Geologic Background:
The Dawson Straits volcanic field, located
between eastern Fergusson and western Normanby islands in
the D'Entrecasteaux island group, contains 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 of
Fergusson Island. The 500-m-high summit of Lamonai is
capped by a steep-walled crater, and rhyolitic lava flows
are exposed on the NE side of the cone. Dominantly
volcaniclastic Oiau cone has also produced obsidian lava
flows. Dobu Island to the south is formed of coalescing
volcanic centers and likewise has produced youthful
obsidian flows.
Historic Activity:
- Last activity in April 1969.
Recent Activity:
- Earthquake swarm in December 1989.
- Earthquake swarm in Nov-Dec 1992.
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Data Sources:
- Global Volcanism Network (V. 15, No. 1, V. 25, No.
12).
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