Geomorphological evidences of natural disasters in the roman archaeological site of Carsulae (Tiber basin, Central Italy)

The Roman town of Carsulae built-up after construction of the “Flaminia Way“, whose track, studied by Caius Flaminius between 220 and the 219 a.C., was realized with the aim to link Rome with the Adriatic coast. Probably arisen from the union of several communities, its importance, testified since I century A.C. by Strabone, Pliny the Younger and Tacit, was related to the excellent elevated geographical position, which allowed the control of the vast underlying lowlands, characterized by abundance of healthy waters and fertile soil. The town, built-up over a wide travertine deposits (early Pleistocene-middle Pleistocene), is located at the bottom of the Martani Ridge at elevation of about 500 m a.s.l., north of the Terni tectonic basin (Tiber Basin). Mountain ridge, made up by Mesozoic and Cenozoic limestones, forms a very thick aquifer that feeds a lot of springs along the pedemountain area; the most important one is that of San Gemini, in the surroundings of Carsulae, well known since ancient times. The passage between travertine deposit and mountain ridge is characterized by thick continental deposits, partly covering travertine itself. Historical sources attributed the progressive decline and abandoning of Carsulae, mainly to the construction of a new track of the Flaminia Way and, more, to strong earthquakes that destroyed almost entirely 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 co-seismic dislocations, also affecting archaeological remnants. First 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, consequently to a strong earthquake and/or to the continuous and progressive dissolution due to surface and groundwater circulation. The latter produced also severe injuries to hydraulic works, as witnessed by historical sources. Besides, huge landslide deposits containing calcareous blocks and widely covering travertine and part of the Roman theater and amphitheatre, have been recognized. Mountainwards, where calcareous bedrock outcrops and in correspondence of an active fault, wide trenches and counterslopes are visible; these landforms are certain evidences of important mass movements (large landslides and/or deep-seated gravitational slope deformations). The present state of knowledge allows to hypothesize, among possible causes of progressive decline and desertion of the town, also the occurrence of large landslides, probably connected to seismic events and to continuous degradation of travertine plate.