Forecasting the evolution of the 2021 Tajogaite eruption, La Palma, with TROPOMI/PlumeTraj-derived SO2 emission rates

As global populations grow, the exposure of communities and infrastructure to volcanic hazards increases every year. Once a volcanic eruption begins it becomes critical for risk managers to understand the likely evolution and duration of the activity to assess its impact on populations and infrastructure. Here, we report an exponential decay in satellite-derived SO₂ emission rates during the 2021 eruption of Tajogaite, La Palma, Canary Islands, and show that this pattern allows a reliable and consistent forecast of the evolution of the SO₂ emissions after the first third of the total eruption duration. The eruption ended when fluxes dropped to less than 6% of their fitted maximum value, providing a useful benchmark to compare with other eruptions. Using a 1-D numerical magma ascent model we suggest that the exponentially decreasing SO₂ emission trend was primarily produced by reducing magma chamber pressure as the eruption emptied the feeding reservoir. This work highlights the key role that satellite-derived SO₂ emission data can play in forecasting the evolution of volcanic eruptions and how the use of magma ascent models can inform the driving mechanisms controlling the evolution of the eruption.