All sorts of queer notions as to what the surface of a glacier is like exist. Indeed I have often heard people inquire if it would be possible to skate upon it!
Let us for a moment imagine ourselves at the head of the great Tasman Glacier, 8,600 feet above sea-level. All around us is snow, either freshly fallen or merging into névé. We begin to walk down, and at first, upon the steeper slopes, cross a few large crevasses and bergschrunds by means of snow bridges; then, as the incline becomes less steep, we walk for six miles or so upon a smooth surface of névé, or perchance knee-deep in fresh snow, and scarcely a crevasse exists. At the beginning of the great turn we gradually leave the névé and find ourselves upon hard, white ice, and soon transverse crevasses appear; these are a little further on cut by longitudinal crevasses forming the surface into huge squares, not flat on the top, but hummocky. A perfect network of crevasses cuts up the whole of the surface, but those parts on the outside of the curve are infinitely more disturbed than those on the inside, owing to the tension put upon them by the faster rate at which they have to move. After rounding the turn the glacier again consolidates and few crevasses appear, only the surface is covered with old wounds—if I may coin such a term—from the rents which have occurred at the turn, and presents a very undulating appearance. The little gullies are formed into watercourses and intersect the glacier in all directions. On our right, now, is the medial moraine formed by detritus from Mount De la Bêche, brought down partly by the Tasman and partly by the Rudolf Glaciers, and it stands up 100 feet or so above the surface of the clear ice on either side of it, owing to the protection from the sun’s rays afforded by it to the ice beneath, so preventing ‘ablation’ or waste going on so quickly. We follow down for another four or five miles, and then cross this moraine (which has in the meantime joined that on the northern side of the Hochstetter Glacier) on to the Hochstetter on our right.
SURFACE TORRENTS AND MOULINS
We are now immediately below the great ice-fall, and the surface of the glacier presents an appearance not unlike the back of some enormous caterpillar wrinkled transversely by crevasses, which close up as we proceed downwards, and furrowed longitudinally by two large or main watercourses whose icy banks are in places 100 feet above their respective torrents. These two small rivers are fed from every direction by minor watercourses, and a mile or two further down discharge all their contents into crevasses and moulins, or water-shafts in the ice.
GLACIER TABLES AND CONES—THE ACTION OF WARMTH
The locality of the glacier on which we now are is very interesting, for Nature’s mills are here seen at work day by day. Glacier tables—blocks of rock perched upon pedestals of ice formed by the protection from the action of the sun’s warmth—are of frequent occurrence. Glacier cones—heaps of sand and small fragments of rock raised by a similar agency (after having been washed to one spot by water)—are in places all around us. Then, strange and contradictory as it may seem, we see thousands of holes, each with a stone at the bottom and filled with the bluest of blue water, formed also in the first place by the rays of the sun warming the stone and causing it to sink in the ice. It is well-known in physics that water at 39° Fahr. is at its heaviest, and as soon as the warm stone—the dark colour of the stone having absorbed more heat than the surrounding ice—begins to sink the warmer water follows it, whilst that in the neighbouring temperature of 32° Fahr. rises to the surface and becomes in its turn re-warmed, and so on. This peculiar current often bores the holes in the ice to a depth of many feet, and is only checked by a preponderance of cold. It is the larger stones, therefore, which rise upon the ice, and the smaller ones which sink.
‘SURFACE’ AND ‘TERMINAL’ MORAINES
We walk on down the ice stream, and soon the moraines on either hand close in upon us and we find ourselves on a mere wedge of ice, at the point of which we step on to the ‘surface’ moraine. Here the swearing begins, and it lasts right on to the terminal face four or five miles below, for it is one continual repetition of walking on loose and tumbling rocks, up one hillock, along a ridge, jumping from
Rock to rock with many a shock,