|Taal Volcano Bulletin, 05 July 2011, 08:00 AM|
|Monday, 04 July 2011 23:26|
This is a notice for the lowering of Taal Volcano’s status from Alert Level 2 to Alert Level 1.
Eleven (11) weeks after Taal Volcano’s alert status was raised from Level 1 to Level 2 on 09 April 2011, the following monitoring parameters have been observed:
1. The number of volcanic earthquakes recorded daily gradually declined to low levels beginning 1st week of June 2011. From June 2 to 5, four (4) to eight (8) volcanic earthquakes were detected per day. Since June 6 to present, the number of recorded volcanic earthquakes further decreased to a daily count of zero (0) to six (6) small events. No perceptible volcanic earthquake has occurred since 02 June.
2. Hydrothermal and steaming activities in the northern and northeast sides of the Main Crater and Daang Kastila area have abated. Since 01 June 2011, 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.
3. Ground temperature and total magnetic field measurements at Daang Kastila and in the Main Crater showed no significant changes in both parameters.
4. Carbon Dioxide (CO2) 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.
5. 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.
The above 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. The public, however, is reminded that the Main Crater should be 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.