Mountaineering Routes : Page 307

Wherever more snow accumulates every year than can melt in place, it forms permanent snowfields (neve), compacts into ice, breaks away from the mountain (at the bergschrund), and flows slowly downhill. Irregularities in its course may break the surface into roughly parallel cracks (crevasses), confluence with other glaciers may buckle it (pressure areas), and the glacier bed may break it up badly (icefalls with their ice-block seracs), or drop it over cliffs (hanging glaciers). Tributary glaciers may join it, either by means of icefalls, by dropping from hanging glaciers, or by simple confluence, and a lake of ice may form (icefield), from which the main glacier descends far below the peaks (valley gla-