Conduit dynamics and post explosion degassing on Stromboli: A combined UV camera and numerical modeling treatment

Abstract Recent gas flux measurements have shown that Strombolian explosions are often followed by periods of elevated flux, or “gas codas,” with durations of order a minute. Here we present UV camera data from 200 events recorded at Stromboli volcano to constrain the nature of these codas for the first time, providing estimates for combined explosion plus coda SO2 masses of ≈18–225 kg. Numerical simulations of gas slug ascent show that substantial proportions of the initial gas mass can be distributed into a train of “daughter bubbles” released from the base of the slug, which we suggest, generate the codas, on bursting at the surface. This process could also cause transitioning of slugs into cap bubbles, significantly reducing explosivity. This study is the first attempt to combine high temporal resolution gas flux data with numerical simulations of conduit gas flow to investigate volcanic degassing dynamics.

[1]  Michael James,et al.  Gas slug ascent through changes in conduit diameter: Laboratory insights into a volcano‐seismic source process in low‐viscosity magmas , 2006 .

[2]  M. Martini,et al.  Shallow-conduit dynamics at Stromboli Volcano, Italy, imaged from waveform inversions , 2008 .

[3]  G. Wallis.  One Dimensional Two-Phase Flow , 1969 .

[4]  Zhanfeng Cui,et al.  CFD modelling of slug flow in vertical tubes , 2006 .

[5]  A. Dukler,et al.  Hydrodynamic model for gas‐liquid slug flow in vertical tubes , 1983 .

[6]  M. Riethmuller,et al.  Flow patterns in the wake of a Taylor bubble rising through vertical columns of stagnant and flowing Newtonian liquids: An experimental study , 2006 .

[7]  M. James,et al.  Viscous plugging can enhance and modulate explosivity of strombolian eruptions , 2015 .

[8]  F. Giudicepietro,et al.  Source mechanisms of explosions at Stromboli Volcano, Italy, determined from moment‐tensor inversions of very‐long‐period data , 2003 .

[9]  Mike Burton,et al.  The SO2 camera: A simple, fast and cheap method for ground‐based imaging of SO2 in volcanic plumes , 2006 .

[10]  B. Hager,et al.  It takes three to tango: 2. Bubble dynamics in basaltic volcanoes and ramifications for modeling normal Strombolian activity , 2010 .

[11]  Piergiorgio Scarlato,et al.  An analytical model for gas overpressure in slug-driven explosions:insights into Strombolian volcanic eruptions , 2012 .

[12]  M. James,et al.  Gas slug ascent in a stratified magma:implications of flow organisation and instability for Strombolian eruption dynamics , 2016 .

[13]  S. Vergniolle,et al.  Strombolian explosions 1. A large bubble breaking at the surface of a lava , 1996 .

[14]  A. McGonigle,et al.  Passive vs. active degassing modes at an open-vent volcano (Stromboli, Italy) , 2012 .

[15]  João B. L. M. Campos,et al.  An experimental study of the wake of gas slugs rising in liquids , 1988, Journal of Fluid Mechanics.

[16]  C. Bean,et al.  Seismicity on volcanoes generated by gas slug ascent , 2008 .

[17]  S. Vergniolle,et al.  Strombolian explosions 2. Eruption dynamics determined from acoustic , 1996 .

[18]  B. Chouet,et al.  Pressure changes associated with the ascent and bursting of gas slugs in liquid-filled vertical and inclined conduits. , 2004 .

[19]  A. Harris,et al.  Thermal observations of degassing open conduits and fumaroles at Stromboli and Vulcano using remotely sensed data , 1997 .

[20]  M. Ripepe,et al.  Thermal, seismic and infrasonic evidences of variable degassing rates at Stromboli volcano , 2002 .

[21]  Robert G. Bryant,et al.  Protocols for UV camera volcanic SO2 measurements , 2010 .

[22]  A. McGonigle,et al.  Recent advances in ground-based ultraviolet remote sensing of volcanic SO2 fluxes , 2011 .

[23]  A. Pichon,et al.  The role of large bubbles detected from acoustic measurements on the dynamics of Erta 'Ale lava lake (Ethiopia) , 2010 .

[24]  A. Bertagnini,et al.  Crystallization Driven by Decompression and Water Loss at Stromboli Volcano (Aeolian Islands, Italy) , 2001 .

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

[26]  C. Oppenheimer,et al.  Use of Motion Estimation Algorithms for Improved Flux Measurements Using SO 2 Cameras , 2015 .

[27]  Vincent J. Realmuto,et al.  Development of an ultra-violet digital camera for volcanic SO2 imaging , 2007 .

[28]  Berthold K. P. Horn,et al.  Determining Optical Flow , 1981, Other Conferences.

[29]  Lionel Wilson,et al.  Mechanisms and dynamics of strombolian activity , 1976, Journal of the Geological Society.

[30]  Michael James,et al.  Modelling the rapid near-surface expansion of gas slugs in low-viscosity magmas , 2008 .

[31]  Maurizio Ripepe,et al.  High-Frame Rate Thermal Imagery of Strombolian Explosions: Implications for Explosive and Infrasonic Source Dynamics , 2012 .

[32]  João M. Miranda,et al.  Wide-ranging survey on the laminar flow of individual Taylor bubbles rising through stagnant Newtonian liquids , 2012 .

[33]  A. Freundt,et al.  Experiments on conduit flow and eruption behavior of basaltic volcanic eruptions , 2000 .

[34]  Mike Burton,et al.  Magmatic Gas Composition Reveals the Source Depth of Slug-Driven Strombolian Explosive Activity , 2007, Science.