A crevasse where moving glacier ice separates from stagnant ice or firn above is called a bergschrund. The term comes from German words meaning “mountain cleft,” and it describes a prominent fracture near the upper edge of a glacier or cirque.
A bergschrund forms because the lower glacier continues to flow while the snow and ice above it remain relatively stationary. The resulting gap may expose bedrock and can extend more than 100 metres deep. In winter, avalanched snow may partially fill it, but summer melting commonly reopens the crevasse.
For mountaineers, a bergschrund can be a major obstacle. Climbers may need to cross it where the gap is narrowest, use snow bridges, or change routes as seasonal conditions alter its width. On Mount Everest’s South Col route, a deep bergschrund lies near the base of the Lhotse Face.
A related feature is a randkluft, where one side of the crevasse is formed by a rock wall. The French term rimaye can refer to either feature, which explains occasional differences in terminology.