The Rabaul Volcano Observatory reported an eruption on Manam Motu, a volcanic island 13 km off the north coast of Papua New Guinea on Friday 31 July 2015, which started at about 11.30 am local time, which resulted in fragments of scoria (a form of basaltic rock) up to 20 cm in diameter landing in the villages of Warisi and Baliau, where two people were reportedly knocked unconscious after being struck. Ashfall was reported across the island and in the villages of Bogia and Potsdam on the Papuan mainland. The Darwin Volcanic Ash Advisory Centre reported an ash column rising 19.8 km above the island, which then drifted 370 km to the southwest.
Image of the ash column over Manam Moto on 31 July 2015 captured by the Himawari-8 weather satellite. Japan Meteorological Agency/Volcano Discovery.
Following the eruption much of the north and west island is reportedly covered by ash 1-2 cm thick. preventing residents from accessing crops and in some cases water, prompting fears of food shortages, Many people in the affected areas have also reported suffering breathing difficulties, and most of the residents have been evacuated to rescue centers outside the affected zones, where it is unclear when they will be able to return home.
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.
The location of Manam Moto. Google Maps.
Manam Motu is one of Papua New Guinea's most active volcanoes; it underwent four eruptive cycles in 2011. The island was inhabited until 2004, when the island's population of ~9000 was evacuated after an eruption killed five people. The Papuan government allowed re-settlement to begin in March 2007, but three people were killed on the island within a month; the island's inhabitance status is currently unclear. Prior to 2004 the most recent fatalities had been in 1996, when a pyroclastic flow (avalanche of hot ash and poisonous gas) hit the village of Budua, killing 13. Despite its small size and inhospitable nature Manam Motu was apparently settled for a long time, having developed its own distinctive language (Manam).
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, fueling the volcanoes of the north Papuan margin.
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Manam Motu is a volcanic island 13 km off the north coast of Papua New Guinea; it 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.
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