Landsliding in the Crati basin, Calabria, italy

Abstract

The Crati basin is flanked on either side by crystalline metamorphic rocks that have been subjected to intensive folding, shearing and crushing, and have hence lost much of their resistance. The basin is filled with Neogene alternations of sand, clay and conglomerates, in a (sub)horizontal position. It is a tectonic depression separated from the metamorphic surroundings by major faults. Post-Calabrían uplift of around 1000 metres, with differential movements superposed, accounts for rapid erosive incision that undercuts the slopes at the foot. Slopes have a further reduced stabitity on account of the loss of coherence in the metamorphics, of frequent faulting and of exposure of water in the slope face, often trapped by Tertiary clay layers and exposed after erosive incision. The main fault-scarp zones separating the basin from the surrounding metamorphics are zones of increased weakness. AII this accounts for an accumulated potential slope instability. Unstable slope zones are identified on air photos, whether they are presently moving or not. Zones in actual movement invariably make part of such larger zones of instability. This movement is mostly triggered off by cutting in the slope for purposes of road construction, frequent in this area under rapid development. Nine characteristic landslides are discussed. The recognition at an early stage in the planning phase, of potentially unstable slope zones from air photos - followed by field verification - allows the foreseeing of difficulties of construction and maintainance of communication lines. This may thus contribute to prevent disasters.