Le volcan Taal déclenche une éruption mineure, 13 événements sismiques

Taal Volcano in Batangas Province recorded its second phreatomagmatic eruption of the month on July 16, according to the Philippine Institute of Volcanology and Seismology (Phivolcs). The eruption, which began at 7:30 a.m., lasted about two and a half minutes and generated an ash-laden, steam-rich plume that rose approximately 600 meters above the main crater before drifting north-northeast. This follows a similar event on July 12, marking the second such occurrence in less than a week. The phreatomagmatic eruption is characterized by the interaction of magma with water, resulting in explosive steam production and fragmentation of volcanic materials. Unlike phreatic eruptions, which involve the rapid heating of groundwater or surface water, phreatomagmatic eruptions occur when magma directly encounters water, leading to more intense and sustained activity. Phivolcs noted that no upwelling of hot volcanic fluids was observed in the main crater lake, nor was any volcanic smog, or “vog,” detected during the monitoring period. Earlier in the week, Taal Volcano had already logged a three-minute phreatomagmatic eruption on July 12, which sent a plume approximately 1,200 meters high into the air. Since June, Phivolcs has documented five similar eruptions, highlighting a pattern of intermittent but notable activity. The agency emphasized that these eruptions remain relatively minor compared to larger explosive events, though they indicate ongoing volcanic unrest. Monitoring data from Phivolcs revealed a sharp increase in sulfur dioxide emissions following a record low. On July 16, the volcano emitted an average of 289 metric tons of sulfur dioxide per day, a significant jump from the 59 metric tons recorded the previous day. This marked the lowest daily sulfur dioxide output since early January, surpassing the prior minimum of 78 metric tons. For context, the highest sulfur dioxide emission recorded this year was 5,287 metric tons on June 4, underscoring the volatility of the volcano's emissions. In addition to the rise in sulfur dioxide levels, Phivolcs observed a volcanic tremor lasting nine minutes on Wednesday. Defined as continuous seismic signals with low-frequency oscillations typically ranging between 0.5 and 5 hertz, these tremors persisted for over a minute and are often associated with magma movement beneath the surface. While the tremor did not trigger immediate alerts, it added to the signs of ongoing volcanic activity. Despite the recent eruptions and elevated emissions, Taal Volcano remains under Alert Level 1, which signifies low-level volcanic unrest. Phivolcs reiterated that this alert level does not imply the volcano has returned to a stable state or that further eruptive activity is unlikely. Instead, the agency cautioned that the volcano continues to exhibit abnormal behavior and urged the public to maintain vigilance and adhere to all precautionary guidelines. The Main Crater, located on Taal Volcano Island within Taal Lake, remains the primary focus of monitoring efforts. The island, known locally as “Pulo,” is home to the active crater and serves as a critical observation point for scientists tracking changes in volcanic behavior. Continuous monitoring of the crater lake, surrounding areas, and atmospheric conditions helps provide timely updates to local authorities and residents. As the situation evolves, Phivolcs will likely continue to assess the volcano’s activity through a combination of seismic, infrasound, and visual observations. With the potential for further eruptions or shifts in emission patterns, the agency remains committed to providing accurate and timely information to ensure public safety.