New FoaLab publication Friday 10th March 2017
The recently published models of Keller & Katz (JPet 2016) demonstrated that small concentrations of volatiles may have a large effect on the style of melt transport. So what are the implications for our understanding of melt transport at mid-ocean ridges? A new paper by Keller, Katz & collaborator Marc Hirschmann published in EPSL addresses this. Channelisation is evident the models, but doesn't have an important effect on melt focusing. An important finding is that of the volatiles mobilised by melting and melt transport, only about 50% are focused to the ridge axis; the rest metasomatise the lithosphere, creating volatile-rich heterogeneity that may freeze into the plate. Simulation movies are on YouTube.
New FoaLab publication Monday 18th July 2016
It has long been understood that the very small content of volatile elements (especially water and CO2) in the mantle drastically lower the melting temperature. This creates a broad region of incipient, low-degree partial melting deep beneath mid-ocean ridges. Now a new publication by Keller & Katz has shown that these deep melts can drastically alter the style of melt transport, leading to channelisation of melt flow near the onset of anhydrous melting. The study, published in the Journal of Petrology, uses a newly-developed thermodynamic calculator called the Reactive Disequilibrium Multi-Component model, or (R_DMC, "run dee em see"), based on ideal solution theory and linear kinetics. A Matlab implementation of the calculator is available here https://bitbucket.org/tokeller/r_dmc.
Check out our new YouTube channel! Monday 18th July 2016
The FoaLab has a YouTube channel! We'll be broadcasting new movies with all your favourite stars: magma, the mantle, fluid dynamics, melting, and more. Stay tuned kids! https://www.youtube.com/channel/UCB1EJ7pMnF9bbWGmosRcRAQ
Jonathan Burley wins Guralp Prize Sunday 26th June 2016
Congratulations to Jonathan Burley on winning the Guralp Prize, which is awarded to a second or third-year DPhil student for excellence in research. Jonathan's research concerns the coupling between ice ages and volcanism. In recent work recognized by the Prize committee, he has shown that variations in sea level could modulate the emission rate of CO2 from mid-ocean ridges. A well-deserved honour!
Katz co-author on comment regarding sea-level and volcanism Tuesday 21st June 2016
Peter Huybers (Harvard) and co-authors including Richard Katz commented on the paper of Olive et al (2016, 10.1126/science.aad0715) in Science. Olive et al argued that the bathymetric fabric of the sea floor is dominated by normal faulting, and that the Milankovitch signal observed by Crowley et al (2015) at the AAD is unrelated to magmatic variations in the mantle. Huybers et al (10.1126/science.aae0451) commented that there are many examples of large constructional topography on the sea floor and that while there is no doubt that normal faults are important, the Milankovitch fingerprint is not fortuitous. They went on to show that at the ridge segment used by Olive et al to exemplify their arguments, the Milankovitch signal is found near the segment end, and seems to show a change in frequency content before 700ka, consistent with the shift in the dominant period of ice ages. Both Huybers et al and the reply from Olive et al et al agree that more research is needed to understand the interaction between magmatism and faulting at mid-ocean ridges.
Burley wins OGG McKarrow Cup Monday 29th February 2016
Jonathan Burley has won the 2016 McKerrow Cup/Young Geoscientist of the Year prize of the Oxford Geology Group. The prize recognises excellence in communicating geoscience to a non-specialist audience and carries an award of £400. Congratulations Jonathan!
Two new FoaLab publications Saturday 7th November 2015
The theory of anisotropic viscosity of partially molten rocks is the subject of two new papers co-authored by Richard Katz. One of them describes laboratory experiments conducted by Chao Qi and David Kohlstedt at the University of Minnesota and comparison of the results of those experiments with predictions for theoretical/computational models. The experiments are conducted in a torsion apparatus on partially molten olivine+basalt aggregates. They show radially-inward melt migration with progressive strain -- also known as base-state segregation. Such segregation is consistent with anisotropic viscosity theory but inconsistent with isotropic viscosity (even non-Newtonian). This striking agreement provides support for the validity of the theory. In the second study, Takei and Katz revisit the question of how dynamic anisotropy modifies the predictions of their earlier work on static anisotropy. The paper uses linearised stability analysis to provide a detailed explanation for why viscous anisotropy that evolves dynamically with the stress state leads to lower-angle bands than static anisotropy. Together, these two papers represent the state-of-the-art in understanding melt segregation in laboratory experiments -- but important discrepancies between experiment and theory remain and point to deficiencies of the theory that will be the subject of future work.
