The Campi Flegrei Deep Drilling Project (CFDDP): New insight on caldera structure, evolution and hazard implications for the Naples area (Southern Italy). (6th December 2016)

• Record Type: Journal Article
• Authors: De Natale, Giuseppe; Troise, Claudia; Mark, Darren; Mormone, Angela; Piochi, Monica; Di Vito, Mauro A.; Isaia, Roberto; Carlino, Stefano; Barra, Diana; Somma, Renato
• Is Part Of: Geochemistry, geophysics, geosystems. Volume 17:Number 12(2016:Dec.)
• Page Start: 4836
• Page End: 4847
• Publication Date: 2016-12-06
• Subjects: Campi Flegrei caldera -- CFDDP drilling -- Ar dating -- caldera‐forming eruptions -- volcanic hazard -- caldera dynamics; Geochemistry -- Periodicals; Geophysics -- Periodicals; Earth sciences -- Periodicals; 550.5
• DOI: 10.1002/2015GC006183
• Languages: English
• ISSNs: 1525-2027

Abstract

Abstract: The 501 m deep hole of the Campi Flegrei Deep Drilling Project, located west of the Naples metropolitan area and inside the Campi Flegrei caldera, gives new insight to reconstruct the volcano‐tectonic evolution of this highly populated volcano. It is one of the highest risk volcanic areas in the world, but its tectonic structure, eruptive history, and size of the largest eruptions are intensely debated in the literature. New stratigraphic and 40 Ar/ 39 Ar geochronological dating allow us to determine, for the first time, the age of intracaldera deposits belonging to the two highest magnitude caldera‐forming eruptions (i.e., Campanian Ignimbrite, CI, 39 ka, and Neapolitan Yellow Tuff, NYT, 14.9 ka) and to estimate the amount of collapse. Tuffs from 439 m of depth yield the first 40 Ar/ 39 Ar age of ca. 39 ka within the caldera, consistent with the CI. Volcanic rocks from the NYT were, moreover, detected between 250 and 160 m. Our findings highlight: (i) a reduction of the area affected by caldera collapse, which appears to not include the city of Naples; (ii) a small volume of the infilling caldera deposits, particularly for the CI, and (iii) the need for reassessment of the collapse amounts and mechanisms related to larger eruptions. Our results also imply a revaluation of volcanic risk for the eastern caldera area, including the city of Naples. The results of this study point out that large calderas are characterized by complex collapse mechanisms and dynamics, whose understanding needs more robust constraints, which can be obtained from scientific drilling. Plain Language Summary: Campi Flegrei caldera is a supervolcano, i.e. a volcanic area where very catastrophic eruptions have occurred, 39, 000 and 15, 000 years ago. It is one of the most risky volcanic areas, because about 3 million people live within 10 km from a potential eruptive vent, and the caldera itself encloses a large part of the city of Naples. This area is experiencing unrest episodes, involving large ground uplift (up to 1 m/year in 1982—1984) and intense shallow micro seismicity (up to magnitude 4). This work sheds new light about the dynamics of this densely populated volcanic area, making use of the data from a recent advanced drilling project, funded by international and European agencies. Data from the first drilled hole, here analyzed, allowed us to better define the limits of the caldera and the mechanisms of the main collapses (the caldera forming events), giving new insight on the eruptive hazard for the city of Naples. Key Points: Scientific drillings of calderas Mechanisms of caldera collapse Risk associated with caldera eruptions