crevasse, large crack in the upper surface of a glacier, formed by tension acting upon the brittle ice. Transverse crevasses occur where the grade of the glacier bed becomes suddenly steeper; longitudinal crevasses, where the glacier spreads over a wider valley or plain. Marginal crevasses are due to the strain built up when the central part moves faster than the sides.

Fissure or crack in a glacier resulting from stress produced by movement. Crevasses range up to 65 ft (20 m) wide, 150 ft (45 m) deep, and several hundred yards long. Crevasses may be bridged by snow and become hidden, and they may close up as the glacier moves.

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