The Philippine Institute of Volcanology and Seismology (Phivolcs) issued a new notice of "increased activity" in Mayon Volcano on Monday, July 10, due to the observation of more pyroclastic density current (PDC) occurrences over the past 24 hours.

Phivolcs recorded 33 PDC events caused by dome collapse from the summit crater of Mayon Volcano as well as the collapsing front and margins of the advancing lava flows on the upper to middle slopes at 5 p.m. on Sunday, July 9.

“The PDCs travelled for approximately one to four minutes down the Mi-isi (south) and Bonga (southeastern) gullies within 3.3 kilometers of the crater,” it said.

PDCs are mixtures of fragmented volcanic particles or pyroclastics, hot gases, and ash that rush down the volcanic slopes or rapidly outward from a source vent at high speeds.

The VMLH infrared camera captured this image of the pyroclastic density current (PDC) events on the Basud Gully, on the eastern flank of the Mayon Volcano, on June 30, 2023. (Phivolcs)

Volcanic gas emission, quakes increase slightly

According to Phivolcs, the volcano's sulfur dioxide emissions also increased on Sunday, averaging 943 tons per day.

However, it pointed out that the measured volcanic gas flux has only been slightly above background for the past three days and remains much lower than the typical ranges of eruption gas flux from Mayon. 

Meanwhile, 109 weak low-frequency volcanic earthquakes have been recorded by the Mayon Volcano Network since 5 a.m. on Monday.

Phivolcs noted that the seismic energy release has been sustained at generally the same level since June 15.

As it closely monitors the frequency of PDC occurrences, Phivolcs urged the communities within the seven- and eight-kilometer radius to be ready in case the current activity worsens.

It also strongly advised that entry into the six-kilometer permanent danger zone be strictly prohibited.

Pilots were also asked to avoid flying close to the volcano because ash from a sudden eruption may pose hazards to aircraft.

‘Intensified magmatic unrest’ continues

Mayon Volcano remains on alert level 3, which means there is still an “increased tendency towards a hazardous eruption.”

Communities near the restive volcano were also advised to maintain increased vigilance against lahars and sediment-laden stream flows along channels draining the volcano edifice, as heavy rainfall could cause channel-confined lahars and sediment-laden stream flows.

According to Phivolcs, communities on the southern side of Mayon Volcano may most likely experience ash fall events based on the current wind pattern.

Phivolcs has upgraded Mayon Volcano’s status twice in the past month, first to level 2 on June 5 and then to level 3 on June 8 due to “intensified magmatic unrest.”