sticks and repair outfit for ski.

I have no space to advise on the choice of ski, but I might warn the

reader against the common illusion that ski for mountaineering should

be markedly shorter than ski for short tours. They should be a couple

of inches shorter, but very short ski should not be used save in the

summer. I have used the longest size obtainable (2·36 in.) for quite

long tours, and the next longest size (2·31 in.) in the High Alps.

Sealskin are detachable, and are fixed on to the ski to prevent the ski

side-slipping while climbing a steep slope. Ski-ing boots are bigger

than mountaineering boots. They should be nailed--lightly nailed, of

course, but on no account entirely nailless. The nailless ski-ing boot

is a superstition imported from Norway, where the hills are milder in

gradient than in the Alps.

For all glacier tours crampons, or, to use another word, ‘ice-claws,’

should be taken. Eight-pointers are best, though good work can be

done with six-pointers. The small four pointers are most insecure and

uncomfortable.

For all further details as to equipment the reader may consult my book

_Cross Country Ski-ing_.

THE ALPINE CALENDAR

The first winter snows usually fall in October: excellent ski-ing

is often obtained at the ordinary winter sports centres in October.

Glacier tours should certainly not be attempted before December, as

the danger from crevasses is at its maximum in October and November.

January and February are the best months for ski tours up to about ten

thousand feet. The winter proper is NOT the best season for glacier ski

tours, though most of the classic ski tours in the High Alps have been

carried out between December and the end of February. Good ski-ing can

be obtained at low levels well on to the end of April, and sometimes

even later. As a rule, the snow lies down to about five thousand feet

on north slopes well on into the middle of May.

MAY AND JUNE ARE THE BEST MONTHS FOR GLACIER SKI-ING, though excellent

ski-ing may be obtained throughout the summer. There is no month in

the year in which the High Alps do not yield good snow, but the best

all-round months for mountaineering on ski are undoubtedly May and June.

SNOW CRAFT

The expert cross-country ski-runner must not only be a fast and safe

runner on all kinds of snow and ground, but he must also possess

a thorough knowledge of snow craft. Unfortunately, there are nine

ski-runners whose Telemarks are perfect for one whose knowledge of snow

is even adequate, and the number of those whose understanding of snow

in all seasons of the year is really expert is indeed small.

Snow craft in winter and in spring is even more complex than in summer,

and requires a special study of its own. Even the most expert guides

whose knowledge of summer snow leaves nothing to be desired require

considerable winter experience before they are thoroughly competent to

lead a party among the High Alps in winter. The same is true of spring;

each season, in fact, requires a separate study.

The ski-runner needs to possess a more exact knowledge of snow than

that which the foot-mountaineer requires. A mountaineer on foot is

mainly interesting to discover whether the snow is hard enough to walk

uphill without sinking in, and whether the snow is likely to avalanche.

Hard snow, soft snow and avalanche snow are the three main categories

in which the foot-mountaineer divides snow. He need not bother with

all the delicate gradations of value that distinguish snow which is so

hard that it will not take a Stemming turn, and snow which, though hard

enough to bear a foot, will yet take a Christiania or even a Telemark.

The ski-runner who neglects snow craft is severely punished for his

carelessness. He runs into fast and sticky snow and pitches heavily

on his face, or from soft snow on to hard snow and falls heavily

backwards. Even the least observant ski-runner soon realizes that

an elementary knowledge of snow is essential to his comfort and his

safety. His knowledge of snow needs to be instinctive. On foot a man

has time to probe and to examine, but on ski he has to diagnose the

snow while travelling at a high speed. He has to possess an accurate

sense of direction so that he can foretell the changes of snow that

occur when travelling from, say, a north-east slope on to an eastern

slope, or an eastern slope on to a south-eastern slope.

Quite as many bad ski-ing falls are caused by deficient snow craft as

by deficient balance.

Precisely because even the most casual ski-runner is bound to learn

from the past experience of nasty falls, ski-ing inevitably teaches

even the most unobservant some knowledge of snow craft. A ski-runner

cannot hand over the whole strategy of the day’s campaign to a guide.

He must think for himself and study for himself. In summer the real

business of climbing usually begins when the glacier or the summer

snowline is reached, but in winter a ski-runner can kill himself in an

avalanche within an hour of the hotel. Snow craft begins in winter at

the hotel door.

The careful study of snow is a fascinating branch of nature study.

More can be learned from books than the reader might imagine. Once a

ski-runner has grasped how snow is affected by altitude, orientation,

wind and sun, he is in a better position to profit by his knowledge in

practice than if he was forced painfully to unravel the laws of snow

by personal observation. In the early days of ski-ing in the Alps the

guides themselves were completely ignorant of the main laws of snow in

winter. They are still, for the most part, ignorant of the subtleties

of spring ski-ing, which is much more difficult to understand than

winter ski-ing. In winter, if a snow slope holds good snow in the

morning it will probably hold good snow throughout the day, but in

spring the same slope goes through a regular cycle of changes. It may

be unskiable at dawn, yield perfect ski-ing at midday, prove absolutely

unsafe at three in the afternoon, and yield good running again in the

evening.

To time a descent accurately, to forecast from a knowledge of the

orientation and altitude of a given mountain that it will yield perfect

ski-ing at a given hour, is to know one of the most satisfactory

intellectual pleasures that the mountains afford.

WINTER SNOW

There are certain forms of snow which are characteristic of certain

seasons. ‘_Powder snow_,’ for instance, is normal in winter and

uncommon in the late spring; none the less powder snow is often found

even in summer, just as certain forms of snow which are characteristic

of spring or early summer are occasionally found even in midwinter.

‘Winter snow’ must then be taken to mean the kind of snow which is

common and characteristic of, but not limited to, winter.

[Sidenote: Powder snow.]

In winter a normal snowfall is accompanied by a temperature below

freezing; snow that falls with the temperature just above freezing

usually descends in the form of sleet. Fortunately, such conditions are

not common.

Snow will even fall when the temperature registers a degree or two of

thaw. I have known dry snow fall with a temperature of two degrees

above zero--centigrade, at a height of 5500 feet above the sea.

Similarly, as icemakers know, water will freeze on a rink even when the

temperature is above freezing-point.

The explanation for this anomaly may be sought in the well-known

law that pressure lowers the freezing-point.[19] It seems a natural

deduction that diminished pressure will _raise_ the freezing-point.

0° centigrade is the freezing-point of water at sea-level. Under a

pressure greater than that of the air at sea-level, the freezing-point

is lowered so that the bottom of a glacier will be in a condition of

liquefaction at a temperature below freezing. It should follow that an

air pressure _less_ than that of the air at sea-level should raise the

freezing-point; or, in other words, that at any point above sea-level

the freezing-point should be higher than zero. From my own observations

I believe that water will freeze and rain turn to snow when the

temperature is 2 degrees centigrade above zero at a height of 5000 feet.

Fortunately, the normal snowfall is accompanied by a temperature below

freezing, for if the snow is on the point of turning to rain, it forms

a crust when the temperature falls. A normal dry snowfall takes the

form of small hexagonal crystals. Newly fallen snow is not compact,

and contains a great deal of air, which slowly escapes as the snow

settles, so that after a day or two the new snow has lost nearly a half

of its apparent depth.

