Their route took them across the upper reaches of two large, heavily crevassed glaciers that gave them some frightening moments — including several crevasse falls. Mawson later recounted one occasion in late November, ‘in the vicinity of many gaping holes leading down into darkness’:

Mertz prepared the lunch and Ninnis and I went to photograph an open crevasse near by. Returning … I heard a bang on the ice and, swinging round, could see nothing of my companion but his head and arms. He had broken through the lid of a crevasse 15 feet wide and was hanging on to its edge close to where the camera lay damaged on the ice. He was soon dragged into safety. Looking down into the black depths we realised how narrowly he had escaped.

The glaciers were later to bear the names of Ninnis and Mertz.

In the 24-hour light the party travelled whenever wind conditions permitted. After a pre-arranged time or when the wind became severe they halted and pitched camp. Aided by the dog teams, and despite the crevasses, they made reasonable progress. In a little over a month they had covered over 500 km.

On 13 December 1912 the men discarded one of their sledges, damaged beyond repair, and put most of its load on to one of the other sledges. That day they heard booms like distant cannon — the sound of a moving ice stream as it creaked its way toward the sea.

After a good night’s sleep following treatment for septic wounds to his fingers, Ninnis started the morning of 14 December in a cheerful mood, ready for the planned short dash to the east before turning back. At noon, Ninnis was in the rear with the heavy sledge pulled by the strongest dogs. Mawson, driving the smaller sledge, and Mertz on skis were ahead, keeping a sharp lookout for crevasses.