The eruptions of Campi Flegrei (Southern Italy), one of the most studied and dangerous active volcanic areas of the world, are fed by mildly potassic alkaline magmas, from shoshonite to trachyte and phonotrachyte. Petrological investigations carried out in past decades on Campi Flegrei rocks provide crucial information for understanding differentiation processes in its magmatic system. However, the compositional features of rocks are a palimpsest of many processes acting over timescales of 10⁰–10⁴ years, including crystal entrapment from multiple reservoirs with different magmatic histories. In this work, olivine, clinopyroxene and feldspar crystals from volcanic rocks related to the entire period of Campi Flegrei’s volcanic activity are checked for equilibrium with combined and possibly more rigorous tests than those commonly used in previous works (e.g., Fe–Mg exchange between either olivine or clinopyroxene and melt), with the aim of obtaining more robust geothermobarometric estimations for the magmas these products represent. We applied several combinations of equilibrium tests and geothermometric and geobarometric methods to a suite of rocks and related minerals spanning the period from ~59 ka to 1538 A.D. and compared the obtained results with the inferred magma storage conditions estimated in previous works through different methods. This mineral-chemistry investigation suggests that two prevalent sets of T–P (temperature–pressure) conditions, here referred to as “magmatic environments”, characterized the magma storage over the entire period of Campi Flegrei activity investigated here. These magmatic environments are ascribable to either mafic or differentiated magmas, stationing in deep and shallow reservoirs, respectively, which interacted frequently, mostly during the last 12 ka of activity. In fact, open-system magmatic processes (mixing/mingling, crustal contamination, CO₂ flushing) hypothesized to have occurred before several Campi Flegrei eruptions could have removed earlier-grown crystals from their equilibrium melts. Moreover, our new results indicate that, in the case of complex systems such as Campi Flegrei’s, in which different pre-eruptive processes can modify the equilibrium composition of the crystals, one single geothermobarometric method offers little chance to constrain the magma storage conditions. Conversely, combined methods yield more robust results in agreement with estimates obtained in previous independent studies based on both petrological and geophysical methods.

The sands of the Ofanto River (Southern Italy) include a volcaniclastic component represented by clinopyroxene, melanite garnet, amphibole and subordinate volcanic lithics. In order to infer the provenance of this component, we have conducted a microanalytical and isotopic study on the volcanic minerals of the sands collected in three different sites along the Ofanto River: (1) upstream sector, where only sedimentary rocks are drained; (2) middle course, along a tributary draining only the Monte Vulture volcanic rocks, (3) the mouth of the Ofanto. Moreover, minerals of the beach sands of the Tyrrhenian Cilento coast were analyzed for comparison. The microanalytical study and the Sr-Nd isotopic composition reveal the existence of two populations of pyroxenes characterized by distinct isotopic signatures and indicating a provenance from two different volcanic sources. One is confidently identifiable with Monte Vulture, and is evident in the minerals of the middle course and mouth sands. The pyroxenes of the upstream sector, isotopically similar to those of the Cilento coast, have a Campanian signature. The simultaneous occurrence of amphibole and garnet point to the explosive eruptions of Mount Vesuvius as the most probable sources of these minerals. The absence of Campanian pyroxenes at the mouth of the Ofanto River could be related to the occurrence of dams limiting the transport of solids along the river.

This study, conducted in the frame of the Pianeta Dinamico project funded by Istituto Nazionale di Geofisica e Vulcanologia, aims to improve the knowledge of radon concentration dissolved in several different waters from some of the Italian volcanic areas and its relationships with lithological and structural settings, fluid chemistry and circulation, volcano dynamics.The study mainly focuses on 222Rn variations over time in thermal waters of the Campi Flegrei caldera at NW of Naples, an active volcanic field hosting an important geothermal system and one of the most dangerous calderas in the world. The caldera, part of the SW-NE trending fissure-like feeding system of the Phlegraean Volcanic District including also Ischia island, lastly erupted in 1538 and, since 2000, has been under a permanent unrest with up 1 metres of uplift, thousands of earthquakes and tons of CO2 emissions.25 sites were sampled and analysed for dissolved 222Rn levels at least twice per year since October 2021; starting from October 2022, 5 waters were then selected for monthly monitoring with the goal of unravelling exogenous (e.g., temperature or rainfall) versus endogenous processes relationships.In order to compare radon concentrations in the caldera with those in the volcanic context of southern Italy, we sampled and analysed as follows: a) 23 cold waters at Somma-Vesuvius, the stratovolcano placed at the intersection of regional NW–SE and NE–SW fault systems east of Naples, showing mild gaseous emissions after the 1944 eruption; b) 8 cold waters from the north of Campi Flegrei caldera, i.e. 7 from a multi-layer aquifer at the base of the extinct Roccamonfina stratovolcano and 1 water at Minturno (northern edge of Roccamonfina); c) 1 thermal water belonging to Ischia at the NW corner of the Gulf of Naples; d) 3 thermal waters of the Vulcano island from the Sicilian Aeolian Arc, characterised by vigorous seismic and fumarolic degassing activities that has shown an abrupt increase on August 2021.The waters are springs, lakes, pools, and groundwater; two are from Le Fumose (Campi Flegrei) and Porto Ponente (Vulcano) submerged emissions.Measurements have been performed by a Radon-in-air detector (RAD7®, Durridge Co.) equipped with Big Bottle RAD H2O and DRYSTIK accessories and processed using the CAPTURE program.Campi Flegrei reaches the highest radon concentrations, varying from 0.20 ± 0.03 to ~1887 ± 13 Bq/L. Somma-Vesuvius shows from almost no radon to 24 ± 1 Bq/L, and Ischia is at 54 ± 2 Bq/L.Roccamonfina area has a discrete variability from 0.2 ± 0.1 to ~ 71 ± 7 Bq/L at SE, being 9.0 ± 0.4 Bq/L at Minturno.Vulcano island attains the lowest detected concentrations, less than 2.4 ± 1.0 Bq/L.Dealing with different areas, the presented results lay the groundwork for better understanding radon behaviour and evaluating the implications on environmental and volcanic hazards assessment. At Campi Flegrei where, in 2012, the alert level was raised from base to warning, radon should be useful to investigate processes from which volcanic dynamics originates and to corroborate the monitoring outcomes.

Fumaroles spread out several elements to the atmosphere and may include radon that contributes to environmental radioactivity. The long-lasting vigorous gaseous emissions of the Campi Flegrei volcanic caldera, i.e., Solfatara and Pisciarelli, occur in densely inhabited areas of Naples where the population may be exposed to ionizing radiation from 222-radon. In 2021, we started a study on radon levels from the Solfatara and Pisciarelli fumaroles by using the RAD7 commercial detector, one of the most widely used instruments for measuring 222Rn, either dissolved in water or in soil gas. However, the local high H2S levels and hot temperatures did not allow direct measurements of Rn, resulting in the instrumentation (RAD7) damage. Thus, we developed a proper technique for sampling and measuring radon gas from fumarolic gases in such a “critical” areas to overcome the instrumental issue.At fumarole sites i.e., Bocca Nuova and Bocca Grande within the Solfatara crater, and Pisciarelli, the gas was periodically sampled in Tedlar® bag of 1 or 3 liters in order to have the possibility to repeat the measurements two or three times to verify the accuracy of the data.In laboratory, at first, H2S traps were prepared by filling silicone tubes with lead acetate powder, bordered, at both ends, by hydrophilic cotton and closed. Then the fumarole gas was transferred from the Tedlar® bag into a glass tube. Finally, radon gas was measured via a closed loop by using the RAD7. Rn printouts obtained from RAD7 were corrected for the time lag between sampling and measurement. RAD7 and charcoal canister measurements were compared to check the obtained results.Preliminary results, published in Iovine et al. (2023), demonstrate that the methodology utilized enables the analysis of Rn concentrations even in H2S-bearing gases, discharged from the fumaroles of the Campi Flegrei volcano and, most importantly, without instrumental issues. Fumaroles sampled and analyzed over time according to the methodology adopted, may be suitable for environmental radioactivity assessment and volcanic monitoring purposes as well. Iovine RS, Avino R, Minopoli C, Cuoco E, Caliro S, Galli G, Piochi M. (2023). A procedure to use the RAD7 detector for measuring 222Rn in soil gases exceeding instrumental limits: an application to chemically aggressive fumaroles of the Campi Flegrei area. Rapp. Tec. INGV, 473: 1­18, https://doi.org/10.13127/rpt/473.

The mechanism driving accelerating unrest at the densely populated Campi Flegrei caldera since 2005 remains debated. Analyzing an unprecedented two-decade geochemical dataset, we show that escalating soil CO ₂ fluxes closely tracks caldera uplift, revealing magmatic fluid pressurization at 3- to 4-kilometer depth and heating as the fundamental driver of the unrest. A critical magmatic gas pulse occurred between 2018 and 2022 specifically focused this outgassing beneath the Solfatara crater. Thermodynamic modeling demonstrates that an increasing mass of ascending fluid pressurizes the hydrothermal system, forcing vapor condensation within the upper kilometer. This condensation transfers latent heat to the crust. We calculate that this released thermal energy is an order of magnitude greater than that required for the 1.6-meter uplift since 2005. Ultimately, this fluid pressurization and heating drive accelerating deformation and seismicity; alongside the 2021 emergence of seismic sequences with short inter-event times, it directly signals an escalating phreatic or magmatic eruption risk.

The Campi Flegrei caldera is a restless, resurgent volcanic system located within the densely populated metropolitan area of Naples, southern Italy. Long-term monitoring indicates that the caldera entered a new unrest phase in 2004, characterized by ground inflation correlating with shallow seismicity and intense hydrothermal activity, such as fumarole and soil CO2 degassing. Here, we present the results of monitored soil fluxes from Campi Flegrei from 1998 to 2026 to better understand the dynamics of the current unrest. Crucially, this extends the previously published record (1998–2016) by ten years, offering new insights into recent dynamics. The dataset consists of 41 campaigns (~400 measurement points each) in an extended area—including Solfatara di Pozzuoli and Pisciarelli hydrothermal site—and 220 monthly campaigns over 63 fixed points in a target area of Solfatara. Modeling these datasets through Sequential Gaussian Simulation (sGs) reveals that both the spatial extent of degassing and total emission of CO2 into the atmosphere have increased since 2004. Analyzing temporal variations over distinct areas reveals a significant shift starting in 2018, where escalating emissions became focused specifically within the Solfatara crater. These escalating fluxes correlate with increased soil temperatures, variations in fumarole gas chemistry, ground deformation, and number of earthquakes. These coupled geochemical and geophysical signals suggest that the current unrest is linked to pulses of magmatic fluid injection, leading to progressive pressurization and heating of the hydrothermal system and ultimately triggering shallow seismicity and ground uplift.