FoaLab at Fall AGU meeting 2015 Thursday 5th November 2015
Members of the FoaLab and collaborators will be presenting our work at American Geophysical Union Fall Meeting this year. Please find us at our poster or talk and discuss the results.
Monday V11B-3062 (invited poster) Grain Size as a Control for Melt Focusing Beneath Mid-Ocean Ridges. A Turner, RF Katz, M Behn. Moscone South, 8:00–12:20.
Tuesday V24A-01 (invited talk) SeaVOICE: Sea-going Experiments to Test Potential Linkages among Sea Level Change, Ocean Ridge Volcanism, and Hydrothermal Activity. C Langmuir et al. Moscone South 102, 16:00–16:15.
Tuesday V24A-02 (invited talk) Variations in Mid-Ocean Ridge Magmatism and Carbon Emissions Driven by Glacial Cycles. RF Katz, J Burley, P Huybers, C Langmuir, S-H Park. Moscone South 102, 16:15–16:30.
Wednesday DI31B-2578 (poster) Constraints on the rheology of the partially molten mantle from numerical models of laboratory experiments. J Rudge, L Alisic-Jewell, S Rhebergen, RF Katz, G Wells. Moscone South, 8:00–12:00.
Friday DI51C-01 (invited talk) Melting and Reactive Flow of Carbonated Peridotite Beneath Mid-Ocean Ridges. T Keller, RF Katz. Moscone South 303, 8:00–8:15.
Friday V53A-3124 (poster) A Climactic Feedback? Variations in Mid-Ocean Ridge CO2 Emissions Driven by Glacial Cycles. J Burley, RF Katz, P Huybers. Moscone South, 13:40–18:00.
New FoaLab publication Thursday 5th November 2015
There is a long-standing question about whether porous flow of magma is fast enough to explain the geochemical evidence for rapid melt transport (in the form of measured uranium-series disequilibria), or whether flow through cracks or dikes must be involved. A new publication by FoaLab alumnus Sam Weatherley and Richard Katz uses computational models of magma segregation from a chemically heterogeneous mantle to predict distributions of melt travel times and speeds. Fertile heterogeneities in the model are associated with channelised flow and rapid transport. But the paper shows that these melts don't always have the shorted travel time -- because they are produced by first melting much deeper in the mantle and remain trapped within their enriched enclave until later melting provides a pathway toward the surface. There is little correlation between fertility of the source and rate of magma ascent. Intermediate compositions, however, lead to melt extraction that is rapid enough to preserve thorium disequilibrium and, in some cases, also radium.
New FoaLab publication Saturday 17th October 2015
Melt-preferred orientation refers to the coherent alignment of melt pockets in partially molten rocks. The emergence of MPO has been long studied by experimentalists who produce it by subjecting partially molten rocks to deviatoric stress. The consequences of MPO are less well known. A new publication by Taylor-West and Katz considers the anisotropy of permeability that may arise from MPO, and develops models of melt segregation under such conditions. They show that anisotropic permeability affects the angle of melt bands that emerge by instability in the calculations. The authors seek to explain the band patterns that occur in experiments where partially molten rocks are sheared to large strains. However, the band angles observed in experiments are not well matched by the models, making it unlikely that anisotropic permeability, by itself, explains their features. Nonetheless, the calculations illuminate an important aspect of the two-phase mechanics of partially molten rocks.
New FoaLab publication Thursday 10th September 2015
Computational models of coupled magma/mantle dynamics are challenging to solve efficiently in two dimensions and prohibitively expensive in three dimensions. A new preconditions for such problems, derived by Rhebergen et al, is now published in SIAM Journal of Scientific Computing. The preconditioner takes a different approach than Rhebergen's previous work. It uses a pressure-splitting to take the problem from two fields (pressure and velocity) to three (compaction and dynamic pressure, velocity). In the process, it enables a more robust and more efficient preconditioner, derived to achieve approximate spectral equivalence. Rhebergen et al prove convergence of the preconditioned system and demonstrate its efficiency with two and three-dimensional simulations. doi: 10.1137/14099718X
Meng Tian wins Roy Soc fellowship to join FoaLab Wednesday 26th August 2015
Meng Tian, PhD candidate at Yale University, has been awarded a Newton International Fellowship by the UK Royal Society. This provides funds for a two-year postdoctoral period at the University of Oxford. Tian is completing his PhD under the supervision of Professor Jay Ague at Yale and is interested in the consequences of compaction and reaction for metamorphism in the deep crust. He'll join the FoaLab in early 2016. Congratulations on the fellowship, Meng!
