Report on Ibu (Indonesia) — November 2013
Bulletin of the Global Volcanism Network, vol. 38, no. 11 (November 2013)
Managing Editor: Richard Wunderman.
Ibu (Indonesia) Growing lava dome; numerous thermal alerts September 2011-March 2014
Please cite this report as:
Global Volcanism Program, 2013. Report on Ibu (Indonesia) (Wunderman, R., ed.). Bulletin of the Global Volcanism Network, 38:11. Smithsonian Institution.
1.488°N, 127.63°E; summit elev. 1325 m
All times are local (unless otherwise noted)
In the first nine months of 2011, Ibu was the scene of frequent avalanches and at least one weak explosion that generated minor white-to-gray plumes (BGVN 36:08). Seismic activity decreased during September 2011, prompting the Center of Volcanology and Geological Hazard Mitigation (CVGHM) to lower the Alert Level to 2 (on a scale of 1-4) on 8 September (the Level rose again later). This report discusses activity from 9 September 2011 through March 2014. The location of Ibu is shown in BGVN 36:08.
According to CVGHM, seismicity increased and volcanic tremor was detected during May through 6 June 2013. The lava dome grew, especially the N part, and by early June had grown taller than the N crater rim. White-to-gray plumes rose 200-450 m above the crater rim. Based on visual and instrumental observations, as well as the hazard potential, CVGHM increased the Alert Level to 3 on 7 June. The public was warned to stay at least 3 km away from the active crater.
CVGHM reported that during 7 June-9 December 2013, the lava dome continued to grow, and incandescent material from the dome filled the river valley in the direction of Duono village, about 5 km NW. The seismicity remained relatively stable. Observers saw occasional weak white-to-gray plumes. On 10 December 2013, the Alert Level was lowered to 2; however, the public was warned to stay at least 2 km away from the active crater, and 3.5 km away from the N part.
Between 1 September 2011 and March 2014, MODVOLC thermal alerts were issued on 70 days, or an average of almost one day every two weeks. Such alerts are consistent with dome growth such as that noted above. (Those alerts are derived from satellite data collected by the MODIS instrument and processed by the Hawai'i Institute of Geophysics and Planetology.) For comparison, between 1 January 2011 and 13 September 2011, these alerts only appeared about once every 2.4 weeks on average.
Geological Summary. The truncated summit of Gunung Ibu stratovolcano along the NW coast of Halmahera Island has large nested summit craters. The inner crater, 1 km wide and 400 m deep, contained several small crater lakes through much of historical time. The outer crater, 1.2 km wide, is breached on the north side, creating a steep-walled valley. A large parasitic cone is located ENE of the summit. A smaller one to the WSW has fed a lava flow down the W flank. A group of maars is located below the N and W flanks. Only a few eruptions have been recorded in historical time, the first a small explosive eruption from the summit crater in 1911. An eruption producing a lava dome that eventually covered much of the floor of the inner summit crater began in December 1998.
Information Contacts: Center of Volcanology and Geological Hazard Mitigation (CVGHM), Saut Simatupang, 57, Bandung 40122, Indonesia (URL: http://vsi.esdm.go.id/); Hawai'i Institute of Geophysics and Planetology (HIGP) MODVOLC 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/).