During 1999 concerned local residents reported two decades of 'unusual growth' of Lif Island, the western island on the rim of the partially submerged ~5-km-diameter caldera of Tanga volcano. An inspection by scientists from the Rabaul Volcano Observatory showed no obvious signs of uplift, but apical spits of raised reef estimated as being up to 1 m above sea level in Wallace and others (1983), were estimated to be more than 2 m high when visited (although it is not certain the same features are being described). Numerous coastal warm springs are present on all three islands marking the submerged caldera rim. A GPS network has been installed to monitor the caldera.

Elderly residents also graphically described the sudden appearance of two islands in the middle of the caldera about 60 years ago (pre-World War II), which they claimed have subsequently grown in size. These islands consist of Bitlik, 300 m in diameter and 35 m high, and Bitbok, 600 m long and 90 m high; both are made up of well-jointed Q-trachyte (Johnson and others, 1976) with dates of 1.08-1.14 m.y. (Wallace and others, 1983). The initial uplift was said to have been accompanied by "big white smoke" and "a big wave people had to run from." Although a British Admiralty Chart of 1886 (no. 2766) shows that the two islands were then in existence and of a similar size, these stories, of the local oral history, may relate to an earlier event. The RVO staff extends their thanks to Deborah Hall (The British Library, Map Library, London) and Brian D. Thynne (National Maritime Museum, London) for their assistance.

References. Johnson, R.W., Wallace, D.A., and Ellis, D.J., 1976, Feldspathoid-bearing potassic rocks and associated types from volcanic islands off the coast of New Ireland, Papua New Guinea: a preliminary account of geology and petrology, in Johnson, R.W. (editor): Volcanism in Australasia, 297-316.

Licence, P.S., Terrill, J.E., and Fergusson, L.J., 1987, Epithermal gold mineralisation, Ambitle Island, Papua New Guinea: Proceedings of the Conference, Pacific Rim Congress 87.

Wallace, D.A., Johnson, R.W., Chappell, B.W., Arculus, R.J., Perfit, M.R., and Crick, I.H., 1983, Cainozoic volcanism of the Tabar, Lihir, Tanga, and Feni Islands, Papua New Guinea: geology, whole-rock analysis, and rock-forming mineral compositions: B.M.R., Aust. Report 243.

Geological Summary. Malendok, Lif and Tefa islands are remnants of the summit of a mostly submerged stratovolcano. In the center of the caldera, the small islands of Bitlik and Bitbok mark remnants of early Pleistocene post-caldera lava domes marking the volcano's latest activity. A small hot spring on Malendok Islands marks the only current thermal activity.

Information Contacts: Ima Itikarai and Steve Saunders, Rabaul Volcano Observatory (RVO), P.O. Box 386, Rabaul, Papua New Guinea.