Report on Ibu (Indonesia) — May 1999
Bulletin of the Global Volcanism Network, vol. 24, no. 5 (May 1999)
Managing Editor: Richard Wunderman.
Ibu (Indonesia) March-May ash plumes are white and rise up to 700 m above crater rim
Please cite this report as:
Global Volcanism Program, 1999. Report on Ibu (Indonesia). In: Wunderman, R (ed.), Bulletin of the Global Volcanism Network, 24:5. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199905-268030.
1.488°N, 127.63°E; summit elev. 1325 m
All times are local (unless otherwise noted)
"White ash emissions" were noted between 9 March and 24 May, rising as high as 700 m above the crater rim but more often 100-200 m. On 11 March it was noted that larger eruptions, accompanied by booming noises and thick ash emission, had decreased to every 10-15 minutes from every 5 minutes during the previous observations on 2 February. Signals from seismic events were dominated by those from the eruptive events, which occurred at a rate of over 100 per day in March and reduced to half that number in April and May.
Geologic Background. 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: Volcanological Survey of Indonesia (VSI), Jalan Diponegoro No. 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/).