I FENOMENI DI SPROFONDAMENTO: STATO DELLE CONOSCENZE ED ALCUNI ESEMPI IN ITALIA CENTRALE

Abstract

Technical literature offers a lot of terms to indicate different types of geological cavities, but recently the term sinkhole seems to be
commonly adopted to indicate underground cavities which are similar in their features but have different morphogenetic origins. That is why the term sinkhole appears to be rather generic or inadequate.
The aim of this work, therefore, is to propose a new terminology for every kind of cavity and to associate a more rigorous definition to
each of them, according to their different morphological genesis.
In the Italian traditional literature the terms “dolina” (divided in various types), “sprofondamento” and “camino di collasso” were adopted to indicate different kinds of sub-circular collapses.
According to the first term the soil dissolution is caused by the infiltration of water in soluble rocks; according to the second one gravity and anthropizzation are the main factors causing these collapses and according to the last one, above the soil dissolution, the predisposing factor is the pressure of the water coming back to the plane surface level.
In the English literature the term doline (still divided in several types) was originally adopted to indicate karst caves as an equivalent of
the Italian word “dolina” but it was later replaced by the term sinkhole. At first this term simply indicated sub-circular depressions due to the landslide of small karst caves, but actually it is adopted to indicate every kind of cavity.
Taking into account the processes that cause the development of a sinkhole, the use of this term seems only suitable to indicate cavities caused by a piping process (“suffosione” in Italian) and therefore it should be a synonymous of the Italian term “camino di collasso” (known as piping sinkhole in the English literature).
The sinkholes in Italy are concentrated in alluvial flats, near carbonatic ridges, in some structural and hydrogeological contexts which
were originated by different causes (earthquakes, dryness, alluviums, water wells etc.).
Impermeable sediments laid on the top of karst carbonatic bedrocks, faults and fractures between the two layers, are the main predisposing factors.
Moreover, the presence of water and gases, such as CO2 and H2S, concurring to the dissolution and the piping processes, has been
detected in almost all the circumstances.