9707193 Silver Extensive geophysical and geochemical evidence indicates that mantle plumes interact strongly with nearby ocean ridges. The PIs propose a four-part study to investigate the dynamics of this process and its geophysical implications. The first involves numerical modeling of plume-ridge interaction using lubrication theory, a 3-D convection model with variable viscosity, and boundary integral methods. The principal aim will be to determine scaling laws for the length of ridge affected by the plume, the fraction of the plume flux reaching the ridge, and the maximum plume-ridge interaction distance. The second task is laboratory experiments on the chemical and thermal the interaction of plumes with stationary and migrating ridges. This work will provide an experimental test of the scaling laws determined in part 1. The third task is the application of the 3-D convection model to the Galapagos hotspot with the goal of constraining critical aspects of the dynamics and structure of the mantle beneath the hotspot, such as the excess temperature and the distribution of buoyant material and geochemical heterogeneities. 3-D dynamical modelling of seismic anisotropy and shear-wave splitting observations near the Iceland hotspot are the fourth project task. The aim is to resolve the controversial question of the width and excess temperature of the plume that generates Iceland. ***
