MANILA – The level of unrest in Mayon Volcano has increased, particularly at its summit or surface level, the Philippine Institute of Volcanology and Seismology (Phivolcs) reported on Tuesday.
In an interview with the Philippine News Agency, Phivolcs Director Teresito Bacolcol said the near-doubling of rockfall events—from 44 recorded between Jan. 4 and 5 to 85 between Jan. 5 and 6—indicates increasing instability at the volcano’s summit, a condition commonly associated with magma rising from below.
The Phivolcs recorded incandescent rockfall from the summit lava dome on Monday night.
An incandescent rockfall involves hot material that appears glowing, especially at night. This indicates that the rocks came from the hot portions of the summit lava dome or from newly exposed volcanic material.
On the other hand, an ordinary rockfall refers to the collapse or rolling of rock fragments from steep parts of the volcano due to gravity or instability.
Bacolcol said this could happen when the material is already cool and does not necessarily involve heat from magma.
In terms of implications, ordinary rockfalls mainly indicate mechanical or structural instability, while incandescent rockfalls could signify the presence of heat and pressurized material near the summit, pointing to active magmatic influence.
Bacolcol said the earlier rockfall events could include incandescent rockfalls. However, most of these have occurred during daytime, thus, personnel could not clearly see whether these were incandescent.
“They will just appear as black or ordinary rocks falling. There were likely rockfall events at night as well, but these may not have been observed as incandescent because the summit was covered by clouds,” Bacolcol explained.
“The recent rockfall events were clearly observed as incandescent rockfall since they occurred at night. “This suggests that some of the earlier rockfall events may also have involved hot material.”
At present, even though Mayon Volcano’s seismicity remains low, the increasing trend in rockfalls, along with deformation, indicates elevated unrest, Bacolcol pointed out.
Mayon Volcano is under Alert Level 2, and entry into the six-km permanent danger zone (PDZ) is strictly prohibited.
“For those residing inside the PDZ, be ready to evacuate immediately if the alert level is raised to Alert Level 3,” the Phivolcs chief said.
He also advised the public to rely only on official advisories from the Phivolcs and local government units. (PNA)