 |
|
|
The Alcantara river basin covers an area of about 573 square
km; its main branch springs from the crags of Chirico,
Musarra (1,254m above sea level), Pietracavallo, Serra
Mosca, Rocca S.Giorgio, Porcheria, Monte Parco, and Punta
Inferno (1,480 m above sea level) mountains and its waters
flow between the Etna volcano in the south and the southern
spurs of Nebrodi and Peloritani mountains in the north,
reaching the Ionian Sea after about 52 km. The basin is
characterized by sedimentary, metamorphic, and volcanic
lithotype outcrops, structurally linked to the sedimentary
sequences of the Sicilian Maghreb Apennines, to the metamorphic
rocks of the Calabro Peloritano Chain – ordered in
layer systems of crystalline and metamorphic soils and
sedimentary units consisting of scaly clays, overlapping
the flysch of Mt. Soro and the Numidian Flysch - and to
the volcanite of Etna. On the left section, the clayey-arenaceous
alternations of the flysch of Capo d’Orlando and
Mt. Soro are well represented, together with low-metamorphic
level rocks, chaotic clay soils, and alluvial deposits
at the bottom of the valley. Along the Valley there are
coarse sandstones often merged in various meter-long banks.
As far as the volcanological aspect is concerned, the Alcantara
riverbed was interested during prehistoric and proto-historic
times by lava flows which repeatedly obstructed or changed
its course.
Near the basaltic lithotypes, the watercourse locally created
the characteristic “ravines” with dozens of
meters high walls characterized by sub-vertical column
structures that can be “organ-pipe shaped”,
slightly bent and “harp-shaped”, “fan-shaped”,
placed horizontally as a stack of wood or chaotically fractured,
more or less evident according to the thickness and the
cooling time of the lava.
In the upper part of the river basin the lake Gurrida formed,
the sole example of lava-dammed lake in Sicily deriving
from a lava flow obstructing the bed of the river Flascio.
The presence of Mt. Moio led at first to ascribe to one
only eruption the magma that, flowing in the paleo-riverbed
of Alcantara, would have reached the Ionian Sea at Capo
Schisò. Recent petrographic, petrochemical, and
geomorphological research activities have led to distinguish
three eruption events coming from volcanic vents opening
in the area of Mt. Dolce, on the middle-lower slope of
Etna, characterized by an effusive activity, while Mt.
Moio is exclusively characterized by an explosive activity.
In the Alcantara basin, the geological formations of volcanological
interest are the small cone of Moio with its stratified
pyroclastic rocks, the gorges with the basaltic prisms,
the pahoehoe Hawaiian lava of Contrada Mille Cocchita,
and the scoriaceous lava of 1981. |
|
