Shangxin Liu’s research has shed new light on the role of subducted slabs and shallow, slow–wave speed anomalies in the dynamics of the North American plate. In his 2022 Geochemistry, Geophysics, Geosystems paper, Shangxin showed that large-scale mantle flow induced by subducting slabs in the western Pacific contributes significantly to the forces driving the North American plate. In addition, he showed that assuming a purely thermal origin for shallow, slow seismic wave speed anomalies beneath southwestern North America, the estimated buoyancy drives North America toward Europe in the hot spot reference frame, opposite of the observed motion. He proposed that the slow–wave speed region beneath southwestern North America represents partial melt, which can strongly affect seismic wave speed while having a minimal effect on density. In addition to geodynamic modeling, Shangxin advanced our understanding of the structure of the eastern North American upper mantle using P-to-S receiver functions from the MAGIC flex array to map the 410- and 660-kilometer discontinuities. The topography on the 410- and 660-kilometer discontinuities is difficult to reconcile with either thermal or hydration variations alone, and he proposes a hot return flow associated with the descending Farallon slab interacting with a hydrous transition zone to explain the observations. In addition to geodynamic modeling and seismic receiver function analysis, Shangxin contributed in multiple ways to the development of ASPECT, an open-source geodynamics software package. He improved the calculation of surface stresses and dynamic topography within ASPECT and benchmarked the Stokes solver against a set of analytic solutions. He also developed an extension of the spectral geoid algorithm for adaptive mesh refinement modeling. This work is described in his 2019 Geophysical Journal International paper, and, like all of his work, these improvements have been contributed back to the community. Finally, he was involved in the work documenting that early forms of the entropy viscosity formulation of the energy equation were overly diffuse. Shangxin has made important contributions to our understanding of the geodynamics of North America while contributing to the development of open-source geodynamics software. —Scott King, Virginia Polytechnic Institute and State University, Blacksburg

It has been my great pleasure to be selected as one of the recipients of the Study of the Earth’s Deep Interior Section Award for Graduate Research after my graduation. It is a surprise and great encouragement for me to get an award that I didn’t expect at all. First, I’d like to express my gratitude to my nominator and my Ph.D. adviser, Dr. Scott King, a pure geoscientist, for his selfless guidance during my exploration in geodynamics. Scott enlightened me a lot with his scientific insight and professional experience. His patience and encouragement allowed me to solve all the technical obstacles step by step and freely explore new scientific directions within a broader horizon. Without his help, I could not make solid progress in my research and get through my tough time during my Ph.D. study. The exploration of the plate motion driving forces is a fundamental but significant topic in geodynamics. Through my endeavor into a numerical mantle flow model constrained by both geoid and plate motions, I’m excited to identify the importance of the far-field slabs, primarily the major segments around western Pacific subduction margins, to provide the dominant large-scale driving forces for North American plate motion through mantle drag. This indicates that plate tectonics is better regarded as a self-organizing interacting system, as opposed to an isolated balance of forces on each plate. I’m glad to make a modest contribution to our understanding of the dynamics of the plate tectonics of Earth. Another important part of my doctoral work is contributing to the development of an open-source mantle convection code, ASPECT. I’m happy to see that my numerical work has improved the capacity of ASPECT to simulate global mantle convection. The development of ASPECT is based on the efforts of a group of hardworking and enthusiastic peers. Among these people, I’d like to express my special acknowledgment to Wolfgang Bangerth, Rene Gassmöller, and Ian Rose. Their pioneering work formed a solid foundation for my further numerical development and from which I was enlightened and learned a lot. “After endless mountains and rivers that leave doubt whether there is a path out, suddenly one encounters the shade of a willow, bright flowers and a lovely village.” This well-known verse by poet Lu You over 800 years ago best characterizes my challenging and colorful scientific journey during my Ph.D. study at Virginia Tech. —Shangxin Liu, University of Florida, Gainesville