Report on Karangetang (Indonesia) — 21 May-27 May 2003
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 21 May-27 May 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, 21 May-27 May 2003. Smithsonian Institution and US Geological Survey.
2.781°N, 125.407°E; summit elev. 1797 m
All times are local (unless otherwise noted)
A reduction in volcanic activity at Karangetang during 12-18 May led VSI to reduce the Alert Level from 3 to 2. Activity during the week consisted of low-level ash clouds rising above Karangetang's South crater, incandescence extending 25 m above the crater, and incandescent avalanches traveling toward Kali Batang to runout distances of 750-1,000 m. In addition, there was a decrease in the number of multiphase earthquakes compared to the previous week.
Geologic Background. Karangetang (Api Siau) volcano lies at the northern end of the island of Siau, north 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 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 has also produced pyroclastic flows.