Manila: Mount Mayon appears to be gathering force ahead of a powerful explosion, a Philippine government expert warned while adding that a seeming lull in volcanic activity could portend an eruption similar to that witnessed in 1984.

“The volcano’s seeming lapse into relative calm compared to previous days could be misleading,” Eduardo Laguerta, resident volcanologist in Legazpi City of the Philippines Institute of Volcanology and Seismology (Phivolcs), was quoted as saying.

Phivolcs, in a bulletin released on Wednesday, said four rockfall events had been observed during the past 24-hours.

“Weak emission of white steam plumes drifting southwest was observed. Crater glow was not observed last night,” it said adding that sulphur dioxide flux had been noticeably lower since September 22, 2014.

However it pointed out that: “Tilt data also indicate continuous inflation at the base of the edifice since August 2014. All the above data indicate that the volcano is still in a state of unrest due to the movement of potentially eruptible magma.”

Mayon, an active volcano in Albay, had undergone upheavals times in the past, the most recent of which was in May 7 last year when it ejected columns of ash several times over for more than a minute.

“It is most likely that Mayon’s impending eruption would be similar to that in September 23, 1984, a vulcanian eruption,” Laguerta for his part said.

The volcano, located some 500 kilometres South of Manila, provided one of its most spectacular outbursts in decades in 1984, with ash columns ejecting to as high as 14 kilometres into the atmosphere. Lava flows nearly covered half of what had been considered as the world’s most perfectly symmetrical volcanic cone.

Laguerta also said that just like the 1984 eruption episode, Mt Mayon had lapsed into calmness before a powerful explosion.

“There are indications that it is gathering force inside it as evidenced by the lower sulphur dioxide emissions,” he said adding that a lava dome 145 metres in diameter and 45.7 metres high is so far serving as a plug that is preventing lava ash from rushing out of the volcano.

“Eventually it will blow its top and it will explode spectacularly,” he said.

Since September 15, the Phivolcs and the Provincial Disaster Risk Reduction and had been observing volcano Alert Level 3 in a six step warning protocol where Level 5 means actual eruption in progress and Level 0 equates to no eruption.

Laguerta said they expect Mayon to eject an equivalent of 150,000 truckloads of ash and lava fragments once it erupts.

According to Laguera, they expect the Albay municipalities of Santo Domingo, Daraga, Camalig to be affected by the eruption as well as Legazpi City.

According to the National Disaster Risk Reduction and Management Council (NDRRMC) some 52,300 people have so far been effected by the impending eruption. These residents have been forcibly evacuated and are housed in some 50 evacuations centres since last week.

The government has banned all activities within the 6km permanent danger zone strewn around the volcano and the 7km no-man’s-land at the southern flank of Mt Mayon.