– Kike Rincón – Europa Press – Archive
SANTA CRUZ DE TENERIFE, 19 Jun. (EUROPA PRESS) –
A new study published in the ‘Journal of Volcanology and Geothermal Research’ and led by a team from IGME-CSIC, reconstructs how magma propagation during the 2021 La Palma eruption resulted in over a hundred secondary emission centres.
Complex Volcanic Activity
“The classic image of a volcano with a single main conduit does not always reflect the actual complexity of an eruption,” explains David Sanz Mangas, a researcher at IGME.
During the ‘Tajogaite’ eruption, “magma propagated through two main dikes, allowing new lava emission points to open far from the cone at different phases,” he added.
The team identified two significant magmatic feeding systems (Dike 1 and Dike 2) whose interaction with pre-existing fractures and geological structures shaped the location of the new eruptive centres.
These episodes created highly fluid lava flows that, in some instances, advanced rapidly at over five kilometres per second, invading urban areas distant from the primary focus.
The so-called ‘Dike 1’ maintained primary activity throughout the eruption, while ‘Dike 2’ spread perpendicularly months later, triggering the opening of emission centres in remote areas.
Interaction with a Heterogeneous Terrain
The magma interacted with a highly heterogeneous landscape (faults, fractures, ancient volcanic edifices), generating a complex eruptive geometry. This resulted in separate lava exit zones upon reaching the surface.
The lavas that emerged from these zones were extremely fluid (pahoehoe type), with very low viscosities and speeds comparable only to historical eruptions such as the San Juan eruption of 1949 or that of Kilauea in Hawaii. These lavas covered dozens of hectares in less than an hour, invading urban areas and making lava intrusion very difficult to predict.
Unlike the initial lava, which was more viscous and slower, these new pahoehoe flows swiftly invaded the terrain, aided by gentle slopes and the formation of channels and tubes.
Subtle Signs Preceding Activity Changes
The findings indicate that some changes in activity were preceded by subtle signals, such as the appearance of fractures in the ground, local deformities, and diffuse gas emissions. However, these signals were obscured by the intense seismic and eruptive activity recorded continuously during the crisis.
This highlights the need to consider the potential emergence of emission centres away from the main cone in volcanic hazard assessments. It also emphasizes the importance of complementing geophysical monitoring techniques with geological field observations, gas tracking, and high-resolution monitoring systems.
“THIS BEHAVIOUR IS NOT EXCEPTIONAL”
“Historical eruptions of La Palma indicate that this behaviour is not exceptional,” states Inés Galindo, a researcher at IGME-CSIC and co-author of the study. She points out that understanding how magma propagates and what controls the opening of new emission centres could enhance preparedness and response to future volcanic crises.
The research conclusions imply an operational shift, as the volcano can open new eruptive centres far from the main focus. Monitoring must extend beyond the active cone and lava flows, as highlighted by IGME.
To address eruptions similar to the one described, the proposed approach involves extensive terrain monitoring (not just of the cone and lava flows), direct observation, intensive use of drones, thermal cameras, remote sensing, the creation of dynamic gas emission maps, and the establishment of a flexible exclusion zoning that could be expanded in real time.
The work has been conducted by a team from IGME-CSIC within their research line dedicated to the study of flow dynamics and the evolution of the Tajogaite eruption, in collaboration with Royal Holloway University of London.
The study forms part of the doctoral thesis of David Sanz Mangas (Complutense University of Madrid), focusing on reconstructing the evolution of the lava field and the geological processes that influenced its development.
