Magmatic plumbing and dynamic evolution of the 2021 La Palma eruption

The 2021 volcanic eruption at La Palma, Canary Islands, was the island's most voluminous historical eruption. During the eruption, seismicity was distributed in two clusters at about 10–14 km and 33–39 km depth, separated by an aseismic zone that coincides with weak pre-eruptive swarms (2017–2021) and depths inferred by petrology for magma storage. Using seismological methods, including 8,488 hypocentral relocations and 156 moment tensors, the study identifies stress heterogeneities and principal-axis flips. Results suggest a long-lasting preparatory stage with progressive destabilisation of an intermediate, mushy reservoir, followed by a co-eruptive stage where seismicity was controlled by the drainage and interplay of two localized reservoirs. These findings provide new insights into the plumbing system, improving the monitoring framework for future eruptions on the island.