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) (Wunderman, R., ed.). Bulletin of the Global Volcanism Network, 27:4. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN200204-266100
Lokon-Empung
Indonesia
1.3644°N, 124.7992°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 |
Geological Summary. The Lokong-Empung volcanic complex, rising above the plain of Tondano in North Sulawesi, includes four peaks and an active crater. Lokon, the highest peak, has a flat craterless top. The morphologically younger Empung cone 2 km NE has a 400-m-wide, 150-m-deep crater that erupted last in the 18th century. A ridge extending 3 km WNW from Lokon includes the Tatawiran and Tetempangan peaks. All eruptions since 1829 have originated from Tompaluan, a 150 x 250 m crater in the saddle between Lokon and Empung. These eruptions have primarily produced small-to-moderate ash plumes that sometimes damaged croplands and houses, but lava-dome growth and pyroclastic flows have also occurred.
Information Contacts: Dali Ahmad, Volcanological Survey of Indonesia (VSI) (URL: http://www.vsi.esdm.go.id/).
