The last significant eruption was in 1538. Compared to these previous two events, it was tiny. It was also big enough to throw ash and pumice 5.5km high. As the column collapsed, it created a “new mountain” (dubbed, quite literally, Monte Nuovo), measuring 123m high – and burying a village beneath it. If this happened today, in the vicinity of Italy’s third-most-populous city, Naples, the damage would be severe.
So what is the possibility of such an eruption happening in our lifetimes?
“Obviously we can’t make estimates,” Morra said, almost languidly. “We know that an active volcano, any active volcano, can erupt. Clearly, in our heart – we hope not.” I looked worried. “Have courage!” he said. “Like Vesuvius, Campi Flegrei is continuously monitored by colleagues at the Vesuvian Observatory, the oldest volcano observatory in the world. This can make us feel more tranquil.”
Close monitoring means an eruption can be predicted months in advance. With enough warning, the hope is that the metropolitan area can be safely evacuated.
Signs of a pending eruption aren’t the only data that volcanologists collect. The Vesuvian Observatory was also the first to discover, and chart, a phenomenon known as “bradyseism”: the slow rising, and sinking, of land over time. As the magma in Campi Flegrei’s massive magma chamber moves 3km below ground, so does the land above – sometimes significantly. Over the last 15,000 years, the movement of the magma has pushed the land above it upward by some 90m. At the same time, other parts of the caldera have fallen.
As a result, like Vesuvius, Campi Flegrei has given the area around it much of what makes it special: its volcanic rocks, soft and easy for building; its volcanic soil, rich with nutrients for vineyards and lemon groves; even the crescent shape of its coast, providing a gulf for splashing and sunning.
But what the supervolcano has given the area, it also can take away – even without an eruption.
On the eastern edge of the caldera, the above-ground archaeological site of Baiae overlooks the sea. A layer-cake of arches, walls and terraces, it was once the ultimate holiday spot for rich and aristocratic Romans, a kind of Las Vegas of the ancient world. Now stripped of most of their marble, frescoes and sculptures – many of which are now at the Archaeological Museum of Campi Flegrei – the buildings look little like they would have millennia ago. Graceful capitals, shorn of their columns, and stucco decorations, dotted with cherubs and swans, hint at its former opulence.