The massive Ross Ice Shelf fades into sea ice close to Scott Base. The motion of the ice shelf is obstructed by the island, which leads to high pressures in the ice. At places where the pressure gets too high, the ice forms steep and jagged pressure ridges. Ice blocks pile up for several metres and holes form in the ice, which are welcomed by seals as breathing holes and exits. The pressure ridges on this picture are around 10 metres high, separated by crevasses. They had to be crossed by early expeditions with sleds weighing more than one ton.