The flow of lava from Mt. Mayon and the amount of sulfur dioxide it emitted have increased, the Philippine Institute of Volcanology and Seismology (Phivolcs) said in its latest bulletin issued yesterday.
"One likely scenario is a shift from lava extrusion to explosive eruption," Phivolcs warned, saying this would be accompanied by deadly mudflows of volcanic ash.
Alex Baloloy, a volcanologist at the Ligñon Hill monitoring station here, noted how Mt. Mayon’s abnormal parameters were cut shorter this time, saying it did not pass the alert level 2 stage and went directly to lava flow.
Bright orange lava flowed 800 meters down the volcano’s slopes over the past 24 hours, Phivolcs said.
In its activities leading to eruption in 2000, Mt. Mayon first recorded four phreatic or ash explosions on May 5, June 22, Aug. 3 and Sept. 22, all in 1999, before it began displaying other abnormal precursors such as increased sulfur dioxide emissions and more frequent low and high frequency volcanic quakes in late January of 2000.
In May of the same year, lava flow followed, accompanied by big explosions and pyroclastic flows.
"With this you will notice that the increase in Mayon’s abnormal activities are way faster than that of the 2000 eruption precursors," Baloloy told The STAR.
An early eruption is likely if the volcano’s present trend is sustained, he said.
The government is still maintaining its six-kilometer radius permanent danger zone (PDZ) around the volcano where no one is supposed to enter, Phivolcs said.
However, local officials and residents said that some farmers were continuing to farm the fertile slopes around Mt. Mayon.
"Our farmers in the six-kilometer danger zone should stop for a while and not enter there because we never know what will happen. There could be a sudden eruption," said Legazpi City Mayor Noel Rosal.
On the other hand, Baloloy did not discount the possibility that Mayon may take a "repose" for several more days or weeks before finally erupting, saying it had already recorded such eruption pattern in the past.
The 8,077-foot tall volcano, famous for its near-perfect cone shape, began oozing lava on Friday.
Lava trickles extending up to 3.5 kilometers were recorded at Mt. Mayon’s southeast quadrant, or along the Bonga Gully which is facing Legazpi City and the towns of Sto. Domingo and Daraga.
In a bulletin yesterday, Phivolcs said its seismic network detected 111 significant tremor episodes related with large rock masses that have detached from the lava flow.
The Phivolcs volcano monitoring center said fragments detaching from the sides and toe of this lava flow are causing a continuous stream of incandescent rockfalls, which come to rest on the upper and middle slopes, about three kilometers from the summit.
Sulfur dioxide emission was measured at 2,211 tons, or double its volume of 1,251 tons last Friday.
A small explosion was detected by instruments at 2:47 p.m. the other day.
Baloloy said their team had actually heard the noise created by the falling rocks and other volcanic debris during an inspection made at the foot of the volcano yesterday.
Alert level three of the five-step alert system has been hoisted over Mt. Mayon. This means that there is "relatively high unrest" in the volcano with volcanic quakes and tremors expected to become frequent ahead of an eruption.
Residents just beyond the permanent danger zone, especially in the southeast portion and facing the Bonga Gully, should be vigilant against a possible eruption and evacuation.
Ed Laguerta, Phivolcs resident volcanologist, explained there are still some parameters missing to justify the raising of the alert level like increased tremors, pressure and in relation to sulfur gas emission.
"We are watching closely the kind of tremors not related to rockfalls, increased sulfur gas emission which indicate the amount of pressure to move old pyroclastic deposit from the previous eruption at the crater," Laguerta told The STAR by telephone.
"The probability for an eruption is already high compared to the probability of downgrading the present alert level 3 to 2," Daep said.
Albay Gov. Fernando Gonzalez said he has ordered the mobilization of all resources and manpower needed in case of a full-blown eruption to ensure "zero casualty."
According to Daep, based on the present resource inventory, the provincial government lacks tents and water containers.
Tents are also needed so that classes in schools that have been turned into evacuation centers can continue.
For Legazpi City, Rosal said he has given the go-signal for the purchase of various items that will be needed for evacuees.
Lt. Col. Manny Orduña, commanding officer of the 65th Infantry Battalion, said Task Force Mayon has readied five M-35 trucks inside Camp General Simeon Ola to bring evacuees to designated evacuation centers if Mt. Mayon erupts.
Orduña said that two more M-35 trucks as well as five Isuzu Elf trucks from the 65th Infantry Battalion based in Barangay Tula-Tula in Ligao City, including vehicles from the 9th Infantry Division based in Pili, Camarines Sur, are ready to evacuate residents.
Gonzales said that when the alert level is raised, 1,484 families or 7,436 people presently living within four kilometers of the permanent danger zone will be evacuated immediately.
There are 10 barangays inside the four-kilometer danger zone — Buhian, Magapo and Buang in Tabaco City; Barangay Calbayog in Malilipot town, Miisi in Daraga, Barangays Anoling, Upper Quirangay with Purok 6 and 7, Upper Cabangan and Sua in Camalig town and Barangay Baligang in Ligao City. — With James Mananghaya, Celso Amo, AFP