A LOOK AT THE VOLTERRA CLIFF (TUSCANY, ITALY) FROM THE MIDDLE AGES TO THE EARLY MODERN AGE AND THE ONSET OF MODERN GEOLOGY

Since the Middle Ages, the horizontal Pliocene strata upon which the Etruscans built the town of Volterra— a coarsening-upward marine succession formed by the triplet mudstone-sandstone-shelly calcarenite — formed the subject of inquiry for philosphers and naturalists seeking evidence of Earth’s past states. In 1282 Restoro d’Arezzo, while outlining the focal points of his Aristotelian cosmology, considered fossils there as evidence of the Noachian flood. Two centuries later, Leonardo da Vinci, author of a Renaissance theory of the Earth, possibly knew of the outcrop, as hinted by his earliest known drawing of 1473. In 1669, the historical significance of the Volterra sedimentary succession was commented upon by Nicolaus Steno in De solido intra solidum naturaliter contento, wherein he also outlined the stratigraphic principles of superposition, lateral continuity, and original horizontality. The geometry and fossil content of the Volterra sandstones disclosed the extent of the Tertiary sea in the eyes of eighteenth century travellers and early geologists in their Grand Tour of Italy. The Stenonian legacy survived in the writings of Giovanni Targioni and Nicolas Desmarest, who visited the cliff in 1753 and 1765, respectively. The first to describe the succession in modern geohistorical terms was Giambattista Brocchi in 1812, commenting upon the landscape as seen from the top of the belltower of the cathedral. His Subappennine Fossil Conchology, published in 1814, brought the outcrop to the attention of the European public, fostering the use of the concept of “Tertiary” strata which he had inherited from his Italian predecessors. Early British geologists who learned about Volterra were William Buckland, George Greenough and, later on, Charles Lyell. From France, Alexandre Brongniart came to see the outcrop with his own eyes in 1822. The Volterra cliff, thanks to available documents that deal with its geological interpretation, uniquely testifies to the unrolling of visions of Earth through at least 740 years of human curiosity about natural history.