Fox Glacier Ice Fall
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As Fox Glacier curves over the ridge projecting from the far wall, the top surface is stretched and breaks. The cracks are mostly transverse to produce a chevron pattern of crevasses. Crevasses do not usually reach to the bed of the glacier, where the ice behaves as a viscous crystalline rock. The base of the glacier moves by viscous flow, not cracking.
Longitudinal crevasses also develop (in fact, these cracks are already in the ice from an even bigger ice fall further up). Ice columns formed by these crossing crevasses are seracs, which lean in an unstable, chaotic manner and provide a challenge to climbers.
Ice on the edge of the glacier is streaked by layers, like a heap of pancakes. Snow previously collected in the neve or accumulation zone high in the alps and each year shows as a separate, compressed ice layer. There has been controversy over this, some claiming the banding is due to layers of ice sliding over each other. While ice layers do slide to produce plasticity, it seems this is at a microscopic level between ice crystals and mainly towards the base of the glacier. These bands are visible right to the top of the glacier, where the top is moving rigidly and breaking into crevasses.
Some crevasses, later covered by snow, develop an ice roof as the snow compresses and become ice caves, several small examples of these being visible.
Note the large rock slip on the far wall. It interrupts the kame terraces we are to see next (page 4). Similar rock slips further back up the glacier provided the surface rocks which coat the glacier and are left behind as marginal moraine (page 1) or in the outwash gravel (page 4).
More truncated spurs, now somewhat eroded and covered with vegetation, show up on the far wall, where the glacier once reached much higher. The peaks above these spurs show the irregular jagged features of freezing water erosion, which have not been smoothed by glaciers.