Katz is now Professor of Geodynamics Monday 20th July 2015
The University of Oxford has awarded Richard Katz full professorship with the title Professor of Geodynamics. Katz chose the title in homage to the textbook that, when he first read it in 1998, inspired him to become an Earth Scientist: Geodynamics by Turcotte and Schubert.
New FoaLab publication Thursday 16th July 2015
The mantle contains about 10000 times as much carbon as the atmosphere and ocean combined. Mid-ocean ridges vent that carbon from the mantle into the climate system. Previous work from the FoaLab modelled and documented changes in mid-ocean ridge magmatism with changing sea level. Could the flux of carbon from mid-ocean ridges also change with sea level? This is the question that is addressed by Burley & Katz in the new paper Variations in mid-ocean ridge CO2 emissions driven by glacial cycles published online in EPSL today. Models developed in this work suggest that variations in sea level could cause up to 10% variation in the global flux of CO2 from the mantle. This is sensitive to assumptions about the permeability of the mantle, which is poorly constrained. Burley and Katz are collaborating with Peter Huybers of Harvard to understand the climate implications of this carbon. The research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Programme (FP7/2007–2013)/ERC grant agreement 279925 (ISMAGiC).
New FoaLab publication Thursday 2nd April 2015
Grain size in the mantle is an important control on viscosity and permeability, but it has received relatively little attention from geodynamicists. In "Grain-size dynamics beneath mid-ocean ridges: Implications for permeability and melt extraction" by Turner, Katz, and Behn (G-cubed doi:10.1002/2014GC005692), we have used a model of grain-size growth and reduction coupled to a single-phase model of mantle flow with composite viscosity to predict the distribution of grain size beneath a mid-ocean ridge. This distribution has a structure that leads us to predict a new mode of melt focusing, along a "soft" permeability barrier caused by grain-size variation. The research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Programme (FP7/2007–2013)/ERC grant agreement 279925 (ISMAGiC).
Melt in the Mantle programme at Isaac Newton Inst Monday 23rd March 2015
In 2016, the Isaac Newton Institute in Cambridge, UK will host a 3-month programme on magma/mantle dynamics and seismology: http://www.newton.ac.uk/event/mim. There are three week-long workshops. The Newton Institute seeks to bring together mathematicians and scientists to collaborate on research problems. Funding is available defray costs, especially for early-career applicants. The programme is co-organised by Katz and others; John Rudge is the lead organiser.
Crowley et at published in Science Thursday 5th February 2015
Science Express published Crowley et al.'s paper entitled Glacial cycles drive variations in the production of oceanic crust today. The paper presents models of how sea-level changes associated with glacial cycles can drive variations in magmatism and the production of oceanic crust at mid-ocean ridges. The work finds the signature of Milankovitch cycles in the ocean floor at the Australian-Antarctic ridge, lending strong support to the hypothesis. News coverage of the paper includes Science, Nature, LiveScience. The research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Programme (FP7/2007–2013)/ERC grant agreement 279925 (ISMAGiC).
FoaLab at AGU Fall Meeting 2014 Monday 27th October 2014
Members of the FoaLab and collaborators will be presenting our work at American Geophysical Union Fall Meeting this year. Please find us at our poster or talk and discuss the results.
V53B-4848 - Reactive Transport of Carbonated Magma Beneath a Mid-Oceanic Ridge: Theory and Numerical Models. Tobias Keller, Richard Katz, & Marc Hirschmann.
MR23C-4382 - Grain-Size Dynamics Beneath Mid-Ocean Ridges: Implications for Permeability and Melt Extraction. Andrew Turner, Richard Katz & Marc Behn.
