Since glaciers are often the easiest way up a mountain, climbing parties
make use of them, starting at dawn so as to have a long day and
following up the rough and rigid slope, zigzagging round crevasses and
avoiding regions of seracs. Toward the upper end there may be fresh snow
bridging the crevasses and the party should be roped together and travel
in single file, the leading guide thrusting his ice axe into the snow at
every step to make sure of safe going. A fall into a crevasse when
unroped may be fatal. Seventeen years ago, while climbing Mt. Gordon
north of lake Louise, Mr. C. S. Thompson slipped 60 feet into a crevasse
where he was wedged in between the narrowing walls. Dr. Collie was
lowered to rescue him, and he was finally pulled out by a glacier rope
fastened round his arms, but it was a narrow escape.
When the sun shines warmly on the glacier melting begins and water
trickles down the ice ridges, and towards afternoon torrents of pale
blue water are racing downwards in ice channels, here and there plunging
into a crevasse. This becomes hollowed into a tube like the penstock of
a water power and the foamy torrent springing into the blue chasm is
called a “moulin,” or mill. In this way the waters thawed from the
surface reach the bottom and there roar along through an ice tunnel to
the end of the glacier, bursting into daylight as a full fledged river.
Glacial streams are capricious. On a frosty morning scarcely any water
flows and one can go far into the ice cave, but in the late afternoon
there is a raging torrent loaded with mud and stones spreading into half
a dozen channels on the broad flood ground. On a rainy or snowy day when
the sun is hidden, the glacial river almost goes out of business, but
comes to life again when the clouds vanish and the sun shines. At those
heights with a clear sky the heat of the sun may be intense though it is
freezing a few feet away where some rock casts a shadow.
_The Work of Glaciers._
One of the most interesting points in a glacier is its carrying power.
Though it is in motion like a plastic substance it is solid and strong
enough to support any weight loaded upon it. Debris quarried by frost
from the mountain side buries its edge so that often one may walk 50
yards out before the ice can be seen. This fringe of broken rock carried
on the edge of the glacier is called a marginal moraine. When two
glaciers join, the marginal moraines between them unite to form a medial
moraine, and when several tributaries combine to make a large glacier
the dark lines of the medial moraines can be followed by the eye for
long distances upwards to rocky peaks rising out of the névé, the source
from which the train of rocks was derived.
Blocks even as large as cottages now and then roll down upon the ice and
are transported without trouble. Medium size blocks a few feet across
called “glacier tables” are left standing on pedestals of ice, as
thawing goes on all round them, since they protect the ice beneath from
the sun.
The whole mass of stony material is carried steadily onwards until the
end is reached where melting is complete and no more burdens can be
borne. Then a terminal moraine is piled up, a steep and rugged crescent
of loose blocks by no means easy to scramble over.
Work just as important is going on out of sight beneath the glacier,
where fragments of stone frozen into the bottom of the ice form tools
for gouging, carving and scouring the rocky floor, both tools and rocks
being ground up into the “rock flour” that makes the glacier streams so
milky and opaque. The ground up material mixed with stones of all shapes
and sizes without any assortment is left behind when the glacier thaws
as “boulder clay.” A little search in this clay shows stones with
polished and striated surfaces, well worn tools, often called “soled
boulders” and the rock surface beneath the boulder clay is seen to be
rounded, smoothed and grooved in a very striking way.
_The Retreat of Glaciers._
Our glaciers, like those of other countries, are now almost all in
retreat, either because the climate is slowly growing warmer so that
thawing goes on faster or because the snowfall is lessening so that the
névé fields no longer feed the glaciers as substantially as before. On
this account one can often see several terminal moraines down the valley
below the one now forming. The nearest to the present end of the ice is
almost bare, the next, a few hundred yards away, may have bushes growing
on it, and others a mile or two away may be covered with ancient forest.
For some years past the Vaux family of Philadelphia, two brothers and a
sister, all admirable photographers, have fixed the position of the end
of all accessible glaciers by marking points and directions on rocks
near by and by photographing the snout of the glacier. This work
determines their rate of advance or recession from year to year, and a
record of the results is published in the journal of the Alpine Club of
Canada and elsewhere.
[Illustration]