About this Research Topic
Large collapse calderas are the most explosive volcanic areas on Earth, with ignimbritic eruptions representing a real threat for mankind. Large calderas are generally associated to large geothermal reservoirs, which characterize also the eruptive activity, often dominated by hydro-magmatic eruptions. Such geothermal systems, besides affecting the eruptive styles, also interact with magma and gas emissions coming from deeper layers, thus perturbing the deep signals in a way which is difficult to discriminate. Such perturbation makes it difficult, during unrest, to discriminate magmatic signals, typically associated to pre-eruptive processes, from purely hydrothermal effects that are not directly associated to magma overpressure and intrusion. A further problem, in these areas, is to discriminate the processes which can build up conditions for very catastrophic ignimbritic eruptions.
In the last decades, several examples of caldera unrest, often involving alternating uplift and subsidence episodes without any eruption, have been observed worldwide. Some of these calderas are located in densely urbanized areas, thus making it crucial to be able to distinguish magmatic unrest from non-magmatic perturbations of the shallow geothermal system. The peculiar behaviour of caldera unrest, as compared with more simple observations at central volcanoes, requires more focused research to deeply understand how to distinguish pre-eruptive patterns from signals coming from hydrothermal system perturbations.
Discriminating magmatic vs. hydrothermal effects at large calderas has hence became compelling for civil protection procedures, mainly in highly urbanised volcanic areas. Campi Flegrei caldera, in Southern Italy, is a typical example of a largely urbanised area, where huge ground deformations (totalling up to 4.0-4.5 m of ground uplift) are occurring for about 70 years. In this area, which is among the best monitored in the world, volcanological research demonstrated all the difficulties to unambiguously interpret geophysical and geochemical data, in order to give useful suggestions for civil protection purposes.
This Research Topic aims to focus on the problem to discriminate, in caldera unrest, purely magmatic signals from hydrothermal perturbations, using geochemical and geophysical data. It hence seeks to develop more specific interpretations, analyses and models capable to refine and improve eruption forecast at calderas. It also welcomes contributions aimed to understand the processes preparing large ignimbritic eruptions in these areas.
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