New snow is very soft and slow, but gives good running on steep slopes;

though, of course, long steep slopes are liable to avalanche. Good

running is also often obtained during a snowfall by choosing south

slopes, previously covered by a hard crust; for there is nothing

pleasanter than two or three inches of snow on hard crust, and during

a gentle snowfall it is possible to enjoy quite good sport on such

slopes. In general, expeditions--even quite short ones--are impossible

till the snow stops, and unsafe for a day or two after a heavy fall.

Newly fallen snow sticks badly in the sun even if the temperature is

well below freezing.

Once, however, that the snow has settled it soon gives perfect running.

One night’s really hard frost is sufficient to produce excellent snow.

_Powder snow_ remains good almost indefinitely in winter on northern

slopes, provided it is not spoiled by wind. It steadily improves. In

sheltered places the crystals gradually grow in size so that sometimes

you find large leaf-like formations, which rustle under the ski like

autumn leaves. Such snow is a dream of paradise.

_Powder snow_ is the ideal running surface. It is equally good for

straight running and for swings. In deep soft powder the Telemark is

the best swing, but in fairly compact powder any turn or swing is easy

and safe.

The ski-runner who visits the Alps in winter, and has good luck, may

run for day after day on perfect powder. He is in danger of thinking

himself a better runner than he is. If he concentrates on Telemarks,

the first tour in the High Alps, where he will meet varieties of hard

and soft crust, will find him out badly. He should therefore make

a point of spending a day or two on south slopes so as to master

the Stemming turn on hard snow. If he is getting pleased with his

Telemarks, let him try a Telemark on the soft breakable crust to

be found on south slopes at midday, and if he can do a series of

fast-linked Telemarks in such crust, he may then return to his powder

snow with a good conscience.

[Sidenote: The Effect of Wind on Powder Snow.]

Snow which is spoiled by the sun is never quite impossible, and is

always curable by a hair of the dog that bit it; in other words, by

another and stronger dose of sun. But snow which has been wrecked by

the wind is the despair of the ski-runner.

The wind does not affect snow that has once been crusted, so that

wind-swept snow is almost unknown in spring. The favourite victim of

wind is precisely that light, dry powdery snow which is so common in

winter.

The effect of wind depends on three factors, the strength of the wind,

the time during which the snow is exposed to the wind, and lastly the

type of snow exposed to the wind. Powder snow is the most sensitive,

the quickest to spoil and the most trying when spoiled. Hard crust is

entirely unaffected; heavy wet snow is very little affected.

A light wind produces on powder snow the markings which are known

as _ripplemark_, a term which has been applied by scientists to the

rippled effects which can be traced, not only in snow, but also in

sand, and even in clouds which have been influenced by wind. Sand and

snow behave very similarly under the influence of wind. A slightly

stronger wind, or a wind blowing for a longer spell, produces caked

powder, which is dense and compact, but has not quite lost its powdery

quality. The ski sink in to a depth of an inch or more, and though

fast running is dangerous and apt to produce broken ski points, a good

runner can derive much pleasure from caked powder, and can force linked

Telemarks without much trouble. The third stage in the deterioration

of snow occurs when the wind produces a hard crust. _Windboard_ is

hard and slippery, but so long as it is not varied with soft patches

of sticky snow or of breakable crust, windboard yields a surface which

may annoy the novice but which should not prove, at any rate on slopes

of moderate gradient, too troublesome to an expert who has mastered

his hard snow turns. Windboard is common during the winter months in

the High Alps; in appearance and texture it is not unlike the hard

marble crust, which is found on south slopes after a long spell of fine

weather, but it is vital to discriminate between windboard and marble

crust, because the former may sometimes break away in slab avalanches

whereas the latter never avalanches. Windboard betrays its origin by

ripple markings, sometimes faint but seldom invisible to the practised

eye. Windboard is often varied by pockets of sticky snow.

If wind produced nothing worse than caked powder or windboard, the

ski-runner would have less cause for complaint. Unfortunately the

wind often produces horrible surfaces which resemble each other only

in their general unsuitability for ski-ing. _Skavla_ is the generic

Norwegian name for wind-swept snow, and skavla is common on the

exposed fjords of Norway and Sweden, where it attains a degree of

unpleasantness seldom matched in the Alps. Skavla varies. Sometimes

skavla consists of patches of glittering ice varied by treacherous

pockets of sticky snow; sometimes a breakable trap crust interspersed

with windboard; sometimes waves of hard, icy snow which occasionally

attain a height of two feet or more. The prevailing wind determines

the direction of the waves and acts in precisely a contrary fashion to

that of wind on water; for wind on snow has a burrowing effect, and

forms these waves by excavating and eroding a slope, gradually forming

a series of steps. In other words, whereas on the sea the wind will be

found to be blowing up the longer slope of a wave, on snow the wind

will have been blowing against the short steep side of the snowy waves.

To sum up: The effect of wind on powder snow is always bad. The

stronger the wind and the longer that it blows, the worse the snow.

Hence in winter avoid exposed slopes and seek out sheltered valleys.

The summit slopes of winter mountains will usually be spoiled by the

wind, which is one of many reasons why spring is so superior to winter

as far as ski-ing in the High Alps is concerned.

[Sidenote: The Effect of Sun on Powder Snow.]

Powder snow acquires a crust if it is exposed to wind, to sun

shining at a sufficiently direct angle, and to an air temperature

above freezing. Wind alone has the power of forming crust without a

preliminary melting of the surface. I do not know why this should be

so, but no doubt the reason is to be found in the law that pressure

lowers the freezing-point, so that the increased pressure caused by

wind lowers the freezing-point, or, in other words, produces the

effects of a thaw at the point where the wind acts even though the

general air temperature may be well below zero centigrade.

At any rate, sun, wind and thaw are alike in producing a surface crust.

The effect of the sun depends mainly upon the angle of inclination. In

midwinter, snow will remain unaffected by the sun on northerly slopes

even though they receive several hours of sunshine in the course of the

day.

In fact, in midwinter eastern and western slopes retain powder snow for

a very considerable time, while a slope that is a few degrees north of

west or a few degrees north of east retains powder snow throughout the

winter, always providing that it is not exposed to wind or to thaw.[20]

I use the term _‘thaw’ to denote a general air temperature above

freezing as opposed to the purely local melting caused by the sun’s

rays_, which may be, and in fact normally is, accompanied by an air

temperature in the shade of several degrees below freezing.

The thermometer will often be registering more than ten degrees of

frost in the shade and twenty or more degrees of warmth--centigrade--in

the sun. It is, as icemakers know, quite common to find a belt of cold

air, two feet in height, just above the snow and just below a strata of

warm air several degrees above freezing-point.

In normal winter weather you may be uncomfortably warm in the sunshine,

and yet the sun has no power to affect powder snow on any slope which

has not a touch of south in it.

The steepest south slopes are the first to lose their powder snow.

Afterwards, the gentler south slopes follow suit. Towards the end of

February western and eastern slopes begin to crust. In March due north

slopes still hold powder,--at any rate above 5000 or 6000 feet,--but

slopes which are only a few degrees north of east or of west begin to

crust. Finally, the level outruns get crusted, then the gentle due

north slopes, and last of all steep north slopes.

Of course at high altitudes winter conditions prevail until well on

into April.

In midwinter good ski-ing is usually to be had on south slopes for

three or four days after a snowfall, though steep due south slopes soon

crust. The time during which gentle south slopes or slopes which are

just south of west or east will hold powder depends on the general air

temperature and on the altitude. I have known pretty steep due south

slopes hold powder below 4000 feet for three days of cloudless weather,

but the temperature was about 15 degrees centigrade below freezing.

