Dr Rhodri Davies

ARC Future Fellow
J2, 147
 +61 2 61253643

Profile

Biography

Positions Held:

2014 - Present: ARC Future Fellow, RSES, ANU.

2013 - 2014: Research Fellow, RSES, ANU.

2011 - 2013: NERC Research Fellow, Imperial College London.

2008 - 2010: 1851 Research Fellow, Imperial College London.

2007 - 2008: Research Assistant, Funded by Shell, Based at the School of Earth & Ocean Sciences, Cardiff University.

2004-2007: PhD, Applying Multi-Resolution Numerical Methods to Geodynamics, School of Earth & Ocean Sciences, Cardiff University / School of Civil & Computational Engineering, Swansea University.

2000-2004: MSci, Earth Sciences, 1st Class Honours, School of Earth & Ocean Sciences, Cardiff University.

Awards:

2015: Media & Outreach Award, The Australian National University.

2014: Outstanding Young Scientist Award: European Geosciences Union, Geodynamics Division.

2014: Strategic Communications & Public Affairs Award, The Australian National University.

Competitive Funding and Fellowships:

2014: ARC Future Fellowship (Australia) - From Plume Source to Hotspot: Quantifying Mixing in Mantle Plumes and its Implications for the Nature of Deep Mantle Heterogeneity

2012: NERC Standard Grant (UK) - The Mantle Transition Zone `Valve'.

2011: NERC Post-doctoral Research Fellowship (UK)  - Pulsing Mantle Plumes: Causes and Geological Consequences.

2009: Research Fellowship - Royal Commission for the Great Exhibition of 1851 (UK) - Modelling Earth's Engine: Innovative Techniques for Simulating Thermo-chemical Mantle Convection.

2009: Research Grant - Shell International Exploration and Production (UK) - Integrating Convection Models, Tomographic Observations and Tectonic Reconstructions.

Research

Research interests

 

Interests (Keywords):

 

Solid Earth geophysics; mantle dynamics; thermal and thermo-chemical mantle convection; large igneous provinces, volcanic hotspots/intra-plate volcanism; mantle plumes; links between Earth's surface and its deep interior; subduction dynamics; subduction-zone magmatism; adaptive mesh numerical methods for geophysical flows.

 

Research Overview:

 

Over the past 5 years, I have developed sophisticated tools for simulating mantle convection, whilst also demonstrating the power of these to improve our understanding of mantle dynamics.

I have worked closely with computational engineers to develop adaptive mesh refinement techniques for mantle convection models. Such schemes use intelligent algorithms to modify the computational grid automatically, placing enhanced resolution only where required, thus dramatically reducing the cost of a simulation (Davies et al. 2007, 2008, 2011).

I have since utilized these powerful techniques to provide significant new insights into a range of processes, for example: (i) mantle plume dynamics (Davies & Davies, 2009); (ii) controls on the distribution of volcanic hotspots (Davies & Goes, 2015); (iii) the origin of intra-plate volcanism beneath the Australian continent (Davies & Rawlinson, 2014); (iv) the flow regime and thermal structure of the subduction zone mantle wedge (Le Voci et al. 2014; Davies et al. 2015); (v) subduction dynamics (Garel et al. 2014); and (vi) the dynamical interpretation of seismic images (Styles et al. 2011), particularly relating to Earth’s deep mantle (Davies et al. 2012; 2015).

Although my research focuses on geodynamical modeling, I also use other research avenues. For example, I have exploited Geographical Information Science (GIS) methods to provide a revised estimate of Earth’s surface heat flux (Davies & Davies, 2010). This estimate exceeds the predictions of previous studies, with important implications for Earth’s internal energy budget and thermal evolution. I have also worked closely with experimentalists, in an attempt to bridge the gap between experiment and simulation (e.g. Hunt et al. 2012). Furthermore, I have worked with applied mathematicians and statisticians to examine the geographical relationship between volcanic hotspot locations, the reconstructed eruptions sties of large igneous provinces and deep mantle seismic structure (Davies et al. 2015).

