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Report on Semeru (Indonesia) — October 2003


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

Semeru (Indonesia) Frequent ash explosions continue through October

Please cite this report as:

Global Volcanism Program, 2003. Report on Semeru (Indonesia) (Venzke, E., ed.). Bulletin of the Global Volcanism Network, 28:10. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN200310-263300



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

All times are local (unless otherwise noted)

Frequent ash explosions at Semeru during 29 September-26 October 2003 produced white-gray ash plumes 400-500 m over the summit. The hazard status remained at Alert Level 2 (on a scale of 1-4) during this time. Although tectonic earthquakes, tremor events, shallow volcanic earthquakes, and avalanches were all detected seismically, the record was dominated by explosions (table 14). Explosions over this 4-week period averaged 95 per day, or one every 15 minutes.

Table 14. Seismicity at Semeru, 29 September-26 October 2003. Four shallow volcanic earthquakes were also detected during 6-12 October. Courtesy of VSI.

Date Explosion Avalanche Tremor Tectonic
29 Sep-05 Oct 2003 636 20 9 4
06 Oct-12 Oct 2003 567 10 -- 7
13 Oct-19 Oct 2003 687 19 22 4
20 Oct-26 Oct 2003 768 16 3 11

Geological Summary. 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, 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/).