Report on Karangetang (Indonesia) — September 2003
Bulletin of the Global Volcanism Network, vol. 28, no. 9 (September 2003)
Managing Editor: Edward Venzke.
Karangetang (Indonesia) Ash explosions and lava avalanches in July; overall activity level declines
Please cite this report as:
Global Volcanism Program, 2003. Report on Karangetang (Indonesia) (Venzke, E., ed.). Bulletin of the Global Volcanism Network, 28:9. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN200309-267020
Karangetang
Indonesia
2.781°N, 125.407°E; summit elev. 1797 m
All times are local (unless otherwise noted)
Ash explosions have been frequent at Karangetang during 2003 (BGVN 28:05 and 28:07). A red glow at night and lava avalanches were reported during 9-15 June (BGVN 28:07). Although detailed observations were not provided by the Volcanological Survey of Indonesia (VSI) for the next two weeks, the hazard status remained at Alert Level 2 (on a scale of 1-4).
VSI weekly reports from 30 June through 3 August indicated that white gas plumes from the S crater typically rose 350-500 m above the crater rim, night glow often extended 25 m above the crater, and white gas plumes from the N crater rose as high as 350 m. Seismic data showed that lava avalanches and shallow volcanic earthquakes in early July were significantly reduced compared to the first half of June (table 8).
Table 8. Seismicity at Karangetang during 2 June-28 September 2003. VSI did not issue reports for Karangetang during weeks not included in the table; a dash indicates no data reported. Courtesy of VSI.
| Date | Deep volcanic (A-type) | Shallow volcanic (B-type) | Explosion | Multiphase | Emission | Avalanche | Tectonic |
| 02 Jun-08 Jun 2003 | 11 | 348 | -- | 233 | 46 | 110 | 26 |
| 09 Jun-15 Jun 2003 | 32 | 438 | 1 | 228 | 21 | 447 | 20 |
| 30 Jun-06 Jul 2003 | 15 | 93 | -- | 446 | 11 | 32 | 11 |
| 07 Jul-13 Jul 2003 | 15 | 93 | -- | 534 | 22 | 35 | 7 |
| 14 Jul-20 Jul 2003 | 21 | 174 | 31 | 672 | 38 | 45 | 22 |
| 21 Jul-27 Jul 2003 | 17 | 112 | 9 | 94 | 131 | 66 | 25 |
| 28 Jul-03 Aug 2003 | 10 | 8 | -- | 312 | 174 | 94 | 10 |
| 01 Sep-07 Sep 2003 | 8 | 44 | 1 | 80 | 341 | 1 | 20 |
| 08 Sep-14 Sep 2003 | 5 | 14 | 0 | 50 | 266 | 5 | 23 |
| 15 Sep-21 Sep 2003 | 6 | 90 | 0 | 3 | 16 | 0 | 74 |
| 22 Sep-28 Sep 2003 | 9 | 60 | 0 | 75 | 130 | 0 | 37 |
During 18-20 July there were ash-producing explosions and lava avalanches. On 21-22 July an ash explosion produced a 150-m-high ash column and a glowing lava avalanche flowed 350 m toward the Beha river. During the week of 28 July-3 August another glowing lava avalanche flowed 1,500 m toward the Beha river and 350 m toward the Batang river. On 29 July volcanic tremor was recorded with a maximum amplitude of 0.5-2 mm.
Karangetang was not included in August reports, but the report for 1-28 September noted white gas emissions from the S crater rising 150-350 m and red glow at night reaching 25 m over the crater, with the N crater exhibiting white gas emissions to 50-150 m above the crater. There were no lava avalanches during this period. The Alert Level remained at 2.
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: Dali Ahmad, Hetty Triastuty, and Nia Haerani, Volcanological Survey of Indonesia (VSI), Jalan Diponegoro No. 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/).
