An Expedition to Mount St. Elias, AlaskaRussell, Israel C. (Cook)
History
An Expedition to Mount St. Elias, Alaska
Russell, Israel C. (Cook)
Alaska -- Description and travel; Saint Elias, Mount (Alaska and Yukon)
Some of the most striking features of the névé are due to the
crevasses that break their surfaces. The orderly arrangement of
marginal crevasses and of the interior crevasses at the rapids in the
Seward glacier have already been referred to; but there are still
other crevasses, especially in the broad, gently sloping portions of
the snow-fields where the motion is slight, which, although less
regular in their arrangement, are fully as interesting. The crevasses
on such slopes generally run at right angles to the direction in which
the snow is moving. On looking down on such a surface, the breaks look
like long clear-cut gashes which have stretched open in the center,
but taper to a sharp point at each end. The ability of the névé ice to
stretch to a limited extent is thus clearly shown. The initiation of
the crevasses seems to be due to the movement of the névé ice over a
surface in which there are inequalities of such magnitude that the ice
cannot stretch sufficiently to allow it to accommodate itself to them,
so that strains are produced which result in fractures at right angles
to the line of general movement. Crevasses found where the grade is
gentle vary from a fraction of an inch to 10 or 15 feet in width, and
are sometimes two or three {182} thousand feet long. Broader gulfs are
seldom formed unless the slope has an inclination of 15° or 20°.
The grandest crevasses are in the higher portions of the névé, and
occur especially on the borders of the great amphitheatres. In such
situations the crevasses are usually fewer in number but are of
greater size than in equal areas lower down. A length of three or four
thousand feet and a breadth of fifty feet or more is not uncommon. The
finest and most characteristic glacial scenery is found among these
great cañon-like breaks. Standing on the border of one of the gulfs,
as near the brink as one cares to venture, their full depth cannot
usually be seen. In some instances they are partially filled with
water of the deepest blue, in which the ice-walls are reflected with
such wonderful distinctness that it is impossible to tell where the
ice ends and its counterfeit begins. The walls of the crevasses are
most frequently sheer cliffs of stratified ice, with occasional
ornamentations, formed of ice-crystals or a pendent icicle. After a
storm they are frequently decorated in the most beautiful manner with
fretwork and cornice of snow. The bridges spanning the crevasses are
usually diagonal slivers of ice left where the clefts overlap; but at
times, especially in the case of the larger crevasses, there are true
arches resembling the Natural Bridge of Virginia, but on a larger
scale, spanning the blue cañons and adding greatly to their strange,
fairy-like beauty. The most striking feature of these cracks is their
wonderful color. All tints, from the pure white of their crystal lips
down to the deepest blue of their innermost recesses, are revealed in
each gash and rent in the hardened snow.
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