The Darwin Volcanic Ash Advisory Centre reported an ash plume above Manam Motu, a volcanic island off the north coast of Papua New Guinea, on 6 December 2018, that rose to 5.2 km above sealevel, and drifted to the southeast. On 8 December a series of seismic events (tremors) were recorded beneath the volcano, followed by an eruption at about 1.00 pm local time, that rose to about 15.2 km above sealevel and drifted to the east and began to dissipate. At about 8.20 pm another eruption produced a column that rose to 8.2 km above sealevel. Residents of the island reported heavy ashfalls, and the villages of Bokure and Kolang on the northeastern flank of the volcano were evacuated voluntarily by their residents.
Eruption on Manam Motu on 8 December 2018. Madang Province News Page/Facebook.
Manam Moto is
essentially a submarine stratovolcano (cone-shaped volcano) with its
tip sticking above the sea, forming a 10 km diameter circular island
with the summit of the volcano at the centre. The island is remarkably
symmetrical, with four valleys at 90° angles leading from the summit to
the sea, which carry ejecta from the frequent eruptions.
Manam Motu is located on the southern margin of the South Bismarck
Plate, close to its boundary with the Australian Plate, which underlies
the Papuan mainland. The Australian Plate is being subducted beneath the
South Bismarck, and as it does so it is partially melted by the
friction and the heat of the planet's interior. Some of the melted
material then rises up through the overlying South Bismarck Plate as
magma, fuelling the volcanoes of the north Papuan margin.
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