ERUPTION CRATERS ASSOCIATED WITH SHALLOW SUBMARINE GAS VENTING OFF PANAREA ISLAND, ITALY

Explosive eruptions of hot water, steam, and non-aqueous gas are a common characteristic of the periodic behavior of subaerial geothermal systems. These highly destructive events may cause loss of life and substantial damage to infrastructure, especially in densely populated areas and where geothermal systems are actively exploited for energy. Here, the occurrence of a large number of eruption craters associated with the offshore venting of gas and thermal waters at Panarea, Italy, is reported, demonstrating that violent eruptions similar to those observed on land are also common in the shallow submarine environment. With diameters ranging from ten to over one hundred meters, the observed circular seafloor depressions record a history of major gas eruptions caused by frequent perturbation of the submarine geothermal system in the past 10,000 years. Estimates of the total gas flux indicate that the Panarea geothermal system released over 70 Mt of CO₂ over this period of time, suggesting that gas venting at submerged arc volcanoes contributes significantly to the global atmospheric CO₂ budget. The findings at Panarea highlight that shallow submarine gas eruptions represent a previously unrecognized volcanic hazard around populated volcanic islands that needs to be taken into account in the development of risk management strategies.