THE STABILITY OF MONUMENTS OVER COASTAL CLIFFS IN THE BAY OF NAPOLI

SUMMARY: the instability of coastal cliffs along the shoreline of the bay of Napoli and its islands often threatens the integrity of monuments existing at the top of the cliff. In most cases the cliff is made by Neapolitan yellow tuff, a soft volcanic rock, and the instability is triggered by the erosive action of sea waves. The cases of Castel dell'Ovo and of three churches belonging to the ancient village of Terra Murata on the island of Procida are reported. Instrumental monitoring of some fissures shows in all cases cyclic displacements, essentially connected to thermal variations, without long term increase. The failure of the cliffs and of the overlying buildings occurs thus suddenly, without forewarnings. The possible preventive and remedial measures are briefly discussed