A crevasse is a deep, wedge-shaped opening in a moving mass of ice called a glacier. Crevasses usually form in the top 50 meters (160 feet) of a glacier, where the ice is brittle. Below that, a glacier is less brittle and can slide over uneven surfaces without cracking.

Do crevasses form in the zone of fracture?

What is glacial till? Crevasses form on the upper portion of the glacier because when a glacier moves over irregular terrain, the zone of fracture is subjected to tension, which forms the crevasse.

Why do crevasses form in glaciers?

A crevasse is a crack in the surface of a glacier caused by extensive stress within the ice. For example, extensive stress can be caused by stretching if the glacier is speeding up as it flows down the valley. Crevasses can also be caused by the ice flowing over bumps or steps in the bedrock.