The tools I have at my disposal now include a next-generation computational modeling framework, Fluidity, developed in collaboration with colleagues at Imperial College London and the Lamont Doherty Earth Observatory, New York (Davies et al. 2011, Kramer et al. 2012). Fluidity: (i) uses an unstructured mesh, which enables the straightforward representation of complex geometries; (ii) dynamically optimizes this mesh, providing increased resolution in areas of dynamic importance, allowing for accurate simulations, across a range of length-scales, within a single model; (iii) is optimized to run on parallel processors and is able to perform parallel mesh adaptivity; (iv) has solvers that can handle the sharp variations in viscosity that occur within Earth’s mantle and lithosphere; (v) incorporates a free-surface; and (vi) has been extensively validated for geodynamical simulation (Davies et al. 2011, Kramer et al. 2012). To put it simply, the code’s functionality opens up a new class of problem to geodynamical research.

 

A series of thermal profiles, displaying the temporal evolution of a mantle convection simulation, with free-slip and isothermal boundaries, at a Rayleigh number of 10^9. Snapshots are spaced 30 Myr apart and are surrounded by a latitude-longitude grid. The scale illustrates the temperature, away from the lateral average. Each snapshot shows a radial surface just above the CMB and a hot isosurface, representing regions of the mantle that are 500K hotter than average for their depth. The most prominent features are hot upwelling plumes. These display a range of characteristics. The majority are long-lived and migrate slowly across the mantle. Others are more mobile and ephemeral. New plumes form and old ones fade, some of which eventually cease. Smaller plumes merge together and coalesce over time, while long-lived plumes often pulse or vary in intensity (Davies & Davies, 2009).

 

Shear wave velocity perturbations beneath Africa from: (a) tomographic model S40RTS (Ritsema et al. 2011); (b) a purely-thermal model; and (c) a thermo-chemical model, where the dense chemical component represents only 3% of the mantle volume (Davies et al. 2012). In the isochemical model, (T,P,X) is converted into seismic velocity assuming a pyrolitic composition, whilst  the thermo-chemical model illustrated assumes a pyrolitic composition for background mantle and an iron-rich composition for the dense chemical component. The structure of a thermo-chemical model with a basaltic dense component has similar characteristics. We account for the geographic bias, smearing and damping inherent to tomographic models using the resolution operator of S40RTS, thus allowing for direct comparison between our models and S40RTS. All images include a radial surface at 2850-km depth and an isosurface at -1.0%, clipped above 1400-km to allow visualisation of lower mantle features. Continental boundaries are included for geographic reference.

 

A 2-D thermo-mechanical dynamic subduction simulation from Fluidity. Temporal snapshots of: (a) temperature; (b) viscosity; (c) the dominant deformation mechanism; and (d) the underlying computational mesh, from a case where subducting/overriding plates are initially 100/20 Myr old at the trench, respectively (black squares indicate initial trench location). White lines in panel (a) mark isotherms from 600-1400 K at 200 K intervals. Black (b/c) and red (d) lines mark the location of the 1300K isotherm. In this class of subduction model, the slab’s buoyancy and distinct rheological properties arise self-consistently, through variations in temperature, pressure and strain-rate, with deformation accommodated through a composite diffusion creep (diff), dislocation creep (disl), Peierls creep (P) and yielding (YS) law. In the example shown, the slab’s excess density drives subduction and trench retreat over time. Upon interaction with the transition zone, the descending slab temporarily stalls and deforms (b/c), before slowly sinking into the lower mantle (d). Note that throughout its descent, the slab maintains a strong core (b), which is a requirement from observations of Benioff seismicity. The underlying computational mesh is adapted at fixed intervals during the simulation, with zones of high resolution analogous to regions of dynamic significance. A local resolution of 500m is required to resolve the slab’s strong core and the interface between subducting and overriding plates (Garel et al. 2014).

 

Variations in P-wave velocity at 100 km depth, beneath the Newer Volcanics region of Southeastern Australia. The horizontal limits of volcanic outcrop at the surface is denoted by a yellow dashed line (Davies & Rawlinson, 2014).

 

Publications

22. Sossi, P. A., Eggins, S. M., Nesbitt, R. W., Nebel, O., Hergt, J. M., Campbell, I. H., O'Neill, H. C., van Kranendonk, M. & Davies, D. R. Petrogenesis and Geochemistry of Archean Komatiites. J. Petrol. doi:10.1093/petrology/egw004 , 2016.

