Campi Flegrei analysis and future possibilities

Written by Harish Iyer, Robbinsville High School Class of 2026

Background:

Campi Flegrei is a Large Caldera Complex in the Campanian Volcanic arc which is also home to the famous Mount Vesuvius. Some people consider it to be a supervolcano due to its previous highly destructive VEI 7 eruption 39000 years ago creating the Campanian Ignimbrites and the volcano’s current largest caldera. These show the potential power that Campi Flegrei can have but eruptions like that are few and far between. The latest eruption of Campi Flegrei was a low end VEI 3 eruption with total tephra ejected being 0.025 km³. For reference, The 1980 eruption of Mt Saint Helens was a VEI 5 with total tephra ejected of 1.4 km³, around 56 times larger than campi flegrei’s last eruption. Another reference would be the November 4th 2024 eruption of lewotobi’s laki laki cone which was also a VEI of 3 and had boulders fly up to 11 km away from its summit with 10 confirmed deaths. This is large but not at the level where it would be considered dangerous assuming the main city area, such as Naples proper, Polluzi,etc, is already evacuated.

Uplift Center and presumed cause

Recently, there have been many concerns due to the increasing number of earthquakes under the Solfatara crater. The uplift at the crater suggests that a magmatic intrusion has moved from its magma chamber to its magma conduit expanding it and the ground around it. This is the case if that wasn’t already clear. This uplift is centered at a specific area near Solfatara Crater. This is corroborated by The Smithsonian Global Volcanism Program which states, “The largest event in the swarm, a M 4.4 located at a depth of 2.6 km beneath the Solfatara, was the largest recorded since the current cycle of seismicity associated with uplift began in 2005. Recently in 2025, there was a magnitude 4.2 earthquake as well. A total of 450 earthquake events were recorded the previous month. The rate of inflation was 2 cm per month and remained unchanged. The report noted that during a 1982–84 seismic crisis there were more than 1,300 monthly events recorded, with associated uplift as high as 9 cm per month”. This high uplift is due to the unique magma conduit of Campi Flegrei which has 2 layers to it. It has a main magma chamber and a small thin layer that is called a sill. The Magma chamber also has different density magma resulting in a central ellipsoid shape being filled with new magma resulting and a compounding of uplift in the Pozzuoli area. This is also the location of the resurgent dome of the edifice’s latest caldera Neapolitan Yellow Tuff.

Magma types and explosivity:

The eruptions caused by Campi Flegrei are destructive due to the relatively high silica and oxide content in its trachyte magma. Due to it being quite viscous, it is able to create a plug and build immense pressure and force a Plinian to an Ultra Plinian eruption. On the larger end, these are massive explosive eruptions that are caldera causing and generally are accompanied by large pyroclastic flows and large ashfall. Plinian eruptions are the type of eruptions at large stratovolcanoes such as Mount Vesuvius.

Future possibilities:

Should we be immediately concerned about this uplift? Possibly but unlikely, The uplift alone doesn’t suggest immediately that a volcanic eruption is imminent but it does show an increase in activity with a possibility of eruption in the future. This is also corroborated by the large melt percentage of the Campi Flegrei magma chamber since generally for a volcanic eruption, a volcano needs at least 35–50% melt while Campi Flegrei is said to have a melt percentage of 80–90%. The main reason a volcanic eruption is not necessarily imminent is the cyclic nature of the volcano. The volcano goes through large periods of uplift and subsidence where it can even get to multiple meters of uplift per year before an eruption occurs. The current uplift is too low at a rate of 50–60 cm per year. Based on the cycle below, an eruption will most likely occur around the year 2150.

InSAR data to show uplift over the year of 2021

Future recommendations: As seen above, there has been a small uplift since at the very least, 2011 and before from other sources. This rate is quite small during the time scales above but during 2023 and 2024, this figure has increased by a factor 2 or even 3 in some cases. This is not necessarily the case for alarm as stated earlier but again this rate does show possibility for truly magmatic eruptions. This, however does not discount the possibilities of phreatic eruptions from groundwater interaction which is very possible considering the extensive hydrothermal system present as well as more hydrothermal explosions similar to the bakers basin explosion in yellowstone recently. I would recommend voluntary evacuation of Naples in the foreseeable future due to this. We can predict that with the current uplift rate of about 50–60 cm per year, there will be increasing earthquakes assuming the intrusion continues. If it continues according to the cycle above from the GeologyHub youtube channel, there could still be hundreds of years before a real eruption. I recommend that there should be at least a 1 kilometer radius exclusion zone around solfatara and keep a watch out for hydrothermal explosions.

