A crevasse is a deep crack or fissure that forms in a glacier or ice sheet. These gaps can be quite dangerous for climbers and hikers, as they can be hidden by snow and may be difficult to see. Crevasses can vary in size, from small openings to large chasms that can be several meters wide and deep. When exploring areas like the Antarctic or Greenland, it's essential to be aware of crevasses. They are created by the movement of ice, which can cause tension and stress, leading to these fractures. Understanding crevasses helps ensure safety during mountaineering or glacier trekking.