Page 1 - valerio agnesi - geographical-phisical aspect Sicily

Sicily in the last one million years*

Valerio Agnesi

1 Geographical-phisical aspects of Sicily

The morphologic set up of Sicily, as regards complexity of geological structure, is
extremely varied and can generally be considered representative of different geomorpho-
logical contexts characterizing the Mediterranean area. The geological structure of Sicily
is schematically divided into three sectors:
1. chain sector, that develops along the northern cost of the island, from the Peloritani

Mountains to the Aegadi archipelago, and consists of geological bodies with different
lithologies tectonically overlapping.
2. foredeep area, that occupies almost the whole mid-southern area of the island, divided
into two sedimentation basins (Caltanissetta Basin and Castelvetrano Basin) separated
by the Sicani Mountains which represent the southern part of the chain.
3. foreland area, situated in the south–eastern portion and made up of mainly carbona-
ceous rocks of the Hyblaean area.
The chain, that representing the continuation of the Apennine is then called Sicilian
Apennine, divides into several reliefs. The easternmost one consists of the Peloritani
Mountains between Capo Peloro and Portella Mandrazzi, whose peaks seldom reach over
1,000 m. The highest summit (1,374 m) is Montagna Grande. They consist of a series of steep
reliefs, made up mainly of metamorphic rocks and, in the western sectors, of sedimentary
rocks in facies of Flysch. Westwards, the Sicilian Apennine continues with the Nebrodi
Mountains, usually higher than the forementioned peaks, reaching even 1,847 m with Mt.
Soro, characterised by smoother features for the outcrops of mainly clayey and arenaceous
rocks, highly erosive. The Peloritani and Nebrodi Mountains are drained by numerous rivers,
with mouth along Tyrrhenian and Ionic shores, characterised by steep slopes and reduced
length of the streams which flow throughout wide alluvial plains (fiumare).
West of the Nebrodi Mountains, separated by the valley of the Pollina River, is the
Madonie Mountains, made up of carbonatic and arenaceous–clayey rocks, reaching 1,979
m with Pizzo Carbonara, Sicily’s second highest peak.
The great diffusion of calcareous rocks had favoured remarkable development of Karst
that has widely shaped the high Madonie’s landscape, and has originated many caves,

* From a paper by Agnesi & al. (1997), which is an expanded and updated version of the manuscrip prepared for
the preliminary seminar to the Sicilian Iter Mediterraneum.
English translation of original texts by Dr. A. M. Terranova (Palermo).