MANILA - (3RD UPDATE) Mayon Volcano shot what appeared to be a huge ash column on Monday, the second in over a week as authorities braced for a possible "hazardous eruption."
Some 27,000 people have been evacuated around the volcano that is renowned for its perfect cone.
Phivolcs Director Renato Solidum said the eruption may have been "phreato-magmatic" since apart from magma, the volcano also spewed steam.
He added, the ash that came from the summit is still not as black as what would have been the ash for a magmatic eruption.
The alert level was raised to level 4, one notch below the highest warning. This indicates a hazardous eruption is "imminent" and that the danger zone has been extended to 8 kilometers radius.
"The public is strongly advised to be vigilant and desist from entering this danger zone. Civil aviation authorities must also advise pilots to avoid flying close to the volcano's summit as ash from eruptions can be hazardous to aircraft," Phivolcs said in its bulletin.
Alert level 3 was raised over the volcano on Jan. 14. It is the third highest in a five-step warning system. Level 5 means an eruption is ongoing.
Phivolcs said the following phenomena can happen directly because of volcanic eruption: lava flow, dome growth, pyroclastic flow, pyroclastic surge, lateral blast, ash fall, volcanic bomb, release of volcanic gas.
The following, meanwhile, may also happen though not directly associated with the eruption: lahar, flooding, debris avalanche, landslide, tsunami, seiche, subsidence, fissuring, secondary/hydrothermal explosion and secondary pyroclastic flow.
Mayon draws thousands of tourists, even during minor eruptions, rises 2,460 metres (8,070 feet) above a largely agricultural region some 330 kilometres southwest of Manila.
It is considered the nation's most active volcano.
Steam-driven eruptions and rockfalls began earlier this month, and the crater began glowing soon after, in what Phivolcs said was a sign of the growth of a new lava dome.
MORE EVACUEES EXPECTED
The number of evacuees may rise to 80,000 with the recent development, said Albay Governor Al Francis Bichara.
"This is the first month of the year and we do not have enough funds, we do not have enough savings, so we will be needing the assistance of the national government because we have to feed these people," he told ANC.