Parameters controlling the density of welded ignimbrites—A case study on the Incesu Ignimbrite, Cappadocia, Central Anatolia

Lepetit, P.; Viereck-Goette, L.; Schumacher, R.; Mues-Schumacher, Ulrike; Abratis, Michael

doi:10.1016/j.chemer.2009.05.004

Cited by 11 publications

(3 citation statements)

References 12 publications

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“…If densities of terrestrial ignimbrites are taken as a rough guide to estimate the density of welded pyroclasts, densities between 1700 kg m À3 and 2000 kg m À3 , corresponding to porosities between 35% and 20%, would be expected (Riehle et al, 1995;Lepetit et al, 2009). Compaction could act to increase density as a function of depth, but this effect does not usually exceed 25% in the upper 10 km of the crust (Wilson and Head, 1994).…”

Section: Discussionmentioning

confidence: 98%

Density and lithospheric structure at Tyrrhena Patera, Mars, from gravity and topography data

Grott

Wieczorek

2012

Icarus

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Section: Discussionmentioning

confidence: 98%

Density and lithospheric structure at Tyrrhena Patera, Mars, from gravity and topography data

Grott

Wieczorek

2012

Icarus

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“…Our model shows that a mass flux of 4 $ 3 Â 10 8 kg s À 1 is required to sustain an explosive volcanic event at the altitude of Scathach Fluctus. Ghail and Wilson (2013) estimate the volume of Scathach Fluctus to be 225-875 km 3 , and the density to be close to 2000 kg m À 3 , consistent with a welded ignimbrite (Lepetit et al, 2009). Assuming a dense rock equivalent density of 2800 kg m À 3 , this implies $ 30% void space.…”

Section: Deposit Emplacement Emissions and Limits Of Detectabilitymentioning

confidence: 93%

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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“…PDCs that result from column collapse are generally hot, but if such PDCs develop density stratification due to particles despite high temperatures they could still propagate as dilute currents for long distances. Density stratification would also inhibit the transfer of entrained fluid at current margins to current interiors, and current temperature would remain high for much of the propagation distance, thus increasing their hazard Dilute but density stratified PDCs could therefore be a mechanism for the emplacement of widespread, welded ignimbrites (G. D. M. Andrews & Branney, 2011; R. J. Carey et al., 2008; Freundt, 1998, 1999; Lepetit et al., 2009; Maeno & Taniguchi, 2009; Wolff & Wright, 1981; Wright & Walker, 1981).…”

Section: Discussionmentioning

confidence: 99%

Density Stratification and Buoyancy Evolution in Pyroclastic Density Currents

O’Donnell,

Johnson,

Breard

et al. 2024

JGR Solid Earth

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Pyroclastic density currents (PDCs) are density‐stratified along their vertical axis, with the near‐bed portion being denser than the upper portion, resulting from particle settling and ambient air entrainment at current margins. Whereas vertical density stratification likely influences mixing, sedimentation, and buoyancy of PDCs, many depth‐averaged models of PDC dynamics assume currents are well‐mixed. We investigated this discrepancy by performing sub‐aqueous laboratory experiments and conducted complementary numerical simulations to interrogate current dynamics at finer scales. Currents with small temperature difference with the ambient fluid become density‐stratified during propagation. The dynamics of such currents resemble two‐phase flows, in which particles move freely and particle concentration becomes stratified, but fluid density remains constant. Currents with large temperature difference with the ambient fluid, however, do not develop density stratification during propagation, due to current dynamics becoming dominated by the fluid phase and the lessening importance of particles. Currents that develop density stratification do not lift off from the bed within the domain of the setup, whereas poorly stratified currents do lift off, forming a rising plume. Strong density stratification within currents inhibits turbulence production, preventing entrained ambient fluid on current edges from mixing into current interiors. Poorly stratified currents are highly turbulent, have vigorous internal mixing, thereby achieving lift‐off. The strongly stratified currents are analogous to PDCs that result from eruption column collapse, maintaining fast velocity, low internal mixing, and high temperature over long distances. The poorly stratified currents are analogous to dilute ash‐cloud surges that develop atop basal avalanches, having short runout distances.

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Parameters controlling the density of welded ignimbrites—A case study on the Incesu Ignimbrite, Cappadocia, Central Anatolia

Cited by 11 publications

References 12 publications

Density and lithospheric structure at Tyrrhena Patera, Mars, from gravity and topography data

Density and lithospheric structure at Tyrrhena Patera, Mars, from gravity and topography data

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

Density Stratification and Buoyancy Evolution in Pyroclastic Density Currents

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