The Paroxysmal Event and Its Deposits

Pistolesi, Marco; Rosi, Mauro; Pioli, Laura; Renzulli, Alberto; Bertagnini, Antonella; Andronico, Daniele

doi:10.1029/182gm26

Cited by 28 publications

(32 citation statements)

References 17 publications

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“…Density values were converted into vesicularity using a dense rock equivalent density of 2850 kg/m 3 for mingled clasts and 2950 kg/m 3 for HP scoria, measured from crushing of the scoria clasts (Pistolesi et al, 2008). One hundred clasts from a Strombolian eruption on 20 November 2004 were also analyzed for comparison.…”

Section: Sampling and Analytical Methodsmentioning

confidence: 99%

Transient explosions at open-vent volcanoes: The case of Stromboli (Italy)

Pioli¹,

Pistolesi²,

Rosi³

2014

Geology

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Stromboli is a persistently active, open-vent basaltic volcano whose activity is controlled by\ud the balance between magma supply, outgassing, and eruptive rates, and is characterized by low-intensity, regular Strombolian explosions. However, two types of large, transient, violent explosive eruptions suddenly occur with no clear precursory activity. These explosions, called “major” and “paroxysmal” depending on size, cover a large variability in intensity and mag- nitude, but are all marked by short duration. Paroxysms have significantly larger intensities (>106 kg/s) than major explosions (104 kg/s) and fundamental differences in the characteris- tics (composition, crystallinity, vesicularity) of the erupted tephra, suggesting that different sources feed these two eruption types. Paroxysms are generated by the explosive fragmen- tation of low-porphyricity (LP) magma mingled with high-porphyricity resident magma in the shallow reservoir, whereas major eruptions are likely associated with destabilization of the lower portion of the shallow magmatic system, continuously hybridized by the arrival of LP magma. In general, the intensity of these explosions is related to the amount of the LP magma erupted (>107 kg in paroxysms and 104–105 kg in major explosions), suggesting that the magma plays a major role in the fragmentation mechanism. Despite its primary impor- tance in the hazards of Stromboli, the total amount of magma erupted in these events in the past 10 years is less than 1% of the total mass erupted by the volcano

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Section: Sampling and Analytical Methodsmentioning

confidence: 99%

Transient explosions at open-vent volcanoes: The case of Stromboli (Italy)

Pioli¹,

Pistolesi²,

Rosi³

2014

Geology

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“…From the isomass map a total erupted mass of 1.1-1.4× 10 8 kg was calculated, corresponding to a volume of 2.2-2.4×10 5 m 3 using a density of 500 kg/m 3 (Pistolesi et al 2008). The average mass discharge rate was calculated in 2.8-3.6×10 6 kg/s, with a possible peak at 1.0-1.2×10 7 kg/s in the 10 s-long initial gas thrust.…”

Section: Size Of the Eruptionsmentioning

confidence: 99%

“…As pointed out by Rosi et al (2006) and Pistolesi et al (2008), emitted products, the impulsive nature of the event, and its eruption dynamics make the 5 April 2003 eruption a key case of Stromboli paroxysms. The comparison between deposits of 5 April 2003 and SSA (1930) and SSB (16th century) suggest that these sequences were emplaced by eruptions driven by similar dynamics.…”

Section: Size Of the Eruptionsmentioning

confidence: 99%

Paroxysmal activity at Stromboli: lessons from the past

2011

Self Cite

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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.

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“…Measurements of the density of clasts were performed following the method suggested by Houghton and Wilson (1989) to calculate sample vesicularity using a dense rock equivalent value of 2,800 kg m −3 (Pistolesi et al 2008). …”

Section: Methodsmentioning

confidence: 99%

A spatter-forming, large-scale paroxysm at Stromboli Volcano (Aeolian Islands, Italy): insight into magma evolution and eruption dynamics

Felice

Landi

2011

Bull Volcanol

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This study focuses on a pyroclastic sequence related to a large-scale paroxysm that occurred during the seventeenth century AD and which can be considered one of the most powerful and hazardous explosive events at the volcano in the past few centuries. Paroxysms are energetic, short-lived explosions which sporadically interrupt normal Strombolian activity at Stromboli and commonly erupt a deep-derived, volatile-rich crystal-poor high-potassium basalt ("low porphyricity" (LP)), together with a shallow, degassed crystal-rich high-potassium to shoshonitic basalt ("high porphyricity" (HP)), which feed normal activity at the volcano. The studied deposit, crops out along the flanks of Sciara del Fuoco and, from base to top, consists of: (1) a layer of HP and LP ash and lapilli; (2) an unwelded layer of coarse HP lapilli and flattened dark scoriae; (3) weakly welded spatter made up of dense HP pyroclasts at the base, overlain by strongly vesicular LP clasts. The textural and chemical zoning of minerals and the glass chemistry of the LP products record repeated mafic recharge events, mixing with an old mushy body and episodes of rapid crystallization due to sudden degassing. Collapse of a foam layer originated by deep degassing probably triggered this large-scale, spatter-forming paroxysm. Decompression induced rapid degassing and vesiculation of the deep volatile-rich magma. The rapid ascent of the foamy magma blob pushed the shallow HP magma out and finally produced a fire fountain that emplaced the LP portion of the spatter.

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The Paroxysmal Event and Its Deposits

Cited by 28 publications

References 17 publications

Transient explosions at open-vent volcanoes: The case of Stromboli (Italy)

Transient explosions at open-vent volcanoes: The case of Stromboli (Italy)

Paroxysmal activity at Stromboli: lessons from the past

A spatter-forming, large-scale paroxysm at Stromboli Volcano (Aeolian Islands, Italy): insight into magma evolution and eruption dynamics

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