Page 3 - copy_of_FalconiS8.7

3

3. Study area

The study is focused on Cala Rossa, Cala del Bue Marino and Cala Azzurra, lo-
cated in the eastern portion of the island, in areas classified with high and very
high landslide hazard (Regione Siciliana, 2006). A calcareous sandstone rich in
marine fossils (bivalves, corals ...), with nearly horizontal layers of about half a
meter thickness, are outcropping all over the area (fig. 2). In the west side of Cala
Rossa and Cala Azzurra, underlying the rock slab, whose thickness varies from
few meters up to 30 and more meters, plastic clays are outcropping. The overlap-
ping of hard rock masses on a plastic substratum leads to mechanical instability
due to the diverse response of the materials to the applied perturbations, such as
man-made excavations, weathering or erosion (Gigli et alii, 2012). The mass
movements can be classified into two different but strictly interconnected typolo-
gies: lateral spread and rock blocks fall (Cruden, Varnes, 1996)

Figure 2 – Bivalves (left) and layers (right) in the calcareous sandstones

4. Methodology

The monitoring activity was launched in October of 2012, will end in April 2014
and is led through the use of direct and indirect instruments. The direct
measurements are made through mechanical joints gauges of different kind (tell-
tale, removable jointmeters, 3D jointmeters) in relationship with the different
characteristics of the walls, discontinuities and types of movement (one-
dimensional or three-dimensional). Altogether were installed 70 mechanical
jointmeters, distributed along the cliffs of the three bays and also within the
numerous cavities that open inside of the cliffs. The indirect measurements are
carried out through laser scanner and GPS instruments with two substantially
different purposes. The laser scanner is used for the acquisition of areal data in all
the three areas object of the study and will permit to identify any movements of
each of the points highlighted by the laser beam along the entire cliffs. For the