Influence of geological heterogeneities on thermal behaviour of Lascaux Cave for conservation purposes

• Lascaux cave has been extensively monitored since 1950. • Temperature trends revealed a general increase in recent years. • Rock mass heterogeneities influence the propagation of thermal waves. • Thermo-aeraulic modelling will be built from these results for conservation matter. The conservation of cultural heritage is becoming an increasingly significant social issue because of climate change. Lascaux Cave, a UNESCO World Heritage Site, is particularly susceptible to disruption, which could result in the alteration of its delicate microclimate and accelerate the deterioration of the decorated walls. To mitigate the impact of these changes, it is essential to gain a deeper understanding of the thermal behaviour within the cave and its surrounding environment. The objective of this study was to examine the thermal behaviour of the cave, with a particular focus on the interactions between external temperature fluctuations, geological heterogeneity, and the internal microclimate of the cave. To investigate this phenomenon, a thermal monitoring system comprising 21 sensors (ALMEMO PT-100) was strategically placed in different zones of the cave, and a thermal station was installed outside the cave. The findings of this study demonstrate a substantial correlation between external and internal temperatures, exhibiting notable phase shifts and relative amplitude changes at varying depths and locations within the cave. The combination of thermal data with the geological heterogeneity of the rock mass demonstrated that the distinct thermal properties of different geological formations exert a considerable influence on thermal wave propagation. Furthermore, we examined how natural convection is caused by temperature differences between the vault and the ground of the cave and between the upper and lower galeries. The findings of this study can be used to develop future thermoaeraulic simulations. Understanding these thermal dynamics is necessary for developing effective conservation strategies.