We have no special word in English for these perpetual snow fields and
so the French term NÉVÉ is commonly used. Snowline is not nearly so
definite as timberline and varies with latitude, exposure and snowfall.
In the eastern Rockies of Alberta, where only a few feet fall in winter,
the line is scarcely below 9,000 feet; while in the western Selkirks,
which catch the full brunt of the Pacific winds laden with moisture and
have a snowfall of 40 or 50 feet in a year, snowline is depressed almost
to timberline, about 7,500 feet. This accounts for the bareness of the
eastern Rockies as compared with the splendid Alpine features of the
Selkirk range, which is the lower of the two.
While one gazes entranced at the array of lakes and valleys, of
snowfields and dark cliffs, the wind rises and mountains to the west put
on a cap of cloud. This grows and darkens and presently a mantle of mist
sweeps up with the wind, the sun is dimmed and in a few minutes the wide
world is shut out by a blizzard. We must make our way down to lower
levels where sleet whitens the closing flowers, and then through a belt
of rain swept hillside into the valley where the sun may still be
shining hotly.
Since snow falls every month in the year on the névé fields and never
melts away one might expect the mountains, especially the Selkirks, to
grow as snowheaps into the sky; but of course this does not take place.
Under the increasing load of snow the lower beds are compressed into
ice; so that the névé, beginning as loose or hard drifted snow above
passes downwards into ice banded with blue and white layers, the whole
sometimes hundreds of feet in thickness.
The snow accumulates only on the gentler slopes or in the higher
valleys. On cliffs it cannot lodge but piles upon the névé beneath; and
on steep slopes it may lie for a time but now and then, especially
toward spring, it breaks loose and thunders down into the valley as an
avalanche.
_The Motion of Glaciers._
The final disposal of the snowfield, turned to ice in its lower parts,
comes by a slow creep downwards. That the névé is actually in motion can
be seen by following the slope of snow to its upper edge against some
mountain wall where a “BERGSCHRUND” generally yawns between the
snowfield and the cliff. This may be several feet wide, and may go down
many feet to obscure depths. No amount of snow fall can fill the chasm
permanently, though it may be bridged with fresh snow for a time, making
a risky passage for the climber.
[Illustration]