A unique electrical resistivity experiment reveals the 3D interior of Piton de la Fournaise

Understanding the internal structure of volcanoes is essential for improving predictions of eruptions and for assessing hazards. However, creating high-resolution models of their interiors remains a significant challenge. At Piton de la Fournaise, we conducted an innovative 3D electrical resistivity tomography to produce a new high-resolution image of the subsurface beneath the Terminal Cone, extending down to 1 km below the summit. Our model not only images a large hydrothermal zone beneath the layered lava flows, but also reveals conductive offshoots extending toward the surface beneath the Bory crater and along faults linked to the Dolomieu crater. These findings suggest that hydrothermal activity is strongly influenced by volcano-tectonic features at the summit. This study provides valuable insights into fluid circulation, magma transfer, and instability, offering a new framework for understanding the present structure of Piton de la Fournaise and proposes a novel approach for studying the spatio-temporal evolution of volcanoes worldwide.