Dobu is one of 3 volcanic centres of the Dawson Strait Group. It forms the small Dobu Island SE of Fergusson Island. Dobu volcano consists of a composite cone with a summit crater and a small satellite cone. It, too, has produced obsidian lava flows.

Dawson Strait Group volcano

from Smithsonian / GVP volcano information:

The Dawson Straits, located between eastern Fergusson and western Normanby Islands in the D'Entrecasteaux island group, contains a volcanic field with several volcanic centers that define a possible partly submerged caldera.

There have been no historical eruptions from this center, but morphology suggests an extremely young age for some lava flows, and the area displays vigorous thermal activity. The most prominent volcanic centers are Mounts Lamonai and Oiau, located about 10 km apart on the SW tip of Fergusson Island.