An international study conducted by the Institute of Geosciences (IGEO), the joint center of the Supreme Council for Scientific Research (CSIC) and the Complutense University of Madrid (UCM), detected magma accumulation near the surface months before a volcanic eruption occurred on La Palma. The research analyzes ground deformation driven by volcanic activity and employs a methodology that blends cutting-edge InSAR satellite radar observations with a fresh interpretation technique developed by IGEO researchers during the 2021 eruption on the island. The study’s findings have been published in a scientific journal.
“A structural model of the island’s subterranean crust, built from the resources provided by this methodology, can help anticipate crack openings or eruption vents during reactivation events and predict the onset timing of future eruptions, alongside other techniques,” explains IGEO researcher José Fernández, the paper’s first author.
The eruption on La Palma began on September 19, 2021, and was accompanied by a seismic swarm that started eight days earlier, on September 11, during which more than 6,600 events were recorded. The study shows that between September 13 and 20, aligning with the final phase of the seismic swarm, shallow fractures formed in the ground, creating fissures that would later feed the eruption.
La Palma’s eruption, as reported by European Press, drew attention to how the magma supply system and related fractures influence surface expressions and ongoing gas emissions in nearby areas such as Puerto Naos and La Bombilla, complications that hinder residents from returning over a year after the event.
The configuration described in this study highlights how the magma system interacted with the local crust, clarifying processes that occurred after the explosion, including sustained gas emissions and the persistence of volcanic hazards in the region.
The research team had previously published work in early 2021, eight months before the La Palma eruption, indicating that the island’s volcanic reactivation had begun between 2009 and 2010. They also detected a significant break in the ground beneath Cumbre Vieja connected to this process in 2019 and 2020.
“This fracture defined a potential pathway for magma toward a zone of structural weakness, which helped form a magmatic reservoir at a depth of two to five kilometers in the Cumbre Vieja area about three and a half months before the eruption began. This reservoir location underscores the importance of understanding the island’s structural pattern and the pathways magma has followed in recent eruptions,” Fernández adds.
The study’s magma supply model and related fractures shed light on gas emissions after the eruption, continuing to affect monitoring and risk assessment efforts in the region.
Approximately two months before the explosion, data gathered by researchers at the end of July 2021 indicated signs of vulnerability in the crust ahead of a larger magma ascent. The IGEO specialist notes that applying the new interpretation technique at that time could have served as an early warning, enabling more intensive surveillance of the area as the eruption entered its final stage in real time.
The study emphasizes understanding not only the magmatic supply system and deep fracturing, but also the crustal structure around potential magma accumulation sites in shallow reservoirs and possible eruption pathways. This knowledge is essential for assessing volcanic risk and for planning infrastructure and urban development, both on La Palma and in other volcanic regions.
Reference work: DOI: 10.1038/s41598-022-23998-w
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