LEGAZPI CITY, Sept. 18 (PNA) -- On its third day, Mayon Volcano’s restiveness continued to heighten as the seismic network of the Philippine Institute of Volcanology and Seismology (Phivolcs) recorded 142 volcanic earthquakes and 251 rockfall events during the past 24-hour observation period.
On Monday’s observation period, it registered 32 volcanic earthquakes and 72 rock fall events while the seismic network recorded 45 volcanic earthquakes and 270 rock fall events during the next 24-hour observation period.
Mayon Volcano’s alert status has been on Alert Level 3.
Phivolcs resident volcanologist Ed Laguerta said moderate emission of white steam plumes that drifted south southwest was observed while rain clouds covered the summit, preventing visual observation.
Laguerta said sulfur dioxide (SO2) flux was measured at an average of 757 tons/day on Wednesday although SO2 emission rates peaked at 2,360 tons/day on Sept. 6.
He added that ground deformation data showed inflationary changes in the edifice from February, based on precise leveling surveys on the third week of August, and edifice inflation from January 2012 baselines based on continuous tilt measurement.
“All the above data indicate that the volcano is exhibiting relatively high unrest due to the movement of potentially eruptible magma,” the volcanologist added.
Earlier, Laguerta said Mayon Volcano is showing parameters likely for a “vulcanian eruption” within weeks.
Cedric Daep, department head of the Albay Public Safety and Emergency Management Office (APSEMO), said that if Mayon Volcano erupts this September, wherein south west monsoon is in effect, ashfalls will be affecting the municipalities of Malilipot, Malinao, Tiwi and Sto. Domingo and Tabaco City.
However, Daep said, if eruption happens during the month of October, where north east monsoon is in effect, Daraga, Camalig, Guinobatan, Oas, Polangui, Libon, Jovellar and Pio Duran towns and Ligao City will be affected while Legazpi City will be spared from the impact of ashfall if ever the wind is either northeasterly or southeasterly.
"The range of ash fall depends on the high altitude wind direction and the wind speed based on the monitoring of the PAGASA," he clarified.
Daep said this kind of eruption will have an explosion of ash movement going up where when it goes down, it will create pyroclastic flow around Mayon Volcano -- seemingly like tentacles of an octopus all around the river channels of the volcano -- covering the three cities of Legazpi, Ligao and Tabaco and the municipalities of Daraga, Camalig, Guinobatan, Malilipot and Sto. Domingo -- which are areas within the 6-7-kilometer radius.
"Its hazard is carbon monoxide -- which is very lethal, with the extreme heat at about eight to 12 times of boiling point – with the surge of the ash flow. So the heat is the major impact that would destroy properties and lives," Daep added.
He said lava has no threat to life, but it will affect property or agriculture as it moves very slowly at about four to five meters per day.
This, the APSEMO chief said, will affect Legazpi City, Daraga and part of Sto Domingo -- areas that are in the southeast quadrant of Mayon.
“While if there is rainfall, all the river systems will be affected with lahar with all deposits mobilized by at least 60 millimeters of rainfall per hour, but with the new deposits of pyroclastic materials,” Daep said, adding “mobilization will be earlier even less than 60 mm rainfall.”
He said that if ever a “strombolian eruption” happens, only the southeast quadrant area -- including Legazpi City, municipality of Daraga and part of Sto. Domingo -- will be affected as the volcano emits or spews lava quietly, without much explosion.
"It would bring more lava flow, lava fountaining, lava trickle, production of pyroclastic rock and smaller rocks or boulders at about two to three kilometers.
Strombolian eruption is a relatively low-level volcanic one consisting of ejection of incandescent cinder and lava bombs to altitudes of tens to hundreds of meters. (PNA) LAP/FGS/AMM/CBD/