Variazioni climatiche e crisi dell'ambiente antropizzato

Abstract

Geoarchaeological research carried out in the Mediterranean basin (North Africa, France, Italy and Egypt) provide important data on natural environmental variations during historic periods (from 2500 y B.P.). Variations are related to periodic climatic changes, which have affected the Mediterranean basin approx. every 500 years. Within these climatic cycles, short climatic crises lasting 100-150 years have been identified in the latitudes ranging between 41° and 35° N. Arid-desert crises are identified by sand dunes and carbonate crusts covering historical settlements dating to the 2nd - 4th centuries A.D. and between the 11th - 14th centuries A.D. (Velia; Sibari; Campanian Plain in the area of the River Volturno; Mutina in the Po Plain; the River Arno plain where a coastline progradation of some kilometers has been identified). Cold-humid crises are characterized by alluvial and colluvial sediments sometimes >10 m thick, covering many archaeological sites dating to the 6th-4th centuries B.C., the 5th-8th centuries A.D. and the 16th-19th centuries A.D. where the progradation of the shoreline extended many kilometers during these crises. In the south (under 30°N) many humid periods are recorded at the same time when arid-desert conditions prevailed in the northern part. The climatic variations which are responsible for these environmental crises are thought to be related to cyclic variations in solar activity controlling the migration (between 8°-10° latitude) of climatic strips northward and southward.