A decade of geophysical monitoring to help conserve the Lascaux cave

The Lascaux Cave has been studied and instrumented for over 60 years. Since 1963, the cave has been increasingly monitored in an effort to order to better examine and manage the various diseases and dissolution linked to environmental factors that have begun to emerge, risking damage to the rock art and the supporting rock. Over the past decade, non-invasive geophysical methods, particularly electrical resistivity tomography, have been employed to study the surrounding massif. This approach combines monthly measurements along profiles and 2D surveys at varying scales, locations and seasons, enabling the reconstruction of 3D models using geostatistics. Analysis of both a decade profile time-lapse and of the 3D models acquired at different periods has improved understanding of water circulation in this unsaturated zone, highlighting temporary reservoirs. Long-term datasets have also been repurposed to, for example, identify the impact of tree felling on resistivity measurements and the massif. Electrical resistivity heterogeneities in 3D models, linked to geological formations and alteration levels, have provided input thermal studies, demonstrating their influence on heat propagation and natural convection within the cave. These findings underscore the critical role of the surrounding massif in preserving the cave.