Eruptive versus non-eruptive behaviour of large calderas: the example of Campi Flegrei caldera (southern Italy)

Abstract

Caldera eruptions are among the most hazardous of natural phenomena. Many calderas around the world are active and are characterised by recurrent uplift and subsidence periods due to the dynamics of their magma reservoirs. These periods of unrest are, in some cases, accompanied by eruptions. At Campi Flegrei caldera (CFc), which is an area characterised by very high volcanic risk, the recurrence of this behaviour has stimulated the study of the rock rheology around the magma chamber, in order to estimate the likelihood of an eruption. This study considers different scenarios of shallow crustal behaviour, taking into account the earlier models of CFc ground deformation and caldera eruptions, and including recent geophysical investigations of the area. A semi-quantitative evaluation of the different factors that lead to magma storage or to its eruption (such as magma chamber size, wall-rock viscosity, temperature, and regional tectonic strain rate) is reported here for elastic and viscoelastic conditions. Considering the large magmatic sources of the CFc ignimbrite eruptions (400-2,000 km 3 ) and a wall-rock viscosity between 10 18 and 10 20 Pa s, the conditions for eruptive failure are difficult to attain. Smaller source dimensions (a few cubic kilometres) promote the condition for fracture (eruption) rather than for the flow of wall rock. We also analyse the influence of the regional extensional stress regime on magma storage and eruptions, and the thermal stress as a possible source of caldera uplift. The present study also emphasises the difficulty of distinguishing eruption and non-eruption scenarios at CFc, since an unambiguous model that accounts for the rock rheology, magma-source dimensions and locations and regional stress field influences is still lacking.

Distributed-Temperature-Sensing Using Optical Methods: A First Application in the Offshore Area of Campi Flegrei Caldera (Southern Italy) for Volcano Monitoring

“…Thus, the installed temperature measurement system represents an important step in the monitoring of this high-risk volcanic area, since temperature changes are among the most robust precursors of gas and magma migration towards the surface, possibly forecasting impending eruptions. Furthermore, the caldera of Campi Flegrei is characterized by a deformation pattern, with transient behavior, that can be explained by the overlapping of short time pulses, that are caused by injection of magmatic fluids into the hydrothermal system and a longer time process of heating the rock [9][10][11][12][13][14][15]. Thus, the thermal monitoring system here presented can be used to better understand the driving processes related to transient phenomena and to mitigate potential hazards.…”

“…The current caldera shape is the result of two collapses related to the Campanian Ignimbrite eruption (CI; 150-200 km 3 dense rock equivalent (DRE); age, 39 ky BP) and possibly to a minor subsidence associated with the Neapolitan Yellow Tuff eruption (NYT; 40 km 3 DRE; age, 12-15.6 ky BP) [21][22][23][24][25]. The caldera is underlain by a primary zone of magma storage that is 1.2 km to 1.5 km thick, and which has a top at about 7.5 km below the surface [26]; there is also a quenched relict of an ancient magma source at a depth of about 4 km [9,16,17], which has possibly been intruded into by new magma during recent unrests [9,16,17]. Main structures and morphological features of the onshore and offshore caldera of Campi Flegeri (after [24]).…”

“…This sector is marked by the presence of minor, normal faults that subsided the apical dome possibly by diffuse pore fluid circulation along the higher permeability zones [24][25][26][27][28][29][30][31][32]. As regards the thermal state of the caldera, there is surface evidence of the presence of a high temperature geothermal system, which is mainly developed in the central part of the caldera at Solfatara crater [6][7][8][9][10][11]. This roughly corresponds to the zone of major collapse filled by volcano-clastic deposits of post-caldera volcanic activity, as testified by gravity anomalies and seismic and geological surveys [33,34].…”

High-resolution morpho-bathymetry of Pozzuoli Bay, southern Italy

“…The Campi Flegrei district is an active volcanic area that covers about 200 km 2 of the coastal zone of SW Italy, a large part of which develops off the Gulf of Naples, and is characterized by at least one large caldera collapse structure. The caldera is represented by a quasi-circular area of 8 km in diameter in the central sector of the Campi Flegrei, including the Pozzuoli inland area and Pozzuoli Bay (Carlino & Somma, 2010;Dello Iacono, Zollo, Vassallo, Vanorio, & Judenherc, 2009;De Natale et al, 2006;Orsi, De Vita, & Di Vito, 1996;Rosi & Sbrana 1987;Sacchi et al, 2009;Scandone, Bellucci, Lirer, & Rolandi, 1991;Sacchi et al, 2014).…”

Hydrology of the Upper Indus Basin Under Potential Climate Change Scenarios

“…De Natale Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Napoli Osservatorio Vesuviano, Napoli, Italy e-mail: stefano.carlino@ov.ingv.it (7-10 km) have been inferred from seismic tomography, gravity and geochemical data, but is still matter of debated (Carlino and Somma 2010, and references therein).…”