G51A-0350 - Variations in Mid-Ocean Ridge CO2 Emissions Driven By Glacial Cycles. Jonathan Burley & Richard F Katz.
MR23B-4351 - Consequences of Anisotropic Permeability and Surface Tension for Magmatic Segregation in Deforming Mantle Rock. Jesse Taylor-West and Richard Katz.
MR23B-4352 - Consequences of Melt-Preferred Orientation for Magmatic Segregation in Deforming Mantle Rock. Richard F Katz, Jesse Taylor-West, Jane Allwright, Yasuko Takei, Chao Qi and David L Kohlstedt.
PP44A-07 - Mid-ocean ridge bathymetry records past variations in sea level: evidence from spectral analysis of abyssal hills and implications for 100 ky glacial cycles. Peter Huybers, Suzanne Carbotte, Richard Katz, & Charles Langmuir.
S53F-02 - Deformation-Driven Melt Segregation: Theoretical Predictions and Laboratory Observations. David L Kohlstedt, Chao Qi, Yasuko Takei & Richard F Katz.
DI43B-07 - Constraints on the Nature of the Lithosphere-Asthenosphere Boundary: Comparison of Observed Textural Evolution to Measured Seismic Anisotropy, Lars N Hansen, Chao Qi, Kathryn Kumamoto, Jessica M Warren, Richard F Katz & David L Kohlstedt
New FoaLab publication Saturday 18th October 2014
Laboratory experiments on partially molten rocks are needed to test the hypothesis of viscous anisotropy. One convenient approach may be to force partially molten rock down a pipe with no-slip walls: a two-phase pipe Poiseuille flow. A new paper by Allwright and Katz in GJI uses linearised stability analysis and numerical simulations to generate quantitative predictions for this problem. Allwright visited the the FoaLab for the Summer of 2013, funded by a NERC Research Experience Placement grant. At the time, she was an undergraduate student in Mathematics at the University of Cambridge. Allwright is now working in the modelling group at The Welding Institute, Cambridge.
New FoaLab publication Wednesday 20th August 2014
Numerical simulations of magma dynamics require the solution of a Stokes-like system of equations where the divergence of the velocity field (the compaction rate) is non-zero and multiplied by a large coefficient (the bulk viscosity). Preconditioners are needed to accellerate the convergence of the iterative methods used to solve the discrete system. In a new publication in the SIAM Journal of Scientific Computation, Rhebergen et al. propose a block preconditioner based on the Elman-Silvester-Wathen preconditioner for Stokes that is optimal in terms of problem size. They also note that this preconditioner is not optimal in problem parameters. In particular, the convergence degrades for large values of bulk-to-shear viscosity. A manuscript in preparation by Rhebergen circumvents this issue. Stay tuned to this channel.
Kyrke-Smith's thesis approved after viva Monday 30th June 2014
Teresa Kyrke-Smith successfully defended her DPhil thesis on Friday 27 June in a 3.5-hour viva voce exam. The examiners were Dr. Ian Hewitt of the University of Oxford and Dr. Richard Hindmarsh of the British Antarctic Survey. Teresa is moving to Limerick, Ireland for a postdoc position at the Mathematics Applications Consortium for Science and Industry. Congratulations Dr. Kyrke-Smith!!
Newton Institute programme on Melt in the Mantle, 2016 Wednesday 26th March 2014
The Newton Institute in Cambridge has agreed to fund a four-month programme entitled Melt in the Mantle that was proposed by Dr. John Rudge (Cambridge) and collaborators (Katz is among them). The goal is to bring together applied mathematicians, software engineers, and geoscientists to address the mathematical challenges associated with models of the partially molten mantle. There will be ~3 workshops and funding is available for longer-term stays at the Newton Institute. The programme runs 15 February - 17 June 2016. For more information please see the Newton Institute web pages, http://www.newton.ac.uk
On the cover of Proc Roy Soc A Thursday 28th November 2013
The new issue of Proceedings of the Royal Society A features a cover image designed by Teresa Kyrke-Smith and Oxford visualisation expert Alfie Abdul-Rahman. The image, showing ice streams above a thin film of subglacial water above saturated till and bedrock, is a representation of the model published in Kyrke-Smith et al, "Subglacial hydrology and the formation of ice streams" (doi:10.1098/rspa.2013.0494). More information here http://rspa.royalsocietypublishing.org/content/470/2162.cover-expansion.
