IAVCEI 2013 Scientific Assembly - July 20 - 24, Kagoshima, Japan
Forecasting Volcanic Activity - Reading and translating the messages of nature for society

3P1_3C-O18

Room A5

Date/Time: July 23 15:45-16:00

Contemporaneous eruptions at 4.0 ka from 5.4 km apart vents within Campi Flegrei
caldera (Southern Italy): a comparison to Rabaul caldera
Celine Formentraux1 , Roberto Isaia2 , Mauro Rosi3 , Alessandro Sbrana3 , Antonella Bertagnini1 , Paola
Marianelli31Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Pisa, Italy, 2 Istituto Nazionale di Geofisica e
Vulcanologia, Osservatorio Vesuviano, Italy, 3 Dipartimento di Scienze della Terra, Universita di Pisa,Italy
E-mail: roberto.isaia@ov.ingv.it

The Campi Flegrei caldera is a collapsed structure mainly resulting from the Campanian Ignimbrite (39ka) and theNeapolitan Yelow Tuff (15ka) eruptions. Post caldera activity has occurred at vents scattered within the caldera
with eruptions concentrated in relatively short time periods (volcanic epochs) alternating with millennia-lasting
volcanic quiscence. The eruptions at different vents within each epoch have been classically considered to occur
in sequence. However, Isaia et al (2009) documented for the first time that the eruption occurred at Averno andSolfatara craters, situated 5.4 km apart, actually occurred, at least in part, simultaneously.
In this study we describe and analyses in detail a key tephra section located about 1.5 km NW of the Solfatara
crater where the deposits originated from the two vents are interstratified. The sequence, about 1m thick, consistsof almost plane-parallel alternatng green and pink colored ash beds that overlie a layer of discontinuos pumice
bombs. The green-colored ash beds forms more than half of the succession, the pink-colored ash consists ofseveral discrete mm- to cm-thick beds. SEM ash clasts characterization coupled with EDS analyses of freshglass shards and pumice matrix, indicate that the fine-grained green-colored ash, consists of hydrothermal alteredmaterials erupted by the Solfatara crater. In contrast, the pink-colored ash consists of fresh glass shards withcomposition range similar to the Averno eruption products. In particular the comparison of the glass chemestry
with the one made on the proximal eruptive sequence of the Averno eruption (Formentraux et al., 2012) enabled
us to assess that the studied section mirrors the entire Averno sequence and that the bomb layer at the base waserupted during the early plinian phase of the eruption.
We conclude that the Averno and Solfatara eruptions started and ended almost contemporaneously.

Thecomparison with the Tavurvur and Vulcan pyroclastic sequences produced during the very recent eruptive
vents occurred in 1994 at the Rabaul caldera shows striking similarities suggesting that the occurrence ofcontemporaneous eruptions at calderas might be more frequent than previously thought. Identifying these typeof event can enhance the volcanic hazards assessment and the expected future eruptive scenarios within active
calderas.
Formentraux C.,

Metrich N.,

Bertagnini A.,

Rosi M. (2012).

Contrib.

Mineral.

Petrol.,10.1007/s00410-012-0720-1.
Isaia R., Marianelli P., Sbrana A., (2009). Geoph. Res. Lett., 36, L21303, DOI 10.1029/2009GL040513.

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