This is, however, unusual, and south slopes soon crust up even in

midwinter. The sun melts the snow by day, and the melted snow refreezes

at night, producing a crust. Such a crust will, at first, be soft and

breakable.

_Soft breakable crust_ is not a bad running surface. It is quite true,

i.e. does not vary in pace from one place to another, and is usually

soft enough to enable the ski-runner to make Telemark swings, either

stop or linked, without much difficulty. Sometimes the crust is harder,

and in this case the jump-round or _quersprung_ is the only possible

manœuvre.

A peculiarly villainous form of crust, fortunately rather rare, is

known by the appropriate name of _Trap crust_. This crust is perfectly

solid at one spot, and bears the weight of the ski without breaking,

only to crack a few yards lower down. The ski-runner skids with great

speed over the hard crust, only to be pulled up suddenly as his ski

break through the soft crust below.

Trap crust is more usual in spring than in winter, especially on slopes

which change in direction, so that the ski-runner passes from snow

which has been sufficiently thawed to form a hard solid crust at night

to slopes which have only been superficially melted. Trap crust is only

found after fairly heavy falls of snow which require considerable time

to form a solid crust. As a rule, trap crust covers a foot or more of

powder snow.

To return, however, to more normal winter conditions. _Under normal

conditions the snow on south slopes in winter is gradually transformed

into crust._

This crust is at first soft and breakable, but the continuous process

of melting and refreezing gradually produces a solid unbreakable crust.

_Unbreakable crust_, as the ski-runner soon discovers, varies greatly

in quality from hard crust which is so hard that the ski slip sideways

without obtaining the least grip, crust which on any slope but the most

gentle is almost unskiable, to the other extreme, crust which though

quite hard and unbreakable is rough enough to permit even a Telemark

and to make Christianias and Stemming turns delightfully easy.

The solid crust formed in winter is usually very hard and slippery

before the sun strikes it. This crust is known as _Marble Crust_. You

find marble crust on southern slopes in winter, and at high altitudes

in spring. It is common in the High Alps. Even at the very end of April

I have known a slope at a height of 12,000 feet remain hard, slippery

and unsoftened for some little time after the sun had struck it because

a bitter north wind had lowered the temperature several degrees below

freezing.

In mid-winter a slope of marble crust will yield good ski-ing after the

sun has struck it, unless the air temperature is several degrees below

freezing. Marble crust, touched by the sun, yields a surface which

will puzzle the beginner but which is pure delight to the man who has

mastered Stemming turns and Christianias. The excellent running that

may be obtained on south slopes is too little exploited, for winter

ski-runners are firmly convinced that good ski-ing can only be found on

north slopes where powder lies.

Mid-winter may be said to last till the end of January. In February you

often find perfect spring snow, Telemark crust, etc., on south slopes,

and in February, as often as not, the best running is obtained on

southern slopes. This type of running will be dealt with later.

[Sidenote: Summary of Winter Snow.]

Winter snow may therefore be summarized as follows. The normal winter

snow which is found throughout the winter on northern slopes and

occasionally on southern slopes is powder snow which is perhaps the

ideal ski-ing snow.

Powder snow deteriorates under the influence of wind and sun. Wind is

the more mischievous. A little wind does no great harm, and the expert

can even ski with pleasure on the hard crust formed by wind, but the

extreme action of wind often produces varieties of snow which are all

but unskiable.

The High Alps and lofty summits in general being most exposed to wind

will usually yield inferior ski-ing to sheltered slopes. The best

ski-ing in winter will therefore seldom be found on the glaciers.

Snow also deteriorates under the influence of sun, which forms a crust.

This crust, however, once formed is often improved by a further dose of

sun.

Though the best ski-ing is usually obtained on north slopes, excellent

ski-ing is often obtained on south slopes by those whose knowledge of

snow craft is sufficient to time their descent and to choose their

route accurately.

Abnormal conditions produced by Föhn and thaw are dealt with on pp.

417-422.

SPRING SNOW

We have seen that good ski-ing in winter depends largely on the absence

of wind. A sudden thaw may also produce a disastrous result, for snow

which has once been rained on and refrozen will remain covered with

crust until there is a new snowfall.

The best winter snow is without rival, but spring snow is, on the

whole, safer and less capricious. In normal spring weather all snow is

crusted in the early morning, for the sun is powerful enough to melt

snow even on northern slopes. But this spring crust, as we shall soon

show, is much less troublesome than crust in winter and yields very

fine ski-ing indeed. Wind, the great enemy in winter, has no effect

in spring, for wind cannot affect hard crust, and if wind blows while

the snow is falling a few days of strong sun will melt any wind-formed

crust and produce exactly the same surface as if the snow had never

been touched by wind. It should, however, be added that, in the early

spring, wind, though powerless on snow which has once been melted

and crusted, is a great nuisance if it blows on snow which is still

powdery, as is usually the case for twenty-four hours or so after a

snowfall; snow which has once been crusted by the wind has a very

strong resisting power to the action of the sun; I have known south

snow in March retain irritating effects of wind action after several

days of strong sun that would have been sufficiently potent to melt any

ordinary crust.

Spring ski-ing is, as a rule, delightful. Snow is troublesome in the

intermediate stage between powder and crust. Once a crust is formed,

the more often that crust is remelted and refrozen the better, as

there is nothing better than old crystalline snow which has been

through the mill of melting and refreezing again and again. Unless wet

Föhn blows such snow will always retain its crystalline character,

even when remelted by the sun, and will always yield good ski-ing. Of

course in the late spring at low altitudes the sun is powerful enough

thoroughly to thaw and drench the snow, and in the middle of May below

7000 feet wet snow in the middle of the day is unpleasant. But in March

and April ski-ing on melted crust is wholly delightful. Incidentally

the best ‘Spring snow’ is often found at the end of or in the middle of

February on southern slopes.

From the beginning of March onwards all slopes, save those at very high

altitudes, begin to crust over. The process is gradual on northern

slopes. There is a period when the northern slopes no longer hold the

dry loose powder of winter but have not yet begun to crust.

_Spring powder_ is common on north slopes in March. It is denser than

winter powder, and is not so dry. It is slightly moist on the surface,

and much heavier. It yields, however, a first-class running surface,

and will take any turn or swing. Its main objection is the fact that it

is peculiarly liable to avalanche.

Gradually, however, Spring powder disappears, save at great heights,

and all slopes are covered by crust. In the afternoon the crust is

melted, and the snow is soft and wet on all slopes. At night the snow

is refrozen.

The normal cycle, then, of a normal spring (say April, at altitudes

between 3000 and 9000 feet) is as follows: Hard crust at dawn; crust

superficially softened between sunrise and midday; soft melted snow in

the afternoon; soft breakable crust as the sun loses in strength; and

solid hard crust after the sunset.

First let us consider the hard crust usually found at dawn.

This differs materially from the marble crust of winter, and from

any of the crusts formed by wind action. It is, as a rule, slightly

softer. What is more to the point, it is rougher. The surface of normal

spring crust is perforated by numberless little holes. Sometimes

these holes are quite small, mere pockmarks, sometimes they are as

large as half-crown pieces. It is the presence of these holes and the

roughness of the crust that makes steering easy, so that control is

not difficult, and linked Christianias or Stemming turns are within the

power of the good runner.

_Perforated crust_, in fact, is a delightful running surface. It is

common at low altitudes in March, at moderate altitudes in April, and

is normal in the High Alps in May, June, July and even August.

