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Contrasting degassing behavior of Kanlaon and Taal volcanoes, Philippines, revealed by campaign monitoring

Jerome Peter Traviña , Eric Lino Arconado, Nicole Mariano, Ma. Antonia Bornas

Abstract

Volcanic gas monitoring in the Philippines supported by current technologies for campaign and continuous measurements has yielded critical data on the currently restless Taal and Kanlaon Volcanoes. Volcanic sulfur dioxide (SO2) measurements in Kanlaon began in 2016 through ground-based campaign surveys using a miniature-UV spectrometer (FLYSPEC). In contrast, only dissolved and diffused carbon dioxide and hydrogen sulfide were measured on Taal Volcano Island Main Crater prior to the 2020 eruption but were subsequently dominated by post-eruption SO2 degassed in plumes and measured using FLYSPEC. Time-series data indicate that Kanlaon and Taal have exhibited different patterns in SO2 degassing. Kanlaon emissions were mainly in the background levels except during and after discrete phreatic eruptions between 2015 and 2017. This was followed by increases leading up to the explosive eruption on 3-June-2024 and subsequent elevated SO2 degassing with peaks of an order of magnitude greater than pre-eruption emissions. In contrast, Taal has exhibited cyclical periods of increasing-decreasing SO2 degassing after the 2020 eruption following a year of negligible emissions. Taal further emitted the highest concentrations of SO2 measured for a Philippine volcano. Its degassing behavior occasionally drives phreatic activity within the Main Crater Lake and produces volcanic smog that affects communities around the volcano. Time-series SO2 data for Kanlaon and Taal have been key parameters in evaluating developing unrest and post-eruption volcanic hazards, respectively, proving critical to early-warning and preparedness. Future directions for gas monitoring are headed to continuous and real-time and multi-gas measurement stations for higher-resolution monitoring, warning and research purposes.