Sinkhole problems at Rome and in the surrounding territories

The city of Rome is among the main sites in Italy affected by occurrence of sinkholes produced by underground cavities. The high frequency of these phenomena is due to a combination of the local geology, characterized by rocks belonging to two different volcanic districts and by the alluvial deposits of the Tiber and Aniene rivers as well, and of the long history at the site, covering more than three thousand years of human presence. The effects caused on the built-up environment by sinkholes are therefore very severe, and have produced casualties in several occasions. The most common typology of underground artificial cavity at the origin of the sinkholes is represented by old quarries, used in the past to extract the building materials for the town. Once abandoned, processes of degradation of the rock material started at these sites, favoured in many cases by anthropogenic actions; the resulting instabilities that occurred underground often had an upward evolution, until developing a sinkhole at the surface. This situation is definitely the most frequent in Italy as concerns anthropogenic sinkholes, as resulted from the analysis of a national chronological catalogue of sinkholes managed by CNR-IRPI (the catalogue includes some 900 events at present, 160 out of which are located in Latium, the region where Rome is). The present article deals with analysis of sinkholes in selected areas of the city of Rome, where recent events resulted in evacuation of some buildings, with many problems for the local inhabitants. Further, the case study of Palestrina (the ancient Praeneste, in the province of Rome) is also described, with particular reference to the event of October 21, 2014, when a two-story building was destroyed by a sinkhole. Luckily, two days before the building had been evacuated, which resulted in damage being limited to economical issues, without any loss of human life.