Ellef Ringnes Island, 11 295 km2, is part of the SVERDRUP group that borders the Arctic Ocean. Most of the island consists of great thicknesses of sedimentary rock, except for an occurrence of the arctic coastal plain in the northwest corner. The island's topography reflects these structural and lithological controls, and is characterized by broad lowlands and dissected uplands. Domal structures, like the 250 m high Isachsen Dome, are the most striking feature of the landscape. Despite generally arid conditions the surface becomes saturated in summer, owing to an active layer derived from water-retentive shale, underlain by impermeable PERMAFROST.