Evacuations ordered after increase in activity from Mount Ibu on Halmahera Island, Indonesia.

Authorities in North Maluku Province, Indonesia, have ordered the evacuation of six villages close to Mount Ibu, a 1325 m stratovolcano on the northwest coast of Halmahera Island, following a series of eruptions in the first two weeks of 2025. Mount Ibu began its current eruptive cycle in June 2024, but January has seen a significant rise in activity, with more than a thousand eruptions have been recorded on the volcano this year, with the largest producing ash columns reaching as high as 4 km over the summit of the volcano. However, to date only one village, with a population of 517 people, has been evacuated, with about 2500 people in the remaining five villages reluctant to leave without first harvesting crops.

An eruption on Mount Ibu, Halmahera Island, on Wednesday 15 January 2024. Azzam/AFP.

The Halmahera Island chain is a volcanic arc formed where the Halmahera Plate, a northeaster extension of the Molucca Sea Plate is being subducted beneath Philippine Plate from the east and the Eurasian Plate from the west, 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. The Halmahera volcanoes are located where the Philippine Plate is overriding the Molucca Sea Plate; to the west the Sangihe Islands lie where the Molucca Sea Plate is being overridden by the Eurasian Plate.

Diagrammatic representation of the subduction zones beneath Halmahera (middle), plus the Philippines (top) and Sulawesi (bottom), with the Eurasian Plate to the left, the Molucca Sea Plate in the middle, and the Philippine Plate to the right.  Hall & Wilson (2000).

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Exclusion area around Mount Ibu, Halmahera Island, extended following new eruption.

The Indonesian Center for Volcanology and Geological Hazard Mitigation has extended the exclusion zone around  Mount Ibu, a 1325 m stratovolcano on the northwest coast of Halmahera Island, following a new eruption on 18 May 2024. A two kilometre exclusion zone had already been put in place after the volcano began erupting on 28 April, but this has been increased to seven kilometres following the most recent eruption, which produced an ash column which rose to 4 km above the volcano's summit, resulting in seven villages needing to be evacuated. 

An ash column and lava fountain above Mount Ibu on the Indonesian island of Halmahera on 18 May 2024. Several lightning discharges can be seen within the ash column; ash columns can build up considerable charge variations leading to frequent electrical discharges. Indonesian Center for Volcanology and Geological Hazard Mitigation/Reuters.

The Halmahera Island chain is a volcanic arc formed where the Halmahera Plate, a northeaster extension of the Molucca Sea Plate is being subducted beneath Philippine Plate from the east and the Eurasian Plate from the west, 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. The Halmahera volcanoes are located where the Philippine Plate is overriding the Molucca Sea Plate; to the west the Sangihe Islands lie where the Molucca Sea Plate is being overridden by the Eurasian Plate.

Diagrammatic representation of the subduction zones beneath Halmahera (middle), plus the Philippines (top) and Sulawesi (bottom), with the Eurasian Plate to the left, the Molucca Sea Plate in the middle, and the Philippine Plate to the right.  Hall & Wilson (2000).

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Islands evacuated after major eruption on Mount Ruang, Indonesia.

The Indonesian Meteorology, Climatology and Geophysics Agency has reported a major series of eruptions on Mount Ruang, an island volcano at the southern tip of the Sangihe Islands, which has prompted the evacuation of both Ruang Island and the nearby Tagulandang Island, more than 12 800 people in total. The volcano erupted three times on Tuesday 30 April 2024, producing ash columns which rose to more than 5 km above sealevel, and drifted west as far as Borneo. Seven airports in Indonesia have been forced to close temporarily due to the dangers of ash from the volcano.

An eruption on Mount Ruang, Indonesia, on 30 April 2024, seen from Tagulandang Island. Endha Reifel Pontoh/Reuters.

The Sangihe Island Arc is a chain of volcanic islands running between the northern tip of Sulawesi and the southern tip of Mindanao. The chain marks the boundary between the Molucca Plate to the east and the Sangihe Plate to the west, with the Molucca Plate being subducted beneath the Sangihe Plate. As the Molucca Plate sinks into the Earth it is heated by the friction and the heat of the planet's interior, causing it to partially melt. Some of the melted material then rises through the overlying Sangihe Plate as magma, fuelling the volcanoes of the Sangihe Arc.

The subduction zones beneath Sulawesi and the surrounding islands. Hall & Spakman (2015).

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Eruption on Mount Ibu, Halmahera Island, Indonesia.

The Regional Disaster Mitigation Agency for West Halmahera District has reported an eruption on Mount Ibu, a 1325 m stratovolcano on the northwest coast of Halmahera Island, Indonesia, on Sunday 28 April  2024 (a stratovolcano is a cone-shaped volcano made up of layers of ash and lava, although Mount Ibu has a truncated shape, having lost its upper part in an explosion at some point in the past). The eruption started at 0.37 am local time, and lasted approximately three minutes and 26 seconds, producing a column of dark ash which rose 3.5 km above the summit of the volcano and drifted to the west. The Regional Disaster Mitigation Agency has asked people not to go within 2 km of the volcano for the time being, and has issued dust masks to residents of 16 villages in the area. Sam Ratulangi International Airport, about 100 km from the volcano in the city of Manado, is closed to flights temporarily.

An ash column over Mount Ibu at 0.44 am local time on Sunday 28 April 2024. Abdul Fatah/Antara News Agency.

The Halmahera Island chain is a volcanic arc formed where the Halmahera Plate, a northeaster extension of the Molucca Sea Plate is being subducted beneath Philippine Plate from the east and the Eurasian Plate from the west, 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. The Halmahera volcanoes are located where the Philippine Plate is overriding the Molucca Sea Plate; to the west the Sangihe Islands lie where the Molucca Sea Plate is being overridden by the Eurasian Plate.

Diagrammatic representation of the subduction zones beneath Halmahera (middle), plus the Philippines (top) and Sulawesi (bottom), with the Eurasian Plate to the left, the Molucca Sea Plate in the middle, and the Philippine Plate to the right.  Hall & Wilson (2000).

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Eruption on Mount Karangetang triggers pyroclasitc flow.

Authorities on the Indonesian island of Siau, in the Sangihe Archipelago to the north of Sulawesi, have extended an exclusion zone around Mount Karangetang, a 1784 m high stratovolcano (cone-shaped volcano) on the northern end of the island, following a pyroclastic flow (flow of heavy superheated gas containing large amounts of hot ash, rocks and debris) on Tuesday 5 February 2019, which blocked a road on the island. Mount Karangetang is one of Indonesia's most active volcanoes, typically erupting several times per year, with the current phase of eruptions having begun in November 2018, after several months of inactivity.

Pyroclastic flow blocking a road on Siau Island, Indonesia on 5 February 2019. 3 alacarta.

Siau Island is quite densely populated with around 22 000 permanent residents, and Mount Karangetang frequently causes problems for the islanders, having most recently caused fatalities in August 2010. The Sangihe Island Arc is a chain of volcanic islands running between the northern tip of Sulawesi and the southern tip of Mindanao. The chain marks the boundary between the Molucca Plate to the east and the Sangihe Plate to the west, with the Molucca Plate being subducted beneath the Sangihe Plate. As the Molucca Plate sinks into the Earth it is heated by the friction and the heat of the planet's interior, causing it to partially melt. Some of the melted material then rises through the overlying Sangihe Plate as magma, fuelling the volcanoes of the Sangihe Arc.

 The subduction zones beneath Sulawesi and the surrounding islands. Hall & Spakman (2015).

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