crevasse

A crevasse is a deep vertical fissure, or a narrow crack, which can form in bedrock or ice. Usually, the term "crevasse" refers to cracks in ice or glaciers, while the term "crevice" refers to those in rocks; Hillerman sometimes uses crevasse to refer to the former. A crevasse is sometimes narrow enough to jump across, but never wide as wide as a ravine or canyon. One of the most overwhelming aspects of a crevasse is its sheer depth, it can appear to be almost bottomless.