This caldera, last erupted in 1538, has shown signs of unrest over the past 70 years.
Researchers have revealed that the Phlegrean Fields, a submerged volcanic caldera northwest of Naples, may be on the verge of an eruption. This unsettling conclusion comes from a recent study by scientists from the University College London (UCL) and the Italian National Research Institute for Geophysics and Volcanology (INGV).
This caldera, last erupted in 1538, has shown signs of unrest over the past 70 years. These include cycles of peak activity in the 1950s, 1970s, and 1980s, and a decade-long slow surge of unease. Numerous minor earthquakes have been recorded during these phases, and the coastal town of Pozzuoli has risen almost 4 meters – roughly the height of a double-decker bus.
An Italian Supervolcano on the Verge of Erupting?
Published in Nature’s Communications Earth & Environment, the study used a volcanic fracture model developed at UCL. Through this model, researchers interpreted patterns of earthquakes and ground uplift. The alarming finding was that parts of the volcano had stretched almost to the point of breaking.
Model in Action
The study’s lead author, Professor Christopher Kilburn, stated, “Our new study confirms that Phlegrean Fields is nearing rupture. But an eruption isn’t a guarantee. The magma still needs to rise in the right place for an eruption to occur.” This is the first time their model, which is based on the physics of how rocks break, has been used in real time on a volcano. Since its initial use in 2017, the Phlegrean Fields have exhibited behavior as predicted, including an increasing number of minor earthquakes suggesting pressure buildup from below.
The study is a groundbreaking development in the quest to improve eruption forecasts globally. It is the first of its kind to predict the rupture of an active volcano.
Earthquakes and the Role They Play
When the crust stretches, faults or fissures slide, causing earthquakes. The earthquake pattern in 2020 suggested that the rock was fracturing, not merely bending. The paper suggests that the cumulative effect of unrest since the 1950s means an eruption might be signaled by weaker precursors, such as slower ground uplift and fewer earthquakes.
However, an eruption is not inevitable. Dr. Stefano Carlino of the Vesuvius Observatory explained, “Like all long-silent volcanoes, the Phlegrean Fields can adapt to a new routine of slow ascent and descent. Or it might simply return to rest. We can’t predict with certainty what will occur, but it is crucial to be prepared for all outcomes.”
Not Your Average Supervolcano
Phlegrean Fields stands out due to its unique structure. Instead of the traditional mountainous form, it’s a depression 12-14 km wide, known as a caldera. Hence, it’s home to around 360,000 people. Over the last decade, the ground below Pozzuoli has been rising about 10 cm each year. Small but persistent earthquakes have been recorded for the first time since the mid-1980s.
Below the Surface
In the last phase, disturbances have been caused by fluid movement approximately 3 km below the surface. These fluids might be molten rock or magma and volcanic gas. This recent unrest seems to be triggered by magmatic gas infiltrating gaps in the rock, permeating the 3km-thick crust akin to a sponge.
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