| What it is | Overhanging wind-blown snow lip |
| Forms on | The lee side of ridge crests |
| Danger | Can collapse; triggers avalanches below |
| Difficulty | Intermediate (hazard) |
A cornice is an overhanging lip of wind-blown snow that builds out horizontally from a ridge crest, like a frozen wave. Cornices can collapse under a climber’s weight or break off naturally, so mountaineers stay well back from the edge and treat the slope below as avalanche-prone.
Why they’re dangerous
A cornice can break behind the visible edge, dropping you off the ridge, and falling chunks can trigger an avalanche below.
Staying safe
Keep a generous margin from the lip, stay on the windward side, and never walk out toward the edge.
Frequently asked questions
What is a cornice?
A cornice is a mass of snow that wind has deposited so it overhangs the edge of a ridge, curling out into space like a frozen wave. It forms on the sheltered (leeward) side of a crest as wind carries snow over the top.
Are cornices dangerous?
Very. A cornice can break under a person's weight, dropping them off the ridge, and chunks can collapse naturally and trigger avalanches on the slope below. The fracture line often sits back from the visible edge, so the ground you're standing on may already be overhanging.
How far back should you stay from a cornice?
Well back — because cornices can break far behind the apparent edge, you should keep a generous margin, ideally staying on the windward side of the ridge and never walking out toward the lip. When in doubt, treat the whole crest area as suspect.
Sources
- Cornice hazards — American Alpine Club
- Avalanche & cornice safety — AIARE