ICE-NEEDLES TO ICE-MOUNTAINS
“In all time,
Calm or convulsed,--in breeze or gale or storm,
Icing the pole, or in the torrid clime
Dark-heaving;--boundless, endless, and sublime--
The image of Eternity,--the throne
Of the Invisible.”--BYRON.
So far most of our thoughts have been given to Earth’s milder regions;
where, indeed, the warm ocean water is at best but a thin slice laid
over vast depths of cold water, yet where, so far as man is concerned,
heat has the upper hand. In other parts, far to north and south, the
Reign of Frost is a dire reality; and that chill monarch “rules the
roost” in a masterful fashion, lording it over land and sea for months
together, with none to resist his sway.
Wherever King Frost waves his sceptre, one result always follows. Water
changes from a liquid to a solid.
Nor is water the only liquid which so changes. Quicksilver, known to
us usually as a liquid, may be frozen, though not without a greater
amount of cold than that which freezes water. Then, again, molten
iron--that is, iron made soft through great heat--is a liquid which
when cold hardens into a solid. Iron as we most often see it is simply
in its frozen state; just as much the frozen form of iron as ice is the
frozen form of water.
And the freezing of the two comes about in the same mode. As molten
iron cools and hardens it crystallizes. Minute needles, far too minute
to be seen, take shape, crossing and re-crossing at various angles,
till the whole becomes a solid mass of interlaced iron needles, held
in position by attraction. When water changes into ice, the same thing
happens. The water-particles shape themselves into tiny needles, and
these ice-needles cross and re-cross, till they are knitted into a
compact mass, something like the mass of iron needles.
Nor are needles alone found in ice. Exquisite forms resembling
ice-flowers are there also, commonly invisible, but composed of
ice-needles woven into various shapes, which again are woven into the
fabric of the solid ice. So a block of ice may perhaps be said to be
formed of ice-flowers, and the ice-flowers to be formed of ice-needles.
Such flowers are of many shapes, but more generally they have six
petals each. If a ray of sunlight is thrown upon a slab of ice, through
a lens, so as to concentrate the heat, then, as the ice melts, the
sparkling of these tiny florets can be seen; and when their magnified
image is cast upon a sheet, the six-petalled flowers become clearly
visible.
Even more beautiful than the ice-flowers embedded in solid ice are the
ice-flowers embedded in snow. They too are made of tiny spicules or
needles of ice; and they too, while varying much in shape, are commonly
six-petalled.
Solid blocks of ice are at first sight so unlike masses of feathery
snow that a child would be surprised to hear a snowflake spoken of
as “ice.” Yet the difference between the two lies mainly in the
arrangement of the little ice-needles, in the way they are put
together. Those of hard ice are more densely packed; those of snow are
more loosely joined, with open spaces between, full of air. It is the
abundance of air, mixed in with ice-needles, catching and reflecting
light, which gives to snow its whiteness.
In some cases, however, as with glacier-ice, the texture is so
close--like that of glass--that neither flowers nor needles are
discernible.
The fact that snow may be, through hard pressure, actually transformed
into firm ice--and this is an everyday occurrence in the high
Alps--shows how closely akin the two are.
Every country in the world has, at a certain height, that which is
called “the line of perpetual snow,” or, more briefly, “the snow-line.”
Below that limit snow may fall in winter, and water may freeze, but
both vanish in the summer. Above that limit snow and ice are found all
the year round, lessening to some extent in summer months, but never
disappearing.
Over the equator the snow-line is about sixteen thousand feet high, or
higher than Mont Blanc; so if Mont Blanc were situated on the equator
it would not be a snow-clad mountain. At the north and south poles
the snow-line is down at the sea-level. Summer warmth there does not
suffice to get rid of winter ice and snow. Between the equator and the
poles the snow-line varies in each country, according to that country’s
position and climate.
Above the snow-line on lofty Swiss mountains heavy falls add
perpetually to the mass of snow. During the summer a certain degree of
thawing goes on, but never anything like enough to balance the wintry
additions. Exactly at the snow-line the quantity of snow which falls
and the quantity which thaws in the year are about equal. Lower down
the yearly thawing exceeds the yearly snowfall.
But if, above that line, more snow is being added year by year than
can thaw and flow away, must it not be that those mountains which wear
perpetual snow are always growing higher?
It certainly would be so _if_ the snow heaped upon those summits had no
other outlet, no other means of escape to the Ocean--the goal of all
Earth’s waters. But another mode of escape is found. Superabundant snow
on mountain heights gets away by means of glaciers.
We have had to think about liquid rivers flowing in the ocean, and here
are solid rivers flowing on the land. Liquid rivers with liquid banks;
solid rivers with solid banks. A curious anomaly in either case.
The higher levels of land are drained by rivers pouring down to lower
levels and thence into the sea; and it is the same with the mighty
snowfields of Switzerland as with any gentle range of English hills,
only here we have rivers of ice instead of rivers of water.
