Magmatic processes associated with the 2020 eruption of Taal Volcano, Philippines, revealed by local seismic source estimates

Abstract

After 43 years of repose, Taal Volcano (Philippines) erupted on 12 January 2020 with plumes reaching 17 km above sea level. To investigate Taal's magma system before, during, and after the 2020 eruption, we performed detailed analyses of local seismic data using the amplitude source location (ASL) method to estimate sources of volcano-tectonic (VT) earthquakes and tremor. Our ASL estimates indicate that magma intruded beneath the northern flank of Taal Volcano Island (TVI) before the main sustained eruption, which started at 06:40 UTC on 12 January 2020 and continued for about 14 h. Within one hour after the start of the eruption, magma emplacement along an inclined magmatic dike from a magma reservoir initiated. Seismically estimated plume heights during the eruption show that plumes were initially almost continuously higher than 10 km, then intermittently fluctuated while the base-level height of the sustained plume gradually decreased. After the eruption, tremor episodes occurred at depths down to 8.5 km beneath TVI along the northern end of a dike. Our study highlights the drastic change of Taal's magmatic system from a closed to an open system during the 2020 eruption. Before the eruption, Taal had been a closed system, and the increased pressure caused by renewed magma supply to a magma reservoir produced heightened VT activity within the edifice. The eruption opened the vent–conduit system, and CO₂ and/or SO₂ degassing within the conduit may have generated gas flows through shear-induced fractures in the conduit margins, triggering tremor episodes at various depths.