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The Campi Flegrei volcano (or Phlegraean Fields) of Campania, Italy, is the site of the largest eruption from a European volcano in at least 200 ka. Here we summarise the volcanic and human history of Campi Flegrei and discuss the interactions between humans and the environment within the “burning fields" from around 10,000 years until the 1538 CE Monte Nuovo eruption. The region’s incredibly rich written history documents how the landscape changed both naturally and anthropogenically, with the volcanic system fuelling these considerable natural changes. Humans have exploited the beautiful landscape, accessible resources (e.g., volcanic ash for pulvis puteolana mortar) and natural thermal springs associated with the volcano for millennia, but they have also endured the downsides of living in a volcanically active region—earthquakes, significant ground deformation and landscape altering eruptions. The pre-historic record is detailed, and various archaeological sites indicate that the region was certainly occupied in the last 10,000 years. This history has been reconstructed by identifying archaeological finds in sequences that often contain ash (tephra) layers from some of the numerous volcanic eruptions from Campi Flegrei and the other volcanoes in the region that were active at the time (Vesuvius and Ischia). These tephra layers provide both a relative and absolute chronology and allow the archaeology to be placed on a relatively precise timescale. The records testify that people have inhabited the area even when Campi Flegrei was particularly active. The archaeological sequences and outcrops of pyroclastic material preserve details about the eruption dynamics, buildings from Roman times, impressive craters that now host volcanic lakes and nature reserves, all of which make this region particularly mystic and fascinating, especially when we observe how society continues to live within the active caldera system. The volcanic activity and long record of occupation and use of volcanic resources in the region make it unique and here we outline key aspects of its geoheritage.

The mobility patterns in the Italian peninsula during prehistory are still relatively unknown. The excavation of the Copper Age and Bronze Age deposits in La Sassa cave (Sonnino, Italy) allowed to broaden the knowledge about some local and regional dynamics. We employed a multi-disciplinary approach, including stable (carbon and nitrogen – C and N, respectively) and radiogenic (strontium-Sr) isotopes analyses and the identification of the cultural traits in the material culture to identify mobility patterns that took place in the region. The Sr isotopic analyses on the human bones show that in the Copper Age and at the beginning of the Bronze Age, the cave was used as a burial place by different villages, perhaps spread in a radius of no more than 5 km. Stable isotopes analyses suggest the introduction of C4 plants in the diet of the Middle Bronze Age (MBA) communities in the area. Remarkably, in the same period, the material culture shows increasing influxes coming from the North. This evidence is consistent with the recent genomic findings tracing the arrival of people carrying a Steppe-related ancestry in Central Italy in MBA.

Assessment of time and space relationships among magmatism, volcanism, and resurgence of mediumsize calderas is a necessary tool to formulate a general model for their dynamics which also permits to forecast their evolution. To define a general hypothesis for the Campi Flegrei caldera, in a persistent state of unrest, the Ischia and Pantelleria medium-size resurgent structures, in variable stages of evolution, have also been investigated. In particular some parameters such as the structural and volcanological evolution, with emphasis on resurgence dynamics and coeval volcanism, and the evolution, present state and role of the magmatic system in resurgence, have been defined. For the Campi Flegrei caldera, the data collected during unrest episodes have also been taken into account, together with those from past eruptions. They corroborate the hypothesis that the unrest episodes are transient short-term events within the long-term deformation related to caldera resurgence. The geometry of the short-term deformation is strictly related to the structural setting of the caldera. The sub-surface processes have been dominated by joint degassing of two magmatic bodies, at 3-4 and 8 (or more) km depth, with the shallower formed by magma ascending from the deeper body. Both bodies contribute to the hydrothermal system, but the shallow magma is fluxed by the continuous upstream of CO2-richer gas released by the deep body. The two-layer degassing magma allows explaining geochemical and petrological features of unrest and volcanism. The joined interpretation of geological, geodetic, and geochemical data on the three calderas is an innovative approach that adds a time-perspective on how resurgent calderas behave. The proposed general hypothesis will help in long- and short-term volcanic hazards assessment and will support Civil Defence Authorities in elaborating actions devoted to volcanic risk reduction.

