Transport of SO<sub>2</sub> by explosive volcanism on Venus

Glaze, L. S.

doi:10.1029/1998je000619

Cited by 29 publications

(40 citation statements)

References 34 publications

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“…Sparks and Wilson (1976) defined the limit of the gas-thrust region as the height at which the minimum upward velocity occurs. While each of the above two heights provides meaningful information, the abrupt transition at each height brings unrealistic discontinuity to the vertical profiles of physical variables, as discussed in Glaze (1999). The smooth transition near a height of M=2M o is consistent with the discussion in this paper and, thus, this height may be useful as an alternative index.…”

Section: Effect Of Gas Mass Fractions At a Ventsupporting

confidence: 70%

Sensitivity of the dynamics of volcanic eruption columns to their shape

Ishimine

2006

Bull Volcanol

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This paper presents a one-dimensional steadystate model to investigate the sensitivity of the dynamics of sustained eruption columns to radius variations with height due to thermal expansion of the entrained air, and decreases in atmospheric pressure with height. In contrast to a number of previous models using an equation known as the entrainment assumption, the new model is based on similarity arguments to derive an equation set equivalent to the model proposed by Woods [Bull Volcanol 50:169-193, 1988]. This approach allows investigation of the effect of gas compressibility on the entrainment rate of ambient air, which has been little examined for a system in which a decrease in pressure significantly affects the density stratification of a compressible fluid. The new model provides results that include two end members: one in which the volume change within the eruption columns affects only the radial expansion without changing the vertical motion, and the other is the converse. The Woods [Bull Volcanol 50:169-193, 1988] model can be regarded as being between those two end members. The range of uncertainty arises because the extremely high temperature of discharged materials from a volcanic vent, and the exceptional terminal height of the eruption columns, allow significant expansion of the gas component in the eruption columns, making them behave differently from common turbulent plumes. This study indicates that the maximum height of the eruption columns is affected considerably by this uncertainty, particularly when the eruption columns extend above a height of 10 km, at which the pressure is about one-fourth the pressure at the ground surface. Column collapse may also be suppressed in wider parameter ranges than previously estimated. However, the uncertainty can be reduced Editorial responsibility: J.D.L. White Y. Ishimine ( ) by measuring column radii through a vertical profile during actual volcanic eruptions. Accordingly, this paper suggests that appropriate observation of eruption column shapes is essential for improving our understanding of the dynamics of eruption columns.

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Section: Effect Of Gas Mass Fractions At a Ventsupporting

confidence: 70%

Sensitivity of the dynamics of volcanic eruption columns to their shape

Ishimine

2006

Bull Volcanol

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“…A case study by Robinson et al (1995) applied the same model to Ma'at Mons and suggested that explosive volcanism could have been responsible for the elevated atmospheric SO 2 concentrations detected by Pioneer Venus (Esposito, 1985). A further suite of studies estimated the overall plume height attainable by explosive volcanic eruption columns over a range of boundary conditions similar to those chosen for this study (Glaze, 1999), and with circular vs. linear vent geometries (Glaze et al, 2011). In this study we link a conduit flow dynamics model, not previously carried out under Venusian conditions, via a jet decompression model, with an established plume dynamics model, which has previously been applied to Venus (Glaze et al, 1997).…”

Section: Explosive Volcanismmentioning

confidence: 93%

“…Using the output from the conduit and jet decompression models described here, subaerial behaviour in some example scenarios was simulated using a previously developed plume rise model (Glaze et al, 1997(Glaze et al, , 2011Glaze, 1999). These example results are explored and described using the following case studies in Sections 4.3 and 4.4.…”

Section: Column Buoyancymentioning

confidence: 98%

Explosive volcanic activity on Venus: The roles of volatile contribution, degassing, and external environment

