Dynamics of wind‐affected volcanic plumes: The example of the 2011 Cordón Caulle eruption, Chile

Abstract

The 2011 Cordón Caulle eruption represents an ideal case study for the characterization of long-lasting plumes that are strongly affected by wind. The climactic phase lasted for about 1 day and was classified as subplinian with plumes between~9 and 12 km above the vent and mass flow rate (MFR) on the order of~10 7 kg s À1. Eruption intensity fluctuated during the first 11 days with MFR values between 10 6 and 10 7 kg s À1. This activity was followed by several months of low-intensity plumes with MFR < 10 6 kg s À1 .Plume dynamics and rise were strongly affected by wind during the whole eruption with negligible upwind spreading and sedimentation. The plumes that developed on 4-6 and 20-22 June can be described as transitional, i.e., plumes showing transitional behavior between strong and weak dynamics, while the wind clearly dominated the rise height on all the other days resulting in the formation of weak plumes. Individual phases of the eruption range between Volcanic Explosivity Indices (VEIs) 3 and 4, while the cumulative deposit related to 4-7 June 2011 is associated with VEIs 4 and 5. Crosswind cloud and deposit dispersal of the first few days are best described by a linear combination of gravitational spreading and turbulent diffusion, with velocities between 1 and 10 m s À1. Downwind cloud velocity for the same days is best described by a linear combination of gravitational spreading and wind advection, with velocities between 17 and 45 m s À1. Results show how gravitational spreading can be significant even for subplinian and small-moderate eruptions strongly advected by wind and with low Richardson number and low MFR.

Water vapour variability in the high-latitude upper troposphere – Part 2: Impact of volcanic eruptions

“…The total erupted mass for Cordón Caulle is determined by multiplying a total erupted volume of 1.9 km 3 (Dr. Elizabeth Cottrelle, Global Volcanism Program, Smithsonian Institution, personal communication, 2015) by an ash density of 2300 kg m −3 appropriate for glass, since most of the erupted mass was glass (Bertrand et al, 2014). Bonadonna et al (2015) estimated the total erupted volume to be 1.1 ± 0.2 km 3 , while Bertrand et al (2014) imply > 3 km 3 . The total erupted mass for Eyjafjallajökull is 480 ± 120 Mt .…”

“…The mass flux rate remained less than 0.017 Mt s −1 during the entire eruptive phase for both studied volcanoes Bonadonna et al, 2015), and thus all of the repeated eruptions were considered "smaller", meaning that Table 2 of Glaze et al (1997) would be applicable to determine radial entrainment of tropospheric water vapour. Eyjafjallajökull is assumed to have erupted through a wet atmosphere based on Fig.…”

“…To include the wind entrainment term, the mass of radially entrained tropospheric water vapour is scaled by 1+1/ , where is the scaling parameter of Degruyter and Bonadonna (2012). This increases the entrained mass by a factor of 11 and 6.6 for Cordón Caulle and Eyjafjallajökull, respectively, as both erupted under windy conditions (Bonadonna et al, 2015;Petersen et al, 2012) and were observed as bent-over plumes, whereas Grímsvötn erupted during low wind speed conditions, and consequently wind entrainment was a minor factor (Woodhouse et al, 2015). The value for Cordón Caulle is appropriate for the early part of its eruptive phase (5-14 June 2011) when most of the mass of volcanic material erupted (Fig.…”

“…The value for Cordón Caulle is appropriate for the early part of its eruptive phase (5-14 June 2011) when most of the mass of volcanic material erupted (Fig. 6 of Bonadonna et al, 2015), and for Eyjafjallajökull, the maximum value of 0.18 is conservatively assumed (Degruyter and Bonadonna, 2012).…”

Paroxysmal Explosions, Lava Fountains and Ash Plumes at Etna Volcano: Eruptive Processes and Hazard Implications

“…It is difficult to univocally forecast plume height because it is related to the conditions and properties of the erupting system, such as magma discharge rate (Carey and Sparks, 1986), exsolved volatiles from magma, magma/water interaction (Schmith et al, 2018), and vent geometry (either elongated fissure or near-circular conduit; Wilson and Head, 1981;Wilson et al, 1995). Given that discharge rate and ultimately erupted volume have been measured from the lava fountain height Carbone et al, 2015;Bonaccorso and Calvari, 2017), there must be a direct connection between lava fountain height and maximum plume elevation, although this last parameter is also affected by wind speed (e.g., Bonadonna et al, 2015).…”