Mayon still unstable – Phivolcs

LEGAZPI CITY, Philippines — The Philippine Institute of Volcanology and Seismology (Phivolcs) warned disaster and local officials not to be complacent, reminding them that Mayon Volcano remains in a highly abnormal and unpredictable state.

Phivolcs director Renato Solidum stressed it is too early to say Mayon is proceeding on a downward trend.

“We have to observe for at least two more weeks before we could come up with a decision to lower the alert status of Mayon, if its present non-explosive eruption episode would be sustained,” Solidum said.

Tourists, however, were seen inside the six-kilometer danger zone at Barnagay Miisi in Daraga, Albay. 

Cedric Daep, Albay provincial security and emergency management office (Apsemo) chief, said he will call the attention of Daraga disaster officials regarding the presence of people inside the danger zone.

“They have to comply with our advisory so we will achieve the objective of zero casualty,” Daep said.

“And to achieve that, (there should be) no human activity at the 6-PDZ (permanent danger zone) and the extended one-kilometer danger zone at the south flank of Mayon,” he said.

Solidum warned Mayon could erupt violently should massive degassing take place inside the magma chamber.

“Besides, our instruments are telling us that Mayon’s surface is still inflated, which means that there are ongoing magmatic processes inside it,” he said.

The National Disaster Risk Reduction and Management (NDRRMC) reported lava flow advanced yesterday to three kilometers from the summit crater and is now well within the six-kilometer PDZ.

NDRRMC executive director and Office of Civil (OCD) administrator Ricardo Jalad said this development was triggered by Mayon’s quiet lava effusion over the last 24 hours.

The lava flow came from a new summit lava dome. The collapsing lava was also accompanied by five rockfall events over the last 24 hours.

The rockfall events as well as the continuing disintegration of lava also pushed ash clouds higher, then drifting towards the southwest direction, the NDRRMC said.

Jalad said Alert 3 remains in effect over Mayon, which means a hazardous eruption is still possible within weeks or even in just days.

Solidum added they are closely monitoring the deflation and inflation of the volcano’s base or its lower portion and upper slopes.

“For example, if the base is inflated then suddenly it becomes deflated, and the upper slope in turn becomes inflated, this could mean that the magma has already ascended from the base to the upper chamber or slope of the volcano,” Solidum explained.

He said they are carefully analyzing all data supplied to them by the monitoring instruments.

Solidum said the present eruption behavior of Mayon is similar to its 2006 to 2009 eruption episodes.

Ed Laguerta, Phivolcs resident volcanologist in Albay, said physical or visual observation is not enough basis to tell the real condition of Mayon.

“I watched Mayon erupt several times already. But despite this, I never dare predict exactly where its abnormal parameters are leading us without closely and carefully reading what the instruments are telling us,” Laguerta said.

He said the eight-year gap that Mayon did not erupt should be taken into consideration.

Laguerta said Mayon’s last explosive eruption was January 2009, followed by a short-duration, non-explosive eruption in 2014.

“This means that for eight years Mayon was silent. It might blow more volcanic materials this time if it will proceed to a full-blown eruption,” he warned.

Both Solidum and Laguerta said an explosive eruption of Mayon could only take place if massive degassing inside the magma chamber occurs.

A total of 6,831 families or 36,940 persons from 32 barangays are still staying at 26 evacuation centers in Albay.

Quiet lava effusion from the new lava dome at the summit, as well as lava collapse events, characterized Mayon’s eruptive activity in the past 24 hours. 

Five rockfall events were recorded by seismic monitoring network. Rockfall events were generated by the collapsing lava front and margins of advancing lava flow on the Miisi Gully and by shedding from the summit dome onto the Bonga Gully. 

Currently, the Miisi lava flow has advanced to three kilometers from the summit crater, well within the PDZ. 

Ash clouds were seen from the rockfall events as well as from the persistent disintegration of lava on the advancing front of the Miisi lava flow before drifting to the southwest. 

Sulfur dioxide gas emission was measured Friday at an average of 1,131 tons a day. 

Electronic tilt measurements indicate a sustained swelling or inflation of the edifice since November 2017, consistent with pressurization by magmatic intrusion.

Alert Level 3 remains in effect over Mayon, which means that it is currently still in a relatively high level of unrest and hazardous eruption is still possible within weeks or even days. 

Maria Antonia Bornas, chief science research specialist and chief of volcano monitoring and prediction division of the Phivolcs, said magma extrusion rate has slackened and sulfur gas emission is not high enough compared to the baseline.

Bornas also warned the inflationary trend of the volcano has not moved down.

“So we can still expect something from Mayon in the coming days,” he said.

Bornas stressed Mayon’s current unrest is not yet over. – With Jaime Laude, Janvic Mateo, Rhodina Villanueva

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