The 2021 La Palma (Canary Islands) Eruption Ending Forecast Through Magma Pressure Drop

Abstract

AbstractForecast of eruptive activity is a core challenge in volcanology. Here, we present an actual forecast for the end of the 2021 La Palma eruption. Using continuous GNSS data, we identified a co‐eruptive quasi‐exponential deflation trend. Assuming mass conservation, magma upflow from an overpressurized reservoir drives the eruptive process. The forecast was carried out during the eruption, however there was uncertainty in the key percentage of drop in driving pressure necessary to stop this eruption. In hindcast, we explore how forecast uncertainty reduces with increase in ingested near‐real time data. We conclude that precise forecasts could have been possible, but only after twice a characteristic exponential decay time‐scale, providing error estimates of 45% of the actual duration. We verify the mass conservation assumption using eruptive material volumes and propose that the eruption dynamics was controlled by a main reservoir at a depth close to Moho discontinuity beneath Cumbre Vieja volcano.