Informally, crevasse refers to any deep crack or ﬁssure in the earth. A breach in a riverbank or levee is called a crevasse, as is a rift in the Earth’s surface caused by an earthquake. Crevasse most commonly refers to a fracture in glacier ice, however, created by the glacier’s ﬂow over uneven terrain or down a steep slope. Crevasses, some of which are too deep to measure accurately, can form both across a glacier’s ﬂow and parallel to it. These longitudinal crevasses splay apart where the ice spreads in a fanlike formation. Chevron crevasses, pointing up-valley, form along a glacier’s edge where ice movement is restricted by valley walls. Multiple crevasses in one section of a glacier constitute a crevasse ﬁeld. In his narrative of the 1899 Harriman Alaska Expedition, John Burroughs describes a view at Glacier Bay of “a perfect wilderness of crevasses, the ice ridged and contorted like an angry sea.”
A place where water broke through was known as a crevasse—a source of terror no less effective than a bursting dam—and the big ones were memorialized, like other great disasters, in a series of proper names: the Macarty Crevasse (1816), the Suave Crevasse (1849).
— John McPhee, “Atchafalaya”