Mount Hagen is an old stratovolcano which has been heavily eroded during several Pleistoceneglaciations. The maximum extent of the glaciers on Hagen was less than half that on the much higher Mount Giluwe, covering an area of up to 50 km² (20 mi²) and extending down below 3,400 m (11,000 ft).
^Löffler, E.; Mackenzie, D. E.; Webb, A. W. (1980). "Potassium-argon ages from some of the Papua New Guinea highlands volcanoes, and their relevance to Pleistocene geomorphic history". Journal of the Geological Society of Australia26 (7–8): 387–397. Bibcode:1979AuJES..26..387L. doi:10.1080/00167617908729105.
^Mackenzie, D. E. (1985). "Giluwe and Hagen; glaciated volcanoes in the rain forests of western PNG". Volcano News. 19–20: 7.