“Mayon Volcano showed increased eruptive activity, which included ashing and volcanic earthquakes happening together,” Phivolcs Director Teresito Bacolcol said,
The strongest of these quakes in Kanlaon were magnitudes 0.7 and 2, and occurred between 4 to 7 km. deep.
“Usually, small amounts of volcanic ash stay at the summit. But if there’s a strong wind, the ash may drift towards populated areas,” Bacolcol said.
According to Phivolcs, intermittent ashing began at around 6 p,m. of July 31. The ashing consisted of low-frequency volcanic earthquakes that typically lasted for 30 seconds.
After the ashing, lava rapidly flowed from the summit crater through established channels with previous lava flows and rockfalls, adding that lava does not necessarily flow rapidly after an ashing.
Bacolcol said the observed eruptive activity was not related to the weather condition.
He noted that it is best for people in those areas to wear face masks to avoid inhaling ash particles as a short, 100-meter gray ash plume was observed drifting northeast.
Lava flows, meanwhile, reached 2.8 kilometers and 600 meters along the Bonga and Basud gullies, respectively.
A total of 258 volcanic earthquakes including one tremor that lasted 1 minute and 30 seconds; 57 ashing events and 100 rockfall events have been recorded during the volcano’s 24-hour observation period.
Volcanic sulfur dioxide (SO2) emission averaged 2,325 tonnes on July 31.
Mayon Volcano is still under alert Level 3 and in a relatively high level of unrest. Hazardous eruption within weeks or days is possible.
Phivolcs reiterated that the 6-km. radius permanent danger zone should remain evacuated due to the danger of lava flows, rockfalls, and other volcanic hazards.
Weak degassing at the summit crater has been observed during the past few days.
Although alert Level 0 (normal) has been maintained over the Bulusan Volcano, Phivolcs said the recorded changes may progress into further unrest and potentially trigger steam-driven or phreatic eruptions from any of the active vents.
Local government units and the public are reminded of the entry into the 4-km. radius permanent danger zone, particularly near the vents on the south southeastern slopes, should be avoided due to the possibility of sudden and hazardous steam-driven or phreatic eruption, rockfall, and landslide.
Phivolcs urged aviation authorities to advise pilots to avoid flying close to the both volcanoes’ summit, as ash from any sudden phreatic eruption can be hazardous to aircraft.