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Report on Lewotobi (Indonesia) — October 2003


Bulletin of the Global Volcanism Network, vol. 28, no. 10 (October 2003)
Managing Editor: Edward Venzke.

Lewotobi (Indonesia) Explosions and ashfall during June-July; seismicity stops in early September

Please cite this report as:

Global Volcanism Program, 2003. Report on Lewotobi (Indonesia) (Venzke, E., ed.). Bulletin of the Global Volcanism Network, 28:10. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN200310-264180



8.542°S, 122.775°E; summit elev. 1703 m

All times are local (unless otherwise noted)

Explosive ash eruptions from the summit crater of Lewotobi sent dark gray plumes 300-350 m high between 2 June and 13 July. Detonation sounds accompanied explosions on 3, 5, and 6 June. Ash fell in the villages of Bawalatang, Duang, and Boru in early June, and was reported at the volcano observatory post in early July. Ash explosions continued during 14-20 July with plumes rising 150 m above the summit. Poor weather conditions prevented observations in late July, although seismic records indicated continued activity; no reports were available for August. In early September an ash plume was reported to rise 25 m above the crater.

Seismicity during June and July was dominated by emissions events, but included tremor, explosion, and shallow volcanic earthquakes (table 2). Early September seismicity consisted of a high number of shallow volcanic events and some deep volcanic earthquakes, but all seismicity ceased after 3 September. Only four tectonic earthquakes were detected after this date, during 6-19 October. The 29 September-5 October report noted an ash plume rising to 25 m above the crater, but over the next two weeks the 25-m-high plume was described as gas emissions. The hazard status was downgraded to Alert Level 1 (on a scale of 1-4) the week of 13-19 October.

Table 2. Seismicity at Lewotobi, 2 June-19 October 2003. Note that no seismicity was recorded after 3 September 2003. Courtesy of VSI.

Date Deep Volcanic Shallow Volcanic Explosion Emission Tremor Tectonic
02 Jun-08 Jun 2003 0 13 7 29 20 12
09 Jun-15 Jun 2003 0 24 -- 40 33 9
30 Jun-06 Jul 2003 0 8 14 26 11 3
07 Jul-13 Jul 2003 0 16 10 52 4 1
14 Jul-20 Jul 2003 4 17 19 24 10 4
21 Jul-27 Jul 2003 1 10 5 25 5 4
28 Jul-03 Aug 2003 0 9 8 20 6 3
01 Sep-03 Sep 2003* 27 257 0 0 0 5

Geological Summary. The Lewotobi "husband and wife" twin volcano (also known as Lewetobi) in eastern Flores Island is composed of the Lewotobi Lakilaki and Lewotobi Perempuan stratovolcanoes. Their summits are less than 2 km apart along a NW-SE line. The conical Lakilaki has been frequently active during the 19th and 20th centuries, while the taller and broader Perempuan has erupted only twice in historical time. Small lava domes have grown during the 20th century in both of the crescentic summit craters, which are open to the north. A prominent flank cone, Iliwokar, occurs on the E flank of Perampuan.

Information Contacts: Dali Ahmad, Hetty Triastuty, Nia Haerani, and Suswati, Volcanological Survey of Indonesia (VSI), Jalan Diponegoro No. 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/).