The action is similar on a small scale to the erosive action of water on a large scale. Water furrows an even mountain side with gullies and a more or less level plain with intersecting ravines that produce a series of hills. And just as in the geological cycle the last stage of a mountainous country is a peneplane, so on snow the action of the sun acts on the ridges and hillocks formed by previous action of the sun and once again reduces the surface to a plain. I have seen in winter one heavy rainstorm furrow the hillsides with miniature ridges and a level snow slope with miniature hillocks, and I have seen the next rainstorm—which followed two days later—erode the ridges and hillocks formed by the first storm and once again produce slopes of even contour and levels unbroken by hillocks.
The Spring Time-table
The spring ski-runner has, in general, the choice of two periods of the day for his descent. He can descend in the morning just after the sun has begun to soften the surface of the hard crust, or in the evening when the soft melted snow is beginning to freeze again. If the day’s run ends at some club hut situated at a reasonable height, say 9000-10,000 feet, he can usually leave the hut about dawn and return about midday, for the snow at this height is usually perfect just before midday; or he can time his descent for just before or just after sunset. If he is descending to the valley, it is usually best to time his descent a great deal earlier. In May the snow below 8000 feet softens very quickly directly the sun touches it, and becomes dangerous on steep slopes. In this case, should the snow on the glaciers be film or perforated crust, he can start his descent before the sun has softened the crust, so as to reach the lowest limits of the snow before they have been softened by the sun.
As this is often impossible, it is best to time the descent from the peak to the club hut for midday, or rather before midday, and then to wait in the hut till sunset, and continue the run down to the valley after the sun has set and the snow begun to freeze again. Guides are often dreadfully impatient, and have the greatest objection to spending a long time on the summit of a peak. Many guides seem to regard summit views with studied malevolence, and very few guides really understand spring snow. If, as often happens, the arrival on the summit occurs after midday, it is absurd to spoil a perfect descent by running down in the afternoon. The amateur must exercise reasonable restraint and insist on waiting. There are many things more unpleasant than to lie about on the summit of some great peak for three or four hours studying the changing effect of a May afternoon on distant hills and valleys, what time the snow gradually improves.
Great judgment is required in spring to get the best value out of the descent; it will often pay a party to wait three or four hours for the snow to improve. Summer climbers seldom linger on the summit, for in summer the wind usually makes itself felt, but in May or June one can bask on the top of a peak in shirt sleeves even after the sun has set.
Eastern slopes, of course, are the first to soften in the morning and the first to freeze at night. The best moment to descend varies with the orientation of a slope. It is often possible to choose one of two alternatives,—an eastern or a western route,—and the wise ski-runner can often improve the quality of the descent by a clever choice of line and slope.
Considerable experience is needed after a fresh fall of snow. Snow usually remains powdery for a day or two on north slopes in May or June. Perfect powder snow is by no means the exception in spring; an inch or two of winter powder on spring crust provides a surface which is absolutely unrivalled. When, however, the powder begins to turn into crust the ski-ing may often be difficult. After a snowfall you should try either to find slopes holding winter snow or slopes holding spring snow, but not slopes on which the snow is just changing from powder to crust. You may, for instance, have spent the night at a club hut at a height of 9000 feet above the sea. You have arrived in the middle of June on the first fine day after a snowstorm. The snow near the hut has been thoroughly melted by the sun before your arrival. The weather is clear, and there is a north wind blowing. You may reasonably expect powder snow on north slopes down to about 10,000 feet, so that if you have a choice of an expedition on north snow, say a peak 13,000 feet high, you should attempt it, and you will probably find powder snow most of the way. On the other hand, a peak of the same height that faced south might be an unpleasant condition, powder turning into sticky snow or crust. It might therefore be best to choose a small peak, say 11,000 feet, facing south, and run down below the hut, remounting in the evening. Such an expedition might yield better ski-ing than a high peak.
After a day or two of fine weather all snow, excepting snow on north slopes at a very great height, is transformed into ordinary spring snow. Thenceforward the ski-runner may count on perfect snow, provided he times his descent right.
It is only with forty-eight hours of a snowfall that there is any real difficulty. During such short periods the experienced spring ski-runner will know whether to go for north slopes in the hope of winter snow or for southern slopes, or north slopes at lower altitudes, in search of spring snow.