Robert Dirk van der Hilst

Employs seismic imaging techniques to study the deep interior structure of Earth and the nature of solid-state convection within Earth's mantle. Contributed research on the long-standing problem of whether or not Earth's upper mantle and lower mantle function as independent convective systems and whether there is large-scale material exchange between the two. With careful refinement of the seismic structure of Earth's mantle, discerned variations in seismic velocity structure in the upper and lower mantle. Showed that the cold dense lithosphere that descends into the mantle at subduction zones sometimes penetrates the boundary between Earth's upper and lower mantle and sometimes is deflected at this boundary, spreading along the interface with complex and fascinating structures. Developed techniques to interpret the anisotropic seismic structure of continental lithosphere in complex regions of continental-continental collision, such as the Austral-Asia region. Recipient of the James B. Macelwane Medal of the American Geophysical Union.