_Film crust_ is found in May and June on the glaciers, and occasionally

at low altitudes in April. It forms a delightful running surface.

Unlike marble and perforated crust, it is not quite homogeneous. It

is composed of a hard under-surface of solid crust, covered by a very

thin, soft, and transparent film of ice, which glistens in the sun like

burnished silver.

This film of soft ice is shorn away as the ski begin to come round on

a turn. It provides a splendid purchase, preventing effectually all

side-slip, and yet not sufficiently strong to make turns difficult.

Film crust is admirable for fast straight running, because at any

moment the pace can be regulated by a swift turn. There is nothing

finer than a run down the glaciers in the early morning on film crust.

We have seen that the cold nights of winter produce marble crust, which

is hard and slippery. Marble crust is the kind of surface which needs

crampons or a chip with the axe if it is climbed on foot.

Further, marble crust, and all forms of crust produced by winter winds,

yield a very unsatisfactory surface, too slippery to give good purchase.

We have seen that the milder nights of April produce perforated crust

which is much rougher and gives good ski-ing, while the even warmer

nights of May and June produce film crust in which Christianias and

Stemming turns are easy and safe. In fact film crust gives such a

wonderful grip that even Telemarks are possible.

From this we deduce the following law:

Provided the night’s frost is sufficient to produce a solid unbreakable

crust, the crust will give the best ski-ing when the frost has been

least severe.

In other words, “THE MILDER THE FROST THE BETTER THE CRUST.”

This rule is important. It often happens in spring that one has to

start down before the sun has produced a surface melting. Again and

again the first thousand feet or so of descent have been spoiled

because the crust was too hard and slippery. But the lower one ran

down the better the ski-ing. The hard marble crust of winter gave way

to the perforated or film crust of spring. In April, in the High Alps,

winter conditions often prevail at high altitudes to give way to spring

conditions lower down. You start a run on marble crust and end on

perforated or film crust. The lower the altitude the milder the night

frost, and hence the better the crust.

But of course the hard crust of dawn is soon changed under the

influence of the sun. At first the sun produces a slight surface

softening which is, however, quite sufficient to make a great deal

of difference. Even marble crust, if superficially softened, yields

excellent running. Gradually the melting process becomes more

pronounced. Sun-touched crust with a slight surface moistening--quite

sufficient to make Christianias and Stemming turns a joy--yields to

crust covered by an inch or two of melted snow. Such crust is known as

_Telemark crust_--not because Christianias are not easy, but because

Telemarks are very simple, whereas Telemarks are difficult, if not

impossible, on hard crust.

Telemark crust is a normal stage in the passage of hard crust to melted

snow. It is the practical certainty of finding Telemark crust at

certain hours in spring that makes spring ski-ing in fine weather such

a delight.[21]

As the sun increases in strength all trace of the underlying crust

disappears. The snow is melted through and through, and becomes

dangerous on steep slopes.

This wet snow is often slow, but it never sticks like the wet snow of

winter. On steep slopes it gives good running--if unsafe.

Snow sticks in the intermediate stage between freezing and thawing.

Thus powder snow which is beginning to thaw sticks abominably, but snow

which is melted through and through does not stick. Snow which has once

been thoroughly melted and then refrozen will never stick badly again.

A surface of wet snow overlying powder will, of course, stick, but

melting snow which rests either on hard crust or on the hard ground

does not stick. It may be slow, but it does not adhere in sticky lumps

to the running surface.

Thus two inches of melted snow on top of crust (Telemark crust) gives

a fine running surface, and an inch or even less of wet snow on grass

also gives excellent sport.

Snow that has been melted and refrozen night after night soon acquires

a crystalline character. When the crust begins to melt after the

sun has struck it, the melting surface is composed of numerous wet

crystals, sometimes about the size of salt crystals, sometimes much

larger.

This _granular_ snow is familiar to all spring runners, and gives an

excellent ski-ing surface. Occasionally towards sunset, as the wet

heavy snow that is usually found in the afternoon during the wet spring

begins to freeze again, you will find the snow assuming a very marked

crystalline formation, which resembles the wet hypo crystals with which

photographers are familiar.

In general, so long as snow retains a crystalline formation it gives

good running. Salt snow or hypo snow yields excellent sport. In May at

_low_ altitudes the sun, however, is so powerful that it dissolves the

crystals and reduces all the snow to one consistent heavy wet slush.

Such snow does not stick--that is to say, it does not adhere to the

running surface--but it is very slow. Furthermore it is dangerous,

because if you run suddenly on to a patch of this very heavy snow you

are liable to be pitched on to your face. Often the snow is not only

melted downwards but upwards, for the ground is very warm in spring,

and thaws the snow from below, so that you will often find a patch of

soft heavy snow resting in the form of a shallow bridge on an empty

space. The ski break down the bridge of snow, and the ski-runner

pitches heavily forward. Such hollow snow is seldom found in April,

but is common in May at lowish altitudes. In May the best ski-ing at

low altitudes (5000-7000 feet) is obtained before 10 a.m. and after 7

p.m. In the early morning and just after sunset I have often enjoyed

first-class ski-ing right down to 5000 feet and lower, well on into the

middle of May.

We may therefore sum up the normal cycle of a spring day as follows:

At dawn every slope will be covered by a hard homogeneous crust. This

crust will be either marble crust, in which case it will yield very

difficult and unpleasant ski-ing, or perforated crust or film crust.

Perforated and film crusts give excellent ski-ing even _before_ the sun

has begun to soften the crust.

When the sun begins to gain in strength the hard crust is superficially

softened, and gives good running even in the case of marble crust.

A later stage is reached when the hard crust is softened to a depth

of about two or three inches (Telemark crust). This again gives good

running.

Either before or after midday, according to altitude and inclination,

all traces of crust disappear, and all slopes at moderate altitudes

are reduced to wet, heavy and more or less water-logged snow. In the

early spring this stage is perhaps only reached on southern slopes.

In the late spring it is reached on all slopes at low altitudes and

on north slopes, save, perhaps, at very high altitudes. In general,

the ski-runner should not be abroad at such hours. Towards evening the

slopes begin to refreeze. There may be an interval of hypo snow--soft

hypo-like crystals in which fast running and every kind of swing is

perfectly safe and easy. This is soon followed by the formation of a

soft breakable crust, which gradually hardens until at last the cycle

is complete by the formation of a hard solid crust.

THUS IN GENERAL THERE ARE TWO PERIODS OF A SPRING DAY WHEN SKI-ING IS

EASY, FAST AND SAFE. THE FIRST PERIOD IS WHEN THE HARD CRUST BEGINS TO

SOFTEN, AND THE SECOND PERIOD IS WHEN THE WET MELTED SNOW BEGINS TO

FREEZE. THE SKI-ING IS LEAST PLEASANT AND MOST DANGEROUS BETWEEN MIDDAY

AND SUNSET.

THE EFFECT OF FÖHN AND THAW

So far we have discussed normal winter and spring conditions. Föhn is,

unfortunately, associated not only with spring but with winter. The

conditions that are produced by Föhn are, however, spring conditions

rather than winter conditions; for Föhn, though by no means uncommon in

winter, is at least abnormal, whereas periods, more or less prolonged,

of Föhn weather may be regarded as normal in spring. The peasants have

a saying that, if the Föhn did not blow, the good God and the warm sun

could do little with the snow. Certainly but for Föhn Switzerland would

still be covered with glaciers.

