The Pomici di Avellino eruption of Somma-Vesuvius (3.9 ka bp). Part I: stratigraphy, compositional variability and eruptive dynamics

Abstract

The stratigraphic succession of the Pomici di Avellino Plinian eruption from Somma-Vesuvius has been studied through field and laboratory data in order to reconstruct the eruption dynamics. This eruption is particularly important in the Somma-Vesuvius eruptive history because (1) its vent was offset with respect to the present day Vesuvius cone; (2) it was characterised by a distinct opening phase; (3) breccia-like very proximal fall deposits are preserved close to the vent and (4) the pyroclastic density currents generated during the final phreatomagmatic phase are among the most widespread and voluminous in the entire history of the volcano. The stratigraphic succession is, here, divided into deposits of three main eruptive phases (opening, magmatic Plinian and phreatomagmatic), which contain five eruption units. Short-lived sustained columns occurred twice during the opening phase (H t of 13 and 21.5 km, respectively) and dispersed thin fall deposits and small pyroclastic density currents onto the volcano slopes. The magmatic Plinian phase produced the main volume of erupted deposits, emplacing white and grey fall deposits which were dispersed to the northeast. Peak column heights reached 23 and 31 km during the withdrawal of the white and the grey magmas, respectively. Only one small pyroclastic density current was emplaced during the main Plinian phase. In contrast, the final phreatomagmatic phase was characterised by extensive generation of pyroclastic density currents, with fallout deposits very subordinate and limited to the volcano slopes. Assessed bulk erupted volumes are 21×10 6 m 3 for the opening phase, 1.3-1.5 km 3 for the main Plinian phase and about 1 km 3 for the final phreatomagmatic phase, yielding a total volume of about 2.5 km 3 . Pumice fragments are porphyritic with sanidine and clinopyroxene as the main mineral phases but also contain peculiar mineral phases like scapolite, nepheline and garnet. Bulk composition varies from phonolite (white magma) to tephri-phonolite (grey magma).

The Pomici di Avellino eruption of Somma–Vesuvius (3.9 ka BP). Part II: sedimentology and physical volcanology of pyroclastic density current deposits

“…The PdA eruption has been the focus of some volcanological, petrological and geochemical studies that are listed in the companion paper (Sulpizio et al 2010), which serves also as reference for the stratigraphy and eruptive dynamics of the PdA eruption.…”

The dispersal of ash during explosive eruptions from central volcanoes and calderas: an underestimated hazard for the central Mediterranean area

“…(1.2 km 3 of fallout deposits and 0.6 km 3 of PDC deposits), and the peak intensities were in the order of 10 7 -10 8 kg/s, which correspond to maximum column heights between 23 and 31 km (Cioni et al, 2000;Sulpizio et al, 2008b). Ash deposits related to the magmatic phases of the eruption were recognised in a wide area (ca.…”

“…As an example, in Figure 2 are reported the dispersal areas of two Holocene eruptions of Somma-Vesuvius volcano. The first is the Avellino Plinian eruption, dated at 3760±70 14 C yr BP (Cioni et al, 2000;Sulpizio et al, 2008b).…”

Volcanology of the Southwestern sector of Vesuvius volcano, Italy

“…The activity of the SommaVesuvius complex started approximately after the Phlegraean Fields Campanian Ignimbrite super-eruption, 39 years ago (De Vivo et al, 2001), while the last Vesuvius eruption occurred in 1944 (Arnò et al, 1987). During the last 4000 years of activity, Vesuvius experienced several main explosive events: the smallscale Plinian eruption of AD 1631 (Rosi, Principe, & Vecci, 1993), the sub-Plinian AD 472 eruption (Arnò et al, 1987;Rolandi, Munno, & Postiglione, 2004;Rosi & Santacroce, 1983;Sulpizio, Mele, Dellino, & La Volpe, 2005, and the two large Plinian eruptions that occurred at AD 79 (Pompei eruption; Sigurdsson, Carey, Cornell, & Pescatore, 1985) and 1995 ± 10 cal BC (Avellino eruption; Rolandi, Mastrolorenzo, Barrella, & Borrelli, 1993;Sevink et al, 2011;Sulpizio, Cioni, et al, 2010). Mild explosive activity (from Strombolian and violent Strombolian to sub-Plinian) took place during intra-Plinian periods (Andronico & Cioni, 2002;Arrighi, Principe, & Rosi, 2001;Cioni, D'Oriano, Bertagnini, & Andronico, 2013;Di Renzo et al, 2007;D'Oriano, Cioni, Bertagnini, Andronico, & Cole, 2011), and a number of lava flows originated from the central crater ('Gran Cratere') or from fissures opened on the main Vesuvius cone ('Gran Cono') .…”

“…The boundary between the Proto-Vesuvius Synthem and the Prehistoric-Vesuvius Synthem is defined by the Avellino eruption-related caldera collapse (following Cioni et al, 1999;Sulpizio, Cioni, et al, 2010) or sector collapse (in the view of Milia, Raspini, & Torrente, 2007Rolandi et al, 2004), and the tuff-ring morphology formed in the last phase of this eruption (Cioni et al, 1999).…”