MANILA, Philippines – State volcanologists observed “increased activity” from the summit crater of Mayon Volcano in Albay on Friday evening, June 30, amid a series of pyroclastic density currents (PDCs).

The Philippine Institute of Volcanology and Seismology (Phivolcs) said in an advisory that four dome-collapse PDCs have been recorded since 6:09 pm on Friday.

These PDCs flowed for around 4 minutes down the Basud Gully or eastern slope of the volcano, within 3 to 4 kilometers from the crater, according to Phivolcs.

There was also a 4-minute-long PDC on the Basud Gully at 1:01 pm on Friday, “observation of which was hampered by cloud cover,” added Phivolcs.

PDCs are made up of fragmented volcanic particles, gases, and ash that travel down volcanic slopes at high speeds.

Phivolcs said the PDCs triggered ashfall, as seen on one of its cameras and as reported by residents of Tabaco City.

The agency also noted that there was a “pronounced increase” in sulfur dioxide (SO2) emission on Thursday, June 29.

On Friday, SO2 emission averaged 1,002 tons per day, which is “still below the typical ranges of eruption gas flux from Mayon.”

There have also been 48 weak low-frequency volcanic earthquakes since 5 am on Friday, “but seismic energy release has been sustained at generally the same level since June 15.”

Mayon Volcano has been under Alert Level 3 since June 8, which means there is an “increased tendency towards a hazardous eruption.”

Phivolcs reiterated that the 6-kilometer-radius permanent danger zone must remain off-limits.

It also advised communities within a 7- to 8-kilometer radius of the volcano to “be prepared in case current PDC activity worsens.”

The Mayon unrest has prompted more than 5,000 families or over 20,000 individuals in Albay to evacuate. – Rappler.com