Föhn, strictly speaking, should be used only for the warm dry wind that

blows from the south, and which has been the cause of so many fires.

The fire of Grindelwald was caused by this type of Föhn. The wind dries

up the wooden chalets, and a spark from a cigar or a kitchen fire,

carried on the wind, is enough to kindle wooden buildings from which

the wind has absorbed every trace of moisture. But the word Föhn is

also used for the warm, damp south-west wind, which is in every way

utterly different from dry Föhn. They are alike only in that both dry

and wet Föhn raise the temperature and melt the snow.

I propose to call the true Föhn DRY FÖHN and the wet, warm south-west

wind WET FÖHN.

Dry Föhn is often associated with long spells of warm dry weather. The

skies are cloudless, and there is no hint of rain to be seen. You know

that there is Föhn in the air by a peculiar warm dryness, a marked

absence of coolness and moisture in the atmosphere.

The wet Föhn always brings rain. Sometimes dry and wet Föhn will fight

for the mastery. Sometimes dry Föhn will emerge into wet Föhn and bring

down the rain, only to recover its mastery a day or two later.

[Sidenote: Föhn in Winter.]

Let us consider the effect of wet Föhn in winter proper. The ski-runner

is bound to detect the first hint of wet Föhn in the air by a slight

stickiness in any powder snow that he may chance to be ski-ing on. If

the wet Föhn is slight, copious waxing will eliminate its effects; but

if it is pronounced, the snow will ball and stick atrociously.

Should the Föhn disappear, it leaves its legacy behind. All slopes of

powder snow which have been affected are covered with a crust, which

will be more or less thick according as the thaw has been more or less

severe. I assume, of course, that the thaw had been followed by the

frost at night, without which crust cannot be produced. Only a new

snowfall can restore a slope of powder snow which has once been melted

by Föhn to its pristine conditions.

Sometimes the Föhn is so slight that the surface of the powder snow is

barely touched. It is not covered by crust, but there is a suspicion of

resistance as the ski drive through due to an embryo crust. Telemarks

are not quite so easy, and a very fast swing is apt to throw the

ski-runner outwards, owing to the fact that the side-slip is less

pronounced; for the snow gives less easily when covered by the first

hint of crust. More usually the Föhn, if it once begins, is accompanied

by rain. Often even in December heavy rain will fall on all slopes

below 12,000 feet. Directly the Föhn disappears the usual winter frosts

will convert such slopes into solid icy crust which is harder and more

slippery than any marble crust produced by sun or wind. I have seen

crust, formed by Föhn followed by frost, so hard that neither ski nor

hobnailed boots left any perceptible trace; and on an easy slope which

a beginner could take straight I have slid down helplessly on my back

some hundred yards, only to be saved from a further and probably fatal

fall by a guide, who thoughtfully received my head in the pit of his

stomach, breaking a thumb in the effort to arrest me.

That was an extreme case of ice crust produced by Föhn, but it is not

uncommon to find every slope below 10,000 feet covered by an icy crust,

on which ski-ing is impossible. The wise ski-runner climbs on crampons,

and selects a due south slope for the descent, and times his descent

for midday. The slight surface softening produced by the sun is usually

enough to produce superficial stickiness, which gives capital running,

provided that you have mastered the Stemming turn and Christiania.

But, except at or near midday, and except on south slopes, ski-ing is

impossible during such periods.

Sometimes good ski-ing is obtained near stream beds when all other

slopes are covered by hard crust. The mist that rises from the stream

bed descends in hoar frost and covers the crust with a layer of

crystals deep enough to take a turn. But such slopes are scarce.

Occasionally the wet Föhn is followed by a period of dry Föhn.

In this case the frost at night is much milder, and you will often

find instead of marble or icy crust typical spring formations. I have

found perforated crust and even film crust in January, when a period

of dry Föhn with high temperatures by day and mild frosts by night had

followed two or three days of rain.

For weeks together I have known the crust formed by dry Föhn to

resemble perforated crust, but formed of a much smoother and more

slippery texture. Imagine a hard surface pitted by numberless smooth

little round hollows about the size of half-crown pieces. This type

of hard perforated crust gives good running, but calls for a thorough

mastery of hard snow turns.

Often the dry Föhn produced a surface-melting to a depth of two or

three inches--_typical spring conditions in midwinter_.

This again is an illustration of the law stated on p. 414: “The milder

the frost the better the crust.” In other words, once the snow in

midwinter has been thoroughly spoiled by thaw followed by frost, the

ski-ing will be best when the conditions approximate as nearly as

possible to those characteristic of spring.

Spring snow is quite common in winter when dry Föhn follows wet Föhn,

and the wise ski-runner will seize every chance of securing spring

conditions once he has despaired of proper winter conditions. He will

choose south slopes instead of north slopes, low altitudes instead of

high altitudes, and time his descent for the sunny rather than the

shady hours. “The milder the frost the better the crust.” From which it

follows that the lower the altitude and the drier the Föhn the better

the ski-ing--once normal winter conditions have been interrupted.

It is most interesting to observe how the same slope will be composed

of typical spring crust one day and of impossible slippery winter

marble crust the next day. The difference is solely due to the fact

that, in the first case, the night’s frost had been mild, and in the

second case severe.

After Föhn you will often, for instance, find a queer kind of surface,

called Foam crust, composed of innumerable overlapping edges, miniature

cornices formed by a little trickle of water, a mere drop, which has

run off a thin small eave of snow. Now hard frozen foam crust is

very unpleasant, but directly the dry Föhn gains the mastery, and

directly the hard foam crust is exposed to a hot sun and a hot dry Föhn

atmosphere, it immediately softens, and yields very fine ski-ing not

unlike the best Telemark crust.

To summarize the effect of Föhn in WINTER:

Wet Föhn followed by frosts produces a crust on all slopes which

have been exposed to thaw. If the Föhn is very pronounced, and is

accompanied by rain, which is followed by frost, all slopes will be

covered by a hard solid crust.

If a period of normal cold winter weather sets in, this crust will be

very hard and very slippery, and will only yield good ski-ing on south

slopes exposed to the sun.

If the wet Föhn is followed by dry Föhn, you will get spring conditions

at any rate at low altitudes--a hard crust, smoother but not unlike

perforated crust, in the early morning, and a soft crust, not unlike

Telemark crust, on south slopes when the sun is shining on them.

[Sidenote: Föhn in Spring.]

The Föhn is less deadly in spring, because snow which has been crusted

by Föhn and frost is remelted by the sun, and the sun and frost

together will always produce the same surface, whatever has gone

before. A wind-swept slope or a Föhn-crusted slope are affected in

precisely the same way. In winter Föhn spoils all snow that it has

affected, and, save for the lucky accident of dry Föhn, one has to

wait for a new fall till normal winter conditions are restored. But

in spring, once the Föhn has ceased, a single sunny day followed by a

single cold night’s frost is sufficient to produce the normal spring

conditions, hard crust in the morning passing through the normal

transformations of the spring day.

Wet Föhn is, however, most unpleasant in spring while it lasts. If you

are caught by wet Föhn in a club hut you are imprisoned till the Föhn

passes, for the wet Föhn brings down the avalanches on every slope

above 23 degrees (see p. 430). Ski-ing, while there is a touch of wet

Föhn in the air, is always unpleasant. Snow which has been melted

by the sun in a dry atmosphere never entirely loses its crystalline

formation, excepting at low altitudes in the very late spring. And even

then sun-melted snow is never so unpleasant as snow melted by the Föhn.

