Introduction to Special Section on Physical Processes in Geodynamics

Abstract

On May 16 and 17, 1992, a meeting was held at Cornell University as part of activities to honor Donald L. Turcotte on the occasion of his 60th birthday (which actually occurred on April 22, 1992). The papers in the following special section are a result of that meeting, which included invited presentations and posters representing the diverse areas of geology and geophysics to which Donald Turcotte has contributed.Three of the papers deal with aspects of mantle convection. A. C. Fowler addresses the problem of initiation of subduction by extending boundary layer theory to a viscoplastic rheology. Turcotte and Oxburgh [1967] pioneered such studies by showing how boundary layer theory could be used to describe the dependence of geophysical observables such as heat flux on distance from a midocean ridge or age of the oceanic crust. D. W. Sparks et al. use a model of three‐dimensional convection beneath a segmented ridge to explore how buoyancy effects and melt production beneath a spreading center influence ridge‐parallel variations in crustal thickness and gravity. Magma migration and the dynamics of midocean ridges have been major focuses of Donald Turcotte's research in papers dating back to 1978 [e.g., Turcotte and Ahern, 1978; Ahern and Turcotte, 1979; Turcotte, 1982a; Kenyon and Turcotte, 1987]. G. A. Glatzmaier and G. Schubert calculate models of three‐dimensional two‐layer mantle convection in a spherical shell and compare with whole layer, spherical shell, three‐dimensional convection models. These models represent the end‐member states of a spectrum of possible modes of mantle convection [Turcotte and Oxburgh, 1972; Oxburgh and Turcotte, 1978; Turcotte, 1979a; Silver et al., 1988].