The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that the eruption at Ibu continued during 22-28 January, with a decrease in eruptive activity resulting in the Alert Level being lowered from Level 4 to Level 3 (on a scale of 1 to 4) at 1700 on 28 January. Additionally, the recommended exclusion zone was adjusted in response to the new Alert Level status, with the public now advised to maintain a distance of at least 4 km from the eruption center, except in the N sector, where the distance extends to 5 km from the N crater wall opening. Eruptive events were recorded daily, generating gray and white-to-gray ash plumes that rose at least 1.2 km above the summit and drifted multiple directions. Webcam images posted with the eruption reports showed incandescence at the summit and occasionally incandescent material being ejected above the summit during explosions. In a special report, PVMBG noted that the lava dome growing in the crater had exceeded the crater wall height, resulting in small collapse avalanches onto the N and NW flanks. Deformation monitoring data (Electronic Distance Measurement surveys) showed a deflationary trend between 1 and 27 January.

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)