David Wallis
Contact
About
Research Area
I investigate high-temperature rock deformation over human timescales, such as post-seismic deformation and anthropogenic glacial isostatic adjustment, and tectonic timescales associated with plate motion and the formation of faults and shear zones. My laboratory can perform creep experiments at temperatures up to 1600°C to calibrate flow laws and we have an in-situ stage capable of deforming samples at temperatures up to 600°C inside the scanning electron microscope to observe their microstructural evolution. We characterise samples using high-angular resolution electron backscatter diffraction to map residual stresses and geometrically necessary dislocations. We test the relevance of the flow laws that we develop by undertaking fieldwork to correlate microstructures between experimental and natural samples.
My current primary research interest is in developing constitutive equations describing transient creep over small strains and short timescales in the aftermath of stress changes, such as those imposed by major earthquakes or melting ice sheets. Investigating transient creep involves high-precision experiments to characterise the viscosity evolution and sensitive microstructural analyses to link the viscosity evolution to underlying microphysical processes. Constitutive equations for transient creep are critical to modelling fault-zone behaviour over the earthquake cycle and coupling between the solid earth and ice sheets during anthropogenic ice loss.
Project Interests
I am interested in developing projects across the broad remit of high-temperature rock deformation. Potential topics could include, for example, the mechanisms of transient creep in the lower crust and upper mantle, the controls on the strength of the lithosphere, the formation and evolution of faults and shear zones, orogenic processes, or coupling between deformation and igneous or metamorphic processes. Projects could include combinations of experiments, fieldwork, microstructural analysis, and/or modelling. I have a wide range of collaborators across leading rock-deformation groups worldwide and would encourage collaborative elements in the project design.
The creep apparatus in the Microgeodynamics Laboratory, here at a temperature of 1500'C, used to perform uniaxial compression experiments to measure the viscosity of minerals undergoing transient and steady-state flow.
The in-situ stage used to deform samples at temperature up to 600°C inside the scanning electron microscope to simultaneously measure mechanical properties and observe microstructural evolution.