Download here: https://petrology.oxfordjournals.org/content/early/2016/02/24/petrology.egw004.full

21. Jones, T. J., Davies, D. R., Campbell, I. H, Wilson, C. R. & Kramer, S. C. Do mantle plumes preserve the heterogeneous structure of their deep-mantle source? Earth. Planet. Sci. Lett. 434, 10-17, doi:10.1016/j.epsl.2015.11.016, 2016.

Download here: http://www.sciencedirect.com/science/article/pii/S0012821X15007141

20. Davies, D. R., Le Voci, G., Goes, S., Kramer, S. C. & Wilson, C. R. The mantle wedge's transient 3-D flow regime and thermal structure. Geochem. Geophys. Geosys. 17, 1-23, doi:10.1002/2015GC006125, 2016.

Download here: http://onlinelibrary.wiley.com/doi/10.1002/2015GC006125/full

19. Tkalcic, H., Young, M., Muir, J. B., Davies, D. R. & Mattesini, M. Strong multi-scale heterogeneity in Earth's lowermost mantle. Sci. Rep. 5, 18416, doi:10.1038/srep18416, 2015.

Download here: http://www.nature.com/articles/srep18416

18. Davies, D. R., Rawlinson, N., Iaffaldano, G. & Campbell, I. H. Lithospheric controls on magma composition along Earth's longest continental hotspot track. Nature, 525, 511–514, doi:10.1038/nature14903, 2015.

Download here: http://www.nature.com/nature/journal/vaop/ncurrent/full/nature14903.html

17. Tosi, N., Stein, C., Noack, L., Huttig, C., Maierova, P., Samuel, H., Davies, D. R., Wilson, C. R., Kramer, S. C., Thieulot, C., Glerum, A., Fraters, M., Spakman, W., Rozel, A., Tackley, P. J. A community benchmark for viscoplastic thermal convection in a 2-D square box. Geochem. Geophys. Geosys., 16, 2175–2196, doi:10.1002/2015GC005807, 2015.

Download here: http://onlinelibrary.wiley.com/doi/10.1002/2015GC005807/full

16. Davies, D. R., Goes, S. & Lau, H. C. P. Thermally dominated deep mantle LLSVPs: a review. In: The Earth's heterogeneous mantle, Eds. A. Khan, F. Deschamps & K. Kawai. Springer, 441-478, doi:10.1007/978-3-319-15627-9_14, 2015.

Download here: http://link.springer.com/chapter/10.1007%2F978-3-319-15627-9_14

15. Davies, D. R., Goes, S. & Sambridge, M. On the relationship between volcanic hotspot locations, the reconstructed eruption sites of LIPs and deep mantle seismic structure. Earth Planet. Sci. Lett. 411, 121-131, doi:10.1016/j.epsl.2014.11.052, 2015.

Download here: http://www.sciencedirect.com/science/article/pii/S0012821X14007523

14. Davies, D. R. & Rawlinson, N. On the origin of recent intra-plate volcanism in Australia. Geology, 42, 1031-1034, doi: 10.1130/G36093.1, 2014.

Download here: http://geology.gsapubs.org/content/early/2014/10/17/G36093.1.abstract

13. Garel, F., Goes, S., Davies, D. R., Davies, J. H., Kramer, S. C. & Wilson, C. R. Interaction of subducted slabs with the mantle transition zone: A regime diagram from 2-D thermo-mechanical models with a mobile trench and an overriding plate. Geochem. Geophys. Geosys. 15, 1739-1765, doi:10.1002/2014GC005257, 2014.

Download here: http://onlinelibrary.wiley.com/doi/10.1002/2014GC005257/full

12. Le Voci, G., Davies, D. R., Goes, S., Kramer, S. C. & Wilson, C. R. A systematic 2-D investigation into the mantle wedge's transient flow regime and thermal structure: Complexities arising from a hydrated rheology and thermal buoyancy. Geochem. Geophys. Geosys. 15, 28-51, doi:10.1002/2013GC005022, 2014.

Download here: http://onlinelibrary.wiley.com/doi/10.1002/2013GC005022/full

11. Davies, D. R., Davies, J. H., Bollada, P. C., Morgan, K., Hassan, O. & Nithiarasu, P. A hierarchical mesh refinement technique for global 3-D spherical mantle convection modelling. Geosci. Mod. Dev. 6, 1095-1107, doi:10.5194/gmd-6-1095-2013, 2013.

