Effective Elastic Thickness of the Continental Lithosphere with Particular Reference to the India–Eurasia Collision System

The effective elastic thickness (EET) of the lithosphere is a measure of the lithosphere’s ability to flex under long-term geological and topographic loads. It is often estimated through analyses of gravity and topographic data. The EET has a significant role in regulating the geodynamic evolution of both the continental and oceanic plates. Estimates of EET derived from geophysical data are consistent with rheological models in the oceanic regions. However, there are extensive debates on the estimates of EET and rheological models over the continental areas; differences are probably due to the complex structure and history of the continental plates. For instance, according to one model of continental rheology, popularly known as the ‘Jelly Sandwich’, the mechanical strength of the lithospheric plate is distributed in the upper crust and the lithospheric mantle. In another model, dubbed as ‘Crème Brulee’, the lithospheric mantle is weak, and the mechanical strength of the lithosphere is limited to the upper portion of the crust. These model differences have arisen because of inconsistent results obtained using different datasets, e.g. the distribution of earthquakes, EET, gravity anomaly and rheology. This article discusses the evolution of these contrasting models and the critical necessity to resolve the model differences.