I'm near Naples, Mount Vesuvius and Pompeii, in the far lesser-known Italian city of Pozzuoli which lies on a huge magma caldera which, over millennia, has created a volcanic landscape known as Campi Flegrei. Lately, this volatile geology has triggered thousands of small earthquakes.

I'm invited to follow scientists at the Vesuvius Observatory from the Italian Institute of Geophysics and Vulcanology as they monitor activity inside a crater whose gas emissions seem particularly intense. "In these areas, gas emissions are coming from deep below ground," says Mauro Antonio Di Vito, the Institute's director, as we walk around the fumaroles (vents in the surface of the Earth where hot volcanic gases and vapours are emitted).