The Plain of Capoterra is a large fault of the Tertiary, NNW-SSE oriented, where the Rio Santa Lucia flows into the Pond of Capoterra, and which is parallel between this area and the mountain range. It is an area that has suffered since the very earliest ages a complex geological structural and lithological evolution. The plain of Capoterra is the outcome of the geomorphological action which moulded the area from the confluence of the Rio Guttureddu and Rio Gutturu Mannu since the Pliocene to date. According to Genesis, it can be divided into three fundamental lithological groups: piedmont deposits in the form of glacis; cones and in a layer of deposits, flooding pebbly, sandy and silty-clay of fluvial-wetland and marine.