The Philippine Institute of Volcanology and Seismology reported a series of phreatic eruptions (explosions caused by magma or other hot volcanic material coming into contact with water) on 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, between about 9.45 and 10.00 am local time on Saturday 9 December 2017. These eruptions were heard as far away as La Castellana, roughly 25 km to the southwest, and produced a column of ash and steam that rose 3-4 km above the summit of the volcano, with ashfalls recorded in the communities of Guintubdan, Ara-al, Sag-ang, and Ilihan.
The volcano has remained active since this event, with 578 seismic tremors recorded beneath it between 8.00 am on Tuesday 12 and Wednesday 13 December. Seismic activity beneath volcanoes can be significant, as they are often caused by the arrival of fresh magma, which may indicate that a volcano is about to undergo an eruptive episode.
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.
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Column of ash and steam over Mount Kanlaon, Negros Island, on 9 December 2017. GMA News.
The volcano has remained active since this event, with 578 seismic tremors recorded beneath it between 8.00 am on Tuesday 12 and Wednesday 13 December. Seismic activity beneath volcanoes can be significant, as they are often caused by the arrival of fresh magma, which may indicate that a volcano is about to undergo an eruptive episode.
The approximate location of Mount Kanloan. 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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