The Föhn disintegrates the snow, destroys the crystalline formation,

reduces the snow to one uniform heavy mass.

Such snow does not stick _in spring_, provided it has been through

the usual process of melting and refreezing on previous days. But

though the spring Föhn does not produce stickiness, it gives the

snow a dragging, clogging grip. It may not ‘ball’ under the ski like

sticky snow in winter, but on all but steep slopes it makes ski-ing

desperately slow. Uphill work is most trying, for the friction between

wet Föhn snow and the ski is very marked. The ski have to be thrust

through the clinging surface, and the wet Föhn not only affects the

snow, it affects one’s whole body and produces a general sense of

lassitude.

SUMMER SNOW

Between July and the end of September the snowline climbs ever higher.

The snow above this snowline obeys the laws that we have tried to

explain in the preceding pages. Snow is transformed into crust by the

action of sun or thaw or wind, and the crust itself affords good or bad

ski-ing, according to the conditions under which it has been produced

and the conditions that affect it when once it has been formed.

In the summer you will meet with every type of snow in the High Alps.

After a fresh snowfall the snow will often remain powdery for days on

northern slopes at great altitudes. Between July and the beginning

of the winter you will find typical winter snow, powder snow or

wind-driven snow: you will find typical spring snow, such as film

crust or perforated crust, but you will not find any type of snow

which can fairly be described as mainly characteristic of the summer.

The conditions in July and the first half of August will approximate

to those of June, though of course there will be far less snow in

August than in June. Towards the end of September the snow conditions

will approximate to those of the winter proper, with the important

difference that the snow at the end of September approaches a minimum.

Once the ski are left behind and the final climb begun on foot, there

will be many complex and difficult problems of snow craft to solve

which, however, hardly come within the scope of pure ski-ing. Of these

the most important is the problem of safety. Once the ski are left

behind, the climber’s interest in the snow is reduced to two main

problems: Is the snow hard enough to make going easy and yet not so

hard as to need step-cutting? Is the snow safe or will it avalanche?

The avalanche question will be treated in its proper place. Summer

Ski-ing will be dealt with on pp. 468-470.

I have tried to condense this section, and, like all condensed and

theoretic writing, it will no doubt prove rather dull reading. In the

later sections I shall try to provide concrete illustrations of the

principles here explained, and to show how the laws of snow craft may

be applied in order to get good ski-ing in the months of the alpine

calendar.

SNOW AVALANCHES

Snow avalanches may be classified either as _Ground avalanches_ or as

_Superficial avalanches_.

GROUND AVALANCHES--the ‘Grundlawinen’ of Continental writers--may be

defined as avalanches in which the entire snow surface is stripped off

a slope, revealing the underlying earth, grass or rock.

SUPERFICIAL AVALANCHES may be defined as avalanches in which a layer of

snow, more or less deep, slides off an underlying layer of snow or ice.

Before proceeding to discuss avalanches in general, and to analyse more

exactly the various subdivisions of these two principal categories, it

is essential to analyse the primary conditions that produce avalanches.

_Primary conditions_ may be defined as those which exist before the

snow has covered a slope, originally bare of snow. These primary

conditions are the _contour_ and _gradient_ of the slope and the

_nature of the surface_ that underlies the snow.

No avalanche has yet been observed on slopes whose gradient is less

than 23 degrees, though, of course, even level slopes have often been

overwhelmed by avalanches falling from steep slopes above.

Other things being equal, the stability of a snow slope depends not

only on its gradient, but also on the gradient of the slopes just below

and the slopes just above.

A concave slope, for instance, which has an even outflow so that there

is no sudden change of gradient and so that the steeper slopes merge

gradually into gentle slopes and these gentle slopes into a level

outrun, is infinitely safer than a convex slope the higher portions

of which are more gradual than the lower portions below. Slopes that

steepen suddenly below a comparatively safe gradient should always be

treated with great respect.

A slope, whose gradient would be perfectly safe if the slope petered

out gradually, may be highly dangerous if the gentler slope ends

suddenly in a steep slope, for the snow on the gentle slope is, so

to speak, ‘in the air.’ It has lost the natural support which is

afforded by a gradual concave base leading out on to the level, and

there is a reasonable chance of the weight of the snow on the safer

slope proving just too much to stand the strain at the point where the

slope steepens. In general concave slopes are safer than convex slopes,

and slopes where the gradient steadily diminishes towards the base

are safer than those in which the gradient increases before the base

is reached. Of course, any slope overhanging a cliff is always to be

treated with very great care, as even a superficial snow slide which

would be quite innocuous if the slope ended on easy safe ground may

prove fatal if it carries the ski-runner to the edge of a cliff below.

The chance of surviving an avalanche depends greatly on the nature of

the ground where the avalanche comes to rest. Many ski-runners have

escaped unhurt after being carried down several hundred feet because

they have managed to keep on the surface of the avalanche and because

the avalanche has gradually spread out fan-shaped on open, gentle

slopes. But an avalanche falling into the bed of a narrow V-shaped

valley with steep sides is almost certain to prove fatal, for the

victim of this avalanche will be buried by the snow falling above,

and this snow will fill up the narrow bed of the valley and freeze

solid instantaneously by pressure. Thus all narrow valleys such as the

Urbachthal, or the upper Rhone valley between Gletsch and Oberwald,

should only be ascended when the snow is thoroughly safe.

An analogous case is where a tributary ridge runs across a hillside. An

avalanche falling down this hillside will pile itself up against the

tributary ridge and a ski-runner will probably be crushed below the

avalanche, squeezed in between the tributary ridge and the main slope.

Often a large moraine fulfils these conditions, so that an avalanche

falling from a neighbouring slope is arrested at the moraine and piled

up against it.

Similarly, if you are caught by an avalanche while ascending a gully,

your chance of escape is much greater if the gully widens below the

point where the avalanche overwhelms you. If it contracts, the pressure

of the snow forcing its way through a narrow space may crush you to

death. Compare the account of the avalanche that killed Bennen quoted

in _Scrambles in the Alps_.

The bottom of a valley is not only dangerous for reasons just stated,

but also because the stream at the bottom of a valley often exercises,

especially in spring, an undercutting effect on the snow slopes that

end in the stream bed.

_The nature of the underlying surface_, apart from its contour and

gradient, is a factor of vital importance, especially in the early

winter and in the spring. At intervening periods most avalanches are

superficial, and slide from an underlying surface of hard snow; but in

the early winter and in the late spring the whole snow slope slides

away, so that the nature of the underlying surface and the probable

support that it affords is of great importance.

Steep grass-slopes form a dangerous under-surface, especially where it

is never or seldom mown; for long unmown grass generally lies facing

downwards, and offers a most slippery surface.

Grass which is regularly mown is usually short and stubby in winter,

and gives better purchase to the snow. A slope covered by stony

boulders, bushes or trees is usually fairly safe, though a big

avalanche, once it is fairly under weigh, will sweep over shrubs and

even over small trees. Fairly dense wood may usually be considered

as safe, provided one avoids the long open clearings made by old

avalanches, which so often run down the middle of a forest.

An elementary knowledge of geology is useful; the excellent geological

maps published by the Swiss Survey can often be consulted with benefit.

Rocks which suffer much surface disintegration provide a better

purchase for snow than very hard and consequently very smooth rocks.

The hard ‘Hochgebirgskalk,’ an alpine variety of limestone, which is

very common, especially in high regions, is slippery, and instead of

disintegrating gradually, as gneiss or granite disintegrates, has a

habit of breaking away along vertical and horizontal joints.

