In the past two days, the Philippine Institute of Volcanology and Seismology (Phivolcs) said Mayon’s sulfur dioxide emission has fluctuated between 1,400 and 1,800 tons per day, while only 31 to 57 tremors that indicated lava extrusion and rockfalls were recorded.
Helma Canon, Phivolcs’ volcanologist based here, said the prevailing alert level 3 around Mayon might be lowered if the decline in Mayon’s restiveness continues in a week or two.
"But this downward trend needs to be consistent or sustained to be the basis of further lowering the alert level," she told The STAR.
Canon said lava extrusion was noted to be intermittent on the volcano’s southeast flank facing this city.
Mayon’s "quiet eruption," which started last July 14, was dominated by lava flows. Last Aug. 7, the volcano had occasional mild explosions, prompting Phivolcs to raise the five-step alert level to four and subsequently forcing over 40,000 villagers living at the foot of the volcano to evacuate.
Phivolcs, however, continues to hoist alert level 3 since Mayon still spews lava and emits sulfur dioxide way above the normal volume of 500 tons per day.
The six-kilometer danger zone, extended to seven kilometers in the southeast sector of the 2,642-meter volcano, remains off-limits, Phivolcs said.