Modelling lithospheric deformation
Why Modelling Nature? To understand lithospheric deformation we need to see it unfolds. Unfortunately, lithospheric deformation develop at a very small strain rate not exceeding a few 0.001% per year. Because of this very slow strain rates, it is difficult to grasp the real dynamics of lithospheric deformation. Yet, lithospheric deformation is indeed very dynamic changing through time and space on a relatively short timescale. It is dynamic because of three main reasons:
1/ The rheology of the continental lithosphere is very dependent on the geotherm which evolves in response to lithospheric deformation (see HeatSld8 and HeatSld9 for details). Hence, the way the lithosphere deforms in response to a set of boundary conditions changes through time even when the boundary conditions remain the same.
2/ Lithospheric deformation is a response of the interplay between the gravitational force, which arise because of lithospheric deformation, and the plate boundary forces. Even if the plate boundary forces remain the same the evolving gravitational forces means that sudden switches in the tectonic regimes are possible.
3/ The rheological profile of the continental lithosphere involves strong vertical rheological variations. In particular the lower crust forms a weak layer in between a much stronger upper crust and upper mantle. This makes possible the mechanical decoupling or the upper crust and upper mantle.

Indeed, predicting using conceptual models how lithospheric deformation evolves through time and space is a very uncertain game. Numerical modelling (using numerical codes and computers) and experimental modelling (using scaled-down physical models) allows us to investigate lithospheric deformation through time and space.
This proud geologist (Henri M. Cadell, 1890), sometime during the late stages of the 19th century therefore long before Plate Tectonics, is experimenting with horizontal shortening. In one big squeeze, he sucessfully models the stacking of crustal nappes, recumbent folds, and gravitational sliding... although proper scaling is not guaranty as the scaling theory (Hubert, 1937) had yet to come.