When the slope beneath a glacier becomes sufficiently steep, the overlying body of ice will fracture into a jumble of hulking, unstable shards that can stand more than one hundred feet tall. The ice blocks that collectively comprise an icefall are known, individually, as séracs—a term coined in 1787 by the Swiss scientist Horace Bénédict de Saussure (who also takes credit for inventing the sport of alpinism). Icefalls on Mont Blanc reminded him of sérac, the ricotta-like white cheese that is a dietary staple in the French Haute-Savoie, and Saussure’s usage was widely adopted. In his book The Shameless Diary of an Explorer, which recounts an unsuccessful ascent of Alaska’s Mount McKinley in 1903, the journalist Robert Dunn described “an enormous sérac, the whole breadth of the glacier, massing into a white Niagara, hinting of the world’s end, the unknown range, and the hidden deserts of the moon.”

Jon Krakauer