Abstract
Welding occurs during transport and deposition of volcanic particles in diverse settings, including pyroclastic density currents, volcanic conduits, and jet engines. Welding rate influences hazard-relevant processes, and is sensitive to water concentration in the melt. We characterize welding of fragments of crystal-free, water-supersaturated rhyolitic glass at high temperature using in-situ synchrotron-source X-ray tomography. Continuous measurement of evolving porosity and pore-space geometry reveals that porosity decays to a percolation threshold of 1–3 vol.%, at which bubbles become isolated and welding ceases. We develop a new mathematical model for this process that combines sintering and water diffusion, which fits experimental data without requiring empirically-adjusted parameters. A key advance is that the model is valid for systems in which welding is driven by confining pressure, surface tension, or a combination of the two. We use the model to constrain welding timescales in a wide range of volcanic settings. We find that volcanic systems span the regime divide between capillary welding in which surface tension is important, and pressure welding in which confining pressure is important. Our model predicts that welding timescales in nature span seconds to years and that this is dominantly dependent on the particle viscosity or the evolution of this viscosity during particle degassing. We provide user-friendly tools, written in Python™ and in Excel®, to solve for the evolution of porosity and dissolved water concentration during welding for user-defined initial conditions.
| Language | English |
|---|---|
| Article number | 115726 |
| Number of pages | 9 |
| Journal | Earth and Planetary Science Letters |
| Volume | 525 |
| Early online date | 19 Aug 2019 |
| DOIs | |
| Publication status | Published - 1 Nov 2019 |
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Keywords
- jet engine
- obsidian
- porosity
- sintering
- surface tension
- tuffisite
Cite this
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A general model for welding of ash particles in volcanic systems validated using in situ X-ray tomography. / Wadsworth, Fabian B.; Vasseur, Jérémie; Schauroth, Jenny; Llewellin, Edward W.; Dobson, Katherine J.; Havard, Tegan; Scheu, Bettina; von Aulock, Felix W.; Gardner, James E.; Dingwell, Donald B.; Hess, Kai Uwe; Colombier, Mathieu; Marone, Federica; Tuffen, Hugh; Heap, Michael J.
In: Earth and Planetary Science Letters, Vol. 525, 115726, 01.11.2019.Research output: Contribution to journal › Article
TY - JOUR
T1 - A general model for welding of ash particles in volcanic systems validated using in situ X-ray tomography
AU - Wadsworth, Fabian B.
AU - Vasseur, Jérémie
AU - Schauroth, Jenny
AU - Llewellin, Edward W.
AU - Dobson, Katherine J.
AU - Havard, Tegan
AU - Scheu, Bettina
AU - von Aulock, Felix W.
AU - Gardner, James E.
AU - Dingwell, Donald B.
AU - Hess, Kai Uwe
AU - Colombier, Mathieu
AU - Marone, Federica
AU - Tuffen, Hugh
AU - Heap, Michael J.
PY - 2019/11/1
Y1 - 2019/11/1
N2 - Welding occurs during transport and deposition of volcanic particles in diverse settings, including pyroclastic density currents, volcanic conduits, and jet engines. Welding rate influences hazard-relevant processes, and is sensitive to water concentration in the melt. We characterize welding of fragments of crystal-free, water-supersaturated rhyolitic glass at high temperature using in-situ synchrotron-source X-ray tomography. Continuous measurement of evolving porosity and pore-space geometry reveals that porosity decays to a percolation threshold of 1–3 vol.%, at which bubbles become isolated and welding ceases. We develop a new mathematical model for this process that combines sintering and water diffusion, which fits experimental data without requiring empirically-adjusted parameters. A key advance is that the model is valid for systems in which welding is driven by confining pressure, surface tension, or a combination of the two. We use the model to constrain welding timescales in a wide range of volcanic settings. We find that volcanic systems span the regime divide between capillary welding in which surface tension is important, and pressure welding in which confining pressure is important. Our model predicts that welding timescales in nature span seconds to years and that this is dominantly dependent on the particle viscosity or the evolution of this viscosity during particle degassing. We provide user-friendly tools, written in Python™ and in Excel®, to solve for the evolution of porosity and dissolved water concentration during welding for user-defined initial conditions.
AB - Welding occurs during transport and deposition of volcanic particles in diverse settings, including pyroclastic density currents, volcanic conduits, and jet engines. Welding rate influences hazard-relevant processes, and is sensitive to water concentration in the melt. We characterize welding of fragments of crystal-free, water-supersaturated rhyolitic glass at high temperature using in-situ synchrotron-source X-ray tomography. Continuous measurement of evolving porosity and pore-space geometry reveals that porosity decays to a percolation threshold of 1–3 vol.%, at which bubbles become isolated and welding ceases. We develop a new mathematical model for this process that combines sintering and water diffusion, which fits experimental data without requiring empirically-adjusted parameters. A key advance is that the model is valid for systems in which welding is driven by confining pressure, surface tension, or a combination of the two. We use the model to constrain welding timescales in a wide range of volcanic settings. We find that volcanic systems span the regime divide between capillary welding in which surface tension is important, and pressure welding in which confining pressure is important. Our model predicts that welding timescales in nature span seconds to years and that this is dominantly dependent on the particle viscosity or the evolution of this viscosity during particle degassing. We provide user-friendly tools, written in Python™ and in Excel®, to solve for the evolution of porosity and dissolved water concentration during welding for user-defined initial conditions.
KW - jet engine
KW - obsidian
KW - porosity
KW - sintering
KW - surface tension
KW - tuffisite
UR - http://www.scopus.com/inward/record.url?scp=85070669904&partnerID=8YFLogxK
U2 - 10.1016/j.epsl.2019.115726
DO - 10.1016/j.epsl.2019.115726
M3 - Article
VL - 525
JO - Earth and Planetary Science Letters
T2 - Earth and Planetary Science Letters
JF - Earth and Planetary Science Letters
SN - 0012-821X
M1 - 115726
ER -