The common rock known as ‘Flysch,’ common in the lower Alps, provides a

much safer surface.

Glacier-polished rocks are, of course, especially dangerous, and the

whole Grimsel region is consequently swept by avalanches throughout the

winter.

The lie of the strata is an important factor. Where, as is usually the

case, the strata are inclined, one slope of a mountain will usually

be safer than the other. Diagrams I and II represent the north and

south slopes of a ridge running more or less east and west. The ridge

is formed by parallel but inclined bands of strata. Rock climbers

know that the slope in Diagram I, though of the same gradient as the

slope in Diagram II, is very much more difficult to climb. It is also

much more liable to avalanche, as the outcrop of the strata provide

a natural check to avalanches in Diagram II; whereas in Diagram I

each outcrop forms a small steep snow slope quite unsupported. If the

outcrops are of reasonable breadth, there will be belts running across

the face of the slope at A’, B’, C’, D’ which will be inclined into the

slope, and provide a safe line of traverse; whereas there is no safe

line for a ski-runner desiring to traverse or ascend the slope A, B, C,

D.

[Illustration: DIAGRAM I.]

[Illustration: DIAGRAM II.]

Geological maps indicate the ‘strike’ of the strata, and therefore

provide useful clues as to the varying liability of slopes to avalanche.

Loose scree guarantees the ski-runner against ground avalanches,

but, as the winter advances, loose scree is soon covered with deep

snow, from which later layers of snow can slide uninfluenced by the

underlying scree. In fact, as the winter advances, the original

underlying surface plays a smaller part in the problem of avalanches.

Hard-crusted snow covered by soft snow is especially dangerous, and

of course ice, as is so often met with in the High Alps, is the worst

under-surface of all. Fortunately, snow often attaches itself firmly to

ice, transforming an ice slope into a snow slope.

The conditions necessary for this transformation will be explained on

pp. 426-427.

So far we have dealt with _primary_ conditions, the nature of the

ground before the snow has begun to fall and the gradient of the slope

from which the avalanche slides. An important factor is the _quantity_

of snow on the slope. It often happens that a shallow superficial layer

detaches itself and carries a ski-runner down the slope. If the slope

ends on gentle ground, no damage is done beyond the loss of height

and the consequent waste of time and effort in reascending to the

spot from which the avalanche started. But if the snow slide carries

the ski-runner over a cliff or into a bergschrund or crevasse, it is

clearly immaterial to the ski-runner whether his original snow slide

was 1 inch or 6 feet in thickness.

I propose to use the word SNOW SLIDE for such small avalanches as are

only dangerous where they carry the ski-runner on to dangerous ground,

such as the edge of a precipice, and to reserve the word AVALANCHE for

avalanches deep enough in themselves to overwhelm and possibly to kill

a ski-runner.

Though a very small layer of snow--an inch or even less--is enough to

produce a snow slide, especially if the shallow layer rests on ice, the

amount of snow necessary to produce a real avalanche is much greater,

and varies very much with the quality of the snow.

CLASSIFICATION OF AVALANCHES

The old writers divided avalanches into ‘Grundlawinen’ (ground

avalanches) and ‘Staublawinen’ (dust avalanches)--a misleading

classification, for a ground avalanche may be composed of dry powder

snow, and produce all the appearance of a ‘Staublawinen’: the clouds

of white snow dust, once supposed to be peculiar to avalanches of

powder snow, are really common in almost every type of big avalanche,

especially where the avalanche falls over steep cliffs. I prefer to

divide snow avalanches into four main classes:

I. Dry powder avalanches.

II. Wet new snow avalanches (i.e. powder snow which has begun to thaw

as differentiated from old wet snow which is formed by crust which has

been thoroughly melted).

III. Snow-slabs.

IV. Wet old snow avalanches--the Grundlawinen of the older authors.

I. DRY POWDER AVALANCHES.--Newly fallen snow, which has not been

subject to thaw or sun, contains a great deal of air until it settles,

and even when it has settled it still imprisons a considerable quantity

of air. This makes for stability, for snow is less likely to avalanche

when it lacks cohesion. I have often experimented on newly fallen snow

at a low temperature, and I have found it almost impossible to start an

avalanche on any slope below about 35 degrees and less than about 200

feet in height. Small snow slides are common enough if the underlying

surface is hard; but as a rule even snow slides come to a standstill

after a few yards. The really dangerous dry powder avalanches only

occur on very long and steep slopes, where the amount and mass of

the snow is sufficient to produce the necessary momentum for a big

avalanche. Dry powder has a strong internal friction, and, as a rule,

some powerful external impact is necessary to start an avalanche.

Of such impacts wind is the most dangerous. A sudden blizzard may

convert a valley, safe when the ski-runner entered it, into a veritable

death-trap. Further, the fall of an avalanche on one side of a valley

may precipitate other avalanches on the opposite side. Partly owing

to the air imprisoned in dry powder, and partly owing to the momentum

of the avalanche itself, the wind caused by a big fall of snow is

extremely powerful and destructive. Houses and trees are torn away by

the blast, even though they may be beyond the track of the avalanche.

The force of the wind is multiplied manifold when the avalanche falls

into a constricted space, such as the floor of a narrow valley. I have

seen a bridge just below Gletsch destroyed by a spring avalanche, or

rather by the wind caused by an avalanche on the opposite side of this

very narrow valley. A large part of the bridge, weighing several tons,

had been thrown _upwards_ to a height of about 150 feet!

After a heavy snowfall the danger of dry powder avalanches may last for

a day or two, or even more; but as a rule two or three days of settled

weather and keen frosts render most northern slopes--in winter, though

not in spring--safe enough. When the powder snow has passed into the

stage known as _Crystal powder_--i.e. when the small light dry powder

has been converted into crystals of an appreciable size--the danger of

avalanches is very remote. On a windless day with a temperature in the

shade below freezing, I should not hesitate to cross almost any slope

up to 35 degrees which was covered by genuine crystal powder snow,

provided that the slope petered out gradually on to the level and did

not overhang a cliff.

II. WET NEW SNOW AVALANCHES.--Directly the powder snow is exposed to

surface thaw, either owing to a rise of temperature or to the sun,

its weight and cohesiveness increase, and the danger of avalanches is

consequently much greater. Sometimes the snow falls with a temperature

above freezing. This wet new snow is dangerous, but as it is also

extremely unpleasant for ski-ing, few ski-runners are likely to be

abroad. On the other hand, ski-runners are often tempted to cross a

southern slope where the powder is beginning to melt. Snow on a steep

southern slope soon gets thawed through the bottom, so that ground

avalanches are quite normal in winter on south slopes. As a rule, south

slopes in winter get rid of their superfluous snow in the first two

or three days of fine weather. The snow that remains is thawed by day

and frozen by night, so that at the end of four or five days the south

slopes have got rid of their avalanches, and the snow that remains is a

crust more or less hard and slippery. This crust by day may become soft

breakable crust, but once it has crusted, a slope in the winter is not

likely to avalanche until there is a new snowfall. A very marked rise

in temperature may make a south slope that has been crusted dangerous

again; but such sudden and marked rises of temperature are rare in

winter.

