Lava starts flowing from the summit crater of Mayon volcano, Philippines
After increased unrest detected since June 5, the activity at Mayon volcano in the Philippines increased further on June 11 with lava flowing from the summit crater.
According to the Philippine Institute of Volcanology and Seismology (PHIVOLCS), the lava flow commenced at 11:47 UTC (19:47 LT) on June 11.
At around 19:00 UTC, the flows emplaced within 500 m (1 640 feet) of the Bonga and Miisi Gullies.
The alert status of Mayon Volcano was raised to Alert Level 2 (Increasing Unrest) on June 5, 2023, following a sharp increase in the incidence of rockfall from its summit lava dome from an average of 5 events/day in May 2023 to 49 events/day on June 5, 2023.
Pronounced increases in rockfall signify the extrusion of new lava beneath the summit lava dome, destabilizing the dome and causing its spalling or collapse, the PHIVOLCS said.
Rockfall activity increased while volcanic earthquake activity was absent to sparse, SO2 emissions were at background or baseline levels and short-term ground deformation consisted mainly of swelling of the middle to upper slopes of the edifice. The extremely slow growth of Mayon’s lava dome was first detected by visual monitoring on August 20, 2022, warranting the raise to Alert Level 2 on October 7, 2022, which was lowered to Alert Level 1 on March 16, 2023. Between August 2022 and May 2023, the summit lava dome grew by approximately 164 000 m3.
Days of increased incidence and volume of rockfall based on seismic records were followed by the generation of short pyroclastic density currents (PDCs) during the morning hours (LT) of June 8.
The PDCs were emplaced on the Bonga (Legaspi City), Miisi (Daraga), and Basud (Sto. Domingo) Gullies as far as 2 km (1.2 miles) from the summit crater.
This indicated that new, less degassed lava was already being spalled from the summit dome and that eruption of very slowly extruding magma had slightly increased.
Alert Level 3 (Increased Tendency Towards Hazardous Eruption) was raised at 12:00 LT on June 8. In the evening thereof, incandescent rockfall generated by the intermittent collapse of an apparent fluidal lava portion of the summit dome was deposited on the above gullies within 1 km (6.2 miles) of the crater.
A new summit dome impinging a remnant on the southeast crater floor was observed in the early morning of June 10.
As a result of increased activity at the volcano, Albay province was placed in a state of calamity on June 9.
On June 10, President Ferdinand R. Marcos Jr. said government funds and food packs are available for those who will be affected by the possible eruption. “Residents who are within the 6 km (3.7 miles) radius permanent danger zone [nearly 17 000] are being evacuated,” Marcos said and urged affected residents to heed the instructions and directives of their local government officials to ensure their safety.
Data from the Albay Public Safety Emergency Management Office showed 4 390 families or 16 823 individuals from nine municipalities namely, Camalig, Daraga, Guinobatan, Ligao City, Malilipot, Tabaco City, Sto. Domingo, Bacacay and Legazpi City, are affected.
Another 40 000 individuals are set to be evacuated from the 7 km (4.3 miles) extended danger zone if Mayon’s status is escalated to Alert Level 4.
Geological summary
Beautifully symmetrical Mayon volcano, which rises to 2 462 m (8 077 feet) above the Albay Gulf, is the Philippines’ most active volcano.
The structurally simple volcano has steep upper slopes averaging 35-40 degrees that are capped by a small summit crater. Historical eruptions at this basaltic-andesitic volcano date back to 1616 and range from strombolian to basaltic plinian, with cyclical activity beginning with basaltic eruptions, followed by longer-term andesitic lava flows.
Eruptions occur predominately from the central conduit and have also produced lava flows that travel far down the flanks.
Pyroclastic flows and mudflows have commonly swept down many of the approximately 40 ravines that radiate from the summit and have often devastated populated lowland areas.
Mayon’s most violent eruption, in 1814, killed more than 1 200 people and devastated several towns.2
References:
1 Nearly 17 000 people evacuating due to unrest at Mayon volcano, Philippines – The Watchers – June 11, 2023
2 Mayon – Geological summary – GVP
Featured image credit: Mayon Volcano Observatory
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