Eruption on Mount Kanlaon.

Mount Kanlaon, a 2465 m stratovolcano (cone shaped volcano made up of layers of ash and lava) on northern Negros Island in the central Philippines, underwent an explosive eruption at 5.51 am local time on Tuesday 8 April 2025, producing an ash column 4 km high which drifted to the west and southwest, according to a bulletin issued by the Philippine Institute of Volcanology and Seismology. The sound of the eruption was heard about 20 km away, and pyroclastic flows were observed on the southern flanks of the volcano, and debris is reported to have set fire to vegetation close to the summit of the volcano. Ash falls were reported up to 50 km from the eruption.

An ash column over mount Kanlaon on 8 April 2025. Philippine Institute of Volcanology and Seismology.

No injuries have been associated with the eruption, but the Philippine Institute of Volcanology and Seismology has recommended that communities within 6 km of  the volcano evacuate the area, and has placed a ban on aircraft overflying the area.

The geology of the Philippines is complex, with the majority of the islands located on the east of the Sunda Plate. To the east of this lies the Philippine Sea plate, which is being subducted beneath the Sunda Plate (a breakaway part of the Eurasian Plate); further east, in the Mariana Islands, the Pacific Plate is being subducted beneath the Philippine Sea Plate. This is not a smooth process, and the rocks of the tectonic plates frequently stick together before eventually being broken apart by the rising pressure, leading to Earthquakes in the process. Material from the subducting Philippine Plate is heated by the temperature of the Earth's interior, causing lighter minerals to melt and the resultant magma to rise through the overlying Sunda Plate, fuelling the volcanoes of the Philippines.

Subduction beneath the Philippines. Yves Descatoire/Singapore Earth Observatory.

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Magnitude 6.2 Earthquake off the west coast of Sumatra.

The Indonesian Meteorological, Climatological, and Geophysical Agency recorded a Magnitude 6.2 Earthquake at a depth of about 29 km, off the West coast of Aceh Province, Sumatra, Indonesia slightly after 6.00 pm Western Indonesian Time (slightly after 11.00 am GMT) on Tuesday 31 January 2025. There have been no reports of any damage or casualties following this event, but people have reported feeling  tremors  across Aceh Province and parts of North Sumatra.

The approximate location of the 31 January 2025 Aceh Province Earthquake. USGS.

The Indo-Australian Plate, which underlies the Indian Ocean to the west of Sumatra, is being subducted beneath the Sunda Plate, a breakaway part of the Eurasian Plate which underlies Sumatra and neighbouring Java, along the Sunda Trench, passing under Sumatra, where friction between the two plates can cause Earthquakes. As the Indo-Australian Plate sinks further into the Earth it is partially melted and some of the melted material rises through the overlying Sunda Plate as magma, fueling the volcanoes of Sumatra.

The Subduction zone beneath Sumatra. NASA/Earth Observatory.

This does not happen at a 90° angle, as occurs in the subduction zones along the western margins of North and South America, but at a steeply oblique angle. This means that as well as the subduction of the Indo-Australian plate beneath the Sunda, the two plates are also moving past one-another. This causes rifting within the plates, as parts of each plate become stuck to the other, and are dragged along in the opposing plate's direction. The most obvious example of this is the Sumatran Fault, which runs the length of Sumatra, with the two halves of the island moving independently of one-another. This fault is the cause of most of the quakes on the island, and most of the island's volcanoes lie on it.

The movement of the tectonic plates around Sumatra. NASA/Earth Observatory.

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Eruption and lahar on Mount Kanloan, Negros Island, the Philippines.

Mount Kanlaon, a 2465 m stratovolcano (cone shaped volcano made up of layers of ash and lava) on northern Negros Island in the central Philippines, erupted on Monday 3 June 2024, producing a 5km high column of ash, and subsequent ashfalls in the area around the volcano. On Wednesday 5 June heavy rainfalls in the area produced a series of lahars (mudslides of volcanic ash) which swept down watercourses in some cases entering villages. There are no reports of any casualties, but the Philippine Institute of Volcanology and Seismology has warned that the mud is likely to be toxic, raising concerns about the availability of safe water in the effected villages.

An eruption on Mount Kanloan, Negros Island, the Philippines on Monday 3 June 2024. Dollet Demaflies/AFP/Getty Images.

The geology of the Philippines is complex, with the majority of the islands located on the east of the Sunda Plate. To the east of this lies the Philippine Sea plate, which is being subducted beneath the Sunda Plate (a breakaway part of the Eurasian Plate); further east, in the Mariana Islands, the Pacific Plate is being subducted beneath the Philippine Sea Plate. This is not a smooth process, and the rocks of the tectonic plates frequently stick together before eventually being broken apart by the rising pressure, leading to Earthquakes in the process. Material from the subducting Philippine Plate is heated by the temperature of the Earth's interior, causing lighter minerals to melt and the resultant magma to rise through the overlying Sunda Plate, fuelling the volcanoes of the Philippines.

Subduction beneath the Philippines. Yves Descatoire/Singapore Earth Observatory.

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Eleven confirmed dead and twelve still missing following eruption on Mount Marapi, Sumatra.

Eleven people have been confirmed dead and another twelve are still missing following an eruption on Mount Marapi, a 2885 m high volcano in West Sumatra Province, Indonesia on Sunday 3 December 2023. The volcano erupted with little warning, producing a 3 km high column of ash as well as ash falls on villages more than 5 km from the summit of the volcano. Seventy five people, including a group of 18 students, were on the volcano at the time of the eruption. Forty nine people of the hikers were able to escape from the mountain promptly, leaving 26 unaccounted for. Over 160 rescue workers were deployed to the mountain, and were able to rescue three of the missing hikers alive, all of who were suffering from burns and one from a broken leg. They also recovered eleven bodies, but were eventually forced to break of the search before accounting for all of the missing persons, due to the ongoing eruption.

