A FEW WORDS ABOUT GLACIERS
Of all the beautiful and interesting things mountain districts have to
show, none surpass the glaciers.
Now a glacier is simply a river of ice, which never melts away even
during the hottest summer. Glaciers form high up on mountains, where
there is a great deal of snow in winter, and where it is never very
hot even in summer. They are also found in northern lands, such as
Greenland, and there, owing to the long cold winter and short summer,
they come down to the very level of the sea.
A glacier is formed in this way: There is a heavy fall of snow which
lies in basins and little valleys high up on the mountain side. The
air is too cold for it to melt, and as more falls on the top of it the
mass gets pressed down. Now, if you take a lump of snow in your hand
and press it, you get an icy snow-ball. If you squeeze anything you
make it warmer. The pressing down of the great mass of snow is like
the squeezing of the ball in your hand. It makes it warmer, so that
the snow first half melts and then gradually becomes ice. You bring
about this change in your snow-ball in a moment. Nature, in making a
glacier, takes much longer, so that what was snow one year is only
partly ice the next--it is known as _nevé_--and it is not until after
several seasons that it becomes the pure ice we see in the lower part
of a glacier.
One would fancy that if a quantity of snow falls every winter and does
not all melt, the mountains must grow higher. But though only a little
of the snow melts, it disappears in other ways. Some is evaporated
into the atmosphere; some falls off in avalanches. Most of it slowly
flows down after forming itself into glaciers. For glaciers are always
moving. The force of gravity makes them slide down over their rocky
beds. They flow so slowly that we cannot see them move, in fact most
of them advance only a few inches a day. But if a line of stakes is
driven into the ice straight across a glacier, we shall notice in a
few weeks that they have moved down. And the most interesting part
of it is that they will not have moved evenly, but those nearest the
centre will have advanced further than those at the side. In short, a
glacier flows like a river, the banks keeping back the ice at the
side, as the banks of a river prevent it from running so fast at the
edge as in the middle.
[Illustration: GENERAL VIEW ON THE LOWER PART OF A LARGE GLACIER.
The surface is ice, not snow. The snow-line may be seen further up.]
A large glacier is fed by such a gigantic mass of snow that it is in
its upper part hundreds of feet thick. Of course when it reaches
warmer places it begins to melt. But the quantity of ice composing it
is so great that it takes a long time before it disappears, and a big
glacier sometimes flows down far below the wild and rocky parts of
mountains and reaches the neighbourhood of forests and corn-fields. It
is very beautiful at Chamonix to see the white, glittering ice of the
Glacier des Bossons flowing in a silent stream through green meadows.
The reason that mountaineers have to be careful in crossing glaciers
is on account of the holes, cracks, or, to call them by their proper
name, crevasses, which are met with on them. Ice, unlike water, is
brittle, so it splits up into crevasses whenever the glacier flows
over a steep or uneven rocky bed. High up, where snow still lies,
these chasms in the ice are often bridged over, and if a person
ventures on one of these snow bridges it may break, and he may fall
down the crevasse, which may be so deep that no bottom can be found to
it. He is then either killed by the fall or frozen to death. If, as I
have explained before, several climbers are roped together, they form
a long string, like the tail of a kite, and not more than one is
likely to break through at a time. As the rope is--or ought to
be--kept tightly stretched, he cannot fall far, and is easily pulled
out again.
The snow melts away off the surface of the glacier further down in
summer. It is on this bare, icy stream, scarred all over with little
channels full of water running merrily down the melting rough surface,
that the ordinary tourist is taken when he visits a glacier during his
summer trip to Switzerland.
[Illustration: A GLACIER TABLE (page 11).]
[Illustration: Taken in Mid-Winter on reaching the Lower Slopes of a
Mountain after a terrific Storm of Snow and Wind. The local Swiss
snow-shoes were used during part of the ascent.]
You will notice in most of the photographs of glaciers black streaks
along them, sometimes only near the sides, sometimes also in the
centre. These are heaps of stones and earth which have fallen from the
mountains bordering the glacier, and have been carried along by the
slowly moving ice. The bands in the centre have come there, owing
to the meeting higher up of two glaciers, which have joined their side
heaps of rubbish, and have henceforward flowed on as one glacier. The
bands of piled up stones are called moraines, those at the edge being
known as lateral moraines, in the centre as medial moraines, and the
stones which drop off the end (or snout) of a glacier, as terminal
moraines.
Besides these compact bands, we sometimes find here and there a big
stone or boulder by itself, which has rolled on to the ice. Often
these stones are raised on a pedestal of ice, and then they are called
"glacier-tables." They have covered the bit of ice they lie upon, and
prevented it from melting, while the glacier all round has gradually
sunk. After a time the leg of the table begins to feel the sun strike
it also. It melts away on the south side and the stone slips off. A
party of climbers, wandering about on a glacier at night or in a fog,
and having no compass, can roughly take their bearings by noticing in
what position these broken-down glacier-tables lie.
Occasionally sand has been washed down over the surface of the ice,
and a patch of it has collected in one place. This shields the glacier
from the sun, the surrounding ice sinks, and eventually we find cones
which are lightly covered with sand, the smooth ice beneath being
reached directly we scratch the surface with the point of a stick.
It is difficult to realise the enormous size of a large glacier. The
Aletsch Glacier, the most extensive in the Alps, would, it has been
said, if turned to stone, supply building material for a city the size
of London.
With regard to the movement of glaciers, the entertaining author of "A
Tramp Abroad" mildly chaffs his readers by telling them that he once
tried to turn a glacier to account as a means of transport.
Accordingly, he took up his position in the middle, where the ice
moves quickest, leaving his luggage at the edge, where it goes
slowest. Thus he intended to travel by express, leaving his things to
follow by goods train! However, after some time, he appeared to make
no progress, so he got out a book on glaciers to try and find out the
reason for the delay. He was much surprised when he read that a
glacier moves at about the same pace as _the hour hand of a watch_!
[Illustration: A DISTORTED AND CREVASSED GLACIER.
Showing the rough texture of the surface of a Glacier below the
Snow-line.]
Many thousands of years ago there were glaciers in Scotland and
England. We are certain of this, as glaciers scratch and polish the
rocks they pass over as does nothing else. Stones are frozen into
the ice, and it holds them and uses them as we might hold and use a
sharply-pointed instrument, scratching the rock over which the mighty
mass is slowly passing. In addition to the scratches, the ice polishes
the rock till it is quite smooth, writing upon it in characters never
to be effaced the history of past events. Another thing which proves
to us that these icy rivers were in many places where there are no
glaciers now, is the boulders we find scattered about. These boulders
are sometimes of a kind of rock not found anywhere near, and so we
know that they must have been carried along on that wonderful natural
luggage-train, and dropped off it as it melted. We find big stones in
North Wales which must have come on a glacier beginning in Scotland!
Glacier-polished rocks are found along the whole of the west coast of
Norway, and there are boulders near Geneva, in Switzerland, which have
come from the chain of Mount Blanc, 60 miles away.
So you see that the glaciers of the Alps are far smaller than they
were at one time, and that in many places where formerly there were
huge glaciers, there are to-day none. The Ice Age was the time when
these great glaciers existed, but the subject of the Ice Age is a
difficult and thorny one, which is outside the scope of my information
and of this book.