Lars Hansen stands apart through his integration of field-based insights, novel experimental work, innovative microstructural analyses and application of results to investigate a wide range of geodynamic processes. The impact of his work is extraordinary — and amenable to investigation by quantitative analysis of natural rocks and comparisons with geophysical data. He is a go-to expert on the application of lab data to investigate lithosphere rheology, processes that produce viscous and seismic anisotropy and the role of grain size evolution on strain localization. His most recent work on transient creep presages new understanding of why the effective viscosity of the mantle depends on the timescale of observation — a culmination of his integrative approach to process-based microphysics. Lars started his career in rock deformation by conducting experiments designed to investigate grain boundary sliding in mantle rocks. Although the importance of grain size-sensitive creep processes had been recognized for more than a decade, Lars completed the first suite of experiments designed to isolate important parameters required to quantify a flow law. His results indicate that grain boundary sliding is a dominant deformation mechanism throughout the upper mantle. Lars then developed innovative techniques to conduct large-strain torsion experiments to quantify relationships for strain localization, the development of crystallographic preferred orientation, and viscous anisotropy of mantle rocks. Much of his recent work focuses on the strength of the mantle lithosphere. Here he and his students and postdocs leveraged and developed new high-resolution microscopy techniques to study the micromechanics of deformation processes. His analysis of scale effects for dislocation interactions during low-temperature plasticity provided important insights for understanding how to apply lab data to constrain the strength of the lithosphere. Previous data for olivine showed large scatter, a problem that plagued the rock deformation and geodynamics community for years. The solution lay in the effect of grain size on strength and a better quantification of strain hardening. By leveraging the physical insights gained from these studies, Lars developed innovative models and experiments to investigate transient creep that provide a new foundation for understanding processes that control glacial isostatic adjustment, postseismic relaxation and seismic attenuation. Lars not only excels in research, but he is also a highly interactive and respected member of the broader solid Earth geophysics community. The respect he has garnered reflects both his incredible research insight and his ethos; he is a kind and thoughtful person who brings out the best in others. — Greg Hirth Brown University Providence, Rhode Island

Lars received his B.S. in Earth science from California Polytechnic State University in San Luis Obispo in 2005 and his M.S. in geology from the University of Wyoming in Laramie in 2007. He received his Ph.D. under the supervision of David Kohlstedt from the University of Minnesota in Minneapolis in 2012. He recently completed an appointment as a postdoctoral scholar working with Jessica Warren at Stanford University. Lars is now a university lecturer in mineralogy and petrology at the University of Oxford in the United Kingdom. His research interests are in the micromechanical behavior of viscously deforming rocks and its relationship to large-scale geodynamic processes.  

Hansen’s thesis is entitled “Evolution of the viscosity of Earth’s upper mantle: Grain-boundary sliding and the role of microstructure in olivine deformation.” Murphy’s thesis is entitled “Thermoelasticity of hexagonal close-packed iron from the phonon density of states.” They both were formally presented with the award at the 2013 AGU Fall Meeting, held 9–13 December in San Francisco, Calif.