Crete Senesi means "Senese clays" and these give the soil of parts of the Val d'Orcia south east of Siena a distinctive grey colouration. This characteristic clay, known as mattaione, represents the sediments of the Pliocene sea which covered the area between 2.5 and 4.5 million years ago. Erosion of the soil has played a major role in the formation of the landscape, with the clay laid bare and forming craggy badlands known as calanchi and clay knolls called biancane or mammelloni.October 2013 | Tuscany, Italy
