The Darwin VAAC reported that on 8 May an ash plume from Ibu rose to 2.4 km (8,000 ft) a.s.l. and drifted ESE based on satellite data. PVMBG noted that at 1821 on 9 May an ash plume rose 600 m above the crater rim and drifted S. Seismic activity was characterized by explosions, tremor, and signals indicating rock avalanches. According to the VAAC an ash plume drifted ESE at an altitude of 1.8 (6,000 ft) a.s.l. on 10 May. A 14 May VONA stated that at 1846 an ash plume rose 800 m and drifted N. The Alert Level remained at 2 (on a scale of 1-4), and the public was warned to stay at least 2 km away from the active crater, and 3.5 km away on the N side.

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: Darwin Volcanic Ash Advisory Centre (VAAC), Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)