Geology and geomorphology

    The first morphological element to be recognized in the Diptych was the small hill on the back of the painting portraying Federico da Montefeltro.

    It’s Mount Fronzoso, a small pyramid shaped hill right at the edge of the alluvial plane of the Metauro River, between Urbania and Sant’Angelo in Vado. In today’s landscape, elements follow the same pattern as in the painting and they match the dense wood and the grassland. The woods are luxuriant thanks to the chalky and marly substrate of the Bisciaro formation, whereas the grassland grows on marlier lithological substrates, which prevent the growing of trees and plants. The gritty texture and dark colours that can be observed right where the river flows are very different from the uniform texture and light colours on the other side of the painting.

    The geomorphology of the landscape in: Ritratto di Federico da Montefeltro by Piero della Francesca

    The only morphological element that seems not to correspond to the landscapes in the Duke’s portrait is the wide river bed, twisting and turning until it flows into a vast lake portrayed in the close up.

    In today’s landscape, instead of a lake, we admire the Metauro valley.

    This wide lake was created artificially in the past, when Duke Federico da Montefeltro ordered to create a lock right below the bridge called “Ponte del Riscatto”.

    Traditional stories linked to the area confirm the presence of this structure allowing the Duke to reach his hunting court (Il Barco) by boat.

    Some recently discovered and faithful reconstructions of the town of Urbania show the signs of these infrastructures as well as differences in height before and after the bridge.

    A specific geomorphological survey, with an analysis of stratigraphies based on geognostic surveys, was carried out. The aim was that of proving the existence of this specific lake. The study allowed us to find evidence that the position of the lake, although not directly registered because of a lack of outcrops, was in line with the heights of that same land 500 hundred years ago.
    After a cooling phase called “the Little Ice Age” the area was subject to intense colluviation made by slopes and to major sedimentation carried out by small rivers.

    The devastating floods, widely mentioned in historic documents, due to the worsening of climate conditions, might have led to the opening of this lock in order to avoid dangerous overflows.

    As a result, the river got all of its erosion power back and contributed to the major erosion process that can still be seen today.