My research interests lie in developing theoretical models for processes that affect the solid earth. Recently, my students and I have been creating computer models of mantle upwelling in the region of melting below a mid-ocean ridge and investigating how it leads to the structural and topographic features we observe on ridges. We are also trying to understand how and why extension of the earth's crust occurs in such a wide variety of ways. In particular, I am interested in the effect of a weak lower crust on patterns of deformation that occur at the surface. For example, a weak lower crust may allow active normal faulting in the core of a mountain belt while thrusting occurs in the outer parts of the belt. My interests extend to deformation patterns and topography on other planets such as Venus, which has a very different style of tectonics than is seen on earth. I believe theorists need to get out and see where the data come from. In recent years I have been fortunate to participate in such diverse field work as collecting rocksamples for radiometric dating in Egypt and in the Mojave Desert, diving on the Reykjanes Mid-Ocean Ridge in a Russian submersible, and helping with GPS surveys on Iceland.