Report on Karangetang (Indonesia) — October 1976
Natural Science Event Bulletin, vol. 1, no. 13 (October 1976)
Managing Editor: David Squires.
Karangetang (Indonesia) New vent on the SW flank erupts lava and pyroclasts
Please cite this report as:
Global Volcanism Program, 1976. Report on Karangetang (Indonesia) (Squires, D., ed.). Natural Science Event Bulletin, 1:13. Smithsonian Institution.
2.781°N, 125.407°E; summit elev. 1797 m
All times are local (unless otherwise noted)
An eruption of lava and pyroclastics from a new vent on the SW flank began on 15 September at about 0700, accompanied by loud rumbling. For 11 days before the eruption, ~120 earthquakes/day had been felt by inhabitants of the area. Continuous volcanic tremor was recorded at Tarorane Volcano Station from 15 September onwards. Through 5 October, an andesitic block lava flow, 20-40 m thick and 100-200 m wide, moved ~70 m/day, threatening the villages of Bubali and Salili, from which 1,800 people were evacuated. By 12 October, the flow rate had slowed to 20 m/day, but one edge of the flow was within 650 m of Ulu City, the capital of Siau Island. One spectator was killed and another badly injured on 19 September by a small avalanche, caused by the collapse of one flank of the flow as it reached the edge of a steep valley. The lava flow destroyed a bridge, 24 homes (44 others in the path of the flow were dismantled to avoid destruction), and killed an estimated 37,500 coconut, clove, and nutmeg trees. The flow is presently being mapped by a team of surveyors.
Geologic Background. 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 island. 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 in the historical record (Catalog of Active Volcanoes of the World: 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: D. Hadikusumo, VSI.