Airey

Mather

Pyle

et al. 2015

Planetary and Space Science

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We investigate the conditions that will promote explosive volcanic activity on Venus. Conduit processes were simulated using a steady-state, isothermal, homogeneous flow model in tandem with a degassing model. The response of exit pressure, exit velocity, and degree of volatile exsolution was explored over a range of volatile concentrations (H2O and CO2), magma temperatures, vent altitudes, and conduit geometries relevant to the Venusian environment. We find that the addition of CO2 to an H2O-driven eruption increases the final pressure, velocity, and volume fraction gas. Increasing vent elevation leads to a greater degree of magma fragmentation, due to the decrease in the final pressure at the vent, resulting in a greater likelihood of explosive activity. Increasing the magmatic temperature generates higher final pressures, greater velocities, and lower final volume fraction gas values with a correspondingly lower chance of explosive volcanism. Cross-sectionally smaller, and/or deeper, conduits were more conducive to explosive activity. Model runs show that for an explosive eruption to occur at Scathach Fluctus, at Venus’ mean planetary radius (MPR), 4.5% H2O or 3% H2O with 3% CO2 (from a 25 m radius conduit) would be required to initiate fragmentation; at Ma’at Mons (~9 km above MPR) only ~2% H2O is required. A buoyant plume model was used to investigate plume behaviour. It was found that it was not possible to achieve a buoyant column from a 25 m radius conduit at Scathach Fluctus, but a buoyant column reaching up to ~20 km above the vent could be generated at Ma’at Mons with an H2O concentration of 4.7% (at 1300 K) or a mixed volatile concentration of 3% H2O with 3% CO2 (at 1200 K). We also estimate the flux of volcanic gases to the lower atmosphere of Venus, should explosive volcanism occur. Model results suggest explosive activity at Scathach Fluctus would result in an H2O flux of ~107 kg s−1. Were Scathach Fluctus emplaced in a single event, our model suggests that it may have been emplaced in a period of ~15 days, supplying 1–2×104 Mt H2O to the atmosphere locally. An eruption of this scale might increase local atmospheric H2O abundance by several ppm over an area large enough to be detectable by near-infrared nightside sounding using the 1.18 µm spectral window such as that carried out by the Venus Express/VIRTIS spectrometer. Further interrogation of the VIRTIS dataset is recommended to search for ongoing volcanism on Venus

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“…Following the method suggested by Glaze [1999] we incorporate the gas thrust region into the model by replacing (4) with d VL…”

Section: Steady State Eruption Modelmentioning

confidence: 99%

Constraints on cooling and degassing of pumice during Plinian volcanic eruptions based on model calculations

Hort¹,

Gardner²

2000

J. Geophys. Res.

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Abstract. During explosive volcanic eruptions, pumice clasts are transported into the atmosphere, and their thermal and degassing histories determine how much volatiles are lost syneruptively. This process is studied by combining a steady state eruption column model with a model for the cooling and degassing of pumice. In the model we investigate the impact of various parameters (e.g., mass eruption rate, Blot number, eruption temperature, and geometry) on the cooling and degassing of If this ratio is larger than 50, degassing of the pumice will be nearly complete with a few percent of the original volatiles left in the outer rind of the pumice. For a ratio of less than 0.1 no volatiles escape the pumice. Typical values for thermal and species diffusivity as well as vesicle wall thickness indicate that in the case of degassing C1 and HeO the transition from 0.1 to 50 will be in the pumice size range of 1-10 cm. Here volatile concentration is a strong function of position inside the pumice, suggesting that values for volatile contents measured on picked matrix glass from crushed samples may not be the best way to estimate the volatile content of matrix glass, a number which is frequently used to estimate the total volatile input of volcanic eruptions. This effect is even more pronounced when looking at hydrogen isotopic fractionation with larger pumices tending toward 5D • -120%o and small samples giving 5D > -800/00 .

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Transport of SO₂ by explosive volcanism on Venus

Cited by 29 publications

References 34 publications

Sensitivity of the dynamics of volcanic eruption columns to their shape

Sensitivity of the dynamics of volcanic eruption columns to their shape

Explosive volcanic activity on Venus: The roles of volatile contribution, degassing, and external environment

Constraints on cooling and degassing of pumice during Plinian volcanic eruptions based on model calculations

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Transport of SO2 by explosive volcanism on Venus

Cited by 29 publications

References 34 publications

Sensitivity of the dynamics of volcanic eruption columns to their shape

Sensitivity of the dynamics of volcanic eruption columns to their shape

Explosive volcanic activity on Venus: The roles of volatile contribution, degassing, and external environment

Constraints on cooling and degassing of pumice during Plinian volcanic eruptions based on model calculations

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Resources

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Transport of SO₂ by explosive volcanism on Venus