Report on Karangetang (Indonesia) — 26 November-2 December 2008
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 26 November-2 December 2008
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2008. Report on Karangetang (Indonesia). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 26 November-2 December 2008. Smithsonian Institution and US Geological Survey.
2.781°N, 125.407°E; summit elev. 1797 m
All times are local (unless otherwise noted)
CVGHM reported that on 28 November seismicity from Karangetang increased and indicated rockfalls. White plumes rose from summit craters I and II to approximate altitudes of 1.8-2.2 km (5,900-7,200 ft) a.s.l. On 29 November white and brownish plumes rose to an altitude of 1.8 km (5,900 ft) a.s.l. Incandescent rockslides from the main crater traveled 250 m S towards the Bahembang River, 250 m W towards the Beha Timur River, and 500-1,000 m S towards the Keting River. Thunderous noises were reported. On 30 November, fog prevented visual observations; the seismic network recorded 160 rockfalls. On 1 December, incandescent rockslides traveled 250 m S towards the Bahembang River, 750 m W towards the Beha Timur River, and 500-1,500 m S towards the Keting River. On 2 December, the Alert Level was raised to 3 (on a scale of 1-4) due to the continuation of elevated seismicity, run-out distances of incandescent rockslides, and height of incandescent material ejected from the summit.
Based on analysis of satellite imagery and information from CVGHM, the Darwin VAAC reported that on 2 December an ash plume from Karangetang rose to an altitude of 3 km (10,000 ft) a.s.l. and drifted W.
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.