Taal: Alert level raised

PHILVOLCS has been reporting for several weeks an increase in seismicity under the large Caldera volcano on Luzon, which caused a stir with an eruption only last January. In addition to numerous volcanotectonic earthquakes, volcanic tremors also increased significantly recently. The total number of volcanic tremor events has risen to 866 since the increased activity began on February 13. The volcanic tremors have increased seismic energy compared to previously recorded episodes and have ranged from 3 to seventeen 17 minute durations. In addition, the other parameters that indicate magma is moving at shallow depths are beginning to change: the acidity of Crater Lake increased, rising (or falling) from pH 2.79 to pH 1.59. The water is becoming more acidic because of increased volcanic gases rising. The water temperature increased to 74.6 degrees. Slight bottom deformation was detected using InSAR imagery. Concomitant changes in microgravity were recorded. New measurements have detected positive microgravity changes throughout the Taal caldera, consistent with density changes due to magma migration, magma degassing, and hydrothermal activity. All of these parameters are of concern and the alert status has been raised to “yellow.” Evacuations have not yet been initiated. Authorities remind that Volcano Island is a permanent exclusion zone. The photo shows the volcano during last year eruption.