As windborne snow crystals accrete and bond atop a storm-swept ridge, they are apt to solidify into a cornice. Sometimes cantilevered spectacularly over the leeward side of the ridge crest on which it forms, a cornice resembles nothing so much as breaking surf frozen in mid-curl. When large cornices collapse—from rising spring temperatures, under the weight of careless skiers and mountaineers, or when they simply become too heavy to support their own unstable bulk—they can trigger cataclysmic avalanches.

Jon Krakauer