Paroxysmal activity at Stromboli: lessons from the past

Abstract

The persistent normal activity of Stromboli is occasionally interrupted by sudden and highly energetic explosive events called Strombolian paroxysms. These phenomena together with landslide-generated tsunamis represent the most hazardous manifestations of presentday volcanic activity at Stromboli. The most recent paroxysms, on 5 April 2003 and 15 March 2007, have drawn attention to these energetic events because they significantly threatened inhabitants and tourists. Historical accounts and field evidence indicate, however, that even larger paroxysms, in terms of volume, dispersal of products and intensity of explosive phenomena, occurred in the recent past. During these paroxysms incipiently welded spatter deposits mantled the north and south rims of the Sciara del Fuoco down to low elevations, extending much farther than the similar deposits from recent observed events (5 April 2003 and 15 March 2007). In order to identify, characterize and discriminate among products of these outstanding spatter-forming eruptions, more than 50 stratigraphic sections were measured and sampled. Stratigraphic, sedimentological and radiometric ( 14 C) data indicate that only two paroxysms produced spatter that reached very low elevations and inhabited areas: the first occurred in the 16th century and the last in AD 1930. Analysis of texture and deposit components reveals that the early phases of the two eruptions were driven by distinctly different eruptive dynamics. Both identified paroxysms are at least one order of magnitude greater than any similar event observed by monitoring systems at Stromboli. These two large paroxysms were the most powerful volcanic events at Stromboli in the last eighteen centuries.

Geochemical heterogeneities and dynamics of magmas within the plumbing system of a persistently active volcano: evidence from Stromboli

“…Samples of pre-1990 activity were dated using stratigraphic, radiometric and paleomagnetic methods Speranza et al 2008Speranza et al , 2004. Stratigraphic trenches dug on the volcano flanks (Rosi et al 2000;Bertagnini et al 2011) provided additional samples. However, because spatial correlations between the tephra layers themselves and/or tephra layers and lava flows are difficult to establish, ages for these samples are more poorly constrained.…”

Chapter 6 Regional stratigraphic correlations across the Aeolian archipelago (southern Italy)

“…The MP products are predominantly composed of rhyolitic, aphyric pumices and minor obsidian clasts. Distal centimetre-thick fallout tephra layers correlated to MP are recognized on Vulcano (Keller 1970), Panarea (Lucchi et al 2008) and Stromboli (Bertagnini et al 2011). Moreover, a turbidite bed derived from the remobilization of a primary MP tephra layer has been recently recognized in a deep-sea core in the northern Marsili basin (Di Roberto et al 2008).…”

The 2009 paroxysmal explosions at Stromboli (Italy): magma mixing and eruption dynamics

“…4 Crystallization and/or mixing relationships between HP and LP glassy matrices. Arrows show the crystallization trends of glassy matrices from scoriae and pumice erupted in the past centuries (data from La Felice and Landi 2011;Landi et al 2008;Bertagnini et al 2008 and references therein). Glass compositions of the products erupted in November 8 follow mixing path between HP and LP end-members Similar features are observed in the products of May 3 explosion, despite the very small volume of LP magma erupted.…”

“…The energy of the paroxysms is highly variable: small-scale paroxysms (also called major explosions) affect only the upper part of the volcano, whereas largescale ones can produce continuous layers of tephra on the flanks of the volcano (Barberi et al 1993;Bertagnini et al 1999Bertagnini et al , 2008Bertagnini et al , 2011Andronico et al 2008;Landi et al 2008;Andronico and Pistolesi 2010). Knowledge of the characteristics and dynamics of the Stromboli feeding system has greatly increased in the last decade through the study of products erupted during paroxysms (Métrich et al 2001(Métrich et al , 2010Bertagnini et al 2003Bertagnini et al , 2008Francalanci et al 2004Francalanci et al , 2005Landi et al 2004). Crystal-poor (hereafter low porphyricity, LP; <10 vol.% crystals), volatile-rich highpotassium basalts (up to 4 wt.% volatile) are erupted only during paroxysms together with crystal-rich (hereafter high porphyricity, HP; ∼50 vol.% crystals), degassed shoshonitic basalts (≤1 wt.% volatile) normally feeding ordinary Strombolian activity.…”