It’s not hard to imagine why Romans and Medieval Christians believed the Phlegraean Fields, also known as the Campi Flegrei, was a gateways to hell. The eight mile-wide caldera west of Naples is home to cinder cones, boiling mud and steamy geysers, indicating that somewhere below the surface, the supervolcano is still geologically active. But now, a new study in the journal Nature Communications suggests that the area may be a little more active than nearby residents would like, reports Sarah Kaplan for The Washington Post.

According to the study, the magma under the caldera is degassing, or releasing water-rich gases that could cause the rock above it to fail, leading to an eruption. In this study, the researchers identify what is known as “critical degassing pressure,” CDP, of the Campi Flegrei, which is the point at which researchers believe an eruption can occur, the study's lead author Giovanni Chiodini, a volcanologist at the National Institute of Geophysics in Rome, tells Kaplan. It's also extremely important in estimating the likelihood of an eruption, Kaplan reports.

In recent years, scientists have noticed changes in the Campi Felgrei, which has registered seismic activity and deformations often seen before eruptions. That caused Italian authorities to raise the alert level on the volcano from green to yellow in 2012, meaning the area needs scientific monitoring. Kaplan reports that researchers have observed “bradyseism” events, or slow movements of the earth’s crust in this region for half a century, which suggests that molten rock is flowing into the caldera’s magma chamber.

Chiodini says other volcanoes including Rabaul in Papua New Guinea and Sierra Negra in the Galapagos “both showed acceleration in ground deformation before eruption with a pattern similar to that observed at Campi Flegrei,” according to the Agence France-Presse.

But Chiodini points out that doesn’t mean Naples and its 500,000 residents are in immediate danger. “In general, unfortunately, volcanology is not a precise science,” he wrote in an e-mail to Kaplan. “We have many uncertainties and long-term provisions are at the moment not possible! For example, the process that we describe could evolve in both directions: toward pre-eruptive conditions or to the finish of the volcanic unrest.”

If the Campi Felgrei does erupt, it may be a minor nuisance or a globally-significant catastrophe. According to the AFP, the volcano had its last minor eruption in 1538. But 39,000 years ago a massive eruption (Europe’s largest in 200,000 years) likely upset the climate, causing a “year without a summer”—similar to the eruption of Mt. Tambora in 1815. Some researchers have argued that the cold snap caused by the eruption could have pushed the already ailing population of Neanderthals in Europe to extinction, though other researchers dispute this claim.

One group of scientists is hoping to get a better grasp of what is happening beneath the Campi Flegrei. A group called the Campi Flegrei Deep Drilling Project is currently cutting a 10,000-foot borehole into the caldera below a decommissioned iron factory. That project, however, has been on again off again over the last half decade over the public’s largely unfounded fears that drilling into the volcano will trigger an eruption.