The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that the eruption at Ibu continued during 27 November-3 December. Daily gray or white-and-gray ash plumes that were often dense rose as high as 1.2 km above the summit and drifted in multiple directions. Daily webcam images posted with the reports showed incandescence at the summit of the inner active cone. According to BNPB an eruptive event at 2144 on 1 December ejected incandescent material 700 m above the summit and lasted about two and a half minutes based on seismic data. The event prompted PVMBG to increase the hazard zone radius to 5.5 km on the N flank; the public was advised to stay 4 km away from the active crater in all other directions. The Alert Level remained at 3 (the second highest level on a four-level scale).

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)