crevasse - / krɪˈvæs / -
noun
A deep crack found in a glacier or ice sheet. These tend to have sheer or almost sheer walls, they can be up to 40 meters deep and 20 meters wide, possibly running to several hundred meters long. They are caused as result of differing rates of movement of the underlying layers of ice. Sheer stress causes the ice to break apart forming a crevasse.
\\ I hear you need to rope up on the Gebroulaz glacier now due to several new crevasses opening up.