Magmas near the critical degassing pressure drive volcanic unrest towards a critical state

Chiodini, Giovanni; Paonita, Antonio; Aiuppa, Alessandro; Costa, Antonio; Caliro, Stefano; Martino, Prospero De; Acocella, Valerio; Vandemeulebrouck, Jean

doi:10.1038/ncomms13712

Cited by 158 publications

(181 citation statements)

References 68 publications

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“…In a given time, which depends on gas pressure and rock permeability, the gas can flow into the overlying rock following preferential pathways, such as fractured zones and pre-existing conduits, or through the porous medium. This degassing mode can increase the subsidence at the end of the intrusion, as it gradually decreases the volume in the region where the sill emplaced, and can power the geothermal system by supplying hot fluids (Chiodini et al, 2016). This mechanism is consistent with the dynamics of semi-plugged felsic calderas , which are typically restless calderas with repeated non-eruptive unrest (e.g., Campi Flegrei).…”

Section: Implication Of Sill Intrusion For Geothermal Activitysupporting

confidence: 50%

A Physical Model of Sill Expansion to Explain the Dynamics of Unrest at Calderas with Application to Campi Flegrei

2017

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Many calderas show remarkable unrest, which often does not culminate in eruptions (non-eruptive unrest). In this context the interpretation of the geophysical data collected by the monitoring networks is difficult. When the unrest is eruptive, a vent opening process occurs, which leads to an eruption. In calderas, vent locations typically are scattered over a large area and monogenic cones form. The resulting pattern is characterized by a wide dispersion of eruptive vents, therefore, the location of the future vent is not easily predictable. We propose an interpretation of the deformation associated to unrest and vent pattern commonly observed at calderas, based on a physical model that simulates the intrusion and the expansion of a sill. The model can explain both the uplift and any subsequent subsidence through a single process. Considering that the stress mainly controls the vent opening process, we try to gain insight on the vent opening in calderas through the study of the stress field produced by the intrusion of an expanding sill. We find that the tensile stress in the rock above the sill is concentrated at the sill edge in a ring-shaped area with radius depending on the physical properties of magma and rock, the feeding rate and the magma cooling rate. This stress field is consistent with widely dispersed eruptive vents and monogenic cone formation, which are often observed in the calderas. However, considering the mechanical properties of the elastic plate and the rheology of magma, we show that remarkable deformations may be associated with low values of stress in the rock at the top of the intrusion, thereby resulting in non-eruptive unrest. Moreover, we have found that, under the assumption of isothermal conditions, the stress values decrease over time during the intrusion process. This result may explain why the long-term unrest, in general, do not culminate in an eruption. The proposed approach concerns a general process and is applicable to many calderas. In particular, we simulate the vertical displacement as occurred in the centre of Campi Flegrei caldera during the last decades, and we obtain good agreement with the data of a leveling benchmark near the center of the caldera.

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Section: Implication Of Sill Intrusion For Geothermal Activitysupporting

confidence: 50%

A Physical Model of Sill Expansion to Explain the Dynamics of Unrest at Calderas with Application to Campi Flegrei

2017

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“…For long‐lived calderas, volcanic unrest is generally characterized by a pressurization of the hydrothermal system (e.g., Acoccella et al, ; Chiodini et al, ) leading to ground uplift and to changes in the composition and degassing rate of fumaroles (Caliro et al, ). Hydrothermal systems constitute therefore a critical element widely used to assess and monitor a renewal activity (e.g., Chiodini, ; Chiodini et al, , ; Gottsmann et al, ; Tassi et al, ; Werner et al, ).…”

