Hundreds of tremors, with the strongest being a 4.2-magnitude earthquake, have shaken a densely populated area west of the Italian city of Naples in recent weeks.
Experts at the National Institute of Geophysics and Volcanology have warned authorities and residents that tremors could intensify in the near future, noting that this kind of seismic behavior is not new to the volcanic area.
‘The seismic activity has been intensifying for months. We have observed over 3,000 tremors since the start of 2023,” Dr. Gianfilippo De Astis, senior researcher at INGV, told The Associated Press.”Only 65, however, were above a 2.0 magnitude.”
The city of Naples is surrounded by three active volcanoes: the island of Ischia and Campi Flegrei to the west, Mount Vesuvius to the east.
The Campi Flegrei or Phlegrean Fields are part of a supervolcano that erupted 37,000 and 15,000 years ago. These two supereruptions formed a 12-kilometer-wide caldera as the ground collapsed over the partially emptied magma chamber. In more recent times there have been 56 smaller volcanic eruptions, with the last happening in 1538.
The area is still active today, with widespread hydrothermal activity and seismic swarms registered in the 1950s, 1970s, 1980s and since the year 2000. The ground also slowly rises up and sinks down again—a process known as bradyseism—every few decades. The coastal town of Pozzuoli sits at the center of the Campi Flegrei caldera and has been lifted by nearly 4 meters in the last 50 years.
A study published earlier this year shows that the uplift and seismic activity have been caused by volcanic gases and fluids seeping into gaps and filling the three-kilometer-thick crust over the magma chamber like a sponge.
This is not necessarily a sign of an imminent volcanic eruption. A very similar effect is happening at Yellowstone, but no major eruptions have occurred here in the past 70,000 years.
“It’s the same for all volcanoes that have been quiet for generations. Campi Flegrei may settle into a new routine of gently rising and subsiding, as seen at similar volcanoes around the world, or simply return to rest. We can’t yet say for sure what will happen. The important point is to be prepared for all outcomes,” study author Dr. Stefano Carlino from the Vesuvius Observatory concluded.