A roadmap for amphibious drilling at the Campi Flegrei caldera: insights from a MagellanPlus workshop

Abstract

Large calderas are among the Earth's major volcanic features. They are associated with large magma reservoirs and elevated geothermal gradients. Caldera-forming eruptions result from the withdrawal and collapse of the magma chambers and produce large-volume pyroclastic deposits and later-stage deformation related to post-caldera resurgence and volcanism. Unrest episodes are not always followed by an eruption; however, every eruption is preceded by unrest.The Campi Flegrei caldera (CFc), located along the eastern Tyrrhenian coastline in southern Italy, is close to the densely populated area of Naples. It is one of the most dangerous volcanoes on Earth and represents a key example of an active, resurgent caldera. It has been traditionally interpreted as a nested caldera formed by collapses during the 100-200 km 3 Campanian Ignimbrite (CI) eruption at ∼ 39 ka and the 40 km 3 eruption of the Neapolitan Yellow Tuff (NYT) at ∼ 15 ka. Recent studies have suggested that the CI may instead have been fed by a fissure eruption from the Campanian Plain, north of Campi Flegrei.Published by Copernicus Publications on behalf of the IODP and the ICDP. 30 M. Sacchi et al.: A roadmap for amphibious drilling at the Campi Flegrei calderaA MagellanPlus workshop was held in Naples, Italy, on 25-28 February 2017 to explore the potential of the CFc as target for an amphibious drilling project within the International Ocean Discovery Program (IODP) and the International Continental Drilling Program (ICDP). It was agreed that Campi Flegrei is an ideal site to investigate the mechanisms of caldera formation and associated post-caldera dynamics and to analyze the still poorly understood interplay between hydrothermal and magmatic processes. A coordinated onshore-offshore drilling strategy has been developed to reconstruct the structure and evolution of Campi Flegrei and to investigate volcanic precursors by examining (a) the succession of volcanic and hydrothermal products and related processes, (b) the inner structure of the caldera resurgence, (c) the physical, chemical, and biological characteristics of the hydrothermal system and offshore sediments, and (d) the geological expression of the phreatic and hydromagmatic eruptions, hydrothermal degassing, sedimentary structures, and other records of these phenomena. The deployment of a multiparametric in situ monitoring system at depth will enable near-real-time tracking of changes in the magma reservoir and hydrothermal system.

Invited perspectives: The volcanoes of Naples: how can the highest volcanic risk in the world be effectively mitigated?

“…Campi Flegrei caldera eruptive activity has been dominated by phreatomagmatic eruptions, whose explosivity is due to the contact of rising magma with the large geothermal system located beneath the caldera, down to about 2.5-3.0 km (Rosi and Sbrana, 1987;Piochi et al, 2014). The collapsed area, as recognised by geophysical data (Cassano and La Torre, 1987;Capuano and Achauer, 2003), has a radius of about 3 km, with the centre approximately located at the Pozzuoli town harbour; more than 50 % of the caldera is below sea level (Somma et al, 2016;Steinman et al, 2018;Sacchi et al, 2019). All the eruptions younger than 10 000 years are located within such an area, occurring more frequently from its borders, marked by buried caldera ring faults (De Natale and Pingue, 1993;De Natale et al, 1997).…”

“…The volcanic hazard at SV has been thoroughly described in a probabilistic framework: first by Rossano et al (1998) and then, in a more complete way, by De Natale et al (2005). The main volcanic hazards are pyroclastic flows and ash and pumice fallout (see also Sacchi et al, 2019Sacchi et al, , 2020 but also associated hazards like earthquakes, lahars, lava flows and floods, which need to be considered (Sacchi et al, 2009). In particular, large floods caused by the remobilisation, due to heavy rains, of the old, loose pyroclastic deposits on the topographic reliefs around Vesuvius caused nearly total destruction and 160 casualties in May 1998 (Mazzarella et al, 2002).…”

Review

“…Here's a list of further detailed comments/suggestions: line 144-145: Consider the possibility of adding (a selection of) the following references: "The main volcanic hazards are pyroclastic flows and ash/pumice fallout (e.g. Sacchi et al, 2005;2019;2020), but also associated hazards like earthquakes, lahars, lava flows and floods (Sacchi et al, 2009), need to be considered". "has a radius of about 3 km, with center approximately located at the Pozzuoli town harbour" (Sacchi et al, 2014;Somma et al, 2015;Steinmann et al, 2016;2018 Sacchi…”

Marine Geohazards of the Bay of Naples (Southern Tyrrhenian Sea, Italy): A Review Integrating Morpho-Bathymetric and Seismo-Stratigraphic Analysis

“…The Bay of Naples, a late Quaternary eruptive region, displays marine geohazards due to volcanism, earthquakes, submarine mass movements, fluid seepages, and anthropogenic impacts. Quaternary volcanism has significantly impacted the sea, controlling the formation of submarine volcanoes, tephra deposits [10][11][12][13][14] (among others), and submarine mass movements [15][16][17][18] (among others). Tephra deposits have been detected in southern Naples Bay and northern Salerno Bay, represented in particular by the proximal deposits of the 79 A.D. eruption, along with those of the interplinian activity at 2.7 ka B.P.…”