Tobias Keller awarded GJI Student Author award Tuesday 19th November 2013
The Editorial Board of the Geophysical Journal International has selected Tobias Keller as a joint winner of the 2013 GJI Student Author Award. The award recognises his paper Numerical modelling of magma dynamics coupled to tectonic deformation of lithosphere and crust (Keller, May, & Kaus, doi: 10.1093/gji/ggt306). The paper was written as part of Keller's PhD work at ETH Zurich. Congratulations Tobias on a well-deserved honour!
Weatherley to join Danish Geological Survey Saturday 9th November 2013
Former FoaLab member Dr Sam Weatherley has accepted a DFF postdoctoral fellowship grant from the Danish Council for Independent Research in the Natural Sciences. He'll be working at the Geological Survey of Denmark and Greenland with collaborators Troels Nielsen (GEUS) and Marian Holness (Cambridge). The title of his project is "The origin of the Daly gap and its consequences for the economic potential of the Gardar Province, South Greenland." Congratulations and best wishes for this new project, Sam!
New FoaLab publication Wednesday 6th November 2013
A new publication by DPhil student Teresa Kyrke-Smith and co-authors Katz and Fowler entitled "Subglacial hydrology and the formation of ice streams" was published online today by Proceeding of the Royal Society A (doi: 10.1098/rspa.2013.0494). The paper analyses the coupled dynamics of ice sheets and the subglacial hydrologic system, showing how a feedback between basal sliding, frictional melting, and water pressure can lead to dynamical instability and the emergence of ice streams. This work contributes to our understanding of how ice streams work---a subject of ongoing research and debate---and helps us to forecast future changes in ice streams, with implications for increase in global sea level.
Two new FoaLab publications with Prof Y Takei Sunday 13th October 2013
New research by Prof Y Takei of the University of Tokyo and Richard Katz was just published by the Journal of Fluid Mechanics (doi: 10.1017/jfm.2013.482 and 10.1017/jfm.2013.483). These papers consider a continuum-scale model of anisotropic viscosity of partially molten rock that is derived from a consideration of diffusion creep at the grain scale. The papers analyse three different flow geometries and show that low-angle porosity band formation is a consequence of anisotropy. They also predict a mode of sample-wide stress-driven segregation. This latter mode is being investigated by experimentalists and should provide a test of the theory.
Jonathan Burley joins FoaLab Sunday 13th October 2013
The FoaLab is pleased to announce that Jonathan Burley has joined as a PhD candidate under the ERC ISMAGiC grant. Burley has an BA in physics and geology and an MSci in Experimental and Theoretical Physics from the University of Cambridge. His masters thesis is entitled "Label-Free Protein Detection with Glass Nanopores" and represents a proof-of-concept for applying using nanopores in protein analysis. Since 2011, Burley has been working in consultancy at OC&C London. In Oxford, Burley will be investigating the coupling between climate, sea-level, and mid-ocean ridge magmatism. Welcome Jonathan!
Kyrke-Smith wins Guralp prize Tuesday 25th June 2013
Congratulations to Teresa Kyrke-Smith on winning the Guralp Prize, which is awarded to a second or third-year DPhil student for excellence in research. Teresa's research concerns the coupling between ice-sheets and subglacial hydrology. In recent work recognized by the Prize committee, she has shown that this coupling can lead to the emergence of ice streams. A well-deserved honour!
Katz wins Philip Leverhulme Prize Thursday 1st November 2012
Richard Katz has been awarded a Philip Leverhulme Prize by the Leverhulme Trust, which is among the UK's foremost research and educational funding bodies. According to the Trust's webpage, the Prize is "awarded to outstanding scholars who have made a substantial and recognised contribution to their particular field of study, recognised at an international level, and where the expectation is that their greatest achievement is yet to come. The Prizes commemorate the contribution to the work of the Trust made by Philip Leverhulme, the Third Viscount Leverhulme and grandson of the Founder." Katz thanks the Trust, his colleagues at Oxford, his scientific mentors, and the members of the FoaLab for their support! Congratulations to Matt Friedman, whose office is next door to Katz's, and who also won a Prize!