Accelerating Uplift at Campi Flegrei

Over the past couple of weeks, there has been an acceleration of ground deformation rates at Campi Flegrei, raising concerns about the potential for future eruptive activity. 

The Campi Flegrei volcanic caldera, located west of Naples, Italy, has a complex history of ground deformation characterised by periods of significant uplift. The most significant uplift events at Campi Flegrei during the 1980s occurred in two distinct phases: 1982-1984 and 1987-1989. The first phase was the most dramatic, with a total uplift of approximately 1.8 metres recorded at the centre of the caldera in the town of Pozzuoli. This rapid ground deformation was accompanied by a swarm of earthquakes, the largest reaching a magnitude of 4.2.

Bay of Pozzuoli

The caldera has exhibited a complex pattern of ground deformation throughout its history.  Since 2004, the caldera has entered a renewed phase of unrest, characterised by ongoing ground uplift, seismic activity, and compositional changes in emitted gases. 

A recent intensification of the ongoing uplift episode at Campi Flegrei has been observed within the last couple of weeks. This intensification is characterised by two discrete, rapid uplift events resulting in a cumulative vertical displacement exceeding 15 millimetres. This represents the most pronounced acceleration in ground deformation since the current uplift cycle commenced in 2004. It is important to note, however, that the current uplift remains below the maximum values recorded during the uplift events of the 1980s.

Furthermore, there has been strong seismicity with numerous earthquake swarms, demonstrating further unrest. These swarms consist of clusters of earthquakes occurring in close temporal and spatial proximity, suggesting stress changes.

INGV assumes that a magma chamber has formed at a depth of 4 kilometers and is fed by a larger magma body at a depth of 8 kilometers. This model of a two-tiered magmatic system is likely based on a combination of geophysical and geochemical observations.

INGV’s model suggests a two-tiered magmatic system beneath Campi Flegrei – a shallow magma chamber at 4 km depth and a larger reservoir at 8 km.

It’s understandable to be concerned, but a large, catastrophic eruption is not the most immediate threat at Campi Flegrei. Scientists believe a smaller eruption within the caldera, or no eruption at all, are more likely outcomes.

Possible other scenarios include:

Gradual Subsidence: The pressure buildup that causes the uplift could lessen over time. Magma may cool and solidify, or fluids may escape through newly formed cracks, leading to a gradual return to background levels of ground level.

Fluctuating Uplift and Subsidence: The pressure could fluctuate as cracks form and get sealed. This might lead to periods of uplift followed by subsidence, a pattern observed elsewhere, like at Yellowstone caldera.

Intensification Leading to Eruption: The uplift could continue until the rock above the magma chamber ruptures, leading to an eruption. The size and nature of this eruption are highly uncertain, depending on the amount of magma involved and the dynamics of the system.

Phreatic Explosions: If existing cracks reach the surface, pressurised fluids (steam, gas) could be released abruptly in steam-driven (phreatic) explosions. These can be dangerous in the immediate area but don’t signify a larger magmatic eruption.

The current activity highlights the need for continued close monitoring and updated risk assessments to ensure the safety of the densely populated region around Naples.



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