The Cave of the “Fossil Tree Trunks”
The Cliff of Orvieto contains countless treasures and one of the most fascinating is the evidence of a far-distant past, way before man appeared on the scene. In some of the caves in the sides of the tufa cliff there are cylindrical cavities, some in a vertical position, others slightly slanted, either completely empty or filled with a dark material, oleaginous to the touch, reminiscent of coal. What we have here is none other than the remains of the trees which were once part of a dense wood that stood the Cliff now rises up over the plain. They tell us that before the Volsini Mountains erupted, the environment here was completely different. The Pliocenic Ocean, to which numerous fossils in the clays at the base of the Cliff bear witness, had given way to an environment with a wealth of rivers and lakes and with woods all around.
Around 320,000 years ago these trees were covered with volcanic matter which slowly carbonized them, but left them in a recognizable form. We see them as they were when they were living trees, for the eruptions that incorporated them were not sufficiently violent to destroy them. In some, if you look carefully, you can see the growth rings, while others have left the imprint of their bark in the tufa. They were discovered when pozzolana, used for building material, was being quarried. Undoubtedly those digging here came upon these remains and had no idea of what they really were. Parts of the trunk were removed while the rest remained imprisoned in the rock. Sometimes the water that percolated through the tufa mass eroded and ate away the coal, leaving only an empty cylindrical cavity. The trees were probably mostly conifers, although they have not as yet been studied more in depth. But we do know that they are rare and important evidence of the history of this region.