Mayon Volcano spewed lava and ash plumes for the sixth time on Thursday, showing a pattern for the first time, Phivolcs said.
Phivolcs noted that Mayon has been releasing lava and ash every four to five hours throughout the day. This does not mean, however, that there would not be any abrupt eruption between these intervals, the agency said.
Mayon first erupted on Thursday at 2 a.m., and again on 6:21 a.m., 8:45 a.m., 11:33 a.m., 2:28 p.m., and 5:45 p.m. It has been spewing lava and ash since Monday.
Phivolcs added that Mayon’s edifice is still swelling, indicating that magma is acting up. The quiet intervals may be the volcano's recharging time, it said.
Disaster officials are confident that they are ready should the volcano erupt violently.
At least 40,000 residents have been evacuated in nearby towns after Alert Level 4, the second highest level in a five-step warning system, was raised over Mayon on Monday, which means hazardous eruption is imminent.
Mayon, known for its near perfect cone, last erupted in 2014. Its most destructive eruption was in February 1841, when lava flows buried a town and killed 1,200 people.