Geomorphological evidences of natural disasters in the Roman archaeological site of Carsulae (Tiber basin-central Italy).

The Roman town of Carsulae was founded after the construction of the “Flaminia Road“, whose track was studied by Caius Flaminius between 220 and the 219 BCE (Before Common Era). The road was realized with the aim to connect Rome with the Adriatic coast. Probably arisen from the union of several communities, the importance of Carsulae, testified since the Ist century BCE by Strabo, Pliny the Younger and Tacit, was related to its excellent elevated geographical position, which allowed for control over the vast underlying lowlands, characterized by the abundance of healthy waters and fertile soil. The town, built-up over wide travertine deposits (early Pleistocene-middle Pleistocene), is located at the bottom of the Martani Ridge at an altitude of about 500 m a.s.l., north of the Terni tectonic basin (Tiber Basin). The mountain ridge, made up of Mesozoic and Cenozoic limestone, forms a very thick aquifer that feeds many springs along the pedemountain area; the most important is that of San Gemini, in the surroundings of Carsulae, well-known since ancient times. Historical sources attributed the progressive decline and abandoning of Carsulae, mainly to the construction of a new track of the Flaminia Road and, moreover, to strong earthquakes that almost entirely destroyed the town. Recent studies, based on historical seismicity, support the hypothesis of catastrophic earthquakes, because of the presence of many active faults; some authors assumed travertine local deformations as real coseismic dislocations, also affecting archaeological remnants. Early geomorphological surveys, evidenced the presence of dolines, even of great extension; a big one hosts the Roman amphitheatre. Deformations observed on the surface and disarticulating the archaeological remnants, can be related to a partial collapse of the doline edge, as a consequence of a strong earthquake and/or of the continuous and progressive dissolution due to surface and groundwater circulation. The latter also produced severe injuries to hydraulic works, as is witnessed by historical sources. Besides, huge landslide deposits containing calcareous blocks and widely covering travertine and part of the Roman theatre and amphitheatre, have been recognized. The present state of knowledge allows to suggest, among the possible causes of progressive decline and desertion of the town, also the occurrence of large landslides, probably connected to seismic events and to the continuous degradation of the travertine plate.