Download here: http://www.geosci-model-dev.net/6/1095/2013/gmd-6-1095-2013.htm

10. Davies, D. R., Goes, S., Davies, J. H., Schuberth, B. S. A., Bunge, H.-P. & Ritsema, J. Reconciling dynamic and seismic models of Earth's lower mantle: the dominant role of thermal heterogeneity. Earth Planet Sci. Lett. 353-354, 253-269, doi:10.1016/j.epsl.2012.08.016, 2012.

Download here: http://www.sciencedirect.com/science/article/pii/S0012821X1200444X

*** This article was highlighted by Nature Geoscience: http://www.nature.com/ngeo/journal/v5/n11/full/ngeo1633.html

9. Kramer, S. C., Wilson, C. R. & Davies, D. R. An implicit free-surface algorithm for geodynamical simulations. Phys. Earth Planet Int. 194-195, 25-37, doi:10.1016/j.pepi.2012.01.001, 2012.

Download here: http://www.sciencedirect.com/science/article/pii/S0031920112000027

8.  Hunt, S. A., Davies, D. R., Walker, A. M., McCormack, R. J., Wills, A. S., Dobson, D. P. & Li, L. On the increase in thermal diffusivity caused by the perovskite to post-perovskite phase transition and its implications for mantle dynamics. Earth Planet. Sci. Lett., 319-320, 96-103, doi:10.1016/j.epsl.2011.12.009, 2012.

Download here: http://www.sciencedirect.com/science/article/pii/S0012821X11007230

7. Davies, D. R., Wilson, C. R. & Kramer, S. C. Fluidity: A fully unstructured anisotropic adaptive mesh computational modeling framework for geodynamics. Geochem. Geophys. Geosys., 12, Q06001, 20 PP., doi:10.1029/2011GC003551, 2011.

Download here: http://www.agu.org/pubs/crossref/2011/2011GC003551.shtml

6. Styles, E., Davies, D. R., Goes, S. Mapping spherical seismic into physical structure: biases from 3-D phase-transition and thermal boundary-layer heterogeneity. Geophys. J. Int., 184, 1371-1378, doi: 10.1111/j.1365-246X.2010.04914.x, 2011.

Download here: http://onlinelibrary.wiley.com/doi/10.1111/j.1365-246X.2010.04914.x/abstract

*** This article received the GJI student paper award for 2011: http://www.ras.org.uk/news-and-press/217-news-2011/2044-2011-gji-student-awards

5. Davies, J. H & Davies, D. R. Earth's surface heat flux. Solid Earth,  1, 5 - 24, 2010, doi:10.5194/se-1-5-2010

Download here: http://www.solid-earth.net/1/5/2010/se-1-5-2010.html

4. Wolstencroft, M., Davies, J. H. & Davies, D. R. Nusselt-Rayleigh number scaling for spherical shell Earth mantle simulations up to a Rayleigh number of 10^9. Phys. Earth Planet. Int., 176, 132-141, doi:10.1016/j.pepi.2009.05.002, 2009.

Download here: http://www.sciencedirect.com/science/article/pii/S0031920109001216

3.  Davies, D. R. & Davies, J. H. Thermally-driven mantle plumes reconcile multiple hot-spot observations. Earth Planet. Sci. Lett., 278, 50-54, doi:10.1016/j.epsl.2008.11.027, 2009.

Download here: http://www.sciencedirect.com/science/article/pii/S0012821X08007383

2.  Davies, D. R., Davies, J. H., Hassan, O., Morgan, K. & Nithiarasu, P. Adaptive finite element methods in geodynamics; Convection dominated mid-ocean ridge and subduction zone simulations. Int. J. Num. Meth. Heat Fluid Flow, 7-8, 1015-1035, doi:10.1108/09615530810899079, 2008.

Download here: http://www.emeraldinsight.com/journals.htm?articleid=1752631&show=pdf

1.  Davies, D. R., Davies, J. H., Hassan, O., Morgan, K., & Nithiarasu, P. Investigations into the applicability of adaptive finite element methods for infinite Prandtl number thermal and thermo-chemical convection. Geochem. Geophys. Geosyst., 8, Q05010, doi:10.1029/2006GC001470, 2007.

Download here: http://www.agu.org/pubs/crossref/2007/2006GC001470.shtml

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