But why not rivers of snow, if a glacier means the draining away of
snowfields?
Well, so they are--rivers of snow. But the heavy weight of overlying
snow above, and the great pressure of descending masses later, welds
the light and delicate snow into hard ice. Those tiny needles, of which
the falling snow was made, are crushed closer and closer, till they
form a solid block, which loses all resemblance to snow. In summer the
melting of the surface by day, and its freezing again by night, help
forward this transformation.
Thus a glacier is literally an Ice-River, a huge long tongue of ice,
squeezed from beneath snowfields, and creeping down a valley.
Such rivers vary much in size. Some of the Swiss glaciers are between
twenty and thirty miles long, in parts two or three miles wide,
and often hundreds of feet deep. Starting above the snow-line they
sometimes reach thousands of feet below it, the milder air failing to
end their existence sooner. So enormous are the ice-masses, that not
all the strength of the summer sun can make away with them. Of course,
each square yard in turn does melt, and does help to feed the river of
water which rushes away from the lower end of the glacier--sooner or
later to reach the ocean.
Switzerland’s grandest glaciers dwindle into insignificance beside the
enormous ice-rivers of the frozen north. When the “Humboldt Glacier”
of Greenland gets to the ocean it is about forty-five miles in width.
A generous gift of water indeed, from land to ocean. Another monster
glacier ends in a cliff of solid ice, rising in parts to four hundred
feet of height. Greenland lies under one unbroken shield of snow and
ice; and the weight of this tremendous “ice-cap” presses out numberless
rivers of ice from its shores into the sea.
These do not, like Alpine glaciers, end in rivers of water, flowing
through milder climates to the ocean. The Greenland glaciers themselves
reach the sea, each thrusting an enormous “foot” far into deep water.
For a while, as it does so, the glacier-ice holds firmly together in
a solid mass, gliding slowly over the ocean-bed, getting deeper and
deeper, till only a small part of it shows above the surface.
But ice naturally floats. The upward pressure of the sea becomes
increasingly great, fighting against the tenacity of the ice, and in
the end old Ocean has the best of the contest. A huge mass of ice
snaps off from the glacier-foot and springs to the surface, making the
waters seethe and swirl with the shock, and sending heavy waves in all
directions. Then the buoyant mass floats away as a newly made Iceberg.
Some Icebergs, broken thus from a Greenland glacier, are two or three
hundred feet high. That is to say, a sailor on board a ship can see two
or three hundred feet of solid ice above the surface of the sea. But
this is by no means the true iceberg height.
When we talk of ice “floating,” we do not mean that the whole piece of
ice rests upon the top of the water. It floats _in_ the water. Only
about one-eighth of it is visible above, and the other seven-eighths
are hidden below. So in the case of an iceberg rising two or three
hundred feet above the sea, we may be sure that at least seven times as
much ice is underneath the ocean-surface. This shows what an enormous
mass the whole of a floating ice-mountain must be.
[Illustration: AN ICEBERG, SHOWING THE SECTION UNDER WATER
For every cubic foot of ice above water there are seven cubic feet below
_Face page 86_
]
No wonder that a certain iceberg, which held its head one hundred and
fifty feet high, should have run aground in water five hundred feet
deep! No wonder, either, that when two such bergs come together,
and an unfortunate ship happens to lie between, it should be smashed
like an egg-shell. In Baffin’s Bay Dr. Kane once counted a pack of two
hundred and eighty bergs, most of them being between two and three
hundred feet high.
The “birth” of such oceanic hills has been watched by travellers, at
the moment of their breaking off from a glacier-foot, with no small
interest, and also with no small danger, if they chanced to be within
reach of the terrific billows started by such an event.
Sometimes icebergs come into existence differently. If the glacier
comes to an end, not in but above the sea, the mass breaks off above
with its own weight, and plunges downward, to float away on its new
career. This was lately witnessed in far southern seas, and the
travellers barely escaped with their lives, so tremendous was the rush
of the ocean-wave following the plunge of the new mountain.
A great deal of carrying work is done by icebergs. Many and many a
block of stone or rock--not to speak of supplies of gravel and sand and
mud--is borne by them to mid-ocean, and there dropped. In the Atlantic
they seldom get further south than the neighbourhood of Newfoundland.
As they journey, they slowly weep and trickle out of existence.
In the Antarctic both glaciers and icebergs are abundant. The northern
bergs are generally higher and more sharply peaked; the southern bergs
of a flatter shape, but much larger and of a deeper blue.
Sea-water does not freeze so quickly as fresh water. On account of
the salt which it contains, it does not become solid until it is four
degrees colder than fresh water needs to be. The freezing-point of
fresh water is 32° F.; that of salt water is 28° F. As ocean-water
freezes, most of the salt is separated from it; and the ice formed is
practically fresh, though often it holds unfrozen salt water in tiny
hollows.