Report on Dempo (Indonesia) — January 2009
Bulletin of the Global Volcanism Network, vol. 34, no. 1 (January 2009)
Managing Editor: Richard Wunderman.
Dempo (Indonesia) Sudden phreatic eruption on 1 January 2009
Please cite this report as:
Global Volcanism Program, 2009. Report on Dempo (Indonesia) (Wunderman, R., ed.). Bulletin of the Global Volcanism Network, 34:1. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN200901-261230.
4.016°S, 103.121°E; summit elev. 3142 m
All times are local (unless otherwise noted)
According to a report by Indonesia's Center of Volcanology and Geological Hazard Mitigation (CVGHM), Dempo had a phreatic eruption on 1 January 2009. The event resulted in a strong sulfur odor and an ash (or cinder) rain that was noted as far as ~ 10 km from the summit. During 27 December 2008 to 1 January 2009, fog prevented direct observations of the summit; clouds over the summit area are a common occurrence. The one available photo of the eruption showed a whitish-colored plume rising perhaps a few kilometers over the summit.
On 1 January authorities raised the alert status from 1 (normal) to 2 (alert, "Waspada" in Indonesian), on a scale that ranges from 1-4. Visitors and residents were advised not to go within a 2-km radius of the summit. A 2 January report from CVGHM noted that both local volcanic and regional tectonic earthquakes were recorded during 27 December 2008 through 1 January 2009 (table 1).
|27 Dec 2008||One local volcanic (A-type), and two tectonic.|
|28 Dec 2008||One local volcanic (A-type), and one air blast event.|
|29 Dec 2008||One local volcanic, five air blasts, and two tectonic.|
|30 Dec 2008||One shallow local volcanic, one air blast, one low-frequency, and one tectonic.|
|31 Dec 2008||One local volcanic, one air blast, and two tectonic not at the volcano.|
|01 Jan 2009||One local volcanic related to the explosive eruption.|
As of early 2009, no thermal anomalies had been measured over Dempo by the MODVOLC infrared satellite system for at least the last 5 years. ASTER images from 2001-2007 show extensive cloud cover.
Geologic Background. Dempo is a prominent stratovolcano that rises above the Pasumah Plain of SE Sumatra. The andesitic volcanic complex has two main peaks, Gunung Dempo and Gunung Marapi, constructed near the SE rim of a 3 x 5 km caldera breached to the north. The Dempo peak is slightly lower, and lies at the SE end of the summit complex. The taller Marapi cone was constructed within a crater cutting the older Gunung Dempo edifice. Remnants of seven craters are found at or near the summit, with volcanism migrating WNW over time. The large, 800 x 1100 m wide historically active crater cuts the NW side of the Marapi cone and contains a 400-m-wide lake located at the far NW end of the crater complex. Historical eruptions have been restricted to small-to-moderate explosive activity that produced ashfall near the volcano.
Information Contacts: Center of Volcanology and Geological Hazard Mitigation (CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://vsi.esdm.go.id/); Hawai'i Institute of Geophysics and Planetology (HIGP) Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/).