After walking along the tunnel for about 70 meters, we notice that the shape of it has changed significantly. At this stage, the tectonic aspect of the profile is evident. In fact, the triangular shape of the vault is given by a difference in angles between the position of the overlying layer(left), significantly different from that of the substrate (right wall). As we have said earlier, the rounded shape of the vault was given by the high influx of water coming from the underground source, which at this point we have passed. We can also see here another important aspect about the modern life of the cave: new calcite formations are gradually covering the dust left by the passage of traffic vehicles, along with the residues of exhausting fumes. The white shiny colour are made by pure calcium carbonate deposited after road closure.
Generally we are told the story of formation growing one centimetre every a hundred or a thousand year according with the mood of the tourist guide. However, growth speed is due to many different elements, such as the rate of Carbon Dioxide (CO2), temperature on the site and flowing rate of water. On San Giovanni’s cave, we have some 15 years old fences already covered by over a centimetre of formation.