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Report on Lokon-Empung (Indonesia) — November 1991

Bulletin of the Global Volcanism Network, vol. 16, no. 11 (November 1991)
Managing Editor: Lindsay McClelland.

Lokon-Empung (Indonesia) Moderate explosions continue

Please cite this report as:

Global Volcanism Program, 1991. Report on Lokon-Empung (Indonesia). In: McClelland, L. (ed.), Bulletin of the Global Volcanism Network, 16:11. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199111-266100.

Volcano Profile |  Complete Bulletin


Lokon-Empung

Indonesia

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

All times are local (unless otherwise noted)


Since the end of the vigorous activity that began on 24 October, 16 explosions from the active Tompaluan Crater have been recorded (figure 2). Ash column heights ranged from 200 m to >250 m above the rim of Tompaluan . . . . The most recent recorded explosion, on 1 December at 1717, was preceded by tremor that morning and the previous day. The press described an apparently unrecorded ash emission episode that produced a 300-m plume during the morning of 11 December. Gas rose to 200-300 m height between explosions. Local seismicity continued at somewhat reduced rates (figure 3).

Figure (see Caption) Figure 2. Number of recorded explosions/day at Lokon-Empung, 24 October-12 December 1991. Courtesy of VSI.
Figure (see Caption) Figure 3. Number of recorded earthquakes at Lokon-Empung, 28 October-12 December 1991. For each day, three bars are shown, distinguishing shallow volcanic earthquakes (left), deep volcanic shocks (center), and tectonic events (right). Arrows indicate tremor episodes. Courtesy of VSI.

VSI warned that additional explosions were still anticipated, and the area designated by their 1986 hazard map remained at risk. The press reported that [~10,000] people had fled the 24 October activity, but most had returned home by early December.

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: VSI; UPI.