Three explosions from the summit crater occurred during October and two others were observed at night during November and early December. Ashfalls reached Ulu, 6 km SE of the summit (figure 1), where ~0.5 mm of ash was deposited.

A 10-minute eruption beginning at 1730 on 15 December produced a thick tephra column that rose 600-700 m above the summit and dropped more than 0.5 mm of ash on Ulu. Sharp explosion sounds were clearly audible from the temporary observatory at Tarorane, about 5 km from the summit. Volcanic tremors were frequently felt, but none were recorded at Tarorane.

Vapor emission from the 1976 vents has stopped, but a solfatara ~ 50 m above the upper vent emitted a thin stream of bluish gas.

Geological Summary. Karangetang (Api Siau) volcano lies at the northern end of the island of Siau, about 125 km NNE of the NE-most point of Sulawesi. The stratovolcano contains five summit craters along a N-S line. It is one of Indonesia's most active volcanoes, with more than 40 eruptions recorded since 1675 and many additional small eruptions that were not documented (Neumann van Padang, 1951). Twentieth-century eruptions have included frequent explosive activity sometimes accompanied by pyroclastic flows and lahars. Lava dome growth has occurred in the summit craters; collapse of lava flow fronts have produced pyroclastic flows.

Information Contacts: A. Sudradjat, M. Kamid, VSI.