In 1839, Crozier again joined Sir James Clark Ross on the Ross expedition, as second-in-command of a four-year voyage to explore the Antarctic continent in the ships and . Crozier commanded Terror, and was appointed to the rank of captain in 1841. Erebus and Terror returned in 1843, having made the most significant penetration of the Antarctic pack ice and discovered large parts of the continent—including the Ross Sea and Ross Island, Mount Erebus and the Ross Ice Shelf.