The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that the eruption at Ibu continued during 8-15 January. Daily gray or white-and-gray ash plumes that were often dense generally rose as high as 2.5 km above the summit and drifted in multiple directions, though ash plumes occasionally rose higher. Webcam images posted with the reports often showed incandescence at the summit or being ejected above the summit of the inner active cone. During 10 and 13-14 January ash plumes rose up to 3 km above the summit. At 1935 on 11 January a dense gray ash plume rose 4 km above the summit and drifted W and, according to BNPB, incandescent lava was ejected as high as 2 km above the summit. The event lasted for three minutes and five seconds based on seismic data. At 0711 on 15 January a dense ash plume rose 4 km above the summit and drifted W and a pyroclastic flow traveled 500 m N. Booming and rumbling sounds were heard at the Ibu Observation Post (9 km W).

In a press release PVMBG noted that taller ash plumes, 3-4 km above the summit, had become more frequent during 1-15 January. Additionally, the number of shallow volcanic earthquakes increased, and deformation data showed inflation on 6 and 13 January. The Alert Level was raised to 4 (the highest level on a four-level scale) at 1000 on 15 January and the public was advised to stay 5 km away from the active crater and 6 km away from the N crater wall opening.

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.

Sources: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM), Badan Nacional Penanggulangan Bencana (BNPB)