In general, therefore, south slopes in winter are safer than north

slopes. They give rise to more avalanches, but such avalanches as

fall off south slopes generally fall within two or three days after

a snowfall, after which a south slope is crusted and safe in winter;

and though after a few days of settled weather most north slopes are

absolutely safe, very steep and very long north slopes, or short steep

slopes overhanging a cliff, are always dangerous. Of course, whenever

the wet Föhn is blowing, or whenever there is a general thaw, _all_

steep slopes, and a great many moderate slopes, become very dangerous

indeed. The effect of the thaw is to give the snow the cohesiveness

and weight which it lacks in its pristine dry condition. The dampness

in the air saturates the snow with moisture and increases its weight.

During a severe Föhn you will often see huge ground avalanches

almost as destructive as those that fall in spring. When the Föhn is

blowing ski-ing is always extremely dangerous. Fortunately, it is

also extremely unpleasant, or fatal avalanche accidents would be more

frequent.

The dry Föhn (see p. 418) is much less dangerous. Unless it is very

pronounced, it will hardly affect northern slopes in winter, though it

may convert a south slope, usually covered by hard crust, and therefore

safe, into soft wet and dangerous snow.

In spring northern slopes usually hold powder snow for a few days at

high altitudes, and even at moderate altitudes in the early spring,

such as March. This powder snow soon loses the dry, light, powdery

characteristics of winter powder. Though it continues to yield

excellent running, spring powder is very liable to avalanche. It is

damper and more cohesive than dry powder, and therefore more dangerous.

Dry powder often rests on the ground below. A northern slope will often

be covered with a homogeneous layer of powder some feet in depth, but

spring powder (see p. 413) invariably rests on a hard-crusted slope

below. It therefore tends to slide away during the warm hours of the

day, and should be treated with very great caution.

Avalanches composed of spring powder are, properly speaking, new wet

snow avalanches. They must be carefully distinguished from old wet snow

avalanches, for old wet snow is formed by the melting of crust, whereas

spring powder is formed by the melting of powder snow, i.e. ‘new

snow.’ Snow may be defined as ‘new’ before it has been crusted, and as

‘old’ when it has been through the crusting process. Thus powder snow

is always ‘new,’ however long it may be since it fell. On the other

hand, a snowfall in June may be turned into crust within twenty-four

hours, and thereby become ‘old snow.’ Crust and soft snow formed by the

melting of crust are both ‘old’ snow.

Spring powder is all the more dangerous, because it yields wonderful

ski-ing at a time when other slopes have been spoiled by the sun.

Furthermore, as spring powder is found on north slopes, ignorant

ski-runners underestimate its danger; for it is a common fallacy among

the inexperienced that south slopes are more dangerous than north. In

spring the reverse is usually the case, for avalanches in spring are

occasioned by the general air temperature just as much as by the sun.

(See also below, p. 438)

III. THE WIND-SLAB.--The _wind-slab_ is the most treacherous of all

avalanches, the most difficult to foresee, and the most incalculable in

effect.

Falling snow is usually accompanied in the High Alps, and often

accompanied in the lower regions, by wind. If the wind is powerful,

the falling snow is driven over exposed ridges in whirlwinds, and

comes to rest on the lee-side and in sheltered hollows. In this way

the snowy avenues leading to glacier passes and the more sheltered

snow-fields receive more than a fair share of snow. This action of

the wind, denuding the exposed ridges and feeding the hollows and

lee-sides, takes place on both a large and a small scale: on a large

scale, when snowy valleys are fed from the snow blown off the exposed

ridges that rise out of them, and on a small scale on any slope exposed

to wind which is divided by ridges, however small. Any tributary ridge

on a slope across which a wind is blowing will have a wind-side and a

lee-side, and will accumulate snow on the lee-side and give off snow on

the wind-side. A stone wall or even a hedge provides an example of this

on a small scale.

Snow driven by wind and settled on lee-sides may either be more or less

powdery, a denser, heavier powder than normal powder, or it may assume

one of the many forms of wind-caused crust. We have described on p. 407

the various forms of winded powder, such as ripplemark, caked powder,

etc., and on p. 408 the various forms of wind-formed crust, such as

windboard and _Skavla_.

In general, the greatest caution should be exercised when crossing

any slope which has accumulated much wind-driven snow. Wind-driven

powder snow is heavier and more adhesive than ordinary powder. It is

more detached from the underlying surface, and is much more conducive

to avalanches. The ski-runner should keep his eyes open for traces of

wind action, and when he finds snow which has obviously been exposed

to severe wind, he should exercise the greatest possible caution on

crossing over to the lee-side of a ridge dividing slopes, whence the

snow has obviously been blown away, from slopes where the wind-driven

snow may have fallen back to earth. Wind-driven powder may in turn be

covered by a new snowfall, which adds to the difficulties of diagnosing

the avalanche risk.

So far we have been dealing with wind-driven snow which still retains

some suggestion of powder, which is soft and dense and caky. A still

more treacherous and dangerous wind formation is the wind-slab, or

‘Schneebrett,’ of Continental authors.

Windboard, as already explained (p. 407), is a hard, slippery crust

formed by wind. Windboard is common on glaciers in the winter months,

and though disagreeable to ski on, it is safe enough in most cases.

Sometimes, however, this windboard, instead of being homogeneous with

the underlying snow, is loosely attached, and in places forms a vault

with a hollow space between the windboard and the snow beneath. The

windboard is, then, properly speaking, a wind-slab. The wind-slab,

or, as some writers prefer to call it, the snow-slab, is formed by

wind-driven snow, which eventually settles into a hard crust. As the

wind-drifted snow is of a different density to the snow on which it

settles, it tends to form a distinct stratum from the underlying snow.

In winter the temperature is usually considerably below freezing, so

that snow which falls, or snow which is drifted by the wind, cannot

bind with the snow below. In order for two strata of snow of very

different density to form a homogeneous whole, there must be a period

when the temperature is just above freezing in order to produce the

melting followed by frost, which is a necessary factor in the fusing

together of two successive layers of different types of snow.

The wind-drifted snow, ultimately transformed into a hard crust,

is then of a different density to the snow below, to which it is

loosely attached. This underlying snow may be either soft snow or hard

crust; in either case the wind-slab forms a covering layer insecurely

attached to the foundation snow. This superficial layer is subject to

different strains from those which affect the underlying snow; for the

tension due to the expansion and contraction which follows changes of

temperature affects the layers formed of snows of different density

and character in varying ways. The surface layer, or wind-slab, may

contract more obviously than the snow below, so that if the slope is

concave in shape, the wind-slab, in contracting, tends to form an arch

above a more or less shallow vault.

There is little if any surface indication to betray the fact that the

wind-slab is not homogeneous with the underlying snow; the ski-runner

may cross some such slope without the least suspicion that the hard,

slippery crust is not quite so solid as it appears. Suddenly he will

hear a sharp cracking noise; the hard crust will settle under him and

cave in; the crust cracks along the line made by his ski, and the whole

slope comes down on top of him in a cataract of tumbling blocks. The

strata formed by the wind comes away, tearing with it much of the soft

underlying snow, and pours down in a floor of hard, icy blocks of snow.

The wind-slab is the most dangerous and deceptive form of avalanche.

Its hard polished surface gives a false sense of security. The

temperature is no guide, for wind-slabs can avalanche at any

temperature. Indeed, extreme frost tends to make the wind-slab more

brittle. It can avalanche after days or weeks of fine weather when all

the more obvious avalanches have fallen. Lastly, this wind-slab is to

be found in the natural line of approach to glacier passes, in the long

sheltered avenues that collect the snow blown off the exposed ridges.