Report on Ibu (Indonesia) — 5 August-11 August 2009
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 5 August-11 August 2009
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2009. Report on Ibu (Indonesia). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 5 August-11 August 2009. Smithsonian Institution and US Geological Survey.
1.488°N, 127.63°E; summit elev. 1325 m
All times are local (unless otherwise noted)
CVGHM reported that white and gray plumes from Ibu rose 300-400 m above the crater rim during 15 July-4 August, and that earthquakes became more frequent during 27 July-4 August. Lava flows were seen on 2 August. Later that day, a thunderous sound was followed by incandescence at the summit. On 3 August, incandescent material was ejected as high as 20 m above the crater. On 5 August, the Alert Level was increased to 3 (on a scale of 1-4). The growing lava dome had reached a height so that it was visible from Duono Village, about 5 km NW. Residents and tourists were not permitted within 2 km of the crater.
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.