The Philippine Institute of Volcanology and Seismology (Phivolcs) recorded a series of weak volcanic earthquakes in Mayon Volcano since July 3, which shows an “increased activity” in the restive volcano in Albay.

“Since 3:47 p.m. (Philippine time) yesterday (July 3), the Mayon Volcano Network began recording a continuous tremor-like series of weak volcanic earthquakes that steadied and increased in strength this morning (July 4) and persists to the present,” Phivolcs said in an advisory issued at 1:30 p.m. on Tuesday, July 4.

It said the volcanic tremors lasted about 11 seconds and occurred at five-second intervals.

“This resulted in an abrupt and sustained increase in the level of seismic energy release beginning July 3,” it added.

A series of pyroclastic density currents, or PDCs, began cascading down the Basud Gully on the eastern flank of Mayon Volcano at 6:09 p.m. on June 30, 2023. The PDCs lasted approximately four minutes and traveled three to four kilometers downslope. (Screengrab from Phivolcs)

Phivolcs also said the increase in seismic activity coincided with satellite detection of a significant increase in sulfur dioxide (SO2) emission on July 3 and a sharp increase in average SO2 emission to 1,558 tons per day on the same day.

“This current phase of unrest is likely driven by magmatic gas activity within the edifice,” it pointed out.

Moreover, rockfall and dome-collapse pyroclastic density current (PDC) events were still being recorded by Phivolcs.

Lava is flowing in three directions, along the Basud, Mi-isi, and Bonga gullies, in the eastern, southern, and southeastern flanks of Mayon Volcano, respectively.

“The PDCs flowed for approximately two minutes down the Basud Gully, Mi-isi Gully, and Bonga Gully within a distance of one to two kilometers from the crater,” Phivolcs said.

Likewise, traces of ash were reported in Guinobatan town and Ligao City.

Alert Level 3 remains in effect

Phivolcs said Mayon Volcano is still at Alert Level 3 due to the presence of magma at the crater and the possibility of a “hazardous eruption within weeks or even days.”

Due to increasing unrest, the Mayon Volcano’s status has been upgraded twice in the past month, first to level 2 on June 5 and then to level 3 on June 8.

Phivolcs strongly advised the evacuation within the six-kilometer permanent danger zone due to PDCs, lava, rockfalls, and other volcanic hazards..

In addition, Phivolcs advised communities to maintain increased vigilance against PDCs, 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.

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

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