brittle upper layers of glacier ice form tension cracks due to: increasing slope angle underlying bedrock features changes in ice flow direction

Chris uses the analogy of the glacier as a snickers bar. The glacier cracks in the same way a snickers bar would if you were to bend it. These cracks are the crevasses. As the glacier is forced to bend around/over obstacles crevasses are created.

are open fissures in glacier ice. Crevasses form where the speed of the ice is variable, such as in icefalls and at valley bends.