Post-eruptive deformation and faulting caused by conduit withdrawal and subsidence of the 2021 Tajogaite craters (La Palma)

Volcano deformation is an important precursor to eruptions, offering the opportunity to obtain information on the internal structure and magma plumbing system. Furthermore, deformation of volcanoes occurring after eruptions may also provide evidence of magma pathways and conduit dynamics, as demonstrated by this study. The 2021 Tajogaite eruption on La Palma was followed by progressive subsidence and the formation of major fracture networks surrounding the active craters. In this study, we analyse time-lapse data acquired using repeat drone photogrammetry and fixed-installation cameras to demonstrate that the aligned conduits withdraw and collapse over a time scale spanning from months to years following the eruption. Topography derivatives and pixel tracking show the convergence and subsidence of material into the possible conduit and the formation of inward-dipping normal faults affecting the inner and outer crater walls. To gain insights into the physical processes controlling the observations, we design models of conduit withdrawal that can reproduce the structures if topography and conduit burial are considered. Our findings suggest that the normal fractures surrounding the Tajogaite crater and numerous other craters are not the result of the eruption itself, but rather the consequence of volumetric reduction in the feeding conduit or dyke after the eruption.