A serac (originally from Swiss Frenchsérac) is a block or column of glacial ice, often formed by intersecting crevasses on a glacier. Commonly house-sized or larger, they are dangerous to mountaineers since they may topple with little warning. Even when stabilized by persistent cold weather, they can be an impediment to glacier travel.
Seracs are found within an icefall, often in large numbers, or on ice faces on the lower edge of a hanging glacier. Examples of the latter in the Alps are found on the northeast face of Piz Roseg, the north face of the Dent d'Hérens, and the north face of Lyskamm. They are well-known obstacles on many of the world's highest mountains, Kanchenjunga (located on the border of India and Nepal) in particular.
Usage examples of "serac".
Seracs reared like fortresses, aretes and nunataks traced in black the shape of buried mountains behind the green-white blister of the ice.
Between these lurid streams, underlying translucent colors and textures teasingly appeared: glassy seracs of ruby and rubellite, rounded moraines in blue tourmaline and amethyst.
The front edge was uneven, accommodating minor local differences in terrain, and a climb to the top would have revealed dips and ridges, seracs, and crevices quite extensive on a human scale, but in relation to its own size, the surface was uniformly level.
They came on ice-fields like mammoth ploughlands, where they scarcely made three miles in the day, and mountainous seracs which would have puzzled an Alpine climber.
The four of us stood there silent for a second, listening to the wind howl around the remaining seracs of the Godwin-Austen Glacier and through niches in the wind-carved boulders.
The South Ridge ran from right to left up early rocky outcrops before forming a long and elegant corniced snow ridge which led to a highly unstable area of seracs that mushroomed to the summit.
Simon must have fallen through the corniced ridge, yet the volume of sound suggested something more like a serac avalanche.
For the first half of its length the tongue of the glacier sloped fairly sharply from right to left down to the nunataks, crescent-fringed by the debris of moraines, that thrust up through the ice at the far corner of the dog-leg: the surface of the glacier was a nightmare of transverse and longitudinal fissures, some of them anything up to two hundred feet deep, great gaping chasms fanged with seracs - the irregular, often needle-pointed ice pinnacles that reached up between the walls of the larger crevasses.