PVMBG reported that activity at Ibu continued during 14-20 August with multiple eruptive events recorded daily. Daily gray or white-and-gray ash plumes that were sometimes dense generally rose as high as 2 km above the summit and drifted N, NW, W, and SW. Some webcam images posted with the reports showed incandescence emanating above the crater rim, possibly reflected in the emissions. At 0118 on 28 August a dense gray-to-black ash plume rose as high as 5 km above the crater rim and drifted SW and W. The Alert Level remained at 3 (the second highest level on a four-level scale) and the public was advised to stay 4 km away from the active crater and 5 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.

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