Manam Moto, a volcanic island off the north coast of Papua New Guinea, erupted on Wednesday 23 January 2019, the latest in a series of eruptions that began in August last year. The eruption was preceded by a series of earthquakes which started at about 2.00 pm local time, followed by an eruption at about 4.00 pm that produced an ash column that rose about 12 200 m above the island, and led to the Darwin Volcanic Ash Advisory Centre issuing a warning to aviation and ashfalls on the island which are reported to have tainted fresh-water supplies, leading to calls for the population to be temporarily relocated to the mainland, the first time this has happened since 2004.
An ash column over Manam Moto on 24 January 2019. Kessy Sawang/Facebook/Le Chaudron de Vulcan.
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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