Tephra sedimentation and grainsize associated with pulsatory activity: the 2021 Tajogaite eruption of Cumbre Vieja (La Palma, Canary Islands, Spain)

Abstract

Long-lasting eruptions are of complex characterization and are typically associated with challenging risk assessment and crisis management due to the usual occurrence of multiple interacting hazards evolving at different temporal and spatial scales (e.g., lava, tephra, and gas). The 2021 Tajogaite eruption of Cumbre Vieja (La Palma) demonstrated how even hybrid events that are mostly effusive can be associated with widespread and impacting tephra deposits as a result of a complex interplay among gas flux, conduit geometry, and magma feeding rate. In this novel study, direct observations, syn-eruptive and post-eruptive sampling, and statistical analysis of pulsatory activity have been combined to provide new insights into eruption dynamics. They show how rapid gas segregation and high magma ascent rate modulated the gas flux at multiple vents, resulting in short-time fluctuations among the different explosive styles (ash-poor gas puffing, Strombolian, violent Strombolian, and lava fountaining) and unsteady tephra ground accumulation. Various size-selective sedimentation processes were also observed, including particle aggregation and ash fingers, which have impacted the overall tephra dispersal. In fact, even though both local and total grainsize distributions of selected layers, units, and of the whole tephra blanket are unimodal with a low fine-ash content, grainsize analysis of 154 samples suggests no correlation of particles <63 μm with distance from vents. Our analyses demonstrate the need to include a detailed characterization of all products of hybrid eruptions for a comprehensive interpretation of eruptive dynamics and to use multiple classification strategies that can capture eruptive styles at different temporal scales.

The spatiotemporal evolution of compound impacts from lava flow and tephra fallout on buildings: lessons from the 2021 Tajogaite eruption (La Palma, Spain)

“…Tephra thicknesses were converted to a load using a deposit density of 1386 kg m −3 to estimate the potential impact of the tephra blanket on the roofs in Corazoncillo, which represents a mean value for the stratigraphic LU and MU units (Bonadonna et al 2023 ). In the absence of a dedicated fragility model for roofs in La Palma, we estimated the roofing stock of Corazoncillo to be comprised in the medium weak (MW), medium strong (MS) and strong (ST) roof classes of Spence et al ( 2005 ) (Table 1 ) and used these fragility curves to illustrate the temporal evolution of collapse probability during the eruption.…”

“…3 a). In our model, we consider that 75% of the rain is infiltrated in the deposit, which is justified by the low to moderate roof pitch and by the absence of fine ash in the deposit (Bonadonna et al 2023 ). Following Williams et al ( 2021 ), the additional load caused by rainfall is prevented to exceed 30%.…”

“…5, 2021 (during the eruption), Feb. 7–18, 2022, and May 14–20, 2022. All campaigns aimed at characterising the tephra blanket, summarised in Bonadonna et al ( 2022 , 2023 ) and conducting post-event impact assessments (post-EIA) of the built environment (Reyes-Hardy et al under review).…”

“…The eruption consisted of the simultaneous emission of lava flows and a range of low to moderate explosive styles ranging from Hawaiian (i.e. sustained fountaining) to violent Strombolian activity (Bonadonna et al 2023 ; Taddeucci et al 2023 ). The final ~ 1.8 × 10 8 m 3 lava flow field was emplaced over an area of 12 km 2 , and the volume of the tephra blanket was estimated to be ~ 2.3 × 10 7 m 3 (Bonadonna et al 2022 ; Civico et al 2022 ; Fig.…”

Health impact of the Tajogaite volcano eruption in La Palma population (ISVOLCAN study): rationale, design, and preliminary results from the first 1002 participants

“…This volcanic process persisted for 85 days until its conclusion on December 13 of the same year. It consisted in a long-lasting, hybrid eruption associated with multiple eruptive styles (effusive, lava fountains, ash emissions, strombolian explosions) with the formation of cones of various heights, widespread tephra blankets and extensive lava-flow fields and was characterized by simultaneous effusive and explosive activity [ 15 ]. The eruption affected the Valle de Aridane, which was greatly impacted by the lava flows, gases, and particulate matter emitted during the eruption.…”