Campi Flegrei, which means in Italian "burning fields", last erupted in 1538 that lasted for eight days. This eruption created the mountain Monte Nouvo. Before this, scientists speculated more eruptions happened during pre-historic eras. One of which considered the largest volcanic episode in the history of Europe over that time.

According to National Geographic, this huge supervolcano situated in Naples metropolitan with half million people inhabiting is currently being observed. After almost 500 years, the super volcano may have wake up. Scientists reported in the journal Nature Communications this week that it is approaching to a critical state.

"We propose that magma could be approaching the CDP (Critical Degassing Pressure) 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," wrote by scientists led by Giovanni Chiodini of the Italian National Institute of Geophysics in Rome.

Although the time of possible eruption is not certain, scientists still warned that a sudden release of hot magmatic gasses which could trigger a large eruption could occur any time in the near future. Italy government's response is the raising of volcano threat level from green to yellow (green, means quiet while yellow, means requires scientific monitoring), The Guardian reported.

It can be recalled that a known volcanic eruption had also occurred partly in this area in 79 AD, specifically in the Bay of Naples as recorded by Pliny the Younger, a Roman administrator and poet. That eruption cost the lives of many people, 1,500 remains were unearthed, but the total casualties are still unknown.

James Quick, geologist at Southern Methodist University in Texas said that there will be another supervolcano eruption. He said referring to super volcanoes in Sesia Valley in the Italian Alps. And it was found just recently.