This Supervolcano Has Not Erupted Since 1538 — Now It’s Slowly Showing Signs of Life

The city of Naples sits on the mouth of a thumping volcanic monster. Locals here walk on live electric wires that could explode at any moment. On roads and streets, steaming manholes are often seen spewing swirls of white smoke as if a monster is smoking a cigarette. At night, when people try to go to sleep, they are restless because the volcanic monster could burst its mouth wide open and rupture the floor of their house. Oftentimes, their windows rattle. But even without cracking, the floors and the grounds here keep on rising and falling, like the monster gulping down soda to cool his throat.

Fear travels through the city like red blood cells running through its veins. The culprit? Campi Flegrei, nicknamed “Phlegraean Fields.” The supervolcano has been sitting beneath this southern Italian town, untamed. But now, it seems to be reawakening after centuries of dormant sleep, according to a report published in Geology.

A few years back, Antonio Costa, an expert in volcanic risk, visited a deserted building in Naples and was enraptured by what he saw, as shared in an episode of NOVA PBS. Inside, the walls and floor of the building were blanketed in thick layers of ooze. Here and there, the erupted volcano had seared holes into these walls, which made them resemble scummy little caverns. In the air, he sniffed the acrid smell of sulfur. This hot, slimy coating on the walls was earlier a bubbling splatter of magma, gas, and dissolved minerals that cooled down after the volcanic eruption.

Millions of years ago, the volcano was quiet. But deep within its dark belly, hot scorching magma stirred furiously. Over the next few years, the churning magma started to rise. And as it arrived at the volcanic mouth, it exploded, ejecting volleys of minerals, ashen particles, dust, and metals into the skies. After the explosion, a void was left in the dark belly, which caused the volcano’s mouth to droop down into a crater, today known as the “caldera.” Spanning 125 miles, the caldera blazes under the bay of Naples and the islands of Capri and Ischia in the city’s outskirts.

After its last eruption in 1538, Campi has been active for the past 39,000 years and now shows the potential for an enormous explosion. The researchers arrived at this conclusion after suspecting unusual quantities of carbon dioxide in the atmosphere. Excess carbon dioxide is often a haunting omen that indicates that the notorious volcano nearby is up to its next mischief. It signifies that somewhere below the ground, the magma is beginning to rise and is therefore exhaling these gassy swirls.

The reason could be agitating magma or unrest in the hydrothermal fluids. No one knows for sure, but the team estimated that about 20 to 40 percent of this unrest stemmed from a non-magmatic source. A spike in carbon dioxide was a clue that hinted that the hydrothermal system churning in Earth’s cauldron was getting hotter and pressurized, which implied that it could burst and shake awake the volcanic monster Campi.

“Episodes of caldera unrest worldwide present major challenges for individuals, scientific institutions, and local authorities, particularly in densely populated regions,” researchers wrote in a recent study published in the journal Science Advances. They warned that if Campi erupts, the traditional risk management strategies, such as displacing residents, could fall short, causing severe economic and social disruptions. Time is ticking. The smouldering mouth of Campi, the volcanic monster, is already salivating at the prospect of devouring up the entire city in its lolling flames.