The 5 April 2003 vulcanian paroxysmal explosion at Stromboli volcano (Italy) from field observations and thermal data

Abstract The 5 April 2003 paroxysmal explosion at Stromboli volcano was one of the strongest explosive events of the last century. It occurred while the effusive eruption, begun on 28 December 2002 and finished on 22 July 2003, was still on going and the summit craters of the volcano were obstructed. In this paper, we present a reconstruction of the sequence of events based on thermal and visual images collected from helicopter before, during and immediately after the paroxysm. One month before the blast, ash emission and temperature increase at the bottom of the summit craters were observed. An increasing amount of juvenile components in the emitted ash during March suggested that the magma level within the crater was rising accordingly. Hot degassing vents at the bottom of the summit craters were not persistent, and the craters remained almost entirely obstructed by talus accumulation until the paroxysm occurred. Three minutes before the explosion, we recorded a significant increase in temperature inside Crater 1, accompanied by a thicker gas plume. Thirty-two seconds before the blast, reddish ash was emitted from Crater 1. The paroxysm produced a vulcanian explosion that opened the feeder conduit, obstructed for over three months. The blast was accompanied by a shock wave recorded by the INGV seismic network at 07:13:37 GMT. Explosions with hot material started from Crater 1, and after 15 s propagated to Crater 3, about 100 m away. The velocity of ejecta was ∼80 m s − 1 , and increased when the eruptive plumes from both craters merged together during the vulcanian phase. An eruptive column rose 1 km above the top of the volcano, and explosions continued mainly at Crater 3. The paroxysm lasted about 9 min, with bombs up to 4 m wide falling on the village of Ginostra, on the west flank of the island, and destroying two houses. This event signalled the start of the declining phase of the effusive eruption, suggesting that the feeder conduit was returning to its former steady conditions, with open vents and continuous, mild strombolian activity.

[1]  A. Harris,et al.  Chronology and complex volcanic processes during the 2002-2003 flank eruption at Stromboli volcano (Italy) reconstructed from direct observations and surveys with a handheld thermal camera , 2005, Journal of Geophysical Research: Solid Earth.

[2]  Roberto Carniel,et al.  Multivariate stochastic modelling: towards forecasts of paroxysmal phases at Stromboli , 2003 .

[3]  Mark Settle,et al.  Statistical analysis of persistent explosive activity at stromboli, 1971: Implications for eruption prediction , 1980 .

[4]  Maurizio Ripepe,et al.  The summit hydrothermal system of Stromboli. New insights from self-potential, temperature, CO2 and fumarolic fluid measurements, with structural and monitoring implications , 2003 .

[5]  A. Bertagnini,et al.  Onset of the persistent activity at Stromboli Volcano (Italy) , 2000 .

[6]  Bernard A. Chouet,et al.  Photoballistics of volcanic jet activity at Stromboli, Italy , 1974 .

[7]  Jonathan Dehn,et al.  Thermal precursors in satellite images of the 1999 eruption of Shishaldin Volcano , 2002 .

[8]  Gilberto Saccorotti,et al.  Image processing of explosive activity at Stromboli , 1993 .

[9]  Maurizio Ripepe,et al.  Lava effusion rates from hand-held thermal infrared imagery: an example from the June 2003 effusive activity at Stromboli , 2005 .

[10]  K. Kelfoun,et al.  Characterisation of the 1997 Vulcanian explosions of Soufrière Hills Volcano, Montserrat, by video analysis , 2003 .

[11]  K. Dean,et al.  Numerical modeling of lava flow cooling applied to the 1997 Okmok eruption: Approach and analysis , 2004 .

[12]  G. B. Cimini,et al.  The Stromboli Volcano landslides of December 2002: A seismological description , 2004 .

[13]  B. Voight,et al.  Transient dynamics of vulcanian explosions and column collapse , 2002, Nature.

[14]  Mauro Coltelli,et al.  Violent explosions yield new insights into dynamics of Stromboli volcano , 1999 .

[15]  D. Patanè,et al.  Dynamics of the December 2002 flank failure and tsunami at Stromboli volcano inferred by volcanological and geophysical observations , 2003 .

[16]  Bruce F. Houghton,et al.  The encyclopedia of volcanoes , 1999 .

[17]  A. Bertagnini,et al.  Stromboli volcano (Aeolian Archipelago, Italy): An open window on the deep-feeding system of a steady state basaltic volcano , 2003 .

[18]  Anthony Finizola,et al.  Fluid circulation at Stromboli volcano (Aeolian Islands, Italy) from self-potential and CO2 surveys , 2002 .

[19]  Jonathan M. Lees,et al.  Vent discrimination at Stromboli Volcano, Italy , 2004 .

[20]  M. Buongiorno.  Recovery of spectral emissivity from Thermal Infrared Multispectral Scanner imagery acquired over a mountainous terrain: A case study from Mount Etna Sicily , 2002 .

[21]  C. Federico,et al.  Anomalous magmatic degassing prior to the 5th April 2003 paroxysm on Stromboli , 2004 .

[22]  L. Brusca,et al.  Geochemical precursors of the activity of an open‐conduit volcano: The Stromboli 2002–2003 eruptive events , 2004 .

[23]  Harry Pinkerton,et al.  Birth, growth and morphologic evolution of the 'Laghetto' cinder cone during the 2001 Etna eruption , 2004 .

[24]  Andrew J. L. Harris,et al.  The morphology and evolution of the Stromboli 2002–2003 lava flow field: an example of a basaltic flow field emplaced on a steep slope , 2007 .

[25]  L. Lirer,et al.  Stromboli and its 1975 eruption , 1978 .

[26]  H. S. Washington.  Persistence of vents at Stromboli and its bearing on volcanic mechanism , 1917 .

[27]  N. Ntepe,et al.  Observations of seismic volcanic signals at Stromboli volcano (Italy) , 1990 .