Bombs behaving badly: unexpected trajectories and cooling of volcanic projectiles

Vanderkluysen, Loÿc; Harris, Andrew J. L.; Kelfoun, Karim; Bonadonna, Costanza; Ripepe, Maurizio

doi:10.1007/s00445-012-0635-8

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Title		Bombs behaving badly: unexpected trajectories and cooling of volcanic projectiles
Authors		Vanderkluysen, Loÿc Harris, Andrew J. L. Kelfoun, Karim Bonadonna, Costanza Ripepe, Maurizio
Published in		Bulletin of Volcanology. 2012, vol. 74, no. 8, p. 1849-1858
Abstract		We collected thermal infrared video of two explosive eruptions at Stromboli in June 2008 and manually traced the trajectories of 95 particles launched during two eruptions. We found that 10–15 % of the analyzed trajectories deviated from predicted curves due to collisions, causing one particle to travel horizontally more than twice as far as expected. Furthermore, we observed an oscillatory cooling behavior for the airborne pyroclasts, with a median period of 0.46 s. Measured cooling was typically much faster than model-predicted cooling with discrepancies of up to 40 % between measured cooling and theoretical modeling. We interpret the measured cooling curves as resulting from the spinning and twisting and tearing of particles during travel: the periodic re-exposing of the hotter core of the pyroclasts to the atmosphere may cause the observed oscillations, and the spinning may accelerate cooling by enhancing convective heat transfer. Current volcanic trajectory and cooling models do not account for projectile collisions, spinning, or tearing and can thus severely underestimate the maximum landing distance and cooling rates of large pyroclasts.
Keywords		Strombolian eruption — Stromboli — Thermal — Ballistic trajectory — Bomb — Pyroclast cooling
Identifiers		DOI: 10.1007/s00445-012-0635-8
Full text		Article (Published version) (560 Kb) - Limited access to UNIGE Other version: http://link.springer.com/10.1007/s00445-012-0635-8
Structures		Faculté des sciences / Section des sciences de la Terre et de l'Environnement / Département des sciences de la Terre
Research group		Physical Volcanology and Geological Risk
Citation (ISO format)		VANDERKLUYSEN, Loÿc et al. Bombs behaving badly: unexpected trajectories and cooling of volcanic projectiles. In: Bulletin of Volcanology, 2012, vol. 74, n° 8, p. 1849-1858. doi: 10.1007/s00445-012-0635-8 https://archive-ouverte.unige.ch/unige:30365