Fenomeni d’instabilità presso l’eremo di Carbaiolo (Arezzo, Toscana)

Conditions of Instability near the Hermitage of Cerbaiolo (Arezzo, Toscana, Italy)

Abstract

The hermitage of Cerbaiolo, founded in 700 AD and currently a Franciscan monastery, is located some 7 km from the village of Pieve S. Stefano (Ar), on the southern edge of a limestone plate (Calpionelle Limestone - Cerbaiolo Unit), which develops along n N-S axis, with a dip of bedding toward NW. The plate is completely surrounded by the clay of the Sillano formation. The marked contrast in competence of the two formations gives rise to mechanisms of instability producing differing effects on the three sides of the perimeter of the hermitage due to mechanical characteristics of the rocky mass. The entire cliff is intensely fractured due to both tectonic and gravitational factors. The clay of the Sillano formation is affected by flows and slumps. In addition to the crumbling and toppling of small pieces, the larger blocks, separated from the underformed substrate, seem to be moving in lateral spreads of the deep-seated block slide type as inferred by trenches in the high part of the slope and swelling in the lower part.