INDIVIDUAZIONE DI AREE A RISCHIO SINKHOLE: NUOVI CASI DI STUDIO NEL LAZIO MERIDIONALE

Abstract

Many sub-circular ponds in Italian territory which originated in historical age, could be due to piping sinkhole phenomena. This
hypothesis is supported by the geological, morphological and structural setting of the area affected by the sinkholes.
The small lakes have diameters from a few, to hundreds of meters and a depth of up to fifty meters. The names are of dialectical origin
and they usually indicate a kind of sinking. Some legends refer the origin of the lakes to a quick catastrophic collapse.
These depression are usually originated by karst erosion (collapse dolines) and the genetic process could sometimes be related to a
deep piping process.
The correlation between collapses and piping sinkholes is confirmed by the “drowning” of the cavity soon after the formation.
Groundwater fills the cavity creating a pond, sometimes with underwater springs that feed the small lake.
The identification of a pond as sinkhole is not easy and needs specific studies such as geological surveys, geophysical, geochemical
and hydrogeological studies. Sometimes it is not possible to make an extensive field survey, due to costs, but it is just possible to suggest some hypotheses. The first step is to verify the geological and structural setting of the area, on the field and from the available literature.
In some cases we have found a lot of information on, the date and the modalities of the cave genesis; for example the Caira sink.
The Caira Lake, unknown in geological literature, is formed by a collapse and after two centuries it is buried. Information about this lake are preserved in few ancient documents in Cassino Mount Abbey. Geological, geomorphological and hydrogeological studies have
been conducted. Some first hypothesis are presented to explain the genesis of Caira lake. The origin of the lake is compatible to
sinkhole sensu stricto (or piping sinkhole); the lake is originated in a plain area over sedimentary cover (up 100 meters of thickness).
After the discovery of the ancient lake, many areas of southern Lazio have been investigated.
The analysis of the aerial photographs has identified the location of many sinkhole ponds and paleoforms, in the same area. Some of
which at the present time are still the seat of the ponds and others are dry. From the historical sources the presence of other numerous lakes, now extinct and of difficult location have been verified.
Examining the concerned area we can conclude that some of these forms have originated from the sinkhole sensu stricto phenomenon.
It has also been possible to determine the presence of a NNE active fault system (Theodicea fault), inside the intermontane basin of
Cassino, not known in literature. It is along this NNE fault system that, in the past there was the distribution of almost all of the springs
and/or ponds. At present the major sinkholes develop and align in this area.
Thanks to these discoveries, this area of southern Lazio can be listed among the Sinkhole Prone Risk Areas. It is therefore necessary to
accomplish a series of detailed technical enquiries before carrying out new infrastructures in order to protect the new constructions
and above all human life.