The Darwin Volcanic Ash Advisory Centre reports that over the period 29 August-3 September 2013, Mount Dukono, an active volcano on the northwestern limb of Halmahera Island, to the east of Sulawesi, produced a series of ash plumes reaching up to 4.3 km above the summit, and drifting up to 240 km to the west and northwest. Dukono has been in more-or-less constant eruption since 1933. It has a complex structure, with multiple overlapping craters and numerous peaks, and explosive eruptions and lava-flows are a regular occurrence, though it had been relatively quiet since June this year.
An ash column from Mount Dukono in June 1991. Vivianne Clavel.
The Halmahera Islands arc a volcanic arc; formed where one tectonic plate is being subducted beneath another, with the underlying plate being melted by the heat of the Earth's interior, and lighter minerals bubbling up through the overlying plate to form volcanoes. However the Halmahera Islands are unique in that they lie on a double subduction zone. The underlying plate, a northeaster extension of the Molucca Plate, is being overridden form the Philippine Plate from the east and the Eurasian Plate from the west. The Halmahera volcanoes are located where the Philippine Plate is overriding the Molucca Plate; to the west the Sangihe Islands lie where the Molucca Plate is being overridden by the Eurasian Plate.
The approximate location of Mount Dukono. Google Maps.
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