Deciphering the effects of human activity on urban areas through morphostratigraphic analysis: The case of Pisa, Northwest Italy

The type, thickness, and volume of anthropogenic deposits buried beneath long-settled cities are good indicators of the human impact on urban environments and topography. Pisa is a multilayered city settled since Etruscan times in the lower Arno Plain. Stratigraphic and geomorphologic data from the urban subsurface show that Pisa today is located on a mound (ca. 4 m high) made up dominantly of anthropogenic deposits. Two types of anthropogenic facies are distinguished: human-modified deposits of Etruscan Age and made-ground deposits dated since the Roman Age onward. Integrating subsurface stratigraphy with ancient ground-level topography, we reconstruct the evolutionary phases of the Pisa urban landscape subject to a dominant human influence. Urbanization processes started in Etruscan times, as testified by the lower boundary of the anthropogenic succession (Pisa archaeosphere). The formation and the highest increase in elevation of the Pisa mound, which is still growing, occurred during the Roman and the Middle Ages. At the same time, the urban fabric moved southward, toward the Arno River, and a thick anthropogenic succession accumulated in the city sector where an ancient ring of walls had been hypothesized. However, the highest acceleration in the urban ground growth rate is recorded since A.D. 1950 onward, corresponding to the Anthropocene “Great Acceleration.”.