Giuliana Madonia

KARST OF SICILY AND ITS CONSERVATION

In Sicily, karst is well developed and exhibits different types of landscapes due to the wide distribution of soluble rocks in different geological and environmental settings. Karst affects both carbonate rocks, outcropping in the northwest and central sectors of the Apennine chain and in the foreland area, and evaporite rocks, mainly gypsum, that characterize the central and the southern parts of the island. The carbonate and gypsum karsts show a great variety of surface landforms, such as karren, dolines, poljes, blind valleys, and fluvio-karst canyons, as well as cave systems. Karst areas in Sicily represent extraordinary environments for the study of solution forms. In addition, they are of great environmental value because they contain a variety of habitats that hold species of biogeographic significance. Unfortunately, karst areas are increasingly threatened by human activity, mainly in the form of grazing and other agricultural practices, wildfires, quarrying, urbanization, building of rural homes, and infrastructure development. The value of karst features has been recognized by the Sicilian Regional Government since 1981 when it enacted laws to create several nature reserves to preserve the peculiar karst landscapes, including caves. At present, the state of conservation of karst areas in Sicily may be considered to be at an acceptable level, yet numerous issues and difficulties need to be overcome for the effective protection and enhancement of karstlands.

Solution and recrystallisation processes and associated landforms in gypsum outcrops of Sicily

Abstract Four small areas of Messinian (Upper Miocene) age gypsum, outcropping in western Sicily, are described. Messinian age evaporites are found in Sicily over a 1000-km 2 area. Here, gypsum outcrops extensively as a consequence of soil erosion induced by human impact. Geomorphological maps show how the rocky surfaces are characterized by a wide range of forms. There are large, medium, small, and microsized forms, which can be identified as belonging to different morphotypes. The morphotypes can be classified into two main categories: those that originated by solution and those that originated through recrystallisation. Four areas, illustrated by geomorphological maps, were specifically chosen to describe a type of medium-sized form: dome-like hills. These medium-sized forms are covered by a mosaic of smaller forms, related to both the previous categories: different types of karren and of “expansion” forms. The types of karren can be explained as the results of the solution process under different hydro-dynamical behaviour; the dome-like hills and other related “expansion” forms are more difficult to understand. These “expansion” forms can be explained by the same process that leads to the development of gypsum tumuli. The outcrops of gypsum lacking soil cover and influenced by alternating seasonal water conditions of surplus and deficit are affected by both solution and recrystallisation processes. During the wet season, the water soaks into the rocky mass, filling all the fissures and pores of the outer rocky layer from a few centimetres to some metres below the surface. During the dry season, there is a capillary upward motion of the water solution. Near the surface, gypsum precipitates from the oversaturated solution, increasing the crystal size or forming new crystals. In this way, during the dry season, there is a pressure increase in the outer gypsum layers, which is responsible for the development of a “gypsum weathering crust” and characterised by many different forms such as gypsum tumuli, pressure ridges, pressure humps, and other related small forms. The crust may also lead to the development of mega-tumuli and dome-like hills. From the morphostructural point of view, the dome-like hills do not seem to be controlled by the strike, dip, or fissuring of the gypsum beds. Their evolution seems to be linked to the fact that on most of the dome surfaces, the weathering crust is evolving through a nearly isotropic field of stresses, resulting in volume increase in the outer gypsum layer.

Evaporite karst in Italy: a review

*jo.dewaele@unibo.it Citation:

Examples of Anthropogenic Sinkholes in Sicily and Comparison with Similar Phenomena in Southern Italy

A sinkhole, occurred in June 2011 and related to an underground quarry in the eastern sector of Marsala, is described in this paper as a case study (Figure 2). The site was selected for the availability of topographic data of the underground quarry, prior to the formation of the Abstract Anthropogenic sinkholes affect several built-up areas of Sicily (southern Italy) representing a great risk to people, buildings, and infrastructures. These phenomena are generally associated with the presence of ancient underground quarries for the extraction of calcarenite rock, used for building or ornamental materials. These quarries were poorly constructed and abandoned throughout history.

Geomorphological evolution of western Sicily, Italy

Abstract This paper proposes a morphoevolutionary model for western Sicily. Sicily is a chain–foredeep–foreland system still being built, with tectonic activity involving uplift which tends to create new relief. To reconstruct the morphoevolutionary model, geological, and geomorphological studies were done on the basis of field survey and aerial photographic interpretation. The collected data show large areas characterized by specific geological, geomorphological, and topographical settings with rocks, landforms, and landscapes progressively older from south to north Sicily. The achieved results display: (1) gradual emersion of new areas due to uplift, its interaction with the Quaternary glacio-eustatic oscillations of the sea level, and the following production of a flight of stair-steps of uplifted marine terraces in southern Sicily, which migrates progressively upward and inwards; in response to the uplift (2) triggering of down-cutting processes that gradually dismantle the oldest terraces; (3) competition between uplift and down-cutting processes, which is responsible for the genesis of river valleys and isolated rounded hills in central Sicily; (4) continuous deepening over time that results in the exhumation of older and more resistant rocks in northern Sicily, where the higher heights of Sicily are realized and the older forms are retained; (5) extensional tectonic event in the northern end of Sicily, that produces the collapse of large blocks drowned in the Tyrrhenian Sea and sealed by coastal-marine deposits during the Calabrian stage; (6) trigger of uplift again in the previously subsiding blocks and its interaction with coastal processes and sea level fluctuations, which produce successions of marine terraces during the Middle–Upper Pleistocene stages.

An Overview of the Hypogene Caves of Sicily

Karst in Sicily develops in both Messinian gypsum and Mesozoic or Tertiary limestone rocks. Caves are also found in the basalts of Mount Etna. Except for some rare cases, until recently most caves developed in limestone were considered to be of epigenetic origin. The discovery of gypsum in some of these caves, and especially detailed morphological studies, have allowed defining a hypogenic origin for a dozen of caves up to now. In some of these, the hypogenic evidences are very clear, while others remain in doubt because of the widespread presence of well-developed condensation-corrosion morphologies not necessarily related to hydrothermal fluids. This paper reports the present knowledge of hypogenic caves in the Island of Sicily.