Denman Glacier, Antarctica. Topography of the seabed and land in the area of the Denman glacier, East Antarctica. Elevation is colour-coded from maximum depths (dark blue) to highest elevations (red). The Denman Glacier has retreated 5 kilometres in the past 22 years, and the shape of the ground surface beneath the ice sheet makes it susceptible to climate-driven collapse. There is a trough (centre right) beneath the glacier which extends 3,500 metres below sea level, making it the deepest land canyon on Earth. As the glacier is retreating, ocean water is entering the trench underneath the ice. Because of the depth of the canyon, increasing areas of ice are exposed to the ocean water with the potential to accelerate the melting of the glacier. This could lead to significant rise in sea levels. Image from Antarctic BedMachine mapping project, based on ice thickness radar soundings and ice flow data.