Page 5 - valerio agnesi - geographical-phisical aspect Sicily

Bocconea 17 — 2004 27

A general tectonic raising of the island is well documented after Eutyrrhenian (125,000
years B.P.); as a matter of fact, throughout Sicily there are Strombus deposits located at dif-
ferent altitudes (even over 100 m above actual sea level in the Peloritani area) which lead
to the hypothesis of areas characterized by different raising values, corresponding to
crustal sectors with different geodynamic evolution: the Aegadi Islands, with a raising rate
of 0,02 meters/per one thousand years (m/ka), the northern sector, with a raising of ca.
0,19 m/ka, the south-eastern sector, with rates of 0,2-0,7 m/ka, as well as the Peloritani area
that raised with velocity ranging from 0,6 to 0,99 m/ka (Cosentino & Gliozzi 1988). The
progressive increase noticeable going from west to east clearly shows the differential rais-
ing the island has undergone in the last 120,000 years, phenomenon due to greater geody-
namic activity of the Calabro-Peloritanous arc, responsible as well of the intense seismic
activity existing in the area of the Stretto di Messina.

In this period, Sicily is also the scene of deep geographic changes connected to an
intense volcanic activity, still persisting. Etna’s great volcanic building, extremely signifi-
cant in the island’s present geography, starts its formation ca. 700,000 years ago with sub-
marine activities, as basal hyaloclastites show, occupying the wide pre-Etna gulf
(Malatesta 1985;); such gulf was situated between the Peloritani and the Hyblaean
Mountains and during the Lower Pleistocene probably extended till today’s Piana di Gela,
being thus a sea sound connecting the Ionic Sea with the Canale di Sicilia. The origin of
the Aeolian archipelago is connected to more ancient volcanic activities; in fact, radio-
metric dating carried out on submarine volcanoes of the archipelago’s western sector have
suggested the starting of submarine vulcanism at 1.3-1.1 Ma, while, as for the more

ancient islands, they emerged ca. at 0.6-0.5 Ma (Savelli 1984). The various buildings,
according to activity and orientation of deep crust fractures to which they are connected,
formed in two different periods. The first, dating 0.33 Ma, saw the coming forth of Alicudi,
Filicudi, Panarea and, partially, also Lipari and Salina. The second period, dating 0.15 Ma,
saw the development of Lipari and Salina and then Vulcano and Stromboli, both still active

volcanoes (Malatesta 1985).
The Ustica island, instead, was originated by the eruptive activity of the late phases
(0.5-0.4) of the stretching tectonics connected with the sinking of the Tyrrhenian basin.
The same age dates the beginning of submarine eruptive manifestations in the Canale
di Sicilia causing the formation of Pantelleria, while more ancient is the volcanic activity
that originated the nearby Linosa, about 1 Ma.
Some paleogeographic information, for a time interval included between some 6-
700,000 years and 450,000 years B.P., result from the study of fossil mammals on the insu-
lar faunal complex of Elephas falconeri, the pigmy elephant exclusive of the paleo
Sicilian-Maltese archipelago.
Paleoambiental information deducible from this association, whose elements have been
modified by processes of endemic evolution, is rather modest, even though the presence of
the insectivorous Crocidura (shrew) would indicate a climate with aridity characters.
Mammals population consisted, besides the forementioned elephant, of three species of
endemic micro mammals (two kinds of dormouse and the shrew) and of an otter. Among
reptiles, there is a typical giant tortoise. Both the characteristics of the existing species and
the structure of association, in which there are neither big size mammals nor big predators,
show a marked endemic character, proving that the paleo Sicilian-Maltese archipelago was