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Textural evolution of pyroclastic products of the Villarrica volcano between 2015-2024: insights into its eruptive style transitions

Flavia Rojas1, Margherita Polacci1, Jorge Romero2, Barbara Bonechi1, Elisa Biagioli1, David Neave1

  • Affiliations:  1Department of Earth and Environmental Sciences, University of Manchester, Manchester, United Kingdom; 2Instituto de Ciencias de la Ingeniería, Universidad de O'Higgins, Rancagua, Chile

  • Presentation type: Poster

  • Presentation time: Monday 16:30 - 18:30, Room Poster Hall

  • Poster Board Number: 218

  • Programme No: 3.6.22

  • Theme 3 > Session 6

Abstract

Style transitions are common during volcanic eruptions but the processes that trigger them remain poorly understood. Understanding these transitions is essential regarding hazards, as they can exacerbate the associated risks. Vesiculation plays a fundamental role in magma dynamics and the resulting eruptive style. The content, size, shape, and distribution of vesicles in volcanic rocks record magma processes and can be correlated to conduit processes and subsequent eruptive behaviour. In this work, we studied the vesicle textures of 20 basaltic and basaltic andesite pyroclasts produced by the Villarrica stratovolcano between 2015 and 2024. Villarrica is the highest-risk and most active volcano in Chile. It has exhibited various eruptive styles ranging from VEI 0 to 3 during its historical activity, displaying Strombolian, Hawaiian and lava fountaining activity. In March 2015, Strombolian activity progressed quickly into a 1.5-km-high lava fountain. After that event, the activity continued shifting intermittently between Strombolian explosions and the open conduit degassing from the active lava lake. We performed textural analyses, including measurements of vesicularity, vesicle shape, number density, and connectivity on three-dimensional volume reconstructions obtained via X-ray computed microtomography. We complemented this method with scanning electron microscope image analysis and bulk-rock compositions. The results provide insights into the textural evolution of the volcanic products related to distinctive eruptive behaviours observed at the surface and with magmatic processes that could trigger these changes. These processes could be related to changes in the degassing rates and/or mechanisms in the conduit or other processes occurring in the shallow plumbing system.