A survivor of the 3 December 2023 Mount Marapi eruption being carried off the mountain by rescue workers. Antara Foto/Reuters.

The Indo-Australian Plate, which underlies the Indian Ocean to the west of Sumatra, is being subducted beneath the Sunda Plate, a breakaway part of the Eurasian Plate which underlies Sumatra and neighbouring Java, along the Sunda Trench, passing under Sumatra, where friction between the two plates can cause Earthquakes. As the Indo-Australian Plate sinks further into the Earth it is partially melted and some of the melted material rises through the overlying Sunda Plate as magma, fuelling the volcanoes of Sumatra.

The Subduction zone beneath Sumatra. NASA/Earth Observatory.

The two plates are not directly impacting one-another, as occurs in the subduction zones along the western margins of North and South America, but at a steeply oblique angle. This means that as well as the subduction of the Indo-Australian plate beneath the Sunda, the two plates are also moving past one-another. This causes rifting within the plates, as parts of each plate become stuck to the other, and are dragged along in the opposing plate's direction. The most obvious example of this is the Sumatran Fault, which runs the length of Sumatra, with the two halves of the island moving independently of one-another. This fault is the cause of most of the quakes on the island, and most of the island's volcanoes lie on it.

The movement of the tectonic plates around Sumatra. NASA/Earth Observatory.

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Around 15 000 people evacuated from their homes following eruptions on Mount Mayon, the Philippines.

About 15 000 people have been forced to leave their homes after the Philippine Institute of Volcanology and Seismology ordered an evacuation of villages within 6 km of Mount Mayon, a 2463 m stratovolcano (cone shaped volcano) on southern Luzon Island. The evacuations were ordered on Sunday 11 June 2023, when the volcano began a new eruption, although a warning that such an evacuation might be ordered has been in place since an upsurge in seismic activity beneath the volcano a week previously. Such seismic activity can be a sign of liquid magma moving into chambers beneath the volcano, itself often a precursor of eruptions. On Sunday 11 June lava was seen oozing from the volcano's crater and descending the mountain's flanks.

Lava flows on the flanks of Mount Mayon on 11 June 2023. Nehemiah Manzanilla Sitiar/Reuters.

Mayon is considered to be a particularly due to the dense population in the area surrounding it. It has a long history of causing fatalities, most recently in 7 May 2013, when a sudden eruption caught a party of tourists by surprise, leading to five fatalities. As well as the direct danger from volcanic eruptions, Mayon has been the cause of numerous lahars (ash-laden flash foods). These tend to occur when ash from the volcano builds up across the path of seasonal waterways during the dry season, leading to temporary damming of water courses then flash floods at the start of the rainy season.

The location of Mount Mayon. Google Maps.

The geology of the Philippines is complex, with the majority of the islands located on the east of the Sunda Plate. To the east of this lies the Philippine Sea plate, which is being subducted beneath the Sunda Plate (a breakaway part of the Eurasian Plate); further east, in the Mariana Islands, the Pacific Plate is being subducted beneath the Philippine Sea Plate. This is not a smooth process, and the rocks of the tectonic plates frequently stick together before eventually being broken apart by the rising pressure, leading to Earthquakes in the process. Material from the subducting Philippine Plate is heated by the temperature of the Earth's interior, causing lighter minerals to melt and the resultant magma to rise through the overlying Sunda Plate, fuelling the volcanoes of the Philippines.

Subduction beneath the Philippines. Yves Descatoire/Singapore Earth Observatory.

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Magnitude 7.3 Earthquake off the south coast of Sumatra, Indonesia.

The Indonesian Meteorological, Climatological, and Geophysical Agency recorded a Magnitude 7.3 Earthquake at a depth of about 84 km, between the islands of Nias and Hibala, off the south coast of Sumatra, Indonesia at about 3.00 am Western Indonesian Time on Tuesday 25 April 2023 (about 8.00 pm on Monday 24 April GMT). There have been no reports of any damage or casualties following this event, but people have reported feeling the event across the Nias Archipelago, Sumatra and southern Peninsula Malaysia, with reports of shaking going on for about 30 seconds. A tsunami warning was issued following the quake, but in the event the wave associated with the quake was only about 11 cm high when it reached Sumatra.

The approximate location of the 25 April 2023 Nias Archipelago Earthquake. USGS.

The Indo-Australian Plate, which underlies the Indian Ocean to the west of Sumatra, is being subducted beneath the Sunda Plate, a breakaway part of the Eurasian Plate which underlies Sumatra and neighbouring Java, along the Sunda Trench, passing under Sumatra, where friction between the two plates can cause Earthquakes. As the Indo-Australian Plate sinks further into the Earth it is partially melted and some of the melted material rises through the overlying Sunda Plate as magma, fueling the volcanoes of Sumatra.

The Subduction zone beneath Sumatra. NASA/Earth Observatory.

This does not happen at a 90° angle, as occurs in the subduction zones along the western margins of North and South America, but at a steeply oblique angle. This means that as well as the subduction of the Indo-Australian plate beneath the Sunda, the two plates are also moving past one-another. This causes rifting within the plates, as parts of each plate become stuck to the other, and are dragged along in the opposing plate's direction. The most obvious example of this is the Sumatran Fault, which runs the length of Sumatra, with the two halves of the island moving independently of one-another. This fault is the cause of most of the quakes on the island, and most of the island's volcanoes lie on it.

The movement of the tectonic plates around Sumatra. NASA/Earth Observatory.

See also...

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