A multidisciplinary study of juvenile material ejected during the September–December 2021 eruption of Tajogaite volcano (La Palma, Canary Islands) was conducted to understand the processes that occurred during pre-eruptive magma ascent and within the conduit system, in order to obtain a reconstruction of the eruptive dynamics. Variations in the physical, morphological, textural, and chemical characteristics of the juvenile material reveal changes in the mechanisms of outgassing, fragmentation, and velocity of magma ascent within the conduits. In agreement with the three main identified eruptive phases, we found that Phase I corresponds to the maximum eruption intensity, when highly vesicular clasts were produced, which show primary vesicularity modes between 54.7 and 68.0% decreasing from the base to the top of the deposit of this phase and Nvm values between 1.6 and 46.3 × 106 cm−3. Morphological parameters show high solidity (a shape descriptor quantifying the complexity of the particle’s outer surface, with values close to 1 indicating a more equable shape), medium to low convexity (measuring surface irregularity, with lower values indicating rougher textures), and low axial ratios (the ratio of a particle’s dimensions, reflecting elongation), indicating the presence of clasts with predominantly irregular morphology and rough and spongy outer surfaces. Phase II was initially characterized by a lower eruptive intensity, producing dense juvenile material with irregular to subspherical morphologies, and afterwards by explosive activity characterized by intermittent episodes of variable intensity. Phase II clasts show vesicularity modes between 60.3 and 61.2% and Nvm values between 13.2 and 59.4 × 106 cm−3. Solidity values are high while convexity values cover a wider range indicating the presence of clasts with both smooth and rough external surfaces. Phase III was characterized by a new increase in eruptive intensity with clasts that show a vesicularity mode at ⁓60.2% and average Nvm values ranging from 8.5 to 85.8 × 106 cm−3. The morphology of the clasts is variable, while solidity and convexity values are higher than the other phases. Syn-eruptive variability confirmed the presence of multiple conduits simultaneously active and defined by different geometries that regulated the processes of outgassing, fragmentation, and crystallization of magma as it ascended to the surface. The tephra clasts are compositionally grouped in the tephrite-basanite field, showing increasingly more mafic compositions with eruption progression, with observed variations likely associated with repeated (more primitive) magmatic inputs that fuelled the eruption over time.
Eruptive dynamics of the 2021 Tajogaite eruption (La Palma, Canary Islands) as revealed by the physical and textural characterization of tephra
Serena Da Mommio;Marija Voloschina;Marco Pistolesi
2025-01-01
Abstract
A multidisciplinary study of juvenile material ejected during the September–December 2021 eruption of Tajogaite volcano (La Palma, Canary Islands) was conducted to understand the processes that occurred during pre-eruptive magma ascent and within the conduit system, in order to obtain a reconstruction of the eruptive dynamics. Variations in the physical, morphological, textural, and chemical characteristics of the juvenile material reveal changes in the mechanisms of outgassing, fragmentation, and velocity of magma ascent within the conduits. In agreement with the three main identified eruptive phases, we found that Phase I corresponds to the maximum eruption intensity, when highly vesicular clasts were produced, which show primary vesicularity modes between 54.7 and 68.0% decreasing from the base to the top of the deposit of this phase and Nvm values between 1.6 and 46.3 × 106 cm−3. Morphological parameters show high solidity (a shape descriptor quantifying the complexity of the particle’s outer surface, with values close to 1 indicating a more equable shape), medium to low convexity (measuring surface irregularity, with lower values indicating rougher textures), and low axial ratios (the ratio of a particle’s dimensions, reflecting elongation), indicating the presence of clasts with predominantly irregular morphology and rough and spongy outer surfaces. Phase II was initially characterized by a lower eruptive intensity, producing dense juvenile material with irregular to subspherical morphologies, and afterwards by explosive activity characterized by intermittent episodes of variable intensity. Phase II clasts show vesicularity modes between 60.3 and 61.2% and Nvm values between 13.2 and 59.4 × 106 cm−3. Solidity values are high while convexity values cover a wider range indicating the presence of clasts with both smooth and rough external surfaces. Phase III was characterized by a new increase in eruptive intensity with clasts that show a vesicularity mode at ⁓60.2% and average Nvm values ranging from 8.5 to 85.8 × 106 cm−3. The morphology of the clasts is variable, while solidity and convexity values are higher than the other phases. Syn-eruptive variability confirmed the presence of multiple conduits simultaneously active and defined by different geometries that regulated the processes of outgassing, fragmentation, and crystallization of magma as it ascended to the surface. The tephra clasts are compositionally grouped in the tephrite-basanite field, showing increasingly more mafic compositions with eruption progression, with observed variations likely associated with repeated (more primitive) magmatic inputs that fuelled the eruption over time.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
