Wednesday 14 June 2023

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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