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.

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, has contained several small crater lakes. The 1.2-km-wide outer crater is breached on the N, creating a steep-walled valley. A large cone grew ENE of the summit, and 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. The first observed and recorded eruption was a small explosion from the summit crater in 1911. Eruptive activity began again in December 1998, producing a lava dome that eventually covered much of the floor of the inner summit crater along with ongoing explosive ash emissions.

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)