A global study of plate rigidity based on the response of the lithosphere to loading.
Plate tectonics is based on the assumptions that the plate interiors are rigid and that deformation is limited to narrow boundaries at their edges. Recent studies, however, have questioned these assumptions pointing out that only ~85% of the Earth's surface is made up of rigid plates. The remaining ~15% is believed to comprise diffuse plate boundaries which represent zones of relatively weak lithosphere. There is evidence, for example, from plate kinematic studies that strain rates are up to a factor of 25 higher in the weak diffuse plate boundaries than in the strong plate interiors. One way that the rigidity of the plates can be independantly estimated is from studies of their response to geological loads such as ice sheets, volcanoes and sediments. By comparing the deformation that results from these loads to predictions based on elastic and viscoelastic plate models it has been possible to estimate the flexural rigidity of the lithosphere in a wide range of tectonic settings. The overall aim of this project is to use the spatial and temporal distribution of these estimates to better understand plate rigidity and nonrigidity. The project will involve the compilation of published flexural rigidity estimates for the continents and oceans, the modeling of lithosphere rheology using different assumptions for the temperature structure, crustal thickness, and strain rate, and the construction of a new flexural rigidity map of the Earth's surface.