Sources

Hrysiewicz, Alexis & Wang, Xiaowen & Holohan, Eoghan. (2023). EZ-InSAR: An easy-to-use open-source toolbox for mapping ground surface deformation using satellite interferometric synthetic aperture radar. Earth Science Informatics. 16. 1–17. 10.1007/s12145–023–00973–1.

“Campi Flegrei.” Vulkane.net, www.vulkane.net/en/volcanoes/campi-flegrei/campi-flegrei.html. Accessed 25 Sept. 2024.

“The 1538 Monte Nuovo Eruption.” Michigan Technological University, www.geo.mtu.edu/volcanoes/boris/mirror/mirrored_html/Montenuovo.html. Accessed 25 Sept. 2024.

Acocella, V., et al. “Understanding Shallow Magma Emplacement at Volcanoes: Orthogonal Dike Injection during the 2002–2003 Stromboli (Italy) Eruption.” Geophysical Research Letters, vol. 35, no. 21, 2008, doi:10.1029/2008GL034242.

“Volcanic Activity Frequency.” Cool Geography, www.coolgeography.co.uk/A-level/AQA/Year%2013/Plate%20Tectonics/Volcanoes/Volcanic%20activity%20frequency.htm. Accessed 25 Sept. 2024.

Chiodini, Giovanni, et al. “Schematized Magmatic System of Campi Flegrei Caldera.” ResearchGate,

www.researchgate.net/figure/Schematized-magmatic-system-of-Campi-Flegrei-caldera-Sources-reconstructed-from-surface_fig1_319066913. Accessed 25 Sept.

“Campi Flegrei.” Global Volcanism Program, Smithsonian Institution, volcano.si.edu/volcano.cfm?vn=211010. Accessed 25 Sept. 2024.

“Campi Flegrei: Europe’s Supervolcano.” YouTube, uploaded by Geology Hub, www.youtube.com/watch?v=F-h_1g185YY. Accessed 25 Sept. 2024.

Global Volcanism Program, 2024. Report on Campi Flegrei (Italy) (Sennert, S, ed.). Weekly Volcanic Activity Report, 15 May-21 May 2024. Smithsonian Institution and US Geological Survey.

Pietro Tizzani, José Fernández, Andrea Vitale, Joaquín Escayo, Andrea Barone, Raffaele Castaldo, Susi Pepe, Vincenzo De Novellis, Giuseppe Solaro, Antonio Pepe, Anna Tramelli, Zhongbo Hu, Sergey V. Samsonov, Isabel Vigo, Kristy F. Tiampo, Antonio G. Camacho,

4D imaging of the volcano feeding system beneath the urban area of the Campi Flegrei caldera,

Remote Sensing of Environment,

Volume 315,

2024,

114480,

ISSN 0034–4257,

https://doi.org/10.1016/j.rse.2024.114480.

(https://www.sciencedirect.com/science/article/pii/S0034425724005066)

Abstract: This paper describes an approach to analyze ground deformation data collected by InSAR (Interferometric Synthetic Aperture Radar) imaging the volcano feeding system (VFS) beneath a caldera. The approach is applied to the Campi Flegrei caldera in southern Italy, a densely populated area at high risk for volcanic eruption. The method is a 4D tomographic inversion that considers a combination of 3D pressure sources and dislocations (strike-slip, dip-slip and tensile) acting simultaneously. This is in contrast to traditional methods that assume a priori geometries and type for the volcanic source. Another novelty is that we carry out a time-series analysis of multifrequency InSAR displacement data. The analysis of these multiplatform and multifrequency InSAR data from 2011 to 2022 reveals an inflating source at a depth of 3–4 km that is interpreted as a pressurized magmatic intrusion. The source broadens and migrates laterally over time, with a possible new magmatic pulse arriving in 2018–2020. The model also identifies a shallow region (at 400 m depth) that may be feeding fumaroles in the area. The analysis also reveals a zone of weakness (dip-slip) that could influence the path of rising magma. This method provides a more detailed dynamic 4 — dimensional image of the VFS than previously possible and could be used to improve hazard assessments in active volcanic areas.

Keywords: Multiplatform satellite radar observation; Multiband radar observation; Inverse techniques; 4D interpretation; Volcano feeding system; Campi Flegrei caldera