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Taal Volcano is one of the most active volcanoes in the Philippines. The magnetotelluric 3D forward analyses indicate the existence of a large high resistivity anomaly (∼100 Ω·m) with a volume of at least 3 km×3 km×3 km, which is capped by a conductive layer (∼10 Ω·m), beneath the Main Crater. This high resistivity anomaly is hypothesized to be a large hydrothermal reservoir, consisting of the aggregate of interconnected cracks in rigid and dense host rocks, which are filled with hydrothermal fluids coming from a magma batch below the reservoir. The hydrothermal fluids are considered partly in gas phase and liquid phase. The presence of such a large hydrothermal reservoir and the stagnant magma below may have influences on the volcano's activity. Two possibilities are presented. First, the 30 January 1911 explosion event was a magmatic hydrothermal eruption rather than a base-surge associated with a phreato-magmatic eruption. Second, the earlier proposed four eruption series may be better interpreted by two cycles, each consisting of series of summit and flank eruptions.

Considerable progress has been made in volcanic disaster mitigation in the Philippines during the last four decades, since the devastating Hibok-Hibok eruption in 1951 and the establishment of the Commission on Volcanology (COMVOL), the forerunner of the Philippine Institute of Volcanology and Seismology (PHIVOLCS) in 1952. The management of the Pinatubo Volcano eruption crisis of 1991-92 marks the highest point in the development of volcanic disaster mitigation in the country. State-of-the-art volcano monitoring techniques and instruments were applied; the eruption was accurately predicted; hazards zonation maps were prepared and disseminated a month before the violent explosions; an alert and warning system was designed and implemented; and the disaster response machinery was mobilized on time. The unprecedented magnitude and lingering nature of the hazards, however, and their widespread, long-term impacts have sorely tested the capability of the country's volcanic disaster mitigation systems. In particular, the lahar threat has triggered controversies and put decision makers in a dilemma of choosing between adaptive versus confrontational/control approaches. At least three strategies have been articulated and adopted in varying degrees and forms: (1) the establishment of a lahar monitoring-warning-evacuation system to deal with the lahar problem on an emergency basis; (2) relocation of settlements from the hazard zones; and (3) installation of engineering countermeasures to control/divert the lahar flows and protect settlements. A combination of the three appears to be the best, but the most effective and least costly mix remains to be determined.