Peter E. van Keken
Thermal and chemical evolution of the Earth; causes and consequences of plate tectonics; finite element modeling of mantle convection, subduction zone dynamics and mantle plumes; integration of geodynamics with seismology, geochemistry and mineral physics; parallel computing; scientific visualization.
B.S., University of Utrecht, The Netherlands, 1989
Ph.D., cum Laude, University of Utrecht, The Netherlands, 1993
Peter van Keken studies the dynamics that underlie plate tectonics. The tectonic evolution of the Earth is driven by the slow release of heat from the Earth's interior that is conducted and advected by the slow solid-state deformation of the Earth's mantle. The melting at mid-oceanic ridges and subsequent recycling of the oceanic lithosphere at subduction zones imparts unique chemical characteristics, which over the long term cause a profound chemical evolution of the Earth's mantle as is seen in mid-oceanic ridge and hotspot lavas.
Van Keken develops computational models that use finite element techniques to solve the governing equations for slow convection in the silicate Earth. These models use constraints from mineral physics and petrology and are tested using observations from geodynamics (such as plate velocities and surface heatflow), seismology (tomography, receiver functions, phase conversions), geochemistry (radiogenic isotope constraints on mantle composition) and petrology (mineral stability under high pressure and temperature). Significant work is performed in collaborative and interdisciplinary projects with researchers in the United States (the University of Michigan, Cornell, UC Santa Barbara, Columbia University) and abroad (Tohoku University, Oxford, Imperial, ETH Zürich).
As part of his specialization in computational geodynamics van Keken develops community benchmarks, high-resolution 3D models of subduction, and tests numerical models against laboratory experiments. He has contributed to reviews on mantle convection and its role in the geochemical evolution of the Earth, the dynamics of subduction zones, and the nature of hot spot volcanism.
In recent years van Keken, together with Carnegie scientist Cian Wilson, a number of NSF and Carnegie Endowment supported postdocs, and with collaboration from external collaborators has made significant advances in a number of areas. These include: i) the development of new finite element modeling approaches and benchmarking based in particular on the FEniCS finite element framework (e.g., Wilson et al., 2017; Geballe et al., 2020; Sime et al., in press); ii) obtaining a better understanding of the importance of the shallow forearc and fluids in determining the thermal structure and dynamics of subduction zones (Abers et al., 2017; 2020; Morishige et al., 2017; 2018; Wei et al., 2017; van Keken et al., 2018; 2019; Shirey et al., in press); iii) establishing quantitative limits on the resolvability of plumes and lower mantle structures using seismic tomography and scattering (Maguire et al., 2016; 2018; Haugland et al., 2018; T. Jones et al., 2020); and iv) further constraining the importance of oceanic crust recycling in the geochemical evolution of the Earth’s mantle (R. Jones et al., 2019; Tucker et al., 2020; T. Jones et al., in press).
Top Image: Mantle convection in the Earth introduces heterogeneity through the subduction of basalt (black tracers) in subduction zones (blue regions). As this heterogeneity warms up it mixes back into the mantle but can also form dense piles near the core-mantle boundary (dark red regions). Inner circle is the core-mantle boundary; outer circle is the surface of the Earth. Mantle mixing calculations such as these allow for quantitative tests of scenarios that have been put forward to describe the chemical and thermal evolution of the Earth’s mantle since its formation. The modeling is described in Brandenburg et al., Earth and Planetary Science Letters, 2008.
Bottom Image: When oceanic plates pull apart the mantle melts to form slabs of lithosphere, which are later recycled back into the mantle at subduction zones. This process of melting and subduction destroys the initial chemical signature of the mantle. Geochemical analyses reveal that some portion of the mantle has avoided this process and retained a chemically “primitive” signature. How this material has survived vigorous convection for ∼4.5 Gyr is an open question. We propose that it may be preserved at the base of the mantle in large accumulations of subducted lithosphere. These accumulations are dominated by dense oceanic crust but can comprise up to 30% primitive material. The intermingling of oceanic crust and primitive material may explain why the chemical signatures of both coexist in volcanic eruptions at Earth's surface.Image credit: Nate Sime and Tim Jones. (https://doi.org/10.1029/2020GC009396).