Ground deformation at Campi Flegrei, Italy: Implications for hazard assessment
Published:January 01, 2006
Francesca Bellucci, Judith Woo, Christopher R. J. Kilburn, Giuseppe Rolandi, 2006. "Ground deformation at Campi Flegrei, Italy: Implications for hazard assessment", Mechanisms of Activity and Unrest at Large Calderas, C. Troise, G. De Natale, C. R. J Kilburn
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Campi Flegrei caldera, west of Naples in southern Italy, has an exceptional documented record of ground deformation from Roman times onwards. Systematic recording began in the nineteenth century. For earlier dates, information has been obtained from archaeological studies and from contemporary descriptions of the locations of buildings, usually Roman, with respect to sea-level. Especially important have been accounts related to the Serapis, a Roman market-place built in the second century bcand now incorporated within the modern town of Pozzuoli. The long-term patterns of ground deformation have conventionally been investigated on the premise that Campi Flegrei naturally tends to a state of static equilibrium. This study argues that, instead, the area naturally tends to a steady rate of subsidence, at about 17 mm a-1. After this background rate has been removed, the data indicate that a permanent uplift of some 33 m has occurred from Roman times (up until the present day: 2005 at the time of writing), attributable to the intrusion of 1.85 km3 of magma, of which only 1% has been erupted. Uplift has occurred in three episodes, the third of which is still in progress. The behaviour can be interpreted in terms of the intermittent ascent of magma between a reservoir of c. 102—103 km3 at depths of 8-15 km or greater, to a much smaller, shallower system at depths of about 3–4 km. Should the current pattern of deformation follow previous trends, uplift is expected to continue for another 80–90 years, during which time Campi Flegrei will be characterized by an elevated possibility of eruption.
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Mechanisms of Activity and Unrest at Large Calderas
Large caldera collapses represent catastrophic natural events, second only to large meteoritic impacts. In addition, some calderas are densely populated, making the risk extreme, even for moderate eruptions. Understanding caldera mechanisms, unrest and the danger of eruption is therefore a crucial challenge for Earth sciences.
Several key features of caldera behaviour have yet to be fully understood. Through a combination of case studies and theoretical modelling, the following topics are addressed in this volume: the conditions required to produce and to release large volumes of magma erupted during caldera formation; how magmatic feeding systems evolve before and after a caldera has formed; the processes that limit the behaviour of precursors to eruptions; how pre-emptive precursors can be distinguished from those that drive unrest without an eruption; and given that post-collapse eruptions may occur across a wide area, the optimum procedures for designing hazard maps and mitigation strategies.