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Report on Semeru (Indonesia) — September 2003

Bulletin of the Global Volcanism Network, vol. 28, no. 9 (September 2003)
Managing Editor: Edward Venzke.

Semeru (Indonesia) Frequent ash explosions continue through September

Please cite this report as:

Global Volcanism Program, 2003. Report on Semeru (Indonesia) (Venzke, E., ed.). Bulletin of the Global Volcanism Network, 28:9. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN200309-263300.

Volcano Profile |  Complete Bulletin


Semeru

Indonesia

8.108°S, 112.922°E; summit elev. 3657 m

All times are local (unless otherwise noted)


Volcanic activity at Semeru between 30 June and 28 September remained at high levels. Except for the middle two weeks of July, ash explosions were reported several times every week, producing white-gray plumes that rose 400-500 m above the summit. Recorded seismic data (table 13) reflected this continued activity, with between 447 and 804 explosion events weekly (~ 88 per day on average over this 90-day period). Avalanche events, tremor, tectonic, deep-volcanic, shallow-volcanic, and flood-related seismicity were also recorded. A pilot report from Qantas noted a plume to twice the height of the volcano (~ 7.2 km altitude) on 9 September that was drifting S. The hazard status remained at Alert Level 2 throughout the report period.

Table 13. Seismicity at Semeru, 30 June-28 September 2003. Courtesy of VSI.

Date Explosion Avalanche Tremor Other Tectonic
30 Jun-06 Jul 2003 611 7 6 -- 7
07 Jul-13 Jul 2003 615 10 18 2 deep 9
14 Jul-20 Jul 2003 579 19 1 -- 8
21 Jul-27 Jul 2003 529 11 7 -- 10
28 Jul-03 Aug 2003 447 21 5 -- 6
04 Aug-10 Aug 2003 499 20 10 1 shallow 5
11 Aug-17 Aug 2003 550 8 16 -- 6
18 Aug-24 Aug 2003 516 13 2 1 shallow 10
25 Aug-31 Aug 2003 804 11 1 -- 7
01 Sep-07 Sep 2003 735 12 0 0 6
08 Sep-14 Sep 2003 699 30 1 1 flood 5
15 Sep-21 Sep 2003 731 11 5 0 8
22 Sep-28 Sep 2003 636 20 9 0 4

Geologic Background. Semeru, the highest volcano on Java, and one of its most active, lies at the southern end of a volcanic massif extending north to the Tengger caldera. The steep-sided volcano, also referred to as Mahameru (Great Mountain), rises above coastal plains to the south. Gunung Semeru was constructed south of the overlapping Ajek-ajek and Jambangan calderas. A line of lake-filled maars was constructed along a N-S trend cutting through the summit, and cinder cones and lava domes occupy the eastern and NE flanks. Summit topography is complicated by the shifting of craters from NW to SE. Frequent 19th and 20th century eruptions were dominated by small-to-moderate explosions from the summit crater, with occasional lava flows and larger explosive eruptions accompanied by pyroclastic flows that have reached the lower flanks of the volcano.

Information Contacts: Dali Ahmad and Nia Haerani, Volcanological Survey of Indonesia (VSI), Jalan Diponegoro No. 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/).