Section: Introductionmentioning

confidence: 99%

Three‐Dimensional Electrical Resistivity Tomography of the Solfatara Crater (Italy): Implication for the Multiphase Flow Structure of the Shallow Hydrothermal System

et al. 2017

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The Solfatara volcano is the main degassing area of the Campi Flegrei caldera, characterized by 60 years of unrest. Assessing such renewal activity is a challenging task because hydrothermal interactions with magmatic gases remain poorly understood. In this study, we decipher the complex structure of the shallow Solfatara hydrothermal system by performing the first 3‐D, high‐resolution, electrical resistivity tomography of the volcano. The 3‐D resistivity model was obtained from the inversion of 43,432 resistance measurements performed on an area of ~0.68 km2. The proposed interpretation of the multiphase hydrothermal structures is based on the resistivity model, a high‐resolution infrared surface temperature image, and 1,136 soil CO2 flux measurements. In addition, we realized 27 soil cation exchange capacity and pH measurements demonstrating a negligible contribution of surface conductivity to the shallow bulk electrical conductivity. Hence, we show that the resistivity changes are mainly controlled by fluid content and temperature. The high‐resolution tomograms identify for the first time the structure of the gas‐dominated reservoir at 60 m depth that feeds the Bocca Grande fumarole through a ~10 m thick channel. In addition, the resistivity model reveals a channel‐like conductive structure where the liquid produced by steam condensation around the main fumaroles flows down to the Fangaia area within a buried fault. The model delineates the emplacement of the main geological structures: Mount Olibano, Solfatara cryptodome, and tephra deposits. It also reveals the anatomy of the hydrothermal system, especially two liquid‐dominated plumes, the Fangaia mud pool and the Pisciarelli fumarole, respectively.

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“…Ground movements and geochemical variation of the main fumarolic fields within the caldera suggest that the volcano likely entered a phase of unrest in the second half of the last century which is not concluded yet (e.g., Chiodini et al, 2012Chiodini et al, , 2016. Recent field-work, deep drilling measurements and submarine survey of the Gulf of Pozzuoli have further constrained the tectonic history of the caldera De Natale et al, 2016;Steinman et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

The Effects of Vent Location, Event Scale, and Time Forecasts on Pyroclastic Density Current Hazard Maps at Campi Flegrei Caldera (Italy)

et al. 2017

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This study presents a new method for producing long-term hazard maps for pyroclastic density currents (PDC) originating at Campi Flegrei caldera. Such method is based on a doubly stochastic approach and is able to combine the uncertainty assessments on the spatial location of the volcanic vent, the size of the flow and the expected time of such an event. The results are obtained by using a Monte Carlo approach and adopting a simplified invasion model based on the box model integral approximation. Temporal assessments are modeled through a Cox-type process including self-excitement effects, based on the eruptive record of the last 15 kyr. Mean and percentile maps of PDC invasion probability are produced, exploring their sensitivity to some sources of uncertainty and to the effects of the dependence between PDC scales and the caldera sector where they originated. Conditional maps representative of PDC originating inside limited zones of the caldera, or of PDC with a limited range of scales are also produced. Finally, the effect of assuming different time windows for the hazard estimates is explored, also including the potential occurrence of a sequence of multiple events. Assuming that the last eruption of Monte Nuovo (A.D. 1538) marked the beginning of a new epoch of activity similar to the previous ones, results of the statistical analysis indicate a mean probability of PDC invasion above 5% in the next 50 years on almost the entire caldera (with a probability peak of ∼25% in the central part of the caldera). In contrast, probability values reduce by a factor of about 3 if the entire eruptive record is considered over the last 15 kyr, i.e., including both eruptive epochs and quiescent periods.

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Magmas near the critical degassing pressure drive volcanic unrest towards a critical state

Cited by 158 publications

References 68 publications

A Physical Model of Sill Expansion to Explain the Dynamics of Unrest at Calderas with Application to Campi Flegrei

A Physical Model of Sill Expansion to Explain the Dynamics of Unrest at Calderas with Application to Campi Flegrei

Three‐Dimensional Electrical Resistivity Tomography of the Solfatara Crater (Italy): Implication for the Multiphase Flow Structure of the Shallow Hydrothermal System

The Effects of Vent Location, Event Scale, and Time Forecasts on Pyroclastic Density Current Hazard Maps at Campi Flegrei Caldera (Italy)

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