Report on Karangetang (Indonesia) — 16 April-22 April 2003
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 16 April-22 April 2003
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2003. Report on Karangetang (Indonesia). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 16 April-22 April 2003. Smithsonian Institution and US Geological Survey.
2.781°N, 125.407°E; summit elev. 1797 m
All times are local (unless otherwise noted)
Karangetang's S crater gave off ash emissions that reached 250 m high during the week of 16-22 April. Just prior, on 15 April, an explosion that sounded like a blast was followed by lava avalanches traveling S and W and reaching ~1 km from their source at S crater. The resulting dark-gray ash column reached 1.5 km above the crater. Ash fell around Dame and Karalung villages, some fell into the sea on the E. Another similar explosion occurred on 20 April, but it generated a pyroclastic flow that extended 2.5 km in length. Blasting noises were audible for ~3 minutes. Seismic records suggested 32 explosion events, 226 multiphase earthquakes, and 26 emission earthquakes. Karangetang=s hazard status was at level 3 (out of a possible 4).
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.