Seismic unrest at Italy’s Campi Flegrei volcano raises concerns

Italy’s Campi Flegrei volcano, one of the most dangerous in the world, is showing growing signs of activity.

Recent studies suggest its past eruptions were more frequent and powerful than previously thought. Ongoing seismic swarms and ground deformation raise concerns about future risks.

Driving the news:

• A new study identified a massive eruption in the Campi Flegrei region 109,000 years ago, similar in scale to the caldera-forming explosion 40,000 years ago.
• Another study found a sharp increase in burst-like seismic swarms and ground uplift since 2021, pointing to continued volcanic unrest.
• Scientists say a large-scale eruption is unlikely in the short term, but the findings provide insight into the volcano’s long-term behavior.

The big picture: Campi Flegrei is a massive caldera spanning the Bay of Pozzuoli just west of Naples. Unlike a single volcano, it consists of a network of craters and fumaroles. The region is home to 500,000 people, making any potential eruption a significant threat.

New research uncovers previously unknown eruption in Campi Flegrei region

A recent paper published in “Communications Earth & Environment” describes the Maddaloni/X-6 eruption, which occurred approximately 109,000 years ago.

• The eruption was nearly as large as the one that formed the caldera 40,000 years ago.
• It produced an enormous layer of ash and pyroclastic flow deposits, covering large parts of the Campanian Plain.
• Study lead author Giada Fernandez, a researcher at Sapienza University of Rome, said, “Despite the relatively large uncertainty, the Maddaloni/X-6 eruption may be, by a wide margin, at least the second-largest explosive event [to have] occurred in the Campi Flegrei area since 109,000 years ago.”

What they’re saying:

• Volcanologist Christopher Kilburn from University College London, who was not involved in the study, said, “It changes the perception of the risk of Campi Flegrei being active again.”
• Researchers are debating whether the eruption originated from Campi Flegrei itself or from nearby volcanic fractures, a distinction that could shape future monitoring efforts.

Increasing seismic swarms, ground uplift suggest ongoing changes beneath Campi Flegrei

Since 2021, scientists from Italy’s National Institute of Geophysics and Volcanology (INGV) and the Institute for Electromagnetic Sensing of the Environment (CNR-IREA) have recorded a sharp increase in seismic activity.

By the numbers:

• 18,500 earthquakes occurred between 2021 and 2024, with magnitudes ranging from -1.6 to 4.4.
• The strongest quake, a magnitude of 4.4, struck in May 2024 at a depth of 2.6 kilometers (1.6 miles) beneath the Solfatara area.
• Ground uplift has reached 1.2 meters (3.9 feet) since 2005, with a monthly rate of 2 centimeters (0.8 inches) recorded in May 2024.

Zoom in:

• The burst-like seismic swarms, which occur in rapid sequences, have become more frequent since 2021.
• A geodetic anomaly has emerged in the Mt. Olibano area, where uplift is occurring at a slower rate than in surrounding regions, signaling complex underground processes.

What they’re saying:

• INGV researcher Flora Giudicepietro, lead author of the “Nature Communications” study, said, “These seismic swarms, defined as ‘burst-like,’ manifest themselves with a rapid sequence of small earthquakes that makes it difficult to distinguish the individual events in the seismogram.”
• Researchers note that similar swarms in other volcanic systems have been linked to phreatic explosions or critical phases of unrest.

Scientists detect increased hydrothermal activity, raising concerns about future eruptions

Scientists have observed growing hydrothermal activity in the Solfatara-Pisciarelli system, adding another concern to the situation.

• CO2 emissions reached 1,557 tons per day in 2024, matching levels seen in active volcanoes with open conduits.
• Seismic swarms are concentrated in the hydrothermal area, suggesting a connection between fluid pressure fluctuations and ground instability.
• “In some studies conducted in other volcanic contexts, ‘burst-like’ seismic swarms have been associated with phreatic explosions and critical phases of unrest,” researchers noted.

What this means for the densely populated Campi Flegrei region and ongoing monitoring efforts

• Campi Flegrei remains under a Yellow alert level, indicating continued volcanic activity requiring close surveillance.
• Kilburn said the entire Campanian Plain, not just Campi Flegrei, should be considered a potential eruption zone.
• Authorities have reinforced emergency preparedness, but evacuating the region’s dense population remains a logistical challenge.

What comes next as scientists monitor Campi Flegrei’s shifting volcanic behavior

• Researchers will continue tracking seismic, geochemical, and geodetic data to refine hazard assessments.
• Future studies will determine whether recent activity signals a lasting shift in the volcano’s behavior or a temporary period of unrest.
• The focus remains on improving early warning systems and risk management strategies to protect those living in the region.