Part of an extensive ice cap that developed in the Tasmanian Central Highlands during the late Cenozoic discharged southwards via a major outlet glacier that occupied the valley of the Derwent River. At least three and probably five phases of glaciation took place. The first and most extensive glaciation may have been early Pleistocene in age, while the most recent and least extensive occurred during the late Last Glacial Stage. When the ice cover was most extensive, the Derwent Glacier was up to 500 m thick. It may have extended to as low as 230 m above sea level, 70 km downvalley. Diffluent lobes of this glacier spread eastwards to merge with other glaciers in the Nive Valley, southwards into the upper Gordon Valley, and westwards into the upper Franklin and Alma Valleys. The ice masses of west-central Tasmania were mainly of temperate maritime character.