By Celso Amo
LEGAZPI CITY --- A scientist at the Philippine Institute of Volcanology and Seismology(Phivolcs) puts the age of Mayon Volcano, fondly called by Bicolanos as Daragang Magayon, at 25,000 years old.
“The estimated age of Mayon Volcano which is 25,000-years-old, more or less, has been computed based on its ejecta per eruption cycle, its whole edifice and facilitated by its conical shape,” Ed Laguerta, Mayon resident volcanologist base at the Ligñon Hill Observatory.
He said the information was based on a research study.
He also said Bulusan Volcano, which is around 70 kilometers southeast of Mayon, is much older at 40,000-years-old based on the super volcano’s past eruption 40,000 years ago which extruded about 100 billion volcanic debris bigger than Mt. Pinatubo in 1991.
“Mayon’s beauty is on its conical shape which also indicates it’s not moving towards a very strong hazardous eruption because of its regular eruption,” said Laguerta.
He said the sputtering of lava flows and lava fountaining result in building up its cone.
“But the volcano’s peak has already been achieved based on the size of its diameter. She has to support her height like what happens when she builds up a dome at the crater,” said Laguerta.
Laguerta said Mayon Volcano’s on-going eruption is characterized by sporadic and weak lava fountaining, lava flow, and degassing from the summit crater for the past 24 hours.
He said about 50 million cubic meters of volcanic debris had been extruded since January 13.
Based on Mayon’s eruption in 2014 and the succeeding accumulation of magma at the chamber the estimated volume of the magma inside the volcano is about 100 million cubic meters.
“What I want to point out is that we are within the range of historical eruption of Mayon,” explained Laguerta.
“It either stops or proceeds to a more explosive eruption because there’s pressure inside,” he said.
“If the lava flow stops, we will have a window to see if its eruption stops,” said Laguerta, adding that” to push a few thousand cubic meters is large enough to trigger a strong eruption.”
He said while there’s lava flow, the threat of a hazardous eruption is still there.
Lava fountaining was observed at 9:00 a.m. on Friday last week.
Laguerta warns disaster and local officials that volcanoes have an internal processes in which lull periods can’t be observed unless there are critical or abrupt changes.
For example, Laguerta said there was a sudden lull before Mayon’s 1964 strong eruption.
At present, the upper two kilometers magma packets are the source of activity where inflation-deflation process is occurring due to continuous lava flows, he said during a press conference at the Apsemo Saturday morning.
Mayon’s conduit’s height is 2.4 kilometers.
Laguerta said a ground deformation survey observed a deflation of one millimeter at the lower slope.
“This could mean that when the ground deformation survey was conducted there was no magma intrusion that was detected from a deeper source,” he said.
So there’s a need to repeat the ground deformation survey because it was that time when a lull occurred, he added.
“Our window of waiting time is two weeks to determine if the wane signals a going down trend or there’s still a potential for a stronger eruption,” said Laguerta.
Precise levelling is now conducted at lower two kilometers portion of the volcano’s edifice, said Laguerta.
Much of the activity produced low white to light-gray plumes, with the exception of one event that produced a 1000 meter-tall gray ash plume at 9:18 a.m. Friday.
Throughout the night, quiet lava effusion fed lava flows in the Miisi and Bonga-Buyuan channels and barrancos between these.
The Miisi and Bonga-Buyuan lava flows have advanced to 3.2 kilometers and 4.3 kilometers, respectively, from the summit crater.
A total of 17 volcanic earthquakes, most of which corresponded to sporadic and weak fountaining events, and 10 tremor events were recorded by Mayon’s seismic monitoring network. Sulfur dioxide gas emission was measured at an average of 1,583 tons a day,also on Friday.
Electronic tilt and continuous GPS measurements indicate a sustained swelling or inflation of the edifice since November and October 2017, consistent with pressurization by magmatic intrusion. Alert Level 4 remains in effect over Mayon Volcano.
Meanwhile, Cedric Daep, Albay provincial security and emergency management office (APSEMO) head, on Friday ordered evacuees outside the 8-kilometer extended danger zone numbering around 4,718 persons to go home, upon approval by Phivolcs.