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NDCC orders close watch on Mayon, Taal volcanoes

July 21, 2009 11:04am

MANILA, Philippines - The National Disaster Coordinating Council (NDCC) ordered regional and provincial disaster management agencies Tuesday to closely monitor Mayon and Taal volcanoes in Southern Luzon.

In a memorandum Monday, NDCC executive officer Glenn Rabonza noted that Mayon Volcano remains at Alert Level 2, while Taal remains at Alert Level 1.

Mayon is located in Albay in the Bicol region while Taal is in Batangas province.

"You are hereby directed to undertake monitoring and precautionary measures in your areas of responsibility. The public and the Disaster Coordinating Council concerned are advised to take appropriate actions and to be on alert for any development," the memorandum said.

Based on the Philippine Institute of Volcanology and Seismology (Phivolcs) alert levels chart for Mayon, Alert Level 1 is hoisted when there is a slight increase in seismicity and sulfur dioxide (SO2) gas output above the background level and when a very faint glow of the crater may occur but no conclusive evidence of magma ascent. At this stage, there is no danger of imminent eruption, but people are not allowed to enter the 6-km radius permanent danger zone (PDZ).

"Alert level 2 is hoisted when there is low to moderate level of seismic activity with episodes of harmonic tremor and increasing SO2 flow with faint intermittent crater glow. Also, when there are confirmed reports of decrease in flow of wells and springs during rainy season, the alert level is announced. The tremors could probably be of magmatic origin that could eventually lead to eruption. In this case, the 6-km radius PDZ may be extended to 7 km," the chart indicated.

When asked by GMANews.TV on Tuesday if the alert levels for Mayon would apply to Taal, Phivolcs’ volcanologist July Samit said: "Alert levels for Mayon could also be applied to Taal Volcano this time, but there are instances where the determination of alert levels would depend on particular circumstances."

Mayon

According to the NDCC report, 15 quakes had been recorded as of Tuesday around the Mayon Volcano area, and 46 volcanic quakes from June 13 to July 19.

Steaming activity at Mayon had been moderate - no change from the moderate steaming activity from June 13 to July 19.

Rabonza said that under Alert Level 2, Mayon is in a state of unrest that could lead to ash explosions or eventually to hazardous magmatic eruptions.

He added that Phivolcs - which raised the alert level at Mayon to 2 last July 10 - had recommended that the 6-km permanent danger zone and the 7-km extended danger zone at the southeast flank of the volcano be off-limits to residents due to the threat from sudden explosions and rock falls from upper slopes.

"Active river channels and those areas perennially identified as lahar-prone in the southeast sector should also be avoided especially during bad weather conditions or when there is heavy or prolonged rainfall," Rabonza noted.

The Albay provincial government had made plans to deal with a possible eruption, including plans to evacuate as many as 75,000 residents.

Taal

On the other hand, there were no volcanic quakes detected at Taal since the detection of nine volcanic quakes from June 13 to July 19.

Rabonza said there had been no steaming activity monitored since the last recorded on June 23.

But Rabonza noted that at Alert Level 1, Taal’s main crater remains off-limits to the public because steam explosions may suddenly occur or high concentrations of toxic gases may accumulate.

“The public is reminded that the Taal Volcano Island is a high-risk area and a PDZ, hence habitation is strictly not recommended," he said.- GMANews.TV