Magma pressure drop as a forecasting tool for the end of the 2021 La Palma eruption (Canary Islands)

Abstract

Accurate forecasting eruptive activity is a core challenge in volcanology. Here, we describe an end of eruption forecast during the 2021 La Palma eruption using continuous GNSS geodetic data. We observed that co-eruptive deflation resembled a quasi-exponential trend and used it to forecast when deflation would cease equating to when the eruption would end. The forecast was done within the eruption, however was not operational due to large uncertainty in the unknown pressure dropt threshold needed to stop magma upflow. In hindcast, we explore minimum datasets needed and how forecast uncertainty reduces with increase in ingested data. We conclude that forecasts could be possible after the time-scale around the e-folding time of the exponential decay and quite accurate ones after twice that time-scale. Our results also indicate that the eruption was controlled by the dynamics of a Moho depth reservoir beneath Cumbre Vieja volcano.

Dynamic subsurface changes on El Hierro and La Palma during volcanic unrest revealed by temporal variations in seismic anisotropy patterns

“…The seismicity is ongoing, though in contrast to El Hierro, the number of events with a magnitude over 2.5 is significantly lower. Here, GPS measurements show a slight deflation of about 4 cm during the eruption (Figure 2B; Charco et al, 2023). Three distinct magma storage levels could be observed around the southern part of the island at 9-13 km, a mushy intermediate one at 18-32 km, and at 33-38 km, based on geodetic and seismological results (del Fresno et al, 2023).…”

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

“…GNSS time series are available at García-Cañada and Domínguez-Valbuena (2024). Matlab scripts for forecast and hindcast analyses are available at Pallero and Charco (2023).…”