Sunday, July 16, 2006

Authorities get ready for major eruption and evacuation

Malacañang mobilized yesterday disaster-related agencies and local governments to ensure a zero-casualty rate in case of a major eruption of Mt. Mayon in Albay.

Press Secretary Ignacio Bunye said the National Disaster Coordinating Council (NDCC) and local government units (LGUs) have been directed to be "on top of all disaster preparedness measures to ensure the safety of the residents who may be directly affected by the volcanic activity."

Bunye also appealed to the people to stay away from the six-kilometer-radius danger zone around the volcano amid signs of restiveness since Friday.

"We appeal to residents and travelers to adhere to the off-limit zones and to abide by the contingency measures being implemented by the authorities. We have to ensure that affected residents are in secure area until our experts declare it safe to go back," he said in a statement.
Mayon Volcano, famous for its near-perfect cone shape, has been unleashing lava and emitting sulfur dioxide from its crater since last Friday, prompting officials to raise the level in the five-step alert system to Alert Level 3.

Alert Level 3 meant there is "relatively high unrest" in the volcano with volcanic quakes and tremors expected to become frequent ahead of an eruption.

"Preparedness and coordination between the concerned government agencies, the local government units, as well as the communities in the area would be the key in maintaining a zero-casualty rate in the event that a major eruption occurs," Bunye said.

Mayon Volcano, one of the country’s 22 active volcanos, last had a major eruption in 2001, forcing the evacuation of around 50,000 people. More than 1,000 people were killed during Mayon’s most violent eruption in 1814.

Flow of lava, rock fragments intensifies, scientists say

The flow of lava and rock fragments from Mayon volcano has picked up, scientists said yesterday, increasing the possibility of a violent eruption soon.

The 2,474-meter mountain, famous for its nearperfect cone, started spilling lava and debris on Friday in what some volcanologists said was the beginning of a silent eruption.

But volcanologist Eduardo Laguerta said Mayon’s lava extrusion rate increased Saturday, and that more tremors associated with the falling rock fragments have been recorded, suggesting old magma from the depth of the volcano is being pushed to the surface.

"With this development, we are now closely watching Mayon volcano,’’ Laguerta said yesterday. "These developments in the behavior right now would mean that the possibility is that the eruption would be coming nearer.’’

He said volcanologists were waiting for other signs, like lava shooting in the air and more tremors. The increase in seismic activity itself did not warrant raising the alert level from two notches below the highest.

Officials have estimated a hazardous eruption could happen within weeks.

Authorities extended a six-kilometer danger zone around the peak of the volcano to seven kilometers on the southeastern slope, where most of the lava and other debris has been rolling down.

On the streets of Legazpi City, the capital of Albay province near the volcano, residents watched boulders and other debris cascading from the crater, raising brownish-gray clouds of dust.
Mayon’s most violent eruption, in 1814, killed more than 1,200 people and buried a town in mud. A 1993 eruption killed 79.

An eruption warning system is already in place for the quick evacuation of nearby communities, and radio stations have been told to broadcast emergency calls, said Jukes Nunez, an operations officer with the provincial disaster officer.

The Philippines is in the Pacific "Ring of Fire,’’ where volcanic activity and earthquakes are common.

In 1991, Mount Pinatubo exploded in the northern Philippines in one of the world’s biggest volcanic eruptions of the 20th century, killing about 800 people.

The Philippine Institute of Volcanology and Seismology (Phivolcs) observed yesterday more than 100 significant tremor episodes, increased lava flow and sulfur dioxide emission in Albay’s Mayon volcano as it continued its restive behavior.

In a bulletin issued by Phivolcs yesterday, the institute said it recorded 111 "significant tremor episodes related with large rock masses that have detached from the lava flow."

Sulfur dioxide emission significantly increased from 2,211 tons per day (t/d) from its previous reading of 1,251 t/d, Phivolcs said, adding that the increase in lava extrusion "has resulted in a lava flow," which formed an "elongated mass from the summit to about 800 meters downslope."
"Fragments detaching from the sides and toes 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," the institute said.

"In general, eruptive activity was dominated by lava extrusion," it said.

According to the institute, a possible scenario is the "shift from lava extrusion to explosive eruption, which could generate pyroclastic flows."

Pyroclastic flow is a volcanic hazard described as a "turbulent mass of ejected fragmented volcanic materials such as ash and rocks, mixed with hot gases that flow downslope at very high speed (greater that 60 kilometers per hour (kph)."

Phivolcs, meanwhile, said Mayon’s six-kilometer Permanent Danger Zone (PDZ) is still off-limits to the public due to major hazards of rockfalls, lava flow and small rock avalanches.

"Residents just beyond the PDZ, especially in the southeast portion and facing the Bonga Gully, should be vigilant against explosive eruption and be prepared for evacuation," Phivolcs said.
Late Friday night (July 14), Phivolcs raised Mayon’s alert level from 1, classified as exhibiting a period of "low level unrest," to 3, classified as "relatively high unrest," after the volcano showed signs of restiveness through increased steaming activity, noticeable crater glow and lava flow.

Last Saturday (June 15), volcanologists noticed that lava fragments had been detached from a lava pile on the volcano’s summit crater as Mayon exhibited 18 high frequency and four low frequency short duration harmonic tremors as well as a minor explosion at 2:47 p.m.

Based on research, harmonic tremors are said to "often precede or accompany volcanic eruptions."

Phivolcs director Dr. Renato Solidum earlier said that the Vulcanian eruption -- a combination of rocks, ashes and gas which go down the slopes at a speed of 60 kph -- is typical of the Mayon volcano as shown during previous eruptions, particularly in the second phase of 1984, 2000 and 2001.

Other types of Mayon’s volcanic eruption included the Plinian eruption -- which occurred in 1814, described as an eruption of great violence characterized by voluminous explosions and ejections of pumice and ashflows with tall eruption columns -- and the Strombolian eruption, or the "fountaining of lava;" in 1993 and 2001.

Towering at 2.46 kms, Mayon volcano was placed on alert level 2 in October 2003. But this was downgraded to alert level 1 in April of this year before its alert level was raised to 3 last Friday.
It had 47 recorded eruptions, with its last major eruption recorded in 2001. Its last quiet eruption prior to this year’s volcanic activity was from September to October in 2005, wherein lava noticeably came out of the volcano and wherein the lava dome grew very slowly.

"That’s already an eruption, an example of a quiet type of eruption," Solidum earlier said.
Other Philippine volcanoes on heightened alert include the Taal volcano, which has been on alert level 1 since November of last year and which exhibited one high frequency volcanic earthquake during yesterday’s 24-hour observation period; Kanlaon volcano, which has been on alert level 1 since June 12; and the Bulusan volcano, which has been on alert level 2 since June 7 after a series of phreatic explosions. It had exhibited two volcanic earthquakes during Phivolcs’s 24-hour observation period.

Scientists at the Philippine Institute of Volcanology and Seismology (Phivolcs) here are predicting a big eruption of Mayon volcano soon based from its past history.

The situation has prompted disaster authorities here to put in place all the necessary precaution in case the volcano erupts.

Volcanologists here said that if the volcano exhibits lava fountain, it is the signal that evacuation should begin even if the alert level is not yet raised to alert level 4.

Ed Laguerta, resident volcanologist at the Ligñon Hill monitoring station here, said Mayon’s current abnormal activities are escalating much faster than during the episode in 2000 when the volcano last erupted.

He said in 1999, Mayon first recorded four phreatic or ash explosions in June 22, September 22, and August 3 before it started to display other abnormal precursors such as increased sulfur dioxide (SO2) 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.
Laguerta noted that this time Mayon’s abonormal parameters were cut shorter, saying it did not pass the alert level 2 stage, and went directly to lava flow.

He said they noticed that the increase in Mayon’s abnormal activities was faster than that of the 2000 eruption precursors.

He added that it the present trend is sustained, Mayon is likely to erupt much earlier this year than in 2000. Mayon’s pre-eruption activities took place for almost a year before it erupted in 2000.
Laguerta said he is not discounting the possibility that Mayon may take it easy for several more days or weeks before erupting, as it had already recorded such eruption pattern in the past.
He said after ejecting lava fragments in the past two days, Mayon ejected new lava the other night that reached some 800 meters down the Bonga channel facing this city, Sto. Domingo and Danage towns.

Meanwhile, Phivolcs monitoring detected some 121 significant tramors up to 1 p.m. yesterday, while its SO2 emission was measured at 2,211 tons, which was double its earlier volume of 1,251 tons last Friday. A small explosion that was not physically observed but merely detected by its instruments took place at 2:47 p.m. the other day.

The Phivolcs bulletin said the extrusion of a lava flow clearly indicated that the tempo of unrest at Mayon had increased.

One likely scenario is a shift from lava extrusion to explosive eruption which would generate pyroclastic flows. At this stage, except for ashfalls, the major hazards of rockfalls, lava flow and small rock avalanches all occur within the six-kilometer radius or the permanent danger zone.
Laguerta said a team sent yesterday to inspect the foot of Mayon heard the noise created by falling rocks and other volcanic debris.

Cedric Daep, on the other hand, personally visited the barangays nearest to the volcano and met yesterday with local officials of the towns with residents that will be evacuated once alert level 4 is raised.

Daep said the move is meant to check whether their prepared evacuation plan is well placed for any eventuality.

Gov. Fernando Gonzalez said he has already ordered the mobilization of all the resources and manpower needed in case of a full-blown eruption to ensure a "zero casualty" contingency plan.

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