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Phivolcs lowers Taal alert level to '1'


Citing lower levels of activity for the last 11 weeks, state volcanologists on Tuesday lowered the alert level at Taal Volcano in Batangas to Alert Level 1. At the same time, the Philippine Institute of Volcanology and Seismology also noted Bulusan and Mayon Volcanoes in the Bicol Region have been relatively quiet. In lowering the alert level at Taal, Phivolcs said in its update: "The ... observations suggest that Taal Volcano’s activity has declined. In view thereof, Phivolcs is now lowering the status of the volcano from Alert Level 2 to Alert Level 1. This means that a large hazardous eruption is now less probable within the immediate future." However, Phivolcs maintained the Main Crater remains strictly off-limits to the public because sudden steam explosions may occur and high concentrations of toxic gases may accumulate. "The northern portion of the Main Crater rim, in the vicinity of Daang Kastila Trail, may also be hazardous when increased steam emission is reactivated along existing fissures. The public is also reminded that the entire Volcano Island is a Permanent Danger Zone (PDZ), and permanent settlement in the island is discouraged," it said. Phivolcs earlier raised Alert Level 2 at Taal in April.

See the complete table on the Phivolcs website.
In lowering the alert level at Taal, Phivolcs cited the following observations:
  • The number of volcanic earthquakes recorded daily gradually declined to low levels beginning first week of June 2011. From June 2 to 5, four to eight volcanic earthquakes were detected per day. But from June 6 to present, the number of recorded volcanic earthquakes further decreased to a daily count of zero to six small events. No perceptible volcanic earthquake has occurred since June 2.
  • Hydrothermal and steaming activities in the northern and northeast sides of the Main Crater and Daang Kastila area have abated. Since June 1, the Main Crater Lake temperature remained at 32.5°C to 33.4°C, and despite becoming more acidic, measured pH of 2.78 – 2.59 vary around the baseline level of pH above 2.5. All other geochemical parameters are returning to background levels. Bubbling activity at the northeastern sector of Main Crater Lake weakened and the activity has ceased in some of the bubbling sites.
  • Ground temperature and total magnetic field measurements at Daang Kastila and in the Main Crater showed no significant changes in both parameters.
  • Carbon Dioxide gas measurements at the Main Crater Lake since March 2011 showed a decreasing trend. From an elevated value of 4,670 tonnes per day (t/d) in March, CO2 decreased to 2,057 t/d in May and then to 1,821 t/d in June.
  • Precise leveling in June 2011 along the flanks of Volcano Island and Global Positioning System (GPS) data from November 2010 to June showed that the volcano is slightly inflated. Ground deformation data, nonetheless, are not suggestive of large pressure build-up within the volcano edifice. Mayon, Bulusan quiet In Albay, Phivolcs said Mayon Volcano’s seismic network did not detect any volcanic earthquake during the past 24 hours. Phivolcs said moderate to wispy emission of white steam clouds drifting southwest and west-southwest was observed from the summit crater. "Fair crater glow (Intensity II – can be seen by the naked eye) was observed (Monday) night," it said in its Mayon update. Alert Level 1 remains in effect over Mayon Volcano, meaning that while no eruption is imminent, the public should not enter the 6-kilometer radius Permanent Danger Zone (PDZ) due to the continuing threat from sudden small explosions and rockfalls from the upper and middle slopes of the volcano. It added active stream/river channels and those perennially identified as lahar prone areas in the southern sector should also be avoided especially during bad weather conditions or when there is heavy and prolonged rainfall. In Sorsogon, Bulusan's seismic network did not record any volcanic earthquake during the past 24 hours while steaming activity at known thermal vents ranged from wispy to weak characterized by emission of white steam clouds creeping downslopes towards west-southwest. Bulusan Volcano’s status remains at Alert Level 1, meaning the source of activity is hydrothermal and shallow. Entry to the 4-kilometer radius Permanent Danger Zone (PDZ) is strictly prohibited, since the area is at risk to sudden steam and ash explosions. — RSJ, GMA News
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