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Report on Semeru (Indonesia) — May 2009


Bulletin of the Global Volcanism Network, vol. 34, no. 5 (May 2009)
Managing Editor: Richard Wunderman.

Semeru (Indonesia) Many ash plumes and some pyroclastic flows during February 2007-March 2009

Please cite this report as:

Global Volcanism Program, 2009. Report on Semeru (Indonesia) (Wunderman, R., ed.). Bulletin of the Global Volcanism Network, 34:5. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN200905-263300



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

All times are local (unless otherwise noted)

Our last report (BGVN 32:03) covered through October 2006 in terms of CVGHM reporting and through February 2007 in terms of Darwin VAAC reporting. As has been the case for decades, Semeru's eruptions continued and were ongoing through this reporting interval, February 2007-March 2009. During the reporting interval, ash plumes were periodically observed over the summit at low altitudes of 3.7-4.6 km. Taller plumes, when they occurred, are noted below. There were several cases of plumes over 6 km altitude and as tall as ~ 7.6 km altitude. Pyroclastic flows ran out to distances as great as 3 km (table 18).

Table 18. Compilation of data on Semeru during February 2007-March 2009. Courtesy of CVGHM.

Date Plume height and drift direction Seismicity and Observations
10-11 Feb 2007 E --
03-05 May 2007 4.6 km; SW --
25 May 2007 4.6 km; W --
18-25 Jun 2007 4.2 km --
06 Aug 2007 6.1 km --
22 Sep 2007 7.3 km --
31 Oct 2007 -- Eruption heard 17 km away.
21 Apr 2008 6.1 km --
15, 17-19, 21 May 2008 -- Increased seismicity. Pyroclastic flows up to 500-3000 m from the crater. On 21 May, incandescent ejections.
22 May 2008 -- Fewer pyroclastic flows and rockfalls; four up to 2.5 km from crater.
05 Jun 2008 -- Decline in seismicity.
07-09 Jul 2008 4.9-7.6 km; SSW --
27 Jul 2008 4.3 km --
05 Aug 2008 4.0-4.3 km Plumes sometimes with incandescent tephra.
07 Aug 2008 4.3 km Incandescent material ejected from the crater.
21-22 Aug 2008 3.7 km; W --
28 Aug 2008 Low-level --
31 Aug 2008 4.6 km; SW --
09 Sep 2008 4.3 km; SSW --
10 Sep 2008 4.3 km --
22 Oct 2008 4.3 km --
Jan 2009 -- Average over 100 daily eruptive earthquakes. Four deep volcanic earthquakes on the 24th.
Feb 2009 -- Average of less than 50 eruptive earthquakes/day.
01 Feb 2009 4.0 km --
21 Feb 2009 -- 18 deep volcanic earthquakes.
03 Mar 2009 -- 5 eruptive earthquakes.
06 Mar 2009 3.7 km 0010 local time (see text).
06, 12 Mar 2009 -- Volcanic seismicity had a maximum amplitude reached ± 34 mm.
12 Mar 2009 4.5 km Ash/cinder eruption accompanied by rumbling sounds lasting ~6 minutes.
15 Mar 2009 4.3 km Eruptive earthquake amplitude ±18 mm. Dense low-pressure ash-cinder eruption; changing to white air-blasts, then gradually diminishing.
16-22 Mar 2009 -- Averaged eruptive earthquakes around 1-30 daily; max. amplitudes less than 10 mm.

October 2007. Based on reports from CVGHM, the Darwin VAAC reported that an unconfirmed eruption was heard 17 km away on 31 October 2007 (table 18). No plume was seen in MTSAT-IR satellite imagery. A news report from Antara News on 5 November 2007 ("Ash blankets town near Indonesian volcano") noted that scientists monitoring the volcanoes confirmed Semeru as the source. The news report stated that initially residents thought the thin layer of ash had come from Kelut, a volcano that went to Alert Level 4 (the highest status) on 16 October. The eruption of Kelut, while emitting a large dome into a crater lake, triggered few if any sustained explosions (BGVN 33:03). Ash fell in Blitar, outside a 10 km danger zone around Kelut; Semeru is ~ 90 km away.

On 15, 17-19, and 21 May 2008 ash plumes, rockfall avalanches, and multiple pyroclastic flows were observed, as well as increased seismic activity. At that time, the alert level was raised from 2 to 3. By 22 May pyroclastic flows and rockfall avalanches had declined in frequency, and consequently on 5 June the hazard was lowered to Level 2. During 7-9 July 2008, ash plumes rose to altitudes of 4.9-7.6 km, the tallest of the reporting interval.

From January to mid-February 2009, explosion earthquakes occurred on average 100-150 times a day (table 18). Ash and cinder eruptions from Jonggring Saloko crater took place daily every 15-20 minutes, with plumes reaching altitudes of 3.7-4.3 km. During a ~ 5 minute interval on 6 March 2009 at 0010, a loud boom was followed by a bluish flash of lightning 5-7 seconds in duration.

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: Center of Volcanology and Geological Hazard Mitigation (CVGHM), Saut Simatupang, 57, Bandung 40122, Indonesia (URL: http://vsi.esdm.go.id/); Antara News (URL: http://www.antara.co.id/en/).