With his glaciers the Ice King ground most of the soil in which now
stand the forests, the grasses, and the flowers. In producing this
soil he sculptured from the solid rock of the earth much of the
scenery, shaped many of the flowing landscapes, and formed the
excavations in which ten thousand lakes now rest in beauty. Long ice
periods have had their sway, then vanished. Most of the earth appears
to have been ice-covered a number of times. Then, after ages, the ice
has returned. These periods appear to have alternated with others
whose climatic conditions were similar to those now holding sway. The
remaining glaciers, the world over, are growing smaller and smaller.
A glacier is a slow-moving mass of ice. It may be as small as an
average steamship; it may be less than a mile wide and several miles
long; or it may cover hundreds of square miles. It may be less than a
hundred feet, or a thousand feet or more, in thickness. It may move
only an inch or two a day, or it may move several feet. Commonly it
moves downward, but occasionally one moves upward. The movement is due
to gravity and to the plasticity or rubbery nature of the ice when
under sufficient pressure or weight. In a large glacier the weight of
the superimposed icy stratum is immense; it is greater than the bottom
layers can support. Under the enormous pressure the bottom layers
crawl or flow from beneath like pressed dough. This forced mass moves
outward in the direction of the least resistance--commonly down the
slope.
Glacier ice is formed by snow accumulating at a given point more
rapidly than it melts. This is due chiefly to wind, snowslides, and
heavy snowfall. The glacier, heavy and powerful, planes, polishes, and
reshapes the surface over which it travels, or the walls with which it
comes in contact. Most of the lake-basins were gouged out by glaciers.
Mountain-ranges have been worn down to hills or plains; cañons and
depressions have been filled, and extensive areas overlaid with
ground-up rocky material. The gentle snowflake has been the earth's
chief maker of scenery and soil. Snowflakes, working _en masse_ and
through long periods of time, have formed glaciers and as such have
wrought wonders.
A moraine is an embankment or delta of boulders and crushed rock
deposited by a glacier or ice river. Though commonly at the end, it
may be both along the side and at the end of a glacier, or of the
channels which the glacier once filled. All the mountainous National
Parks have important glacial records or ruins that almost entirely
cover them. These are moraines, soil-deposits, glaciated cañons, and
lake-basins.
Vast is the quantity of material picked up and transported by
glaciers. Mountains are moved piecemeal, and are ground to boulders,
pebbles, and rock-flour in the moving. Besides the material the
glacier gathers up and excavates, it carries the wreckage thrown down
upon it by landslides, and also the eroded matter poured upon it by
streams from the heights. Most of the material that falls upon the top
of the upper end of the glacier gradually works its way to the bottom.
At last, with the other gathered material, it is pressed against the
bottom and sides and used as a cutting, rasping, or grinding tool till
worn to pebbles or powder.
A part of the rocky material gathered is carried to the end of the
glacier, where the melting of the ice unloads and releases it. This
accumulation at the end is called the terminal moraine, and
corresponds to the delta of a river. For years the bulk of the ice may
melt away at about the same place; thus at this point accumulates an
enormous amount of débris. An advance of the ice may plow through
this and repile it, or the retreat of the ice, or a changed direction
of its flow, may pile débris elsewhere. Many of these terminal
moraines are an array of broken embankments with small basin-like
holes and smooth, level spaces.
Many of the lakes have been filled with sediment, and in them and on
them forests now flourish. The glacier lakes were slowly created. Most
of them are being slowly filled. Those most favorably situated may
still live on for thousands of years, but an avalanche may extinguish
one in a single day. Eventually all must be filled and lost. They come
into existence as a part of the work of the glacier. For a period they
lie beautiful in the sunlight; then they are gone forever.
The extensive glacial records that show the past triumphs of the Ice
King sometimes make the mind restless, and it wants to know: "Will the
Ice King come again? Will mountains of white and silent snow again
pile upon a lifeless world?"