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Report on Lokon-Empung (Indonesia) — April 2002

Bulletin of the Global Volcanism Network, vol. 27, no. 4 (April 2002)
Managing Editor: Richard Wunderman.

Lokon-Empung (Indonesia) Ash eruptions and increased seismicity in mid-April, Alert Level raised to 3

Please cite this report as:

Global Volcanism Program, 2002. Report on Lokon-Empung (Indonesia). In: Wunderman, R. (ed.), Bulletin of the Global Volcanism Network, 27:4. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN200204-266100.

Volcano Profile |  Complete Bulletin


Lokon-Empung

Indonesia

1.358°N, 124.792°E; summit elev. 1580 m

All times are local (unless otherwise noted)


An eruption at Lokon on 9 February, triggered by extensive rainfall, sent ash plumes to 1 km and deposited ash in surrounding villages. Activity then decreased significantly and remained low through February 2002 (BGVN 27:02). During February through at least April, Tompaluan crater emitted plumes 50-350 m above the crater rim.

During early April deep and shallow volcanic earthquakes increased (table 2). Eruptions on 10 and 12 April ejected glowing material from the crater. A thick white-gray ash plume rose 1 km above the crater rim. During 13-14 April gas/ash explosions occurred nearly continuously, with eight explosions on 13 April and five on the 14th. Ash explosions rose 50-75 m above the crater rim. Tremor amplitude increased from 0.5-2 mm on 11 April to 4-48 mm by 14 April. The Volcanological Survey of Indonesia (VSI) raised the Alert Level to 3 on 12 April. A total of 25 and 68 small explosions per week were registered during 22-28 April and 29 April-5 May, respectively. During the following weeks the number of small explosions dropped to only 6 per week. As of 26 May, tremor fluctuated (0.5-30 mm amplitude) and gas explosions continued.

Table 2. Earthquakes recorded at Lokon during 11 February through 26 May 2002. Courtesy VSI.

Date Deep volcanic (A-type) Shallow volcanic (B-type) Tectonic
11 Feb-17 Feb 2002 -- 2 17
18 Feb-24 Feb 2002 4 1 41
25 Feb-03 Mar 2002 -- 3 16
04 Mar-10 Mar 2002 -- 1 34
11 Mar-17 Mar 2002 -- 1 28
18 Mar-24 Mar 2002 10 11 11
25 Mar-31 Mar 2002 -- 1 17
01 Apr-07 Apr 2002 44 78 12
08 Apr-14 Apr 2002 90 184 10
15 Apr-21 Apr 2002 -- 34 43
22 Apr-28 Apr 2002 13 81 35
29 Apr-05 May 2002 2 7 25
06 May-12 May 2002 111 482 18
13 May-19 May 2002 84 207 35

Geologic Background. The twin volcanoes Lokon and Empung, rising about 800 m above the plain of Tondano, are among the most active volcanoes of Sulawesi. Lokon, the higher of the two peaks (whose summits are only 2 km apart), has a flat, craterless top. The morphologically younger Empung volcano to the NE has a 400-m-wide, 150-m-deep crater that erupted last in the 18th century, but all subsequent eruptions have originated from Tompaluan, a 150 x 250 m wide double crater situated in the saddle between the two peaks. Historical eruptions have primarily produced small-to-moderate ash plumes that have occasionally damaged croplands and houses, but lava-dome growth and pyroclastic flows have also occurred. A ridge extending WNW from Lokon includes Tatawiran and Tetempangan peak, 3 km away.

Information Contacts: Dali Ahmad, Volcanological Survey of Indonesia (VSI) (URL: http://www.vsi.esdm.go.id/).