Cornices

The shape of a ridge crest helps determine the extent of cornice-building (fig. 12-41). A ridge that slopes on one side and breaks into an abrupt cliff on the other is a good candidate for a gigantic cornice. A knife-edge ridge or one gentle on both sides will have only a tiny cornice, if any at all.

When the physical features are right for building cornices, wind direction decides their exact location. Because storm winds have definite patterns in each mountain range, most cornices in the same area face the same way. In the Pacific Northwest

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region of the United States, for example, most storms blow from the southwest so the wind-drifted snow of the cornices mostly overhangs on the north and east. These same northern and eastern exposures were steepened by past glaciation, making the ridges ideally shaped for cornice formation.

Temporary or local wind deflection can contradict the general pattern. In rare instances cornices are even built one atop the other, facing in opposite directions, the lower one partially destroyed and hidden by later formations.

Approaching from windward: A cornice gives little sign of its presence as you approach from windward. It simply appears to be a smooth snow slope that runs out to meet the sky. Look at nearby ridges for an idea of the frequency, size, and location of cornices in the area.

Not every snowy ridge conceals a cornice—but be sure to find out whether the ridge you are on does. Try to view the lee side of the ridge from a safe vantage point, such as a rock or tree jutting through the crest. If you can't, have a belayed climber approach the ridge at right angles while probing with an ice axe or reversed ski pole to see if the snow is solid. Look for a crack or indentation in the snow, which could indicate a cornice that has partially collapsed.

It's hard to judge the extent of a cornice overhang and the danger it presents. Don't be misled by appearances. For a mature cornice, the probable line of fracture could be 30 feet or more back from the lip—no doubt farther back than an examination would lead you to expect. And although rocks and trees projecting from the snow suggest safety, they could be on the tops of buttresses with a connecting ridge that curves far back into bays supporting wide cornices. Lots of climbers have had the enlightening experience of looking back along a ridge and discovering their tracks on snow poised above a chasm. The safe course along a corniced crest is well behind the probable fracture line.

Approaching from leeward: You can't miss a cornice from the leeward side. Resembling a wave frozen in the act of breaking, a large cornice close above you is an awesome sight. If you doubt the stability of the cornice, stay among trees or on spur crests as you travel below it. At times, it's quite safe to climb under a cornice. The colder the weather, the more secure the cornice. A late-sea-son cornice, almost completely broken down, is not a problem.

Climbers sometimes even push directly through a cornice to force their way to a ridge crest or pass. It's easiest to penetrate an overhang at a rock spur or where the cornice already has partially collapsed. The leader cuts straight uphill at the point of least overhang, undermining as little of the mass as possible. Generally though, the safest bet with cornices is to avoid traveling on them, under them, or through them.

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Responses

  • myley
    How to safely cross over a cornice in mountaineering?
    2 years ago
  • Tanika
    What is cornices in mounteneering ?
    1 year ago
  • leonie zimmermann
    How do you climb a ridge with cornices on?
    7 months ago

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