Major terrain features present both obstacles and opportunities (fig. 12-40). Some you use, some you avoid, but they all have to be reckoned with.
A main avenue for all mountain climbing is provided by angled gullies (couloirs). They can hold the key to upward progress because their overall angle is often less than that of the cliffs they breach, offering less technical climbing.
Deeply shaded couloirs are more often lined with ice than snow, especially in late season. Even in spring, however, when open slopes are deep in slush, the couloirs are likely to hold hard snow or ice caused by freezing or avalanche scouring.
Safe passage through a couloir usually depends on the time of day. They can be safe in early morning when the snow is solid and rocks and ice are frozen in place. It's often a different story later in the day, when they can turn deadly. Gullies are the garbage chutes of mountains and with the arrival of the sun they begin to carry down such rubbish as avalanching snow, rocks loosened by frost-wedg-ing, and ice blocks weakened by melting. Most of the debris comes down the center. But even if you keep to the sides, listen for suspicious sounds from above and keep an eye out for quiet slides and silent falling rock.
Avalanches erode deep ruts in many steep couloirs. Climbers usually avoid these ruts or cross them rapidly. However, early in the year the floors of the ruts offer the soundest snow available, and in cold weather they may be quite safe, particularly for a fast descent. Try to be out of a couloir before the sun hits. This means an early start for a round trip, or else a bivouac or an alternative descent route.
Couloirs can become increasingly nasty the higher they are ascended, presenting extreme steepness, verglas, moats, rubble strewn loosely over smooth rock slabs, and cornices. Many lead to difficulties, as when the gentle angle at the bot-
Fig. 12—40. Alpine terrain features
1. Horn or aiguille
3. Rock arete
5. Glacier basin
7. Fallen seracs
8. Erratic blocks
12. Lateral moraine
14. Moraine lake
15. Terminal moraine
16. Glacial runoff
17. Rock band
20. Coulior or gully
22. Hanging glacier
24. Cirque or bowl
27. Ice wall
29. Ice arete
30. Towers or gendarmes
31. Avalanche chute
32. Avalanche debris
33. Snowfield torn is more than balanced by a frosty vertical chimney at the top. However, when the couloir ends at a col (small, high pass), it can offer a lower average angle than the face.
If the bed of the couloir is too steep, try the moat along the sides, formed when the snow melts and settles away from the rock. Moats can be rather deep and will vary in width. Portions of a moat can require bridging between the snow and the rock wall, while other parts present either a tight squeeze or a gap too wide to bridge. You might crampon or step-cut up the couloir, and then drop into the moat on the way down to avoid a nerve-wracking descent on steep ice and exposure to rockfall.
Despite the problems, many snow and ice routes follow couloirs. The techniques are usually simple cramponing and step-kicking, but the frequent presence of moats, crevasses, suncups, and blocks of fallen rock and ice make rock-climbing techniques useful. Some of these irregularities are welcome as a good place to set up a belay.
Continue reading here: Cornices
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