Tephra Deposits of the Tajogaite Volcano, La Palma: Changes of Magnetic Properties Through the 2021 Eruption

Abstract

We report the results of a rockmagnetic study of tephra material produced by the Tajogaite volcano, in La Palma (Canary Islands), during 19 September through 13 December 2021. Our magnetic analysis reveals a change of rock magnetic properties through the eruption. Ti-magnetite particles are the main magnetic carrier in both lapilli and ash, and significant grain size changes are observed through the magnetic properties. Notably, we notice a progressive decrease in bulk magnetic susceptibility, largely due to the change in concentration of magnetite nanolite particles. Superparamagnetism is apparent in particular during the early stages of the volcanic activity, and the behavior is progressively masked upsection due to the abundance of Ti-magnetite SD and PSD particles. We hypothesize that the reported edifice collapse occurred on 25 September and a coeval, abrupt change of magnetic properties, are both related to the viscosity change of the magma feeding the volcano.