Paola Del Carlo

Discovery of a Plinian basaltic eruption of Roman age at Etna volcano, Italy

Basaltic Plinian eruptions are rare and poorly known volcanic phenomena. Etna is an active basaltic volcano, the activity of which is dominated by effusive eruptions that represent a continuous threat to a large populated area. We report on a Plinian eruption of basaltic composition that occurred in 122 b.c. Lapilli fallout caused extensive damage to the southern flank of the volcano. The discovery of this large explosive eruption raises important issues for previous hazard assessment at Etna and other basaltic volcanoes: An effusive basaltic volcano, generally nonhazardous for humans, can become very dangerous.

Eruptions of Mt. Etna during the past 3,200 years: A revised compilation integrating the historical and stratigraphic records

A critical re-examination of the original chronicles and previously published summaries of Etnean activity, within the context of recently available stratigraphic, mapping, and radiometric data, has made possible a detailed reconstruction of Etnas historical eruptions during the past three millennia. Our compilation, updated to the 2002 flank eruptions, lists only those events for which both age and the corresponding deposit are known, thereby eliminating inaccurate, uncertain, or poorly located volcanic events contained in the previous compilations. Not surprisingly, discrepancies between the historical and stratigraphic databases were noted for the events before 1600 AD, after which, however, the two databases are in good agreement. By excluding questionable eruptions, our compilation necessarily underestimated the number of pre-1600 events, when compared with that determined from historical sources. Our study indicates that, during the period from 1600 to 1975, the eruption frequency and lava output of Etna were relatively uniform; since 1975, however, both these parameters increased markedly. To understand the significance and possible implications of this increased activity during 1975-2000, a more complete reconstruction of Etnas prehistoric and historical eruptive history will be essential.

Magma dynamics within a basaltic conduit revealed by textural and compositional features of erupted ash: the December 2015 Mt. Etna paroxysms

In December 2015, four violent explosive episodes from Mt. Etna’s oldest summit crater, the Voragine, produced eruptive columns extending up to 15 km a.s.l. and significant fallout of tephra up to a hundred km from the vent. A combined textural and compositional study was carried out on pyroclasts from three of the four tephra deposits sampled on the volcano at 6 to 14 km from the crater. Ash fractions (Φ = 1–2) were investigated because these grain sizes preserve the magma properties unmodified by post- emplacement processes. Results were used to identify processes occurring in the conduit during each single paroxysm and to understand how they evolve throughout the eruptive period. Results indicate that the magmatic column is strongly heterogeneous, mainly with respect to microlite, vescicle content and melt composition. During each episode, the heterogeneities can develop at time scales as short as a few tens of hours, and differences between distinct episodes indicate that the time scale for completely refilling the system and renewing magma is in the same order of magnitude. Our data also confirm that the number and shape of microlites, together with melt composition, have a strong control on rheological properties and fragmentation style.

The Large Explosive Activity of Mt. Etna as Recorded in Distal Tephrostratigraphy

Mt. Etna is renowned for being the most active and highest volcano in Europe. Lava flows and weak explosive eruptions characterize its activity, but intermediate to large explosive eruptions have punctuated its eruptive history. Marine and lacustrine distal records are excellent archives for the recognition of past large explosive activity at Mt. Etna, as testified by the recognition of distal tephra layers of Pleistocene to Holocene age. These data are, to date, neither organised nor correlated to the proximal stratigraphic and chronological records. Here, we propose the reorganisation and correlation of the distal tephra layers from Mt. Etna in order to decipher the timings and frequency of its major explosive eruptions.