A Multidisciplinary Study in the Archaeological Park of Valle dell’Aci: Exploring Ancient Settlements, Hot Springs, and Fluid Emissions to Reconstruct its Geological-Structural Framework

The archaeological park of Valle dell’Aci represents a suitable open-air laboratory favourable to multidisciplinary studies aimed at integrating historical, archaeological and geological data to gain a comprehensive understanding of the area’s history and geology. This work seeks to analyze and connect historical and archaeological remains, focusing mainly on the ruins of Greek-Roman thermal baths, volcanological observations, structural data, and their correlation with geothermal fluids emissions. The site of Santa Venera al Pozzo, located within the municipality of Aci Catena (Catania, eastern Sicily), holds a particular significance due to its millennia-history and unique proximity to Mt. Etna, the largest active volcano in Europe. The thermal baths date back to the Greek period and have given rise to myths, including that of Akis, transformed into a river whose springs sometimes take on a reddish colour due to the sulphureous nature of thermal waters. These legends, besides being an integral part of the area’s cultural heritage, provide valuable clues about geology and hydrothermal dynamics of the surrounding environment. Our research approach began with a meticulous analysis of historical sources to identify the hydrothermal fluid presence, known since ancient times. Three additional sites were identified, in addition to Santa Venera al Pozzo, where buildings attributable to ancient thermal structures were found. Subsequent fieldwork involved the identification of anomalous gaseous emissions, in particular CO2, with the aim of discerning deep geological structures. The resultant CO2 map not only confirmed the presence of flow anomalies in proximity to archaeological sites with hot springs, but also facilitated its correlation. By integrating this evidence with existing geological data, such as documented faults and subsurface ruptures caused by seismic events (251 AD and 2018), alongside an analysis of the region’s geomorphological features, we are able to identify structural weakness conducive to the ascent of geothermal fluids. This study therefore lays the basis for identifying new buried volcano-tectonic structures thus enhancing our knowledge of the seismotectonic model of the area.