Scientists are sounding the alarm that a huge volcano could be inching ever closer to a cataclysmic eruption. The volcanic area known as Camp Flegrei near Naples, Italy doesn’t resemble a typical cone-shaped volcano, but is instead a complex of hotspots over a large geographic area that would result in a supervolcano if it erupted.

In a new study published in Nature Communications, scientists say this supervolcano near the densely populated Naples area may be waking up and getting every closer to a “critical state.” The volcano lies mostly underwater, and its characteristics are similar to that of the one at Yellowstone, in that it isn’t very recognizable as a volcano but it would cause massive destruction if it erupted.

Scientists say that the magma at Camp Flegrei is approaching critical degassing pressure (CDP), and a sudden release of gases in the near future could trigger an epic eruption. That doesn’t mean it will happen anytime soon, but it could. The science just isn’t exact enough for us to know when a volcano will erupt.

In response to the news, Italy has bumped the volcano threat level from green to yellow, or from quiet to requiring scientific monitoring.

“During the reawaking of a volcano, magmas migrating through the shallow crust have to pass through hydrothermal fluids and rocks,” the paper’s abstract states. “The resulting magma–hydrothermal interactions are still poorly understood, which impairs the ability to interpret volcano monitoring signals and perform hazard assessments. Here we use the results of physical and volatile saturation models to demonstrate that magmatic volatiles released by decompressing magmas at a critical degassing pressure (CDP) can drive volcanic unrest towards a critical state.

“We show that, at the CDP, the abrupt and voluminous release of H2O-rich magmatic gases can heat hydrothermal fluids and rocks, triggering an accelerating deformation that can ultimately culminate in rock failure and eruption. We propose that magma could be approaching the CDP at Campi Flegrei, a volcano in the metropolitan area of Naples, one of the most densely inhabited areas in the world, and where accelerating deformation and heating are currently being observed.”