Convective Instability of a Thickened Convecting Boundary Layer (and Thickened Lithosphere)

p.i.和合作者将对机械增厚边界层的对流不稳定性进行调查，目的是了解在造山过程中地壳（可能还有地幔岩石圈）增厚时，山带下可能发生的过程。他们将在2维和3维流体中进行数值实验，具有依赖于深度和温度的粘度和非线性粘度。他们寻求简单的标度定律，将实验结果与温度和应变速率相关的粘度转移到地球上合理的条件范围内。三维计算将集中于确定平台如何依赖于具有深度依赖粘度和后来的温度依赖粘度的流体边界层的扰动的大小和分布，无论是否移动顶部边界。二维计算将着重于非线性粘度对不稳定性增长率和边界层减薄幅度的影响。预计他们将发展出将扰动和流变结构的量级与岩石圈变薄的增长率和量级联系起来的标度定律，而岩石圈变薄又与观察到的地质结构和测量到的山带下过程的时间联系起来。＊＊＊

9725648 Molnar The P. I. and collaborators will carry out an investigation of convective instability of a mechanically thickened boundary layer, with the goal of understanding processes that might occur beneath mountain belts when crust, and presumably mantle lithosphere too, is thickened during mountain building. They will perform numerical experiments with fluids in 2 and 3 dimensions, with depth- and temperature-dependent viscosity and with non- linear viscosity. They seek simple scaling laws that will allow a transfer of experimental results with temperature-dependent and strain-rate-dependent viscosity to the range of plausible conditions in the earth. Three-dimensional calculations will concentrate on determining how planforms depend on magnitudes and distributions of perturbations to the boundary layers of fluids with depth-dependent viscosity and later temperature-dependent viscosity, both with and without moving top boundaries. Two- dimensional calculations will focus on the effect of non-linear viscosity on growth rates of instabilities and on magnitudes of thinning of the boundary layer. It is anticipated that they will develop scaling laws that relate magnitudes of perturbations and rheological structure to growth rates and magnitudes of lithospheric thinning that can relate observed geologic structures and measured timing of processes beneath mountain belts. ***