On 21 August 1986 almost 1800 people were asphyxiated by a CO2 cloud violently released by Lake Nyos, Cameroon. Post-1986 monitoring of Lake Nyos revealed that CO2 steadily accumulates in bottom waters through recharge from soda-rich aquifers. The 1986 lake roll-over event triggered scientific research on volcanic lakes, creating “Nyos biased” interpretations: the search for dissolved CO2 in other lakes might have led to over- interpretations regarding hazard assessment. In this study, a thorough review of the historical literature on Lago Albano over the past approx. 2800 years shows no clear evidence of Nyos-type bursts, contrary to previous ideas. In 1989 Lago Albano was affected by a large CO2 pulse, concomitant with a seismic swarm below Colli Albani volcano. Tracing back in historical literature, at least two similar anomalous degassing episodes occurred out of five seismic crises between 1829 and 1927. Partial temperature- and density-driven roll-over of the top-9 m of Lago Albano commonly releases accumulated CO2 each winter (Chiodini et al., 2012). This degassing dynamics avoids long-term CO2 accumulation in bottom waters, as is the case at permanently stratified lakes in the tropics, such as Lake Nyos. Here we show that Lago Albano is an “anti-Nyos-type" lake: sudden recharge and regularly periodic release of CO2 (Lago Albano) vs. steady recharge and sudden release of CO2 (Lake Nyos). Despite past evidence of ha- zardous events, (1) the intensive well pumping from the Albano aquifer might lower lake level, and hence decrease the CO2 saturation pressure threshold, and (2) the absence of cold winters, hence avoiding yearly lake roll-over favoring CO2 accumulation at bottom layers, are modern factors that rise the need to revise hazard assessment and future monitoring strategies. Despite the fact that CO2 concentration in bottom waters was far from saturation conditions during the last survey (May 2010; Chiodini et al., 2012), making a limnic eruption highly unlikely, it is necessary to know the saturation state of CO2 in bottom waters and physical lake stability at any time, in order to be prepared for a next anomalous co-seismic CO2 degassing event of unknown quantity near Lago Albano.

The Campi Flegrei volcano (or Phlegraean Fields), Campania, Italy, generated the largest eruption in Europe 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 and more recent times. 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 archaeo- logical 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 par- ticularly 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.

Vulcano Island has experienced recurrent historical eruptive activity from the La Fossa and Vulcanello cones, including predominantly phreatomagmatic, Vulcanian, and occasionally Strombolian eruptions. It has also produced several effusive events and phreatic explosions. Despite extensive geological investigations and numerous radiometric and palaeomagnetic age determinations, significant gaps persist in the chronology and source attribution of historical eruptions. These gaps largely reflect stratigraphic complexity and the limited availability of reliable tephrostratigraphic markers. This study presents a critical reassessment of the eruptive chronology and vent locations of the La Fossa and Vulcanello cones from the 4th century BCE to the 18th century CE. We employ a multidisciplinary approach integrating historiographical analysis with recent volcanological and stratigraphic data. A systematic review of historical texts and iconographic sources was conducted, using rigorous philological criteria, to assess their reliability and their temporal and spatial resolution independently of existing volcanological interpretations. Key results include: (1) The identification of the initial emergence of the Vulcanello cone and associated lava platform between 183 and 126 BCE, and its subsequent stabilization in later centuries; (2) The reconstruction of the definitive formation of the isthmus connecting Vulcanello to the rest of Vulcano, attributed to the progressive accumulation of eruptive material from the La Fossa cone. This likely occurred at the beginning of the 16th century and culminated with the 1525–1526 CE eruption; (3) The absence of conclusive textual evidence for modern-era eruptions at the Forgia Vecchia crater, despite geological indicators of older explosive phases during the early development of the La Fossa cone; (4) The refinement of the chronology of the 18th-century Pietre Cotte eruptive cycle, with emplacement of a rhyolitic lava flow in 1739 CE and an associated pumice fallout in 1771 CE, each emitted from different summit vents of the La Fossa cone. The study outlines five major eruptions or eruptive cycles exceeding the typical intensity and magnitude of vulcanian-type explosions. These occurred in the late 4th century BCE, 1444 CE, 1525–26 CE, 1739 CE, and 1771 CE. No major phreatic eruptions are documented in historical sources, aside from the well known and historiographically transparent Breccia di Commenda eruption. However, geological evidence indicates that numerous (minor) phreatic explosions occurred during initial vent-opening phases. These findings demonstrate the value of historical sources in reconstructing Vulcano’s eruptive history and underline their potential to enhance the temporal resolution of probabilistic hazard scenarios for the island.