The Pomici Principali Tephra (10.3 ka) is one of the two highest-magnitude eruptions of the Campi Flegrei caldera over the past 15 ka. This caldera is active and largely inhabited, consequently it is one of the most dangerous volcanic areas on Earth. Stratigraphic and stratimetric studies carried out on an area of about 1000 km2 allowed us to reconstruct both eruption sequence and dynamics. On the basis of both lithological characteristics and dominant emplacement mechanisms, the sequence has been divided in five members: A) a basal ash fallout member, produced by a phreatomagmatic opening phase; B) a second member composed of coarse fallout layers deposited by a pulsating Plinian column; C) a third member which includes an alternation of ash and coarse pumice layers, generated during a magmatic-phreatomagmatic explosion phase; D) a fourth member composed of three thick coarse fallout layers separated by ash layers and generated by a mainly magmatic phase, during which a pulsating column reached the maximum height of about 22 km; E) an upper and fifth member, composed of fine- to coarse-ash surge beds, produced by a phase dominated by phreatomagmatic explosions. During this final phase pyroclastic surges flowed both inside and outside the caldera depression. The Pomici Principali erupted products were investigated through geochemical and isotope analyses and glass inclusion studies in order to shed light on the processes operating in the plumbing system. Whole rocks and glasses, representative of the complete stratigraphyc sequence, have a fairly homogeneous chemical composition. The isotope data on whole rocks, glasses and mineral phases suggest that at least two isotopic components were extruded during the course of the eruption. One of these components, the least radiogenic one, is represented by light-green pyroxenes. The most radiogenic component is represented by glasses and the majority of the separated minerals. Glass inclusion data were collected to highlight the pre-eruptive storage conditions of the erupted magma

The paper aims at merging the first results from the analyses of the georesources exploited in the site of Piano dei Cardoni (Ustica island, Italy) during the Neolithic phases of its occupation (Middle-Late Neolithic, 4.7-4.2 ka cal BC). Grinding tools consist of a very varied typology of local volcanic rocks, easy to collect and available very close to the investigated site. A selection of shapes and lithology is applied to reach the best performance of the tools. The elevated number of grinders, pestles, mortars testify to an intense activity of food/plant processing in the site. The absence of chert or obsidian resources on the island pushed the human communities to import such raw materials from the Aeolian islands and probably from the north-western area of Palermo. Pumice is collected on the same island, probably due to the local availability and its good quality. Similarly, local clay resources are used for the manufacture of ceramics, mostly burnished and incised wares. Ustica was therefore almost autonomous for the exploitation of resources, with volcanic rocks readily available in abundance and with the most significant exception being chert and obsidian. This last one probably imported and worked on the island and then moved towards North-Western Sicily.

The ongoing unrest at the Campi Flegrei caldera (CFc) in southern Italy is prompting exploration of its poorly studied offshore sector. We report on a multidisciplinary investigation of the Secca delle Fumose (SdF), a submarine relief known since antiquity as the largest degassing structure of the offshore sector of CFc. We combined high-resolution morphobathymetric and seismostratigraphic data with onshore geological information to propose that the present-day SdF morphology and structure developed during the initial stages of the last CFc eruption at Monte Nuovo in AD 1538. We suggest that the SdF relief stands on the eastern uplifted border of a N-S-trending graben-like structure formed during the shallow emplacement of the Monte Nuovo feeding dike. We also infer that the high-angle bordering faults that generated the SdF relief now preferentially allow the ascent of hot brines (with an equilibrium temperature of 179°C), thereby sustaining hydrothermal degassing on the seafloor. Systematic vertical seawater profiling shows that hydrothermal seafloor venting generates a sizeable CO2, pH, and temperature anomaly in the overlying seawater column. Data for the seawater vertical profile can be used to estimate the CO2 and energy (heat) outputs from the SdF area at ∼50 tons/d (∼0.53 kg/s) and ∼80 MW, respectively. In view of the cause-effect relationship with the Monte Nuovo eruption, and the substantial gas and energy outputs, we consider that the SdF hydrothermal system needs to be included in